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E. 1. . . -. .. . .J x u... u... t........_. v........ Fla... ........ .K.".....I.,..v~ caco/ . . . - . t . .34“ v...o§ér..é.. wh.‘.....r..\uota..lf..o .I l. . ,. I Q... .s "a ‘6 9-1 I, ..o. O. A . . . or . TI . . '1‘. oL: I tfov" ’..§+o .0. km... .nc .psl.O=b..‘.n....Oo. h. «I; .u. ‘5. . ‘o|q .. . . . a - IIIE LIBRARY Michigan State University ABSTRACT EVALUATION OF SOIL MAPS FOR DELINEATION OF FLOOD HAZARD AREAS IN SOUTHERN MICHIGAN by Guy H. Earle, Jr. Increasing population and urbanization in southern Michigan has created a critical need for sound land use planning and development to protect the remaining soil and water resources. An important segment of this need for overall land use planning is the need to identify those areas subject to flooding and to plan and regulate the development of these areas in order to protect human life and prOperty. Areas subject to flooding, or poten- tial flood hazard areas, make up 3.3 per cent, or 500,000 acres, of southern Michigan. About 76,000 of these acres occur in areas that are subject to rapidly expanding housing and industry. A major problem facing state and local governments is the identification of potential flood hazard areas. Historically, detailed engineering studies have been used for this purpose. Only sixteen of these studies have been made in southern Michigan. It is readily apparent that Guy H. Earle, Jr. this technique of identifying flood hazard areas cannot begin to meet the increasing demand for flood information in the foreseeable future. On the other hand, about 5,000,000 acres, or one-third of southern Michigan, has modern, detailed soil maps which show areas that consist of flood deposited materials. The objective of this thesis is to test the hypothesis that, in the absence of engineering and hydro- logic information, soil maps can be used to delineate potential flood hazard areas. The hypothesis is based on the premise that present soil characteristics are related to the presence or absence of past flooding. To evaluate modern, detailed soil maps, boundaries that indicated the extent of alluvial and adjacent organic soils were compared with engineering flood boundaries of various flood frequencies by means of map overlays. Four study areas were used: Plaster Creek, Buck Creek, Clinton River, and the Lookingglass River. The Plaster Creek and the Lookingglass River areas represented water- sheds of moraines and till plains with moderately developed drainage valleys. The Buck Creek study repre- sented mostly a drainage basin of former glacial drainageways with poorly developed drainage valleys. The watershed of the Clinton River study represented a lake plain with narrow, incised, drainage valleys. Guy H. Earle, Jr. The engineering data used in these study areas were from published reports by the Soil Conservation Service and the U.S. Army Corps of Engineers. The soil data were from published and unpublished soil surveys by the Soil Conservation Service in cooperation with the Michigan Agricultural Experiment Station. Data for the study areas were analyzed, for the most part, by areal measurements of the soil and engineering based flood hazard areas and by the comparison of soil and engineering flood boundaries at selected valley cross sections. The results of this study indicate that soil maps are useful for delineating potential flood hazard areas in southern Michigan. Their use must be selective depending on the type of glacial landscape. In watersheds with predominantly till plain and moraine landscapes and having moderately developed drainage valleys, soil maps reflect reasonably well the flood areas equivalent to floods of 50 to lOO-year return frequencies. Soil maps do not reflect these flood frequencies in other types of glacial landscapes. In most glacial landscapes with moderately developed drainage valleys, soil maps indicate the most hazardous part of the flood hazard area. The shape and gradient of the channel bed in some areas will influence the kind and extent of soils flooded. Stream down cutting will tend to reduce the areas of alluvial soil subject to frequent flooding. Interpretations of soil maps for the Guy H. Earle, Jr. identification of potential flood hazard areas should be done by an experienced soil scientist. The study also indicates the need for better tech- niques to classify and identify soils derived from alluvium, to identify those alluvial soils that have not been sub- ject to flooding for a considerable period of time. Modern, detailed soil maps at a scale of 1:15,840 (4 inches equal one mile) provide sufficient information to make soil interpretations for potential flood hazard areas. For planning and land use purposes, enlargements of published soil maps are necessary, particularly for those published soil surveys at a scale of l:20,000 (3.168 inches equal one mile). Soil maps are most useful in rural areas to identify flood hazard areas. Intensive and wideSpread agricultural drainage in some rural areas, however, may greatly affect the natural soil-flood water relationships. In urbanizing areas, the suitability of soil maps is directly related to the degree and kind of man-made dis- turbance. They are most applicable in urbanizing areas with scattered upland developments and least applicable in those areas with extensive disturbance within the physi- ographic flood plain. In summary, soil maps can be used to provide flood hazard area information for many areas in southern Michigan. EVALUATION OF SOIL MAPS FOR DELINEATION OF FLOOD HAZARD AREAS IN SOUTHERN MICHIGAN by Guy H. Earle, Jr. A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Resource DevelOpment 1973 ACKNOWLEDGMENTS With a deep sense of appreciation, the author wishes to thank the following persons and organizations: Dr. Milton H. Steinmueller, major advisor, and Professor Ivan F. Schneider, minor advisor, for their sound guidance throughout the program of graduate study; Mr. Dirk van der Voet, former State Soil Scientist in Michigan, for his encouragement in this undertaking and for the fine example he set for others to follow; Mr. Rodney F. Harner, the present State Soil Scientist in Michigan, for granting leave at crucial moments and for his enthusiastic support oftiufiseffort; Messrs. Russell H. Bauerle, John L. Okay, and Karl E. Pregitzer of the Soil Conservation Service for their assistance and counsel; my wife, Frances, for her steadfast and patient support throughout these four years of part-time graduate study and for her typing of the original manuscript, and the U.S. Department of Agricul- ture, Soil Conservation Service, for providing much of the original data used in this thesis. Pictures used for the Buck Creek study and to illus- trate soils were provided by the Soil Conservation Service. The picture of flooding along the North Branch of the Clin- ton River was provided by the Macomb County Drain Commission. ii' TABLE OF CONTENTS ACKNOWLEDGMENTS . . . . . . . . . . LIST OF TABLES . . . . . . . . . . . . LIST OF FIGURES . . . . . . . . . . . . Chapter I. INTRODUCTION . . . . . . . . . . Reasons for the Study . . . . . . Scope of the Study . . . . . . . II. III. IV. Definitions . . . . . . . . . TECHNIQUES FOR DELINEATION OF FLOOD HAZARD AREAS O O I O O O O O O O O 0 Introduction . . . . . . . . . Engineering Surveys . . . . . . . Interpretation of Soil Maps . . . . REVIEW OF LITERATURE . . . . . . . THE PLASTER CREEK STUDY . . . . . . Introduction . . . . . . . . Description of the Watershed and Study Area . . . . . . . . . Source Materials and Methods of Study Results and Discussion . . . . . . Conclusions . . . . . . . . . . THE BUCK CREEK STUDY . . . . . . . Introduction . . . . . . . Description of the Watershed and Study Area . . . . . . . . . . . Source Materials and Methods of Study . Results and Discussion . . . . . . Conclusions . . . . . . . . . . iii Page ii vi Wk!“ 11 ll 13 17 27 36 36 36 44 51 69 73 73 74 85 88 102 Chapter Page VI. THE CLINTON RIVER STUDY . . . . . . . 105 Introduction . . . . . . 105 Description of the Watershed and Study Area . . . . . . . . . . 106 Source Materials and Methods of Study . . 117 Results and Discussion . . . . . . . 119 Conclusions . . . . . . . . . . . 128 VII. THE LOOKINGGLASS RIVER STUDY . . . . . . 131 Introduction . . . . . . . 131 Description of the Watershed and Study Area . . . . . . . . . . 132 Source Materials and Methods of Study . . 137 Results and Discussion . . . . . . . 139 Conclusions . . . . . . . . . . . 145 VIII. CONCLUSIONS AND RECOMMENDATIONS . . . . . 147 Conclusions . . . . . . . . . . . 147 Recommendations . . . . . . . . . 150 BIBLIOGRAPHY . . . . . . . . . . . . . . 153 APPENDIX . . . . . . . . . . . . . . . 156 iv LIST OF TABLES Summary of Flood Hazard Area Data, Plaster Creek Study Area Relation of Soil and SO-Year Flood Hazard Area Boundaries at Engineering and Randomly Selected Valley Cross Sections, Plaster Creek Study Area Summary of Flood Hazard Area Data, Buck Creek Study Area Relation of Soil, SO-Year, and lOO-Year Flood Hazard Area Boundaries at Engineering and Randomly Selected Valley Cross Sections in the Lower Reach of the Buck Creek Study Area . . . . . . . . . . . Summary of Flood Hazard Area Data, Clinton River Study Area . . . Relation of Soil and 1947 Flood Hazard Area Boundaries at Selected Valley Cross Sections on the Main Branch of the Clinton River Study Area . . . . . . . . . . . Summary of Flood Hazard Area Data, Lookingglass River Study Area Page 53 67 89 99 120 127 140 Figure 10. 11. 12. 13. 14. 15. 16. LIST OF FIGURES Map of Southern Michigan Showing Study Areas . Glendora Soil . . . . . . . . . Map of Plaster Creek Study Area Flooding on Little Plaster Creek . . . . . Escarpment Bordering the Alluvial Bottom Land . . . . . . . Flood Area Map Showing Encroachment by a Subdivision on the Physiographic Flood Plain . . . . . House Located within the Flood Hazard Area of Plaster Creek . . . . . . . . . . . Fill Area and a Commercial Building on Alluvial Soils along Plaster Creek . . Overlay of Soil and Engineering Flood Hazard Areas . . . . . . . . . . . . . Broadmoor Avenue Prevents Flooding of Alluvial- Organic Soils by Diking . . . . . The Effect of Road Crossings on the Relation— ship of Flood Hazard Areas . . . . Flooded Point Bend Areas along Plaster Creek Landscape of a Point Bend Area Downstream from Breton Avenue . . . . . . . Landscape of a Point Bend Area Upstream from Breton Avenue . . . . . . . . . Map of Buck Creek Study Area Recent Flooding along Buck Creek vi Page 20 38 39 42 45 46 47 49 55 58 60 61 62 75 78 Figure Page 17. Landscape of the Buck Creek Study Area . . . 80 18. The Low Banks and Level, Adjoining Land along Buck Creek . . . . . . . . . . 81 19. Buck Creek at the Beginning of the Lower Reach . . . . . . . . . . . . . 83 20. Disturbed Areas along Buck Creek . . . . . 86 21. Lowland Flooding along Buck Creek . . . . . 91 22. Flooding along the North Branch of the Clinton River . . . . . . . . . . . 109 23. Map of Clinton River Study Area . . . . . 110 24. Boyer Soils Occur on Deltaic Outwash Plains . 115 25. Map of Lookingglass River Study Area . . . . 134 Vii CHAPTER I INTRODUCTION Reasons for the Study In recent years, the proper use of areas subject to flooding has been a growing concern in the management of Michigan's soil and water resources. Increasing popu- lation and urbanization, particularly in the southern part of Michigan, has greatly increased the pressures for maximum development of flood hazard areas. In the past, uncontrolled development of these areas has often been detrimental to communities. The increased occupancy of areas subject to flooding and adjacent upland areas by houses, industries, utilities, and transportation facili— ties has resulted in increasing damage from floods over the years. A report by the Detroit District Corps of Engineers records 190 communities in Michigan having popu- lations greater than 2,500 people that are influenced by flooding conditions.l Sound usage and regulation of flood prone areas require adequate knowledge of flood hazards. A major problem currently facing state and local government lU.S. Army Corps of Engineers, List of Urban Places with Information about Flood Problems (Detroit, Michigan: Detroit District, 1967). officials is the lack of this information. Flood hazard areas must be identified and delineated to provide a sound technical basis for land use regulation. In Michigan, this information is obtained by engineering methods, using hydrologic and hydraulic analysis and historic flood records. These engineering studies require considerable time and highly trained personnel and are somewhat costly.l These studies have not been able to meet the increasing demands for flood hazard information requested by many Michigan communities. Recently, these demands have been given impetus by the National Flood Insurance Program which requires the development of suitable flood plain use regu- lations by local governments within a certain time period. Wolman in his analysis of the progress in flood plain map- ping in relation to demand states: Since 1961 approximately 1150 floodplain information reports have been approved. The current average costs are approximately $25,000 per report, and the total expenditures have been $29 million. Initially progress was at the rate of about 40 reports per year. More recently the rate is closer to 150 per year. In either event, assuming that 4000 urban places really need such information and adequate funding, it appears that decades will be required to complete floodplain reports on these urban loca- tions. During ths interval the demand itself will continue to rise. 1M. Gordon Wolman, "Evaluating Alternative Tech- niques of Floodplain Mapping," Water Resources Research, Vol. 7 (1971). pp. 1,383-92. 2 Ibid. Until the time that detailed engineering studies meet the needs for flood hazard information, are there any alternatives open to state and local governments? One alternative may be the use of detailed soil survey mapsf Much soil survey information is available in Michigan. The use of soil maps as an aid in delineating flood hazard areas, based on the assumption that present soil charac— teristics are related to the presence or absence of past flooding, has long been proposed by soil scientists.1 The primary objective of this thesis is to test this concept-- by evaluating soil maps for the delineation of flood hazard areas in southern Michigan. This evaluation is based on the comparison of soil survey data to engineering data for four study areas in southern Michigan. If rela— tionships between soils and engineering hydrologic data can be established in these study areas then the value of soil maps to delineate flood hazard areas can be ascer— tained for use in other areas that have soil survey informa- tion, but lack detailed engineering studies. This would permit some degree of flood area management in those areas--an interim measure——until more highly specialized information on flood elevation, flood velocity, etc., based on Specific flood frequencies is determined by detailed engineering studies. 1A. A. Klingebiel, "Bases for Urban Development," Planning (May, 1963), pp. 39-47. Studies on evaluating soil surveys for the deline- ation of flood hazard areas have been done in Wisconsin, Ohio, and in several eastern states. To the author's knowledge, no study of this type has been done in Michigan. It was felt that a similar study would be worthwhile in Michigan because much of the previous work was done on landscapes different from those of southern Michigan. Part of the Wisconsin studies were located on similar glaciated landscapes, but, as in Michigan, the scope and areas involved were limited because of the lack of engi- neering information. Scope of the Study This study covers four individual areas in south- ern Michigan; Plaster Creek and Buck Creek in Kent County, the Clinton River in Macomb County, and the Lookingglass River in Clinton County (Figure 1). Southern Michigan is defined as that area of the state south of a line from Bay City to Muskegon. It is about 15,000,000 acres in size or about 41 per cent of the land area in the state. It contains over 8,000,000 people or 91 per cent of Michigan's population. The large metropolitan areas, most of the urbanizing areas, and most of the prime agri- cultural lands are located in this part of the state. Southern Michigan has a temperate, humid climate typical of the lower Great Lakes Region. It is quasimarine along the Great Lakes, changing to continental climate in the Z .3. &P MASON LAKE OSCEOLA CLARE BLAowuN ARENAC ‘5 6 Y3- J_._. v MECOSTA ISABELLA MIDLAND BAY HURON , ' JsCOLA SANILAC 9S‘ MONTCALM GRATIOT SAGINAW ) KENT LAPEER—i 1,1909 - ’1 ENESEE . T.CLAIR “5‘40 IONIA CUNTON/_ §..'AWA 1“ LOOK no Glass 2 C” .0 R ‘ 7 ' 9 \ f OAKLAND “s 5 )ALLEGAN BARRY EATON INGHAM LNINGSTN E I CIlnton 3- vu- w 3 VAN BUREN )KALAMA. ALHOUN JACKSON WASHTENAW WAYNE K. 3 . O as SIJOSEPH BRANCH HILLSOALE LENAWEE MONROE Baumm ) Scale in M1!» 33 so 75 Figure l.--Map of southern Michigan showing study areas. interior. Because of prevailing westerly winds, the influence of Lake Michigan is strong. Because of Lake Michigan, winters are milder, summers are cooler, and snowfall is greater in the western part of the state. Average annual snowfall varies from about 74 inches along Lake Michigan to about 40 inches in the interior. Average annual precipitation is about 30 inches and is fairly evenly distributed throughout the year. The physiography of southern Michigan resulted from glaciation. The glacial ice that once covered the entire area melted about 9 to 12 thousand years ago, during the Cary (Late Woodfordian) substage of the Wisconsin glaciation. As the ice melted, it left a thick mantle of raw soil material or glacial drift over most of the area. This drift was deposited as moraines, as till plains, and as glaciofluvial material on outwash plains, glacial spillways or drainageways, and lake plains. From these geomorphic features the present topography of southern Michigan developed. An intricate mixture of hilly moranic areas, undulating to rolling till plains, nearly level and pitted outwash plains, nearly level or depressional glacial drainageways, and small lake plains is character- istic of the interior of southern Michigan. Along Lakes Michigan, Erie, Huron, and the Saginaw Bay are fairly extensive, slightly undulating, lake plains. These were formed by the waters of the more extensive glacial lakes, forerunners of the present day Great Lakes. Detailed, modern, soil maps are available for 12 of the 37 counties in southern Michigan, representing about 5 million acres, or one-third of the total area. Data summarized from these soil maps indicate that potential flood hazard areas comprise about 3.3 per cent of the total area. This is based on the assumption that these areas consist of alluvial soils and adjacent, very poorly drained organic soils. This figure for southern Michigan is in line with previous national estimates of flood prone areas. Hoyt and Langbeinl estimate flood plains at 2.5 per cent of the total land surface. Sanders and Black2 in the 1958 Yearbook of Agriculture estimate the total land in flood plains as about 5 per cent of the total land surface. Although 3.3 per cent is a small percentage of Michigan's total land surface, it represents almost 500,000 acres of potential problem flood areas in southern Michigan. More significantly, it is estimated that some 2,295,000 acres in southern Michigan are subject to rapidly expanding housing and industry.3 This would include approximately 76,000 acres of potential flood hazard areas. 1William G. Hoyt and Walter B. Langbein, Floods (Princeton, N.J.: Princeton University Press, 1955). 2J. T. Sanders and N. A. Black, "Wanted: Partner— ship to Manage Water," U.S. Department of Agriculture Yearbook--Land (Washington, D.C.: Government Printing Office, 1958), pP- 347-55. 3U.S. Department of Agriculture, Soil Survey Plan of Operations, Michigan, Fiscal Year 1973 (East Lansing, Michigan: Soil Conservation Service, 1972). More than 60 per cent of these rapidly urbanizing areas have detailed soil survey information. The availability of engineering and soils data was the primary reason for the selection of the four study areas (Figure 1). An "in depth" study, including field investigations, was made in the Plaster Creek area. Because of the nature of the available data and constraints of time, less detailed studies were made of the other three areas. In general, the Plaster Creek and the Lookingglass River study areas were in watersheds having dominantly till plain and morainic landscapes. A large part of the Buck Creek study area was in a former glacial drainageway or spillway. The Clinton River study area was almost entirely in a lake plain. The four study areas consisted of approximately 11,000 acres, or about a 2.2 per cent sample of the potential flood hazard areas in southern Michigan. Definitions Considerable confusion exists in the literature and among people as to the exact meaning of the term "flood plain." To the soil scientist, hydrologist, geomorphologist, land use planner, and others, the general term "flood plain" often has different meanings and results in different interpretations. In this thesis, the term "flood plain" is used only when referring to other literature or regulations that make use of the term. Instead, the terms alluvial bottom land, physiographic flood plain, and flood hazard area are used in the thesis in an attempt to eliminate some of the confusion noted above. The term flood hazard area is further restricted to soil based flood hazard area and engineering based flood hazard area. The terms used in this thesis are defined as follows: Alluvial bottom land is the lowest part of the physiographic flood plain and it contains alluvial soils along the ‘watercourse. It is used to des— cribe a landscape feature only and it does not imply an area of flooding. Physiographic flood plain is a unit of land- scape that is a nearly level area adjacent to a stream, river, watercourse, or another body of water and is formed from sediments transported and deposited by water. It is frequently marked at its margins by distinctive landscape breaks, ranging from short, steep slopes of a few feet to escarpments of many feet. The physiographic flood plain and the alluvial bottom land may be the same in many areas, but in other areas, particularly along rivers and large streams, the physiographic flood plain contains terraces, deltas of tribu- taries, and areas of local coluvium as well as alluvial bottom land. Flood hazard area consists of that land adja- cent to a stream, river, watercourse, or another body of water which has been or hereafter may be covered by flood water. A soil based flood hazard area is that flood hazard area determined by the extent of alluvial soils and adjacent depressional or level organic soils. An engi- neering based flood hazard area is that flood hazard area determined by engineering hydrologic and hydraulic studies and it is commonly expressed as to its specific recurrence interval; that is, 50-year flood hazard area, lOO-year flood hazard area, etc. An engineering flood hazard area of a particular recurrence interval may be less than or exceed the soil based flood hazard area or the physiographic flood plain. 10 Other terms used in this thesis that require definition are given in a "Glossary of Terms" in the Appendix. The principal sources for the definitions are: Regulation of Flood Hazard Areas to Reduce Flood Losses, Vol. I, Parts I—IV, U.S. Water Resources Council, 1971; Resource Conservation Glossary, Soil Conservation Society of America, 1970; and "Report of Definitions Approved by the Committee on Terminology" (of the Soil Science Society of America), Soil Science Society of America Proceedings, Vol. 20, No. 3, 1956. CHAPTER II TECHNIQUES FOR DELINEATION OF FLOOD HAZARD AREAS Introduction Over the years several techniques have been pro- posed and used in the delineation of flood hazard areas. The use of physiographic features, vegetation, soils, and various engineering procedures have been the principal techniques. Historically, engineering methods basedon hydrology and hydraulics have been the most commonly used. Wolman, in his recent paper, "Evaluating Alterna- tive Techniques of Flood Plain Mapping," gives an extensive and detailed review of the advantages and disadvantages of each of these techniques.1 The use of physiographic features to map flood hazard areas is based on the correlation of specific topographic features with flood discharges of known frequency. The méthod of using vegetation is based on the hypothesis that in some regions specific assemblages of plants may correlate with specific water levels. The morphological characteristics of soils and their positions in the landscape are the basis for using soils to delineate flood hazard areas. lWolman, op. cit., pp. 1383—92. 11 12 The use of engineering methods is based, in part or all, on past records, experience, and the principles of hydrology and hydraulics. These engineering methods result in several types of flood maps. The occasional or experienced flood maps are based on aerial photographs taken during the flood event, high water marks, historic records, personal observations, or other factual data. The flood or floods shown on these maps are not designated as to frequency. Regional, or flood height, flood maps are based on the fact that in a physiographic region flood heights of chosen frequencies may be mapped on a regional basis from records at selected localities. Wolman states: -The method is based on observations at stations in the region of the heights above the channel bed attained by floods of different magnitudes. By relating flood heights of different return periods to parameters such as drainage area and mean annual flood discharge, curves can be drawn that permit flood heights to be determined at ungaged sites of known drainage area within the region. ‘ Another type of flood map showing flood lines for selected flood frequencies is based on detailed engineering surveys and subsequent hydrologic and hydraulic computa- tions. Stream flow data and historic flood records are also used, where available, for this engineering flood map. This type of flood map is normally contained in flood hazard area reports by the Corps of Engineers and the Soil Conservation Service along with high water lIbid.. p. 1386. 13 profiles, valley cross sections, selected flood dis- charges, and other detailed engineering information. In view of the fact that this study involves only the compari- son of soils and detailed engineering techniques for delineating flood hazard areas, these techniques are discussed in greater detail. Engineering_Surveys To date, the hydrologic method based on detailed engineering studies is the most commonly used method in delineating flood hazard areas in southern Michigan. In essence, this method determines the longitudinal profile of the water surface during peak flows from which, by use ' of topographic maps, the flood hazard area for a particu- lar flood is shown. Stream flow data is based on actual stream flow measurements or, in the absence of such measurements, it is based on estimated precipitation and surface runoff. The latter method is known as synthetic rainfall-runoff relationships. This method was used by the Soil Conservation Service in the Plaster and Buck Creek study areas. In the Lookingglass and Clinton River study areas, the Corps of Engineers used stream flow data from one or more stream gauges. In Michigan, the com- parison of flood lines determined by these two methods has shown little difference. The technical procedures used by the Soil Conserva- tion Service illustrate one way in which detailed 14 engineering studies are made to identify flood hazard areas.1 In beginning a study, a careful search is made for maps, aerial photographs, stream flow records, mete- orological records, and other useful information. The history of flooding in the study area is obtained by checking neWSpaper files and interviewing local officials and residents. Physical data is obtained from U.S. Geologi- cal Survey topographic maps, locally available contour maps, surveyed valley cross sections, and surveyed road and bridge sections. In some flood hazard study areas for which adequate topographic coverage is lacking, two foot contour working naps are developed by the Kelsh Plotter on low-level aerial photography. Water surface profile determinations are made by the Soil Conservation Service's Automatic Data Processing programs to establish elevation- discharge relationships. In making computations, normal bridge flow conditions are assumed. No consideration is made for openings blocked by ice or other debris. Hydro- logic soil-cover relationships are calculated by standard Soil Conservation Service procedures to determine rainfall- runoff relationships. Runoff computations are based on existing watershed land use and cover conditions. 1U.S. Department of Agriculture, Soil Conservation Service, National Engineering Handbook; Section 4, "Hydrology," 1971; Section 5, "Hydraulics," 1956 (Washing- ton, D.C.: Government Printing Office); and Richard D. Leisher, "The Soil Conservation Service's Flood Hazard Analysis Program" (paper presented at the 1972 Winter Meeting, American Society of Agricultural Engineers, Chicago, Illinois). 15 In some studies, additional hydrologic and hydraulic evaluations are made for future conditions based on esti- mates of land use changes and development expected in the watershed. These estimates are generally made for periods of 10 to 25 years in the future. Flood routings are also computer programmed to determine peak discharge-frequency relationships based on actual watershed hydraulics. The water surface profile elevation-discharge relationships are used to establish flood elevations for various flood events at each surveyed section. The Soil Conservation Service usually evaluates several selected-frequency flood events, with three or four the maximum. These selected events are shown on flood profiles and the approximate areas subject to inundation by each flood event are deline- ated on aerial photomosaic maps. There are several important advantages in deline- ating flood hazard areas by detailed engineering methods. Engineering studies provide information on velocity of flow, height of flood water, rate of rise, and duration of flooding for various flood frequencies. Another very desirable advantage of the engineering technique is that the high and low hazard parts of the flood area can be delineated, thus permitting regulation of the flood hazard area according to the indicated level of risk. At the time that the study is made, the special effects on flooding resulting from road crossings, fill areas, and 16 other man-made objects can be determined. High water profiles give specific flood elevations throughout the watercourse, permitting determinations of inundated areas by additional surveying. The main disadvantages of using engineering studies for delineation of flood hazard areas are that they are costly and require considerable detailed field surveying, particularly if detailed topographic information is not available. Wolman estimates that costs for detailed engineering studies, including topographic mapping, range from $400 to $1,000 per mile.1 These estimates appear to be low for the midwest region. Costs may run as high as $5,000 per mile for some Studies in this area. Addi- tional limitations inherent in engineering methods are that in usingpast flood records it is assumed that there is no change in channel or other factors affecting flooding and that flood records, if available at all, represent relatively short sampling periods for a few points, at most, along‘a watercourse. A short record at any indi- vidual station may vary considerably from the actual long-term flood frequency relationship. As Lee, and others, have pointed out, precise delineation of flood hazard area boundaries from hydrologic data requires lWolman, op. cit., p. 1384. 17 detailed and highly accurate topographic maps, preferably with contour intervals of 5 feet or less.1 Synthetic rainfall-runoff evaluation judgments have to be made in extrapolating precipitation data between stations, in estimating ground cover, antecedent moisture, and other factors for calculating surface runoff rates. Interpretation of Soil Maps The theoretical basis for using modern, detailed soil maps to delineate flood hazard areas is that alluvial soils shown on such maps indicate by their morphological characteristics and landscape position that they are the product of flood water sediments. Using these soil charac- teristics and the distinctive physiographic surfaces along watercourses, alluvial soils are identified and their boundaries plotted on aerial photographs by soil scientists. By outlining the total area of alluvial soils shown on the soil maps, it is possible to construct an interpretive map showing areas that have been frequently flooded in the past and are likely to flood in the future. The pro- cedure used in this study was to include the adjacent, very poorly drained, depressional to nearly level, organic soils with the alluvial soils in determining the soil 1G. B. Lee, D. B. Parker, and D. A. Yanggen, Development of New Techniques for Delineation of Flood Hazard Zones, Part I: By Means of Detailed Soil Surveys (Madison: The University of Wisconsin Water Resources Center, 1972). 18 based flood hazard area. This was done because most of these organic soils in this landscape position are under- lain by alluvium. Soil is developed by soil-forming processes acting on materials deposited or accumulated by geologic actions. The characteristics of the soil at any given point are determined by (l) the physical and mineralogical composi— tion of the parent material such as glacial till or alluvium, (2) the climate under which the soil material has accumulated and existed since accumulation, (3) the plant and animal life on and in the soil, (4) the relief, or lay, of the land, and (5) the length of time the forces of soil formation have acted on the parent material. Climate, plants, and animal life are active factors of soil formation. They act on the parent material and slowly change it to a natural body of soil that has genetically related layers called horizons. The effects of climate and plant and animal life are conditioned by relief. The parent material also affects the kind of soil that is formed and determines the limits of chemical and mineralogical composition of the soil. Finally, time is needed for changing the parent material into a soil with genetic horizons. It may be much or little, but some time is always required for differentiation of soil hori- zons.' Usually, hundreds of years are required for the development of distinct horizons. 19 The Morley soils, on the upland surfaces of the Plaster Creek watershed, have a distinctive genetic horizon sequence. The A horizon, or the surface layer is leached of bases and clay and has generally accumulated organic matter. Below the A horizon is the B horizon, or subsoil, in which clay and other minerals have accumulated. Beneath the B horizon is the C horizon, or substratum, which is slightly weathered, unconsolidated, parent material. In contrast to the Morley soils are alluvial soils, such as the Glendora soils which lack the distinc- tive horizon sequence (Figure 2). The frequent deposits of recent sediments on the Glendora soil prevent the development of distinct horizons by the soil-forming processes in the soil profile. Alluvial soils are young soils and have few developed characteristics beyond those 1 Stratification of inherited from the alluvium itself. the soil materials is common; that is, layers of a given texture alternate with layers of other textures. An irregular decrease of organic carbon with depth in the soil profile is an additional characteristic of alluvial soils. Most of the alluvial soils in southern Michigan are classed as Aquents or Aquolls at the suborder level 1Soil Survey Staff, U.S. Department of Agriculture Handbook No. 18, Soil Survey Manual (Washington, D.C.: Government Printing Office, 1951). 20 Figure 2.--G1endora soil. The lack of distinctive horizons and an irregular decrease of organic matter with depth are characteristics of alluvial soils. Note the dark layer of increased organic matter at 3 feet. 21 in the new soil taxonomy.1 The soil series and the soil phase are the categories of the classification system most used in a local survey. Soils that have profiles almost alike make up a soil series; for example, the Morley series. Except for different texture in the surface layer, all the soils of one series have major horizons that are similar in thickness, arrangement, and other .characteristics. Soils of one series can differ in tex- ture of the surface layer and in slope, stoniness, or some other characteristic that affects the use of the soils by man. On the basis of such differences, a soil series is divided into phases. The name of a soil phase indicates a feature that affects management. For example, Morley loam, 12-18 per cent slopes, is one of several phases within the Morley series. There are areas where the soil material is so disturbed, so shallow, or so severely eroded that it cannot be classified as a soil series. These areas are shown on the soil map, but are called land types and are given descriptive names.’ Cut land and Fill land are examples of a land type. A soil map shows the location and areal extent of different kinds of soils and land types in relation to other prominent physical and cultural features of a landscape. These maps are made by soil scientists of the lU.S. Department of Agriculture, Soil Taxonomy of the National Cooperative Soil Survey, unedited text (Washington, D.C.: Government Printing Office, 1970). 22 Soil Conservation Service and the Michigan Agricultural Experiment Station in southern Michigan as part of the National Cooperative Soil Survey Program. There are many 'kinds of soil maps; however, there are three basic types ‘ of original soil maps-—exploratory, reconnaisance, and detailed maps. Exploratory and reconnaisance soil maps generally have small scales, l:63,360 (one inch equals one mile) or smaller, and are made in the field by observ- ing soils at wide intervals. The small scale of these maps usually prohibits their use in delineating flood hazard areas. Modern detailed soil maps are generally made at a scale of 1:15,840 (4 inches equal one mile). Soil boundaries are plotted by soil scientists in the field on aerial photographs from observations made throughout their course. Modern detailed soil maps are usually published at scales of l:20,000 (3.17 inches equal one mile) or 1:15,840 (4 inches equal one mile). In contrast to the modern detailed maps, there are many older soil maps published prior to the 19405 at a scale of one inch equals one mile. The small scale of these maps severely limits their usefulness in deline- ating flood hazard areas. For special projects, such as the Plaster Creek and Buck Creek flood hazard study areas, detailed soil maps were made and published at a scale of 1:4,800 (one inch equals 400 feet). The detail of these soil delineations, however, were controlled at a scale 23 level of 4 inches equal one mile to permit future publi- cation at that scale for the entire county. Detailed soil maps at 4 inches equal one mile have been made by the Soil Conservation Service for numerous, individual farms. For counties without completed soil maps, these maps of individual tracts of land often provide much useful information for general planning of larger areas. Another type of soil map is the general soil map. This is a map for an entire county published at a scale of 3 or 4 miles equal one inch. The map units shown on these general maps are soil associations, or groups, of geographically associated soils. These maps are designed for very general planning purposes only and, due to scale limitations, often do not show narrow areas of alluvial soils. Soil maps and interpretive information are availa- ble from local county offices of the Soil Conservation Service or the COOperative Extension Service and from the Department of Crops and Soil Sciences, Michigan State Uni- versity. This information is available in several different forms. There are published soil surveys of counties, special advanced reports for a county or for parts of a county, and single sheets of soil mapping along with soil interpretation sheets for smaller areas. In summary, the only soil maps of sufficient detail to interpret flood hazard areas are the modern detailed 24 soil maps made on an original base scale of 4 inches equal one mile with an aerial photographic background. On soil maps, individual soil areas, or mapping units, are outlined and identified by a symbol. The name of the mapping unit can be obtained by referring to a soil identification legend. Special symbols are used in some areas. These symbols represent land features such as escarpments, wet spots, and gravel pits. Each soil mapping unit consists of a phase of a soil series, or predominantly so, as it may contain small inclusions of other soils. At the standard scale of 4 inches equal one mile, these inclusions may be of one to three acres in size and constitute up to 15 per cent, or more, of the mapping unit. If these inclusions are of soils so con— trasting to the named unit as to require different management, they are also shown by special map symbols. The boundaries of soil mapping units often represent transitional zones because soils occur as a continuum on a natural landscape where one kind of soil grades into another. These boundary transitional zones may range in width from a few feet to several yards. Where there is a gradual slope from alluvial soils upward to soils formed from glaciofluvial deposits, the boundary often repre- sents a transitional zone. The scale of the base map, as mentioned before, controls the detail of the soil map and the composition of soil mapping units. As Lee, and others, pointed out, 25 One should also keep in mind that it is the scale of the base maps used for soil mapping that is important in assessing accuracy. Enlarging a 4 inch to the mile map to a scale of 8 inches to the mile may make it easier to use in some cases but does not improve its accuracy. Individual interpretive or factor maps showing the relative suitability or degree of limitation of soils for a specific purpose can be developed by using soil maps and accompanying interpretive information. These interpretive maps may be made for flood plain conservation districts, wet land districts, green belt areas, and for many other special purposes. Once the map is completed, the patterns of soil limitations, often designated by different colors, are readily apparent. The user then can quickly select areas that have a potential for a particular use and, at the same time, identify those areas with severe limitations. There are several advantages in using this tech- nique of interpreting soil maps for the delineation of flood hazard areas. The foremost advantage is their availability for many communities and areas. About 5,000,000 acres, one-third of southern Michigan, is cov- ered by modern detailed soil maps. Soil maps are less costly than detailed engineering studies.2 It is esti- mated that soil maps for the Plaster Creek flood hazard area study cost about $132 per mile of channel. The lLee, Parker, and Yanggen, op. cit., p. 16. 2Wolman, 0p. cit., p. 1384. 26 interpretation of soil maps technique gives the areal extent of the flood hazard areas based on soil charac- teristics throughout the entire reach of the watercourse; whereas the engineering technique projects, by the use of topographic maps, the outer boundaries of the flood hazard area between the valley cross sections. The principal disadvantage of using soil maps to delineate flood hazard areas is that the technique does not give important hydrologic information such as flow velocities, flood water heights, rate of rise and fall, and duration of flooding for various flood frequencies. Soil maps do not indicate the high-low flood hazard parts of the flood area. At the standard base map scale of 4 inches equalcnuamile, small flood plain areas, generally less than 150 feet across, are not outlined on soil maps. Also, at this base scale, gently sloping footslopes are often included in steeply sloping map units on landscape scarps. Soil maps also do not reflect the effect of disturbed areas on flood boundaries in urban developed or urbanizing areas. Accuracy of flood lines based on soil maps is limited in some areas because of transitional zones along soil boundary lines. The difficulty of iden- tifying and separating alluvial soils from soils formed in glaciofluvial deposits is a problem on landscapes of outwash plains, glacial drainageways, and lake plains. CHAPTER III REVIEW OF LITERATURE The use of soil maps to delineate flood hazard areas for management and regulation of these areas has been done in Fairfax County, Virginia;1 Buffalo County, Wisconsin;2 Montgomery and Centre Counties, Pennsylvania;3 and in an increasing number of other areas. In Montgomery County, Witwer indicated that the Flood Plain Conservation District Ordnance was based on soil maps because the cost of detailed engineering studies made for larger streams was far too expensive and elaborate to be applied to the many smaller streams and tributaries in the county. The use of soil information to establish a Flood Plain Conserva- tion District is illustrated by the 1970 ordinance of College Township, Centre County, Pennsylvania.4 1C. 8. Coleman, "How Fairfax County Tackes Soils and Land Use Problems," Agricultural Engineering, Vol. 44 (1963), PP. 614-15. 2D. A. Yanggen, M. T. Beatty, and A. J. Brovold, "Use of Detailed Soil Surveys for Zoning," Journal of Soil and Water Conservation, Vol. 21 (1966), pp. 123-26. 3David B. Witwer, "Soils and Their Role in Planning a Suburban County," in Soil Surveys and Land Use Planning, ed. by L. J. Bartelli, et a1. (Madison, Wisconsin: Soil Science Society of America, 1966), pp. 15-30. 4College Township, Centre County, Pennsylvania, Ordinance, Flood Plain Conservation District (1970). 27 28 Only a limited number of definitive studies has been done on the use of soil maps to delineate flood hazard areas for purposes of land use regulation. For Gwynn Falls Valley, Maryland, Wolman states: ". . . the mapping of a 50-year flood zone based on an approximate regional flood height correlated relatively well with a specific soil type mapped in a recent soil survey."1 Witwer reported that alluvial soils along Wissahickon Creek, as indicated by the soil survey, followed very closely the edge of the 50-year flood hazard area as defined by the U.S. Army Corps of Engineers.2 In the glaciated region of southerwestern Ohio, McCormack evaluated the frequency of flooding and depth of flood waters on alluvial soils and on stream terraces in selected sections of the Great Miami River and its tributaries, the Stillwater River and Twin Creek.3 The boundaries of experienced floods of 1913 and 1959 were compared to the boundaries of alluvial soils and soils on stream terraces. McCormack reports: Essentially all of the alluvial soils were inun— dated in both floods. About forty percent of the area of terrace soils were inundated in 1913, but less than ten percent in 1959. It is estimated that the frequency of flooding of alluvial soil is more frequent than once in forty years, and lWolman, op. cit., p. 1385. 2Witwer, op. cit., p. 28. 3Donald E. McCormack, "Use of Soil Surveys in the Identification of Floodplains," The Ohio Journal of Science, 71(6) (1971), pp. 370-75. 29 that only the very lowest portions of the ter- races are inundated during floods of that frequency. Analysis of the data indicate soil surveys can be used to delineate those areas where the probability of flooding is greatest, and thus where the need for land use restric- tions, such as zoning, to minimize damages due to flooding is most urgent. In spite of the great variation between watersheds and in the many hydrologic factors that may cause considerable variation in the frequency of flooding on alluvial soils and terrace soils, McCormack indicates that this frequency variation is likely to be confined within the limits dic- tated by, or related to, alluvial soils and their presence in the terrace soils. He further states that soil survey information should be helpful in extending flood area- information between known points of detailed engineering studies and for delineating zoning districts that will restrict land uses in flood hazard areas for smaller streams that lack engineering data. The most detailed and extensive studies on the use of soil surveys to delineate flood hazard areas has been done in Wisconsin by Lee and his colleagues.1 These studies were located along watercourses varying in size from small creeks to large rivers in a variety of water— sheds having different types of landscapes. In all, six study areas were investigated. The Mississippi River, the small streams of Otter and Taintor Creeks, and the frequently flooded Kickapoo River are located in the lLee, Parker, and Yanggen, op. cit. 3O non—glaciated southwestern part of Wisconsin. The Des Plaines River and the Root River, young rivers with low gradients, and the Turtle Creek, an older creek with a moderate gradient, are located in the glaciated area of southeastern Wisconsin. These last three studies are reviewed in detail as they are on glaciated landscapes similar to those of southern Michigan. The Des Plaines River study area was in a glaciated watershed consisting mostly of level to gently sloping ground moraine with low ridges of subdued recessional moraines, and a thin veneer of fluvial deposits in stream valleys and depressions. Within this study area, the river did not have a well defined physiographic flood plain. Narrow strips of alluvial soils occurred along the stream in the lower reaches, but none were mapped in the upper reaches. The U.S. Army Corps of Engineers study data and field sheets of a recent detailed soil survey by the Soil Conservation Service were the source materials for the study. A direct correlation was not found in that the boundaries of flood hazard areas did not closely follow any soil boundary lines. Two generaliza- tions were made from this study. Both alluvial and organic soils occurred predominantly within the flood hazard area. The frequency interval of the flood hazard area, however, was not specified. The well and moderately well drained soils formed in glacial till, although very common in the area, were not included in the flood hazard area for 31 the most part. Soils that commonly occurred on both sides of the flood line were of fluvial origin or had restricted drainage, or both. Several reasons were given for the poor correlation of soils and flooded areas along the Des Plaines River. In most cases, the flood boundary was on nearly level soils making it extremely difficult to delineate the flood hazard area with accuracy, since a small error in elevation would result in a large error in predicting areal extent of flooding. A 10 foot contour interval topographic map was used as a base map in the engineering study. The Root River study was located in a watershed of young, glaciated landscape of low relief. The physi- ographic flood plain was poorly defined. Two reaches of the Root River were studied. One seven mile reach was at the upstream confluence of the North and South Branches of the stream; the second was a three mile reach on the main stem, about five miles from its outlet. Gentle slopes extended from the stream on to the uplands in the conflu- ence area. The main stem was somewhat entrenched and formed a nearly level flood plain which joins with the sloping uplands. The upper part of the watershed on the North Branch is urbanized in part; the remainder consists mainly of rural agricultural areas. A synthetic flood routing study of 10 and lOO-year floods based on 2 foot contour interval topographic maps, and copies of field 32 sheets of a soil survey at a scale of 4 inches equal one mile were the source materials. The results of this study indicate that soil maps showing the distribution of allu- vial soils identify the most hazardous parts of the flood plain. The lO—year and lOO-year flood hazard areas, however, exceeded the limits of alluvial soils in some places. Poorly and very poorly drained soils adjacent to, or connected to, alluvial soil areas were particularly susceptible to flooding. Somewhat poorly drained soils occurring on slightly higher elevations in the landscape were also susceptible to flooding, but to a lesser degree. Well and moderately well drained soils did not flood unless they were on low slopes or terraces adjacent to the stream bottom. It was also reported that the use of soil maps to delineate flood patterns in urbanizing areas was very difficult because man-made disturbances had greatly altered the natural hydrology of the river. A better design of mapping units in this study would have improved the accuracy of flood hazard area delineations based on soil maps. Particularly needed are mapping units to identify soil areas having a thin, but identifiable, veneer of recent alluvium. The use of more special sym- bols to indicate escarpments Or steep slopes along the border of an alluvial bottom or terrace was suggested. The Turtle Creek study was an evaluation of allu- vial and adjacent somewhat poorly drained soil areas 33 compared with the lOO-year flood hazard area as delineated by the U.S. Army Corps of Engineers. In addition, the extent of flooding of upland and terrace soils by the lOO-year flood was studied. The study included 3 indi- vidual reaches of Turtle Creek, each of which had a somewhat different gradient. Turtle Creek drains a 238 square mile watershed in a glaciated region. Landscapes were somewhat older and more mature than those of the Des Plaines and Root River watersheds. Much of the land immedi- ately adjacent to the Turtle Creek bottom lands consisted of glacial outwash deposits, but in places the stream flowed through ground moraine. The source materials were copies of soil survey field sheets at a scale of 4 inches equal one mile and a U.S. Army Corps of Engineers study. The engineering study was based on 2 foot and 5 foot contour interval topographic maps and long-range records of river stages. The Intermediate Regional Flood, approximately a lOO-year flood, and the Standard Project Flood, the largest flood that could be expected, were delineated. Results for the total study area of 1,100 acres bordering an 11.7 mile reach of Turtle Creek were that 3.5 per cent of the alluvial and associated somewhat poorly drained soil area was not inundated by the engineering floods. In addition, 16.6 per cent of the total 100-year flood hazard area consisted of soils not expected to flood on the basis of soil data alone. When the 11.7 mile reach 34 was divided into three parts, based on differences in stream gradient, the results showed important differences between the three subreaches. The gradients of the sub- reaches were 8.45 feet per mile, 4.70 feet per mile, and 3.50 feet per mile, decreasing in the upstream direction. The data indicate that, with increasing distance down- stream, the percentage of soils which were expected to flood, but which did not, gradually increased; while soils which were not expected to flood, but did, decreased. In other words, the results indicated a relatively good fit between the lOO—year engineering flood boundary and the boundary delineated by interpretation of soil maps for the downstream reach, while a much poorer fit resulted in the upstream reach. The study reports that this difference of fit seemed to be related to the average gradient of each of the reaches. The poor fit upstream was due to a dam and the lower gradient of Turtle Creek in that reach. In the downstream reach, it was found that only 70 per cent of the alluvial soils were flooded by the lO—year flood frequency. In some places, well drained upland or terrace soils were subject to flooding. These soils were apparently not examined in this study to determine if they had any characteristics which would be diagnostic of flooding. The conclusions of the Wisconsin report were: Most soils formed in alluvium along streams . . . and peat and muck deposits that are a part of the stream bottomlands, are inundated by floods of high return frequency. Exceptions to this general 35 rule are soils protected by dams, dikes, embank- ments, or other flood control structures, or soils on alluvial plains where considerable down- cutting of the stream has occurred in recent times. Rare floods, for example, the lOO-year recurrence flood . . . will frequently inundate other areas in addition to those occuped by allu- vial soils, and stream bottom Histosols. Non- alluvial soils most apt to be flooded or ponded by infrequent floods include somewhat poorly to very poorly drained mineral soils associated with the alluvial soils, or connected to the alluvial bottomlands by waterways of low gradient. . . . Soil maps are less definitive of flood plain boundaries in young landscapes, especially where slopes have a low gradient and the drainage pat- tern is poorly defined, than in mature landscapes where the physiographic elements of the landscape are clearly defined. . . . The recommendations made in the Wisconsin study were: Detailed soil maps (i.e. 1:15,840) can be used to delineate reasonably accurate 100 year return fre— quency floodplain boundaries, economically and rapidly, in many places. They are most useful in rural areas, little disturbed by dams, buildings, or other structures and where land values are rela- tively low. They are not recommended for highly developed areas. They are not recommended where the necessary engineering data is available. Interpretation of soil maps for the purpose of delineating floodplains should be done by someone skilled in interpretation of soil maps (preferably a soil scientist), and familiar to some degree with soil patterns in the area of concern. Improved design of soil mapping units, larger scale, greater use of symbols to indicate scarps, etc., and improved precision of sketching would all serve to improve the accuracy of soil map interpretations in regard to floodplain boundaries. . . CHAPTER IV THE PLASTER CREEK STUDY Introduction In this study the boundary of alluvial soils and the adjacent, level, organic soils was compared with the boundary of the 50-year flood hazard area. Information is presented on the relationship of these soils to the lOO-year and BOO-year flood hazard areas. The study area is part of the Plaster Creek watershed which lies entirely in the southern part of Kent County in southwestern Michigan (Figure l). The landscape of that portion of the watershed containing the study area is predominantly moraines and till plains which represent extensive areas in southern Michigan. A total area of about 1,000 acres and a combined channel length of about 20 miles were studied. The study area included reaches of Plaster Creek and its tributaries--Whiskey Creek and Little Plaster Creek. Description of the Watershed and Study Area Plaster Creek, a tributary of the Grand River, drains an area of about 58 square miles. In the northern part of the watershed, Plaster Creek has two major tributaries--Whiskey Creek and Little Plaster Creek. Both 36 37 enter the main stream within the city of Kentwood. The watershed is approximately 13 miles long and 3 miles wide (Figure 3). It is a small watershed undergoing fairly rapid urbanization. It has relatively equal portions of agricultural, urbanizing, and established urban land. Portions of the cities of Grand Rapids, Wyoming, and Kentwood are located in the watershed. The average annual precipitation in the watershed is about 33 inches and it is fairly evenly distributed throughout the year with more intense rainfall occurring during the summer months. Snowfall averages between 50 to 60 inches per year. Surface runoff in the watershed is usually high in the spring because of large amounts of rain and snowmelt along with conditions of low soil reten- tion. It is during this time that the five major floods of record occurred in the study area. Minor flooding occurs throughout the year. Figure 4 shows flooding of Little Plaster Creek in an upstream rural area during December of 1971. The study area within the Plaster Creek watershed consisted of the BOO-year flood hazard area and any adja- cent alluvial soils. The study area extended along Plaster Creek from valley cross section 20.3, located about 1,200 feet upstream from Eastern Avenue to 60th Street, a channel distrance of approximately 15.9 miles; along Little Pflaster creek from its confluence with Plaster Creek 38 Figure 3.--Map of Plaster Creek study area. (.\ N — — k ) I \ ORAO‘OID SY ‘-_:;-"- - — i! 1‘) g. SCALE '1 70.000 SCALE I/3l.680 ”K I EAST , GRAND I a AVE -l— .- ‘ ‘ SPLUI DIN F ” / I] D 4 T) O r A w AVE E; .42 I u 4., ' 1"" I?" 23 4 9\ 3‘ - —--/ E! P , L , g .1 ENTWOOO .. m 51 I T__-'. -‘ -. 1:;::’ «(L S» lEAS '- 52 ND 31’ IPAYYERSON AVE I . \ ‘. I .I\ “i: I'/ w o u 7 Av" :7 ""\ “44 A) I. """T \I INA. Y 1.4- .69 no 57 ' " . .. v' " - , ‘ “—"‘ 7T? 1 I I SOIL CONSERVATION SERVICE .mmmhm pHmNm: UOOHH mcflummcflamp How mmmum anus“ CH Homom: umoa mum mama HHom .xmmuo “mummHm mauuflq co mcflpoonln.v musmflm 40 to 28th Street and Patterson Avenue, a channel distance of 3.7 miles; and along Whiskey Creek from its confluence with Little Plaster Creek to valley cross section 52.0 at Broadmoor Avenue, a channel distance of 1.1 miles. The lower reach of Plaster Creek, that is, downstream from valley cross section 20.3 to its confluence with the Grand River, a distance of about 6 miles, was not included in the study area. This portion of the watershed consists of almost completely established urban land, with extensive disturbance of the physiographic flood plain and the adjoining landscape. For the same reason, the upper reach of Whiskey Creek from valley cross section 52.0 at Broad- moor Avenuetx>28th Street, a distance of about 0.6 of a mile, was also excluded from the study. In essence, the study area was in the urbanizing and agricultural portions of the watershed. The glaciated landscape of the Plaster Creek study area is predominantly till plains and moraines, resulting in undulating to hilly topography. These upland areas consist mostly of glacial till deposits. The relatively narrow valleys of Plaster Creek and its tributaries con- tain mostly glacial outwash deposits formed by streams flowing from melting glacial ice. These nearly level to gently sloping outwash deposits are underlain by lacus- trine material in many places. Within the outwash of the valleys are depressional to level deposits of alluvium, adjacent to the entrenched streams. Downstream from 41 Kalamazoo Avenue, past the beginning of the study area at valley cross section 20.6 to about Chicago Drive, Plaster Creek cuts through and drains a former glacial drainageway channel of the Grand River. The reach of Plaster Creek upstream from Kalamazoo Avenue to Shaffer Avenue drains a morainic area in which are located the Little Plaster Creek and Whiskey Creek tributaries. From Shaffer Avenue upstream, or south, to 60th Street, Plaster Creek generally divides a till plain on the east from a high moraine on the west. In the study area, both the valleys and the streams within the valleys meander considerably. Changes of 90 degrees in course are common. The Plaster Creek valley is approximately 1,600 feet wide at Kalamazoo Avenue, 2,100 feet wide at Breton Avenue, and ranges in width from 400 to 800 feet upstream, including the two main tributaries with occasional wider areas. Escarpments, 20 to 50 feet high, occur on the border of the valleys in many places (Figure 5) . The channel gradients within the study area are quite variable along indi— vidual reaches. The overall channel bed profile of Plaster Creek, however, is strongly convex downstream from Kalamazoo Avenue and slightly concave upstream for most of the study area. It averages about 8 feet per mile below Kalamazoo Ave- nue in the study area. Above Kalamazoo Avenue, it is about 3 feet per mile upstream to Shaffer Avenue, increasing to about 4.5 feet per mile to 52nd Street, and to about 6.5 feet per mile to 60th Street, the end of the study area. The channel bed gradients of its tributaries are somewhat steeper. 42 Figure 5.--Escarpment bordering the alluvial bottom land. This is a common landscape feature along Plaster Creek. Note ponding on bottom land from recent flooding. 43 Little Plaster Creek averages about 13 feet per mile from its confluence with Plaster Creek upstreamtx>its confluence\vith Whiskey Creek, decreasing to about 8 feet per mile above. Whiskey Creek's gradient averages about 7.5 feet per mile to the end of the study area. The soils in the Plaster Creek study area reflect the landscape feature on which they formed. The Morley, Blount and Pewamo soils formed in moderately fine textured glacial till of the till plains and moraines. The Rimer and Metamora, fine subsoil varient, soils formed in a thin veneer of coarse textured outwash over fine textured lacustrine material in the stream valleys. The Shoals, Sloan, and Sloan, sandy subsoil varient, soils consist of medium textured alluvium and are the most extensive of the alluvial soils. Other alluvial soils occurring in the study area are Abscota, Algansee, Ceresco, Cohoctah, and Glendora. These alluvial soils are coarser textured than the Shoals and Sloan soils. Also occurring in a few places in the alluvial soil area is the Houghton soil that consists of deep organic material. There are many disturbed areas within the Plaster Creek study area because of the urbanizing nature of the watershed. As previously stated, the study area itself was restricted within the watershed because of dense urban development and extensive disturbance of the landscape, particularly along the lower reaches of Plaster Creek in the cities of Grand Rapids and Wyoming. Subdivisions 44 nearly cover the adjacent uplands from the beginning of the study area to about one and one-fourth miles upstream from Kalamazoo Avenue. At several points, these subdi— visions encroached on the physiographic flood plain (Figures 6 and 7). Upstream from this area there are scattered apartments, houses, churches, schools, indus- tries and the like, usually located in strip developments along the roads. Numerous roads with their fills and bridges cross the valley throughout the study area. Several roads parallel short reaches of the streams in the physiographic flood plain. Sanitary sewers, fill areas, small industries, and invididual houses are also scattered throughout the physiographic flood plain (Figure 8). Source Materials and Methods of Study Soils and engineering data for this study were taken from the Soil Conservation Service's report, £1229 Hazard Analysis, Plaster Creek, Kent County! Michigan, published June, 1971. The report contains soil maps and flood hazard area maps on an aerial photomosaic base at a scale of one inch equals 400 feet. The report also contains high water profiles, a few typical valley cross sections, selected flood discharges, soil descriptions, and a table of soil interpretations. On the engineering flood hazard area maps, three predicted floods are out- lined; the 50, 100, and SOO-year floods. The engineering analysis for this watershed was based on topographic maps 45 Figure 6.--Flood area map showing encroachment by a subdivision on the physiographic flood plain. Note the flooded point bend areas at valley cross secitions 22.0 and 22.3. 46 Figure 7.--House located within the flood hazard area of Plaster Creek. The attached garage on the right has been flooded in recent years. Note the escarpment in the background. 47 .hmp mEmm mnu.:0 cmxmu mumB mOHSuOHm :uom .v musmwm CH away on uoHoo Emmuum mummfiou .pmoH unmeflpmm paw :oflumNflHmccmco Emmuum muoz HmummHm mcon mHHOm HmH>DHHm co mcflpafisn HMfloumEEoo m cam mwum HHHmII.m wusmflm .xmouu 48 with contour intervals of 5 feet or less. For the Plaster Creek study, the engineering analysis and the soil survey were completely separate operations by the Soil Conserva- tion Service. This was intentionally done to permit an analysis and comparison of the flood hazard areas. The primary reason for the soil survey in this flood hazard analysis was to provide soils information for the manage- ment and use of the flood hazard area by the local units of government. An overlay was prepared from the soil map that indicated the extent of the alluvial and organic soil areas. This overlay was then placed on the engineering flood hazard area map to compare the bOundaries of soil based and engineering based flood hazard areas (Figure 9). Flood hazard area boundaries derived by engineering studies were used as criteria by which to measure the accuracy of boundaries derived by interpretation of soil maps. Most of the areas having discrepancies between the two boundary lines were field reviewed. The differences between the alluvial-organic soils boundary and the predicted flood frequency boundaries were determined and measured by the following methods: 1. Areas of the alluvial-organic soils and the 50, 100, and SOD-year floods were planimetered. Measure- ment was made on 29 individual but continous reaches along 20.7 miles of channel of Plaster Creek, Little 49 ‘ .- u'u K 2C! "in ' V'AI L17. A"! D-UI Juno“ .1 .y o ‘ I. " " I. F... ‘0' I.” ‘u I ".3 I '1' ”4.9 Figure 9.--Overlay of soil and engineering flood hazard areas. Colored areas denote engineering flood areas. Black lines indicate the extent of alluvial-organic soils. Note the correlation between the two types of flood hazard areas. 50 Plaster Creek, and Whiskey Creek. The measured reaches varied from 1,700 to 7,500 feet of channel distance and their lengths were determined primarily by the extent of individual map sheets and prominent measuring points of match lines, valley cross sections and roads. The only exception to this was that measurements were designed to avoid the division of point bend areas. Areas of alluvial soils in the minor tributaries were excluded above the 50-year flood line. Measurements of individual alluvial and organic soils not flooded by the 50-year flood and of individual non-alluvial-organic soils flooded by the 50- year flood were made with a planimeter. 2. Another method used to measure the difference between the alluvial-organic soil boundary and the 50-year flood boundary was to determine the percentage of the distance on both sides of the valley that these two boun- dary lines were within 100 feet of each other. The distance measured by this technique represents straight line segments using the alluvial soil boundary as a guide. These distances varied from one-half again as much to twice as much as the distance of the stream channel in the various reaches. At the junction of minor tributaries and drainageways that contained alluvial soils, the 50-year flood boundary was used to determine the distance. The percentage of the total distrance in which both the alluvial-organic soils and the 50-year flood boundaries 51 were within a 100 foot interval for the individual reaches were averaged together to give a percentage for the entire study area. 3. The difference between the alluvial-organic soils boundary and the 50-year flood boundary was measured at selected valley cross sections in the study area. A total of 151 valley cross sections were measured, averaging one cross section per 735 feet of channel. These included 45 engineering cross sections from the report and 106 randomly selected cross sections. The location of the randomly selected cross sections was determined by measuring upstream from valley cross section 20.3 in straight line segments in the approximate center of the physiographic flood plain, at intervals of 400, 500, 800, 700, 300, 100, 200, 900, and 600 feet. The interval sequence was based on numbers selected by chance from the random numbers table. If the randomly selected cross section fell within 200 feet of roads or railroads crossing the valley, large fill areas, or coincided with an engineering cross section, it was not plotted and the next interval in the sequence was considered. All selected cross sections were plotted perpendicular to the channel. Results and Discussion Areal measurements of the flood hazard areas in the Plaster Creek study area indicate a good correlation 52 between flood areas of the 50-year or the lOO-year floods and the flood area determined by the extent of alluvial and adjacent organic soils. Data listed in Table 1 show that for the total reach in the study area there were 805.5 acres of alluvial-organic soils, 793.8 acres of the 50-year flood area, and 827.3 acres of the 100-year flood area. These figures show that the soil based flood hazard area falls between the 50-year and lOO-year flood areas in extent. Throughout the study area, however, there was little difference between the 50-year and the lOO-year flood areas, as the difference of 33.5 acres in the total area indicates. The boundary lines of these two flood areas coincided in many places. The general relationship of the flood hazard areas for the total reach, as expressed by the amount of alluvial-organic soils contained in each of the engineering flood areas, was 100 per cent for the 50-year flood, 97.5 per cent for the lOO-year flood, and 85.2 per cent for the SOD-year flood. These results are the total values for the entire 20.5 miles of channel studied. The figures, however, represent a whole array of results for the 29 individual reaches that were measured separately. Data in Table 1 show that the results, based on the 29 individual reaches, give a less precise relationship between the flood hazard areas. Based on individual reaches, 96.4 per cent of the 50-year flood area, 93.5 per cent of the 53 TABLE l.--Summary of Flood Hazard Area Data, Plaster Creek Study Area. Flood Hazard Areas SO-yr. lOO-yr. 500-yr. Aéiu:;::‘ Flood Flood Flood 9. 50115 Total Acres 793.8 827.3 945.8 805.5 Flood Areas Containing Alluvial-Organic Soils Based on Total Reach Acres 793.8 805.8 805.5 Per cent 100.0 97.5 85.2 Basedcn129 Individual Reaches Acres 765.1 773.2 800.3 Per cent 96.4 93.5 84.6 Areas of Alluvial- Organic Soils Not Flooded by? Acres 40.4 32.3 5.1 Per cent 5.0 4.0 0.6 Areas of Non-Alluvial-Organic Soils Flooded by? Acres 28.7 54.1 145.4 Per cent 3.6 6.5 15.4 a . Based on measurements for each of the 29 reaches. bBased on total area inundated by flood. 54 lOO-year flood area, and 84.6 per cent of the 500-year flood area contain alluvial-organic soils. These results still represent a good correlation between the soil based flood area and the 50 and lOO—year flood areas. The difference of 11.7 acres between the alluvial-organic soils and the 50-year flood hazard areas for the total reach actually represents the difference between 40.4 acres of alluvial-organic soils not flooded and 28.7 acres of non-alluvial-organic soils flooded by the 50-year flood. The figures and the per cent relationship based on the 29 individual reaches reduce the amount of the flood area containing alluvial-organic soils by the amount of non- alluvial-organic soils flooded by the frequency flood. The acres and per cent of alluvial-organic soils not flooded by the 50-year, lOO-year, and SOD-year floods and the acres and per cent of non-alluvial-organic soils flooded by these frequency floods are shown in Table l. The 40.4 acres of alluvial-organic soils not flooded by the 50-year flood in the Plaster Creek study area represent the following soils and their extent: 1.4 acres of well or moderately well drained Abscota and Landes soils; .1oh5 acres of somewhat poorly drained Shoals and Ceresco soils; and 28.5 acres of poorly drained Sloan, Sloan sandy subsoil varient, and Glendora soils. The non-flooding of 10 acres, or 25 per cent, of the alluvial— organic soils was the direct result of the diking effect of Kenosha Drive and Broadmoor Avenue (Figure 10). 55 Figure lO.--Broadmoor Avenue prevents flooding of alluvial-organic soils by diking. Note the non-flooded island area to the left of Broadmoor Avenue. This is the area shown in Figure 8. 56 The 28.7 acres of non-alluvial-organic soils flooded by the 50-year flood represent about 23 acres of glaciofluvial soils, or about 80 per cent of the non— alluvial-organic soils flooded, and 5.7 acres of upland till soils. The glaciofluvial soils flooded by the 50-year flood were 3.5 acres of the well drained Metea, fine substratum variant, 2 to 6 per cent lepes, 9 acres of somewhat poorly drained Metamora, fine substratum variant, 0 to 2 per cent slopes; and 10.5 acres of somewhat poorly drained Rimer, O to 2 per cent and 2 to 6 per cent slopes. The upland till soils flooded were 3.2 acres of well drained Morley on lepes ranging from 6 to 25 per cent or more; 1.5 acres of somewhat poorly drained Blount, 2 to 6 per cent slopes; and 1 acre of well drained Chelsea, 2 to 6 per cent slopes. The difference in the flood boundaries based on the alluvial-organic soils and the 50-year calculated flood was due to several causes. Disturbed areas within the study area were a major reason for the difference. The dike effect of roads in preventing flooding of alluvial-organic soils has been noted. Construction fill areas in the alluvial bottom lands and road crossings prevented the flooding of alluvial soils in several areas. The effect of road crossings on the relation of alluvial- organic soils to engineering flood areas was not as great as was anticipated. The Crossings of Breton Avenue, 57 Broadmoor Avenue, and 44th Street showed little effect on the flood hazard areas (Figures 9 and 10). On the other hand, the 52nd Street crossing appeared to reduce the immediate downstream flooding of alluvial soils (Figure 11). The greatest effect of roads on flood hazard areas in this study occurred where they roughly paralleled the channel area in the stream valley and created artificial dikes to potential flooding, as in the examples of Kenosha Drive and Broadmoor Avenue. Disturbed areas also affect the flooding of non-alluvial-organic soils. Two areas of well drained Metea soils were graded down to produce higher elevations on the adjacent alluvial bottom lands in the subdivision area upstream from Kalamazoo Avenue. A large portion of these graded areas are now within the engi- neering flood areas (Figure 6). The flood hazard area data of the individual reaches along Plaster Creek indicated a pattern to the flooding or non-flooding of alluvial-organic soils and non-alluvial-organic soils. In the upper portion of the study area, from the vicinity of 52nd Street upstream on the Plaster Creek and along the tributaries of Little Plaster and Whiskey Creeks, there were about 30 acres, or 75 per cent, of the alluvial-organic soils that did not flood. With the exception of the reach below Kalamazoo Avenue that contained disturbed areas, the areas of alluvial-organic soils not flooded by the 50-year 58 Figure 11.--The effect of road crossings on the relationship of flood hazard areas. Plaster Creek flows toward the tOp of the map. Note the lack of flooding on alluvial-organic soils immediately downstream from 52nd Street. 59 flood generally decreased and areas of non-alluvial- organic soils that flooded increased with increasing dis- tance downstream. This flooding pattern is opposite of that reported for the Turtle Creek study in Wisconsin.1 The relation of this flooding pattern to channel bed gradient was not clear for the individual reaches, the gradients of which varied considerably. In looking at the total reach, however, a relationship of the flooding pattern to the channel's slightly concave longitudinal profile appeared. In the upstream areas, where most of the alluvial—organic soils that did not flood occurred, the gradient averaged 6.5 feet per mile or steeper. Downstream, where most of the non-alluvial-organic soils that flooded occurred, the gradient was less than 3 to 4.5 feet per mile. In the upstream area, the occurrence of alluvial soils not flooded by the 50-year or loo-year floods appeared to be the result of stream down-cutting. Over one-half of the 28.7. acres of non-alluvial- organic soils that were flooded by the 50-year flood occurred in point bend areas (Figure 12). These areas occur where the stream channel makes a sharp bend, usually approaching 90 degrees, and is cutting the Opposite valley side, which is characterized by steep slopes, or escarp- ments- This landscape feature is illustrated in Figures 13 and 14. The soils in the seven point bend areas that lLee, Parker, and Yanggen, 0p. cit., p. 67. 60 Figure 12.--Flooded point bend areas along Plaster Creek. A and B arrows indicate point bends. 61 Figure 13.--Landscape of a point bend downstream from Breton Avenue (A arrow in Figure 12). The alluvial- organic soil boundary is marked by the line of white Sycamores and bushes on the right. Note the level topog- raphy within the point bend area. 62 Figure l4.--Landscape of a point bend area upstream from Breton Avenue (B arrow in Figure 12). Tree-brush line marks the alluvial-organic soil boundary. The escarpment in the background is across Plaster Creek. The church indicates the difference in elevations. 63 occurred in the study were glaciofluvial outwash soils on dominantly O to 2'per cent slopes, but ranging up to about 4 per cent slopes. Field investigations were made in four of these point bend areas to ascertain if any evidence of flooding was present in the soils. Investi- gations were made in the point bend areas upstream and downstream from Breton Avenue, Shaffer Avenue, and the Paris Park Drive area. No evidence of recent surface deposits was found, although two of the areas are not presently farmed. Only two borings in the point bend area upstream from Breton Avenue gave evidence of posSible irregular distribution of organic matter in the soil pro- file. Stratification of soil material was common in all of the point bend areas. This, however, does not separate alluvial from outwash or lacustrine derived soils in a glaciated area. Most of the soils in the point bend areas had substrata of highly stratified, clayey, lacus- trine material overlain by poorly stratified sandy deposits. In summary, the field investigations failed to find evidence of recent flooding or alluvial deposits in the point bend areas. The soils in these areas were cor- rectly mapped as non-alluvial soils. There may be several reasons for this lack of soil evidence for flooding. The flooding of point bend areas may be a rather recent phenomenon due to changes in the watershed caused by farming and its extensive drainage systems, mostly within 64 the past 150 years. There is no evidence of surface deposits but this may be caused by past cultivation on all of the areas investigated. Floods of short duration or high velocity would also tend to leave little evidence of surface deposits in these areas. Another reason for the difference in the flood boundaries, based on the extent of alluvial-organic soils and the 50-year engineering flood, was the placement of soil lines on the soil map. The tendency of soil scien— tists to overestimate the width of the steeply sloping areas adjoining the alluvial-organic bottom land was evident. Part of this was due to "slope stripping," or extending slope units to include very narrow slope areas and their adjacent foot slopes, in order to delineate acceptable cartographic units. This tendency to over- estimate slope widths was the primary reason for the flooding of 5.7 acres of upland till soils. The steeply sloping map units often included gently sloping foot slopes adjacent to the alluvial-organic bottom lands. A more extensive use of special map symbols to indicate the narrow, steeply sloping, soil areas would have improved the accuracy of soil interpretations for delineating the flood hazard area. The accuracy of the soil mapping in the Plaster Creek study area was reasonably good when two factors are considered. First, the mapping of stream valleys is often more difficult than mapping of the upland 65 areas, due to restricted accessibility. Second, soil scientists are accustomed to mapping on a standard scale of 1,320 feet equals one inch and judging the distance and reading the photographic base map accordingly. To adjust to a much smaller mapping scale of 400 feet equals one inch takes considerable practice and time. The tendency to overestimate slope widths in the study area was undoubt- edly the result of using the unfamiliar mapping scale. Another contributing factor to the difference of the flood hazard area boundaries, and also to the accuracy of soil and engineering maps, was the errors inherent in the analysis procedures and in any cartographic reproduc- tion and printing of maps. The tracing of flood boundaries on overlays to compare the flood hazard areas, the printing in color of the engineering maps, and the factor of map control, or the elimination of distortion from the photo- graphic base, are all causes for slight, but often accumulative, errors. At the scale of the maps used in this study, soil and overlay lines represented a ground distance of 10 to 20 feet; therefore, where the flood area boundary lines were within a 50 foot interval, they were considered to have a high degree of correlation. By direct measurement, about 89 per cent of the length of the soil based flood boundary and the 50-year flood boundary lines fell within an interval of 100 feet. If two reaches containing the subdivision upstream from 66 Kalamazoo Avenue and the very upper end of Plaster Creek near 60th Street were excluded, about 92 per cent of the length of the flood boundaries would fall within an interval of 100 feet. Although the results of these two methods of analysis, areal and direct measurements of boundaries, are not directly comparable, it is interesting to note that areal measurements indicate that 96.4 per cent of the 50—year flood area contained alluvial—organic soils. Table 2 lists the difference between the alluvial- organic boundary and the 50-year flood boundary at selected valley cross sections. These differences are summarized as to the number of times the boundary lines fell within a certain interval of distance and the per cent that this number represented of the total of the valley cross section sides. Results of measurements of the engineering valley cross sections, the randomly selected valley cross sections, and the two together are shown in Table 2. By this method of evluation, the soil based flood boundary and the 50-year flood boundary fell within an interval of 50 feet at 210, or 70 per cent of the 302 valley cross section sides. As noted previously, due to cartographic and analysis limita4 tions, this result essentially represents the per cent that the flood boundaries coincided, or nearly so. For the interval of 100 feet, the correlation of boundary lines rises to 92 per cent of the 302 valley cross section sides 67 TABLE 2.—-Relation of Soil and SO-Year Flood Hazard Area Boundaries at Engineering and Randomly Selected Valley Cross Sections, Plaster Creek Study Area. Flood Boundary Valley Cross Sections Lines within an Interval of: Engineering Randomly Selected Total feet. 1121 36. 11.0.; :6. Be. 1 0 - 50 65 72 145 68 210 70 51 - 100 82 91 197 93 279 92 101 — 150 86 96 206 97 292 97 151 - 200 87 97 209 99 296 98 201 or more 90 100 212 100 302a 100 aRepresents two measurements at 151 valley cross sections from the centerline of channel to right and left flood boundaries. measured. This result compares favorably with the 89 per cent of the length of the two boundary lines within an interval of 100 feet, as obtained by the direct measure- ment method. Although not directly comparable, the 92 per cent of the soil based and 50-year flood boundaries within an interval of 100 feet at valley cross sections relates favorably to the 93.5 per cent of the 50-year flood area containing alluvial-organic soils derived by the areal measurement technique. McCormack and other investigators have suggested that the use of soil maps to supplement engineering data VWDuld improve the flood hazard area boundaries between 68 the surveyed valley cross sections.1 Although field investigations in the study area indicated that this may be valid in several areas, the data in Table 2 does not support this view. When the results from engineering cross sections are compared with the results from randomly selected cross sections, little difference is noted. If the engineering flood area lines were not as accurate between surveyed valley cross sections as at these points, the degree of correlation between the soil based and engineering flood boundaries should be much less at the randomly selected cross sections than at the surveyed cross sections. In this study area, this was not the case. The engineering cross sections indicated a slightly better correlation of 4 per cent within the 50 foot inter- val while, for intervals of 51 to 100 feet or greater, the results at randomly selected cross sections show only a l to 2 per cent better degree of correlation. In this study area, the engineering determinations were based on topographic maps having contour intervals of 5 feet or less. This would assure greater accuracy to the plotting of engineering flood lines and account for the relatively little difference in results between the engineering and randomly selected cross section data. lMcCormack, op. cit., p. 375. 69 Conclusions In the Plaster Creek study area there was little difference between the engineering flood areas for 50 and lOO-year frequency floods. The correlation between these flood areas and the flood hazard area based on the extent of alluvial-organic soils was good. Based on measurements of 29 reaches, the 50—year flood area contained 96.4 per cent of alluvial-organic soils and the lOO-year flood area contained 93.5 per cent. For the entire reach of the study area, the soil based flood boundary was within 100 feet of the 50—year flood boundary for 89 per cent of the length of the soil boundary. At 151 valley cross sections, the soil based flood boundary line fell within 50 feet of the 50-year flood boundary for 70 per cent of the cross sections and within an interval of 100 feet for 92 per cent. In view of these results, soil maps are useful in delineating flood hazard areas in watersheds having similar characteristics to those of the Plaster Creek study area. These characteristics are a relatively mature landscape and valley area. The landscape of this study area represented the geomorphic surface features of moraines and till plains. The valley area is well developed and the alluvial- organic bottom lands are slightly to moderately entrenched in the valley floor. The study area was predominantly rural, although urbanizing conditions were present in parts of the area. 70 Results from the study also indicated that alluvial—organic soils along the upper reaches of streams in this type of watershed often reflect flooding of greater magnitude than the lOO-year flood. The results of this study support the findings of other investigators in that soil maps are most useful in rural areas for delineating flood hazard areas.1 This study. however, also indicated that soil maps may be useful in urbanizing areas that are characterized by scattered subdivisions and strip type developments. The degree of usefulness is in direct proportion to the degree and kind of urbanization. Certain types of disturbed areas, for eXample, land fills within the alluvial bottom lands and roads parallel to the channel area, greatly influence the degree of correlation between soil and engineering flood hazard areas. Data for the lower reach of Plaster Creek that was not included in this study clearly indicated that soil maps are not suitable to predict flooded areas in built-up or nearly completed urbanized areas. Finally, this study shows that improved predic- tions of flood hazard areas by interpreting soil maps will result if the following actions are taken by soil scientists: lLee, Parker and Yanggen, op. cit., p. 71. 71 1. Point bend areas should be identified and evaluated. The evaluation should include a careful examination of the soils for evidence of recent flooding. The possible limitations of these areas should be brought to the attention of local officials and the need of sup- porting engineering data to determine the flood hazards for these areas emphasized. 2. If the watershed being evaluated for flood hazard areas on the basis of interpreting soil maps is subject to urbanizing influences, a field review of the area is a necessity to determine the extent of disturbed areas. Field investigations in the Plaster Creek study area were made approximately one year after the comple- tion of the soil survey and engineering study. Within this short interval of time, several disturbed areas were created. Development in the area of 28th Street and Broadmoor Avenue completely masked the soil survey information for the upper segment of Whiskey Creek. An area of the alluvial bottom land was in the process of being filled and extensive storm sewer construction was observed during the few weeks in which field investiga- tions were being made. 3. More accurate placement of soil lines and a greater use of special symbols to designate landscape breaks would improve the usefulness of soil maps. Par- ticular attention should be given by soil scientists to 72 the line that separates alluvial or adjacent organic soils from non—alluvial-organic soils. This is especially true for those areas that lack distinctive landscape breaks and for those areas where the non-alluvial-organic soils are formed in glaciofluvial deposits. In those areas where the alluvial boundary line is marked by dis— tinctive landscape break, it is still necessary to review the line steroscopically for accurate placement. In urbanizing areas, the review of old photographs to ascer- tain the condition of the landscape before it was modified or masked by urbanization would improve the judgment needed to determine soil conditions in these areas. CHAPTER V THE BUCK CREEK STUDY Introduction In the Buck Creek study, the extent of the flood hazard area delineated by alluvial and adjacent organic soils was compared with the 50-year, lOO-year and SOC-year flood hazard areas as determined by a detailed engineering study. The study area is along Buck Creek whose watershed lies mostly in southern Kent County, south of Grand Rapids (Figure 1). This watershed adjoins the Plaster Creek watershed which lies to the north and east. The channel of Buck Creek comes within about two miles of Plaster Creek, as they both approach the Grand River. The land- scape of the Buck Creek watershed, however, differs considerably from that of the nearby Plaster Creek water- shed. The moraines of the Buck Creek watershed are divided by several distinct, fairly broad, former glacial drainageways. These nearly level to gently sloping drainageways make up about 45 per cent of the total water- shed. The Buck Creek study area is located almost entirely within the broad glacial drainageways, whereas the Plaster Creek study area represented a narrow valley of outwash and alluvium among moraines and till plains. 73 74 Description of the Watershed and Study Area Buck Creek has a drainage area of about 51 square miles (Figure 15). Its headwaters begin in Allegan County and flow in a north and northwesterly direction, mainly through Kent County, to its confluence with the Grand River in the city of Grandville. The watershed is about 11 miles long and varies from one to seven and one-half miles in width. Like Plaster Creek, it is a small water— shed undergoing fairly rapid urbanization. The upstream portion of the drainage area above 68th Street is largely rural. An area of about equal size downstream from 68th Street is largely urban and industrial. The lower reach of Buck Creek has considerable development in the flood hazard areas, including residential and commercial develop- ment. Portions of the cities of Grandville, Wyoming, Kentwood, and Grand Rapids lie within the watershed. During glacial times the Grand River had several distributary channels which served as outlets to the former glacial lakes of present day Lake Michigan. One of these channels, or glacial drainageways, extended due south from the Grand River Valley at Grand Rapids, through the cen- tral part of the present Buck Creek watershed, to the vicinity of Dorr, about 5 miles south of the watershed. This glacial drainageway has a width of about four and one-half miles in the northern part of the Buck Creek watershed, narrowing to a relatively uniform width of about 75 Figure 15.--Map of Buck Creek study area. GRAND CITY OF RAPIDS rrrrrr KENTNOOD ,./ SOIL CONSENWTION SERVICE za-I zen-4 we. \I ...< w' ) ‘ 9‘ I 76 one to one and one-half miles south of 60th Street. The 700 foot contour line marks the general boundary of this landscape feature. Another channel of about the same age branched southeastward from the Grand River Valley, several miles down from Grand Rapids, through North Byron north of Byron Center. Here it turns eastward entering the Buck Creek watershed from the west, along Goose Creek. The present day confluence area of Goose Creek and Buck Creek, south of 68th Street, marks the junction of these two glacial drainageways within the watershed. The North Byron drainageway is about one mile wide. The lower part of the Buck Creek drainage area downstream from the aban- doned railroad near Byron Center Avenue represents yet another, but younger, glacial drainageway. This glacial drainageway is part of the present day Grand River Valley and is separated from the North Byron and Dorr glacial channels by a sharp drop in elevation. The 650 foot con- tour line marks the approximate boundary of this glacial drainageway. Subdued moraines border most of the Dorr and North Byron glacial drainageways. In the southeastern part of the watershed, south of 84th Street, steep, hilly moraines occur. The climate of the Buck creek drainage area is the same as for the Plaster Creek watershed. About 33 inches of rainfall is fairly evenly distributed throughout the year. High intensity summer storm rainfall is com- mon. Floods are often caused by wet or frozen soil 77 conditions and rapidly melting snow with warm rain. Ice and debris cause obstructions at bridges, compounding flood problems. Snowfall averages between 50 to 60 inches per year. Damaging floods have occurred along Buck Creek in March, 1904; June, 1905; April, 1947; March, 1948; May, 1956; September, 1961; and June, 1970. Recent flooding along Buck Creek is shown in Figure 16. The study area within Buck Creek watershed is about 2,200 acres and contains a channel of about 16.2 miles. It extended along Buck Creek from 108th Street, on the Allegan-Kent County line, downstream to Wilson Avenue, in the city of Grandville. It included the 500- year flood hazard area, plus any adjacent alluvial and organic soil areas. The 1.3 mile reach downstream from Wilson Avenue to the Grand River was excluded from the study because of backwater flooding from the Grand River and extensive disturbed areas. Because Buck Creek flows through several distinct landscapes, the study area was divided into three parts: the upper, middle, and lower reaches. In the upper reach, extending from the Allegan- Kent County line downstream 1.23 miles to 108th Street, Buck Creek cuts through a moraine. The valley in this hilly area is narrow, 200 to 400 feet wide, and is rela— tively straight. The alluvial bottom land is fairly distinct in its depressional position. The channel gradient is steep, 31.7 feet per mile. At 100th Street, 78 Figure l6.--Recent flooding along Buck Creek. 79 in the vicinity of Hilton Lake, Buck Creek enters the Dorr glacial drainageway. The middle reach of the study area extends from this point northward to the crossing of U.S. 131 highway near the confluence of Heyboer branch, a channel. distance ecu cw unavoon vooummopflz OGSHOCA uoc 06 monslo .683 E 63355 noun ~33 :0 woman u .Aomou Husvw>wvcw some HON musclwusnmoa so vomumo .aucmum 9:63: now monummu use: 05. £3.33 fiuoz Mom mono-wow 5:55 .5585 5.3! 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A ah ah owcmmuo . > Hm m an Iamfl>s~H¢ u tom hvma IHOA>DHH< u lam boon Iamfi>5HH¢ u tom hvma anonmum muppflz nocwnm :uuoz mnocwum can: mmoH< phenom vocab .38.. spasm 92.2 coucfiu .38 Bonus coo: «0 aungd an. 121 while the less entrenched and fairly narrow valleys of the Middle and North Branches failed to contain a considerable portion of the predicted flood waters. Once the height of the flood waters in these branches became greater than the depth of the entrenched alluvial bottom lands, the flood waters inundated large areas of the level upland lake plain. ‘ Based on the total measurements for each of the 8 individual reaches along the Main Branch, 93.3 per cent of the 1947 flood area and 83.7 per cent of the 50-year flood area contained alluvial-organic soils. These figures indicated a relatively good correlation between the soil based flood hazard area and the 1947 flood (29- year frequency) and a fair correlation with the 50-year flood area. As with most watercourses, these generalized relationships varied considerably along the Main Branch. In-the upper reach, from Dequindre Road downstream to Kleino Road, a channel distance of about 11 miles, the alluvial-organic soil flood hazard area generally contained both the 1947 and 50—year flood areas. As a result, most of the alluvial-organic SOils that did not flood in the Main Branch occurred in this reach. About 84 per cent of the alluvial-organic soils that were not flooded by the 1947 flood and 92 per cent of the alluvial-organic soils that were not flooded by the 50-year flood were in this reach. There was no relationship between the kind of 122 alluvial soil and the fact that it did or did not flood. The flooding of non-alluvial-organic soils in the upper reach was very minor. A review of the overlays showed that a few small bench terraces of Wasepi, Metea, and Boyer soils were inundated. The greater part of the upper reach, from the crossing of M-53 highway above Kleino Road to Dequindre Road, has a channel bed gradient of 6 to 8 feet per mile, the steepest gradient on the Main Branch. This indicates that the river is down-cutting in the reach and, as a result, less and less of the alluvial-organic soils are inundated by flood waters of low frequency floods. The steep gradient would also result in greater velocities of flood flow, thus reducing the floodway area necessary to contain the flood waters. This relationship between the amount of alluvial-organic soils not flooded, steep stream bed gradients, and loca- tion in the upper reach of the watercourse was also observed in the Plaster and Buck Creek study areas. In the middle reach of the Main Branch, from Kleino Road downstream to a point east of 17 Mile Road, a channel distance of about 6 miles, the flood hazard areas had an entirely different relationship. In this reach, the amount of alluvial-organic soils not flooded by the 1947 and 50—year floods was negligible while the amount of non-alluvial-organic soils inundated by these floods was the greatest. In this reach of the Main Branch, 123 most all of the non-alluvial-organic soils flooded by the 1947 flood and about 88 per cent of non-alluvial-organic soils flooded by the 50-year flood occurred. Apparently, this was the direct result of the flood waters from Red Run which enters the Main Branch in this reach. Just above the confluence area, an estimated 70 acres of somewhat poorly drained Selfridge soil above a low escarp- ment were flooded. Additional non-alluvial-organic soils were flooded in the narrow divide area with Plum Brook ——§-"u— aim‘ ‘. T ‘ and downstream from the confluence with Red Run. Both Red Run and Plum Brook tributaries drain a largely urban area. The Red Run has been deepened and straightened to carry storm flows. The effect of these added flood flows to the flood areas in this reach was judged to be the primary cause for the extensive flooding of non-alluvial- organic soils. The gradient of the channel bed averages about 2.4 feet per mile in this reach, thus indicating considerably less down-cutting by the river. Throughout the rest of the Main Branch and River, downstream to the spillway wier, the soil based flood hazard area generally contained the 1947 flood and most of the 50-year flood. The added flood waters from the Middle and North Branches in the confluence area apparently caused the flooding of most of the non-alluvial-organic soils along this reach. The gradient of the channel bed in this lower reach is further reduced, averaging about one foot, or less, per mile. 124 Road crossings on the Main Branch appeared to have little effect on the relationship of the flood hazard areas. Only at the crossing of Ryan Road does road fill appear to reduce the amount of alluvial—organic soils not flooded downstream. No upstream effects from the road crossing were noted. The effect of roads on diking flood waters and preventing the flooding of alluvial- organic soils was limited, occurring only along the Clinton River Road south of Canal Road. The difference between soil and engineering based flood hazard areas along the north Branch of the Clinton River was fairly great. Measurements of 7 reaches indicated 82.6 per cent of the 1947 flood area (20-year frequency) and 62.5 per cent of the 50-year flood area contained alluvial soils. The only pattern of soil flood- ing along the North Branch occurred in its upper reach. from 26 Mile Road downstream to 23 Mile Road. ’In this reach, the amount of non-alluvial soils flooded gradually increased downstream. The correlation between the soil based and the 1947 flood hazard areas in this reach was relatively good. Based on individual reach measurements, the soil based flood hazard area was about 50 acres less than the 1947 flood area. Below 23 Mile Road, however, the 1947 and 50-year floods rose out of the narrow, incised valley to inundate considerable areas of non- alluvial soils. The non—alluvial soils that flooded on 125 the lake plain were dominantly level areas of somewhat poorly drained Del Rey and poorly drained Lenawee soils. In the confluence areas of the branches and tributaries, the lake plain soils between the joining watercourses were commonly inundated. The well drained Metea soils and the somewhat poorly drained Selfridge soils were in these areas. Three point bend areas occurred along the North Branch, the only ones encountered in the study area. Two of the point bend areas resulted from confluence with tributaries. All of the point bend areas were flooded by the 1947 flood. About 60 acres of Del Rey soils were flooded in two of the point bend areas. Road cross- ings for the most part did not significantly affect the flood hazard areas along this branch. The figures listed in Table 5 for the Middle Branch of the Clinton River give only an approximate picture of the relationships between the flood hazard areas. This is due to the exclusion of an area of widespread flooding in the vicinity of 24 Mile Road. Even without including this area, there was a poor corre- lation between soil and engineering flood hazard areas. Based on total measurements for each of the 9 reaches, 64.3 per cent of the 1947 flood (ZS-year frequency) and 46.4 per cent of the 50-year flood area contained alluvial soils. The pattern of soil flooding along the Middle Branch was similar to that of the North Branch. Above 126 25 Mile Road in the upper reach, the soil based flood hazard area generally contained both the 1947 and 50—year floods. Here, also, were the greatest amount of alluvial soils that did not flood. Below 25 Mile Road, the 1947 and 50-year floods greatly exceeded the soil based flood hazard area. In this downstream reach, non-alluvial soils that flooded were mostly the somewhat poorly drained Selfridge and the poorly drained Toledo and Lenawee soils. Unlike the other branches, road crossings along the Middle Branch had a great effect on the relationship of the flood hazard areas. Above the crossings of Hall Road, 22 Mile Road, and 24 Mile Road, extensive areas of non- alluvial soils were inundated. Below the crossing of 25 Mile Road, areas of alluvial soils were not flooded by the engineering predicted floods. In Table 6, the relation of soil and 1947 flood area boundaries are indicated at selected valley cross sections on the Main Branch of the Clinton River. The flood area boundaries were within an interval of 100 feet for 59 per cent of the total 132 valley cross sectional Sides, and within an interval of 200 feet for 77 per cent of the valley sides. When compared to the Plaster and Buck Creek studies, these results indicated a poor correlation betwen flood boundaries. AS in the other studies, the valley cross section technique of analysis gave a lesser degree of correlation between flood 127 TABLE 6.--Relation of Soil and 1947 Flood Hazard Area Boundaries at Selected Valley Cross Sections on the Main Branch of the Clinton River Study Area. Flood Boundary Lines Within an Interval of: Valley Cross Sections ESEE 82; i 0 - 100 78 59 101 - 200 101 77 201 - 300 113 86 301 - 400 122 92 401 or more ' 132a 100 a Represents two measurements at 66 valley cross sections from the centerline of channel to right and left flood boundaries. hazard areas than was indicated by the areal measurement method (Table 5). The relative difference between the results of the two methods of analysis was greater for this study area than for the Plaster and Buck Creek studies. The scale of the soil maps used as the baSis for analysis was undoubtedlyeacontributing factor to this difference. The l:20,000 (3.168 inches equal one mile) scale of the soil maps reduced the accuracy of measurement of flood line distances at selected valley cross sections. It is estimated that, at this scale, the width of the printed soil lines represents about 35 feet of ground distance and that pencil overlay lines equal about 50 feet of ground 128 distance. Although a pair of dividers was used to measure distance intervals between the channel and flood area boundary lines, the small intervals involved, as compared with the other studies on the larger scale maps, made accuracy of measurement less reliable. Conclusions The results from the Clinton River study Show that the use of soil maps to delineate flood hazard areas equivalent to 50—year, or higher, frequency floods is generally not applicable in lake plain areas. The nearly level lake plains are drained by watercourses that have incised, deep, generally narrow, drainage valleys. Once the predicted flood waters reached heights greater than those of the valley escarpments, widespread flooding of the upland areas occurred. The engineering studies Show that floods of the magnitude of 20 to 50-year frequency floods will crest above valley sides, particularly in the lower reaches of relatively narrow watercourses or in confluence areas of the major tributaries. This resulted in a poor correlation of soil and engineering based flood hazard areas for the lower reaches. A fair to good correlation between the alluvial-organic soils and they 1947 and 50-year flood hazard areas resulted in the upper reaches. Another reason for the poor correlation of soil and engineering flood hazard areas is the modification, 129 by man, of the watershed's hydrology. The effects of man on the hydrology of the Clinton River watershed is appar— ently more widespread than was realized at the beginning of the study. The high degree of urbanization in the Main Branch and Main River portions of the study area was noted previously in the description of the watershed. The poor correlation between the flood hazard areas was, therefore, not unexpected in these portions of the water- shed. The concentration of storm runoff from the urbanized areas, particularly in Red Run, vastly altered most of the natural soil-flood water relationships. In the northern rural part of the study area, the effect of man's activities on the hydrology of the watershed was also apparently great. Most of the soils in this part of the watershed, drained by the North and Middle Branches, are wet, moderately fine, or fine textured. The extensive farming of these soils requires intensive and widespread surface and subsurface artificial drainage systems. Drain- age ditches and tile lines grid nearly all of the area. The effect of these drainage systems, particularly during the spring flood season when the antecedent moisture of the soils is high, is to greatly increase the magnitude of runoff. The extensive flooding along the lower reaches of the North and Middle Branches reflects this effect of extensive agricultural drainage on flood areas. 130 In spite of the overall poor correlation between soil based and engineering flood areas, the interpreta- tion of soil maps for flood hazard areas on lake plains still has considerable value. The data indicated that soil based flood hazard areas generally contain the most hazardous parts of the physiographic flood plains. In ‘ the lower reaches of the branches, these areas were almost I entirely within the flooding of the 1947 flood or higher i flood frequencies. In the upper reaches of the branches, é particularly of the Main Branch, the correlation of soil based flood hazard areas with the 1947 flood area was reasonably good. The interpretation of soil maps for flood hazard areas along watercourses similar to the deeply entrenched, relatively wide, Main Branch of the Clinton River may be useful for preliminary planning pur- poses for other watersheds that are not highly urbanized. Parts of the Black and Raisin Rivers in southeastern Michigan would be in this category. CHAPTER VII THE LOOKINGGLASS RIVER STUDY Introduction The study area of the Lookingglass River is located in Clinton County in south central Michigan (Figure 1). It includes the reach of river from the Ionia-Clinton County line upstream to the crossing of U.S. 27 highway, a channel distance of about 22.6 miles. The landscape of this study area is Similar to that of the Plaster Creek study area. In the study area, the Looking- glass River flows through a well defined valley that consists of outwash deposits bordered by uplands of moraines and till plains. The extent of the alluvial and adjacent organic soils as delineated on soil maps was compared with the flood hazard areas of the 1947 flood of record and the predicted lOO-year flood frequency from a study by the U.S. Army Corps of Engineers.1 The engineer- ing study indicates that the 1947 flood of record varied one to three feet lower than a predicted SO-year frequency flood. 1 U.S. Army Corps of Engineers, Flood Plain Informa- tion, Lookingglass River, Clinton County, Michigan (Detroit, Michigan: Detroit District, 1969). 131 132 Description of the Watershed and Study Area The Lookingglass River drains an area of approxi- mately 306 square miles. Most of its headwaters are in Shiawassee County. The river then flows west through Clinton County and outlets to the Grand River at Portland in Ionia County. The drainage basin is oriented in an_ east-west direction and has a long, narrow shape. The drainage basin is about 42 miles long and 3 to 12 miles wide. The watershed of the Lookingglass River is almost entirely rural. Most of the upland areas are intensively farmed. Scattered small woodlands and large, partially wooded swamps occur throughout the watershed. In the study area, the Lookingglass river valley is mostly wooded. The small cities of DeWitt and Portland are the only established urban areas along the river. The basin of the Lookingglass River consists of broad, undulating till plains, interspersed within a series of distinctive moraines. The slopes of the morainic uplands are rather steep and drop sharply into numerous marshes and drainageways. There are numerous pot holes and Shallow swales having no developed outlets into drainageways. The till plains are level to gently sloping with an occasional hogsback ridge. The climate of the Lookingglass River watershed is similar to that of Plaster Creek and Buck Creek. The total 133 annual precipitation is about 33 inches, two-thirds of which falls during the period of April to October. High intensity summer storm rainfall is common. Snowfall is about 41 inches a year, somewhat less than further west in the Plaster and Buck Creek watersheds. Floods generally occur during late winter and spring as the result of wet or frozen Soil conditions and rapidly melting snow with heavy rainfall. According to the Corps of Engineer's report, "The greatest flood known to have occurred in the Lookingglass River watershed was the flood of March, 1904." The most damaging of the recent, recorded floods was the one of April, 1947. This flood was caused by 2.37 inches of rain in two days on 9 inches of snow over frozen ground, accompanied by a sharp rise in temperature. From 1947 to 1968, eleven significant floods have occurred in the watershed; three in February, three in March, three in April, one in May, and one in July. Flood durations of one to two weeks are not unusual. The study area is in the narrow river valley portion of the Lookingglass River watershed, extending from the Ionia-Clinton County line upstream to the crossing of U.S. 27 highway, a mile east of DeWitt (Figure 25). The study area consisted of about 1,300 acres and included the lOO-year flood hazard area (Intermediate Regional Flood Area), plus adjacent alluvial and organic soil areas. The reach of the Lookingglass east of U.S. 27 in Clinton County I i I I IONIA. COUNTY fl CLINTON COUNTY I In E r: -I Z O -I 2 0 Z 0I 8 8 ‘3 c * 5 .< I I , I s P~ fir ‘— BWVDS NI ’— 5 A ‘ 8 '3. ‘I o I Figure 25.--Map of Lookingglass River study area. 135 was excluded from the study because of the poorly defined river valley and the many large swamps in this part of the watershed. The other reaches of the river outside of Clinton County were excluded because no engineering data were available. The river valley of the study area lies between two hilly moraines, oriented in an east-west direction. The Portland moraine borders the area to the north and the intermittent Ionia moraine to the south. Several till plains break the Ionia moraine and border the river valley. The Lookingglass River valley Contains remnants of glaciofluvial outwash deposits which border the present day alluvium on the valley floor. The floor of the river valley is about 40 to 50 feet below the general surface elevation of the surrounding uplands. This results in steep slopes, or escarpments, along much of the valley. The river valley is relatively straight from U.S. 27 downstream to Lowell Road. From here downstream to the county line, the valley is characterized by broad meanders, about one meander every two miles. The river itself has a somewhat similar pattern. Its channel is relatively straight to a point one and one-half miles east, or upstream, from Lowell Road. From here downstream to the county line, the river has numerous meanders with only a few straight reaches. The width of the valley is variable throughout the study area, ranging from about 150 to 1,200 136 feet. From Bridge Street in DeWitt upstream to U.S. 27, the valley is more narrow, 150 to 300 feet, than it is in the rest of the study area. The channel bed of the Lookingglass River has an average gradient of about 3.1 feet per mile. It is convex in Shape with the gradient increasing downstream. From U.S. 27 highway downstream to Lowell Road, the gradient is about 1.5 feet per mile, increasing to 3.0 feet per mile downstream to Wright Road, and to 4.3 feet per mile further downstream to the county line. The soils of the study area are representative of large areas in southern Michigan. The uplands are domi- nantly Miami, Celina, Conover, and Brookston soils. I These soils formed in medium textured glacial till. Hillsdale and Lapeer soils are also on the uplands. They formed in moderately coarse textured glacial till. In the valley, between the alluvial soils and the uplands, are soils formed in sand and gravel glaciofluvial deposits. These soils are the well drained Boyer and Fox, the some- what poorly drained Wasepi and Matherton, and the poorly drained Gilford and Sebewa. The alluvium in the Study area is predominantly medium textured. The poorly drained Sloan soils extend from U.S. 27 highway downstream to Bauer Road. The somewhat poorly drained Shoals soils are dominant from Bauer Road to the county line, with the exception of the reach between Wright Road and a point 137 three-fourths of a mile west of Grange Road. In this reach, the poorly drained Cohoctah soils are most common. Adja- cent to the alluvial soils throughout the study area are the very poorly drained Adrian, Carlisle, and Houghton organic soils. There are only a few disturbed areas within the Lookingglass River study area because of the rural nature of the watershed. Sectional road crossings, with their road fills and bridges, and several large gravel pits are the principal effects of man within the flood hazard areas. Two Made land areas, or extensive fills, Occur in the river valley at DeWitt. Source Materials and Methods of Study The soil maps used in this study were copies of field sheets of a recent detailed soil survey by the Soil Conservation Service, in cooperation with the Michigan Agricultural Experiment Station. The detailed engineering flood information was obtained from a study made and pub- lished by the U.S. Army Corps of Engineers.1 The engineering study utilized historical flood records and stream gauging data to determine the extent of flood hazard areas. Three flood hazard areas were delineated in this study, the 1947 flood of record under 1968 condi- tions, the Intermediate Regional Flood, and the Standard 1 op. cit. U.S. Army Corps of Engineers, Lookingglass River, 138 Project Flood. The actual flood hazard area boundaries were based on a 10 foot contour interval topographic map that the engineering report indicated did nor permit precise plotting of the flooded area boundaries. The base maps Showing the engineering flood hazard areas were enlargements of topographic maps and were at a scale of one inch equals 500 feet. The soil maps were made at a scale of one inch per 1,056 feet (5 inches equal one mile) on an uncontrolled aerial photograph base. Field investi- gations were not made in this study. Acetate overlays were made of the engineering flood hazard areas and of the alluvial-organic soil areas. The engineering overlays were reduced to the scale of the soil map as they were projected on the soils overlay by a Kargel reflecting projector. It soon became apparent that a direct comparison of the flood hazard area bounda- ries derived from the two different sources was not practical because of the distortion of the soil maps. Much of the Lookingglass River valley area occurred at the edges of the individual soil field sheets. The inherent distortion of aerial photographs at their outer edges or "join" areas is well known. As the result of this difficulty of photograph distortion, an indirect comparison was made by measuring the engineering flood and the soil areas separately, each on their original base maps. Measurements were made for the 1947 flood of record fi“ 4...“: F 139 which was calculated to be one to 3 feet lower than a 50—year frequency flood, the Intermediate Regional Flood (lOO—year frequency flood), and the alluvial-organic soil area for 14 separate, but continuous, reaches along the channel. These measured reaches ranged in channel distance from one—half to 3 miles. In this study, additional evaluation by the point method at valley cross sections was not made. The distor- tion of the soil map base and the lack of landmarks on the engineering base maps made this method of evaluation impractical. Results and Discussion Results of the Lookingglass River study showed that the soil based flood hazard area falls about mid-way between the 1947 and the lOO-year flood areas in extent. Based on the criteria of percentage of engineering flood areas containing alluvial-organic soils, there was a good correlation between the soil based and the 1947 flood hazard areas. A fair correlation was indicated for the soil based and lOO-year flood hazard areas. The summary of flood hazard area data is listed in Table 7. Based on total measurements of each of 14 individual reaches, 96 per cent of the 1947 flood area and 80 per cent of the lOO-year flood area contained alluvial-organic soils. A review and comparison of the soil and engineering flood maps strongly suggested that if the distortion of the Wen—bwfl 140 TABLE 7.--Summary of Flood Hazard Area Data, Lookingglass River Study Area. Flood Hazard Area 1947 lOO-yr. Aéiu:;::' Flooda Flood 9. , Soils : 5. Total Acres . 881.7 1301.8 1104.4 f Flood Areas Containing Alluvial-Organic Soils Based on Total Reach Acres 881.7 1104.4 Per cent 100.0 84.4 Based on 14 Individual Reaches Acres 846.1 1041.8 Per cent 96.0 80.0 Areas of Alluvial-Organic Soils Not Flooded bybv Acres 258.3 62.5 Per cent 23.4 5.7 Areas of Non-Alluvial-Organic Soils Flooded byb Acres 35.6 260.2 Per centC 4.0 20.0 a1947 Flood is one to three feet lower than a 50-year flood. bBased on measurements for each of the 14 reaches. CBased on total area inundated by flood. 141 soil maps were rectified and if engineering flood lines were based on tOpographic maps with much less than 10 foot contour intervals, the correlation between the flood hazard areas would be greatly improved. Throughout the study area, the irregular pattern of alluvial—organic soil lines appeared to outline the potential flood areas more clearly than did the gently curving engineering flood lines. The acres of alluvial-organic soils not flooded and acres of non-alluvial-organic soils flooded by the 1947 and lOO-year floods are listed in Table 7. The data Show that a significant amount of alluvial-organic soils, 23.4 per cent, were not flooded by the 1947 flood and that the 100-year flood inundated considerable areas of non- alluvial-organic soils. About 20 per cent Of the total lOO—year flood area consisted of non-alluvial-organic soils. Conversely, the amount of alluvial-organic soils not flooded by the 100-year flood, 5.7 per cent, and the amount of non-alluvial-organic soils flooded by the 1947 flood, 4.0 per cent, were not highly significant. The amounts of alluvial-organic soils that did not flood and of non-alluvial-organic soils that did flood varied considerably within the total reach of the study area. Analysis of the data for the 14 individual reaches gave the following soil flooding pattern for the total reach. About 90 per cent of the non-alluvial-organic soils 142 that were flooded by the lOO-year flood occurred in the upper reach, from U.S. 27 highway downstream to Lowell Road. The amount of flooding of non-alluvial—organic soils flooded by the lOO-year flood rapidly decreased downstream, about 9.0 per cent for the middle reach, between Lowell Road and Wright Road, and less than 1.0 per 1 cent for the lower reach between Wright Road and the Ionia- ,“ Clinton County line. The non-flooding of alluvial- I organic soils by the 1947 flood was just the reverse of the above flooding pattern. In the upper reach, about 1.0 per cent of the alluvial-organic soils were not flooded by the 1947 flood, 38 per cent was not flooded in the middle reach, and 55 per cent was not flooded in the lower reach. These soil flooding patterns were also reflected in the degree of correlation between flood hazard areas. With increasing distance downstream, increasingly better cor- relation between soil based and the lOO-year flood hazard areas resulted. The degree of correlation between soil based and 1947 flood hazard areas, however, decreased with increasing distance downstream. These soil flooding patterns and the degree of correlation between flood hazard areas appear to be related to the shape and gradient of the channel bed. The overall longitudinal profile of the Lookingglass River within the study area is slightly convex. The upper reach has an average gradient of 1.5 feet per mile, the middle 143 reach 3.0 feet per mile, and the lower reach 4.3 feet per mile. As previously stated, with increasing distance downstream, decreasing amounts of non-alluvial-organic soils were flooded by the lOO-year flood and increasing amounts of alluvial-organic soils were not flooded by the 1947 flood. This relationship is Similar to that reported by Lee, and others, for Turtle Creek.1 Turtle Creek also has a convex shape channel bed. The effect of the shape of the channel bed on soil flooding patterns appears to be of major importance in interpreting soil maps for flood hazard areas. The soil flooding-channel bed Shape rela- tionship fortflmaother study areas was the reverse of the above pattern for the Lookingglass River. In the other study areas, however, the channel bed was generally concave in shape, thus causing the different pattern of soil flooding. ‘ As the result of the convex channel bed, downcut- ting of the channel is occurring in the lower reach. This is most likely the main cause for the non—flooding of alluvial-organic soils in this reach. A review of the maps, however, indicated other possible causes. The amount of alluvial-organic soils not flooded by the 1947 flood may be lower than indicated because of the place- ment of engineering flood lines. Evidence for this is that much of the alluvial—organic soils not flooded lLee, Parker, and Yanggen, Op. Cit. “Jfi-“JF 144 occurred within the valley in the confluence areas of numerous tributaries. Downstream from Grange Road, a tributary entered the main valley at an upstream angle and joined the river on the outside of one of its pro— nounced bends. The engineering flood maps failed to indicate any extensive flooding of the alluvial soils at the mouth or in the lower part of the tributary, despite 1.. its downstream position. Also, narrow areas of organic 1 soils and of alluvial soils between the channel and )- escarpments were only partially inundated. Most of the non-alluvial-organic soils that flooded in the middle and lower reaches were level to gently sloping, poorly drained or somewhat poorly drained soils formed in glaciofluvial deposits. Wasepi and Gilford soils were prevalent in these areas. One small point bend area and a partial large point bend area occurred in the lower reach.l A large portion of the Wasepi soils in these areas was flooded. About 27 per cent of the non—alluvial-organic soils that were flooded by the lOO-year flood occurred in the 1.7 mile reach between DeWitt and U.S. 27 highway. In this reach, gently sloping areas of well drained Boyer soils and moderately well drained Bronson soils were flooded. The reasons for the flooding of these relatively high, better drained 1A partial point bend area has only a part of the opposite upland slopes as escarpments, or steeply sloping areas. 145 glaciofluvial soils appeared to be hydrological. The combined effects of the narrow river valley, the low gradient of the channel bed, and a large depressional, swampy, basin upstream apparently caused the flooding of these soils. An estimated 50 acres of flooded gravel pits were also included in the total of non-alluvial- organic soils that flooded in the upper reach. Conclusions Based on the data from the Lookingglass River study, soil maps are suitable to delineate flood hazard areas for 50-year floods in watersheds having similar landscapes. The landscape of the study area consisted of moraines and till plains. The valley was well formed and bordered by distinctive landscape breaks for much of its length. The study area was almost entirely rural. Con- sidering the possible inaccuracies of the source data, that is, the distortion of the photographic base map used for soil mapping and the 10 foot contour interval base maps used for engineering analysis, the correlation of the soil based and engineering flood hazard areas was relatively good” .Areal neasurements indicated that 96 per cent of the 1947 flood area and 80 per cent of the lOO-year flood area contained alluvial—organic soils. Most of the non-alluvial-organic soils that flooded were low lying, wet, glaciofluvial soils. 146 The study indicated the importance of the shape and gradient of the channel bed to soil flooding patterns and, consequently, to the interpretation of soil maps for flood hazard areas. The convex, longitudinal channel bed gradient of the Lookingglass River in the study area apparently caused a decrease in flooding of non-alluvial- organic soils and an increase in the extent of alluvial- F4 organic soils not flooded with increasing distance a ‘> '-.'O.-o. it; downstream. In this study, this resulted in an increas- ingly better correlation between the soil based and the lOO-year flood hazard areas with increasing distance downstream. Where engineering flood maps are based on topo- graphic maps having a 10 foot contour interval, soil maps will give a better definition to the flood area boundaries. In comparing the soil and engineering maps used in this study, it was clearly evident that the soil lines gave a better picture of the configuration of potential flood boundaries between surveyed valley cross sections than the gently curving engineering flood boundaries. CHAPTER VIII CONCLUSIONS AND RECOMMENDATIONS Based on results from the four study areas in southern Michigan, the following conclusions and recom- mendations are presented. Conclusions 1. Soil maps can be used for delineating flood hazard areas. Their use for this purpose must be selec- tive. In watersheds with predominantly till plain and moraine landscapes and having moderately mature drainage valleys, soil maps reflect, reasonably well, flood areas equivalent to floods of 50 to loo-year return frequencies. Soil maps do not reflect these flood frequencies in other types of glacial landscapes. In large glacial drainage- ways, flood hazard areas based on the extent of alluvial- organic soils are equivalent to floods of lower return frequencies. On lake plains, the extent of alluvial- organic soils along most streams is equivalent to floods of higher return frequencies. In most glacial landscapes with moderately developed drainageways, soil maps indicate the most hazardous part of the flood hazard area. 147 148 2. Between surveyed valley cross sections, soil lines give a better definition of flood area boundaries in relation to landscape features than do engineering flood lines based on the interpretation of 10 foot, or greater, contour intervals. Where engineering flood lines are based on contour intervals of 5 feet or less, there is little difference in the definition of landscape features between soil and engineering lines. A review of soil maps should be a standard engineering procedure in flood hazard analysis. The comparison of soil boundaries with engi- neering flood boundaries between surveyed valley cross sections may indicate possible areas for field checking. 3. The longitudinal shape and gradient of the channel bedrmnrhave a significant effect in some areas on the patterns of soil flooding and will influence the accuracy of soil interpretations for flood hazard areas. Watercourses with a convex bed slope show that, with increasing distance downstream, the amount of alluvial soils not flooded will increase and the amount of non- alluvial soils flooded will decrease. Watercourses with a concave channel bed profile show just the opposite relationship. The degree of convexity and concavity required to produce the above relationships is not known and undoubtedly varies in different watersheds. The need to recognize stream down cutting areas is important in making interpretations of soil maps for flood hazard areas . “A. 149 4. Soil maps are most useful in rural areas for delineating flood hazard areas because these are generally the least disturbed by man. Caution must be used, how- ever, in interpreting soil maps for flood hazard areas in rural landscapes. Intensive and widespread agricultural drainage may affect the natural soil—flood water relation- ships in some watersheds. The use of soil maps in urbani— zing areas is more applicable than previously thought. The suitability of soil maps for use in these areas is directly related to the degree and kind of disturbance. They are most applicable in those urbanizing areas which have scattered deveIOpment on the uplands and least applicable in those areasshiwhich disturbed areas occur within the physiographic flood plain. 5. In using soil maps to delineate flood hazard areas, individual reaches of watercourses must be examined. This is especially true if the watercourse flows through contrasting landscapes. Soil maps may be useful only in certain reaches of a watercourse for delineating flood hazard areas depending on the type of landscape, the extent of disturbance, and other factors. 6. Detailed, modern soil maps at a scale of 1:15,840 (4 inches equal one mile) provide sufficient information to make soil interpretations for flood hazard areas. The construction of map units, for the most part, is satisfactory for this purpose. Increased use of 150 special map symbols, particularly for narrow landscape breaks, and improved precision of plotting soil lines would improve the accuracy of interpretations. The use of old photographs to identify disturbed areas in an urbanizing watershed would also improve the accuracy of the soil map for interpreting flood hazard areas. *. Recommendations t 1. As information becomes available, the analysis { of the relationship between soil and engineering data for delineating flood hazard areas should be continued. Pri— orities for engineering flood hazard analysis studies in Michigan should include several pilot rural areas having modern soil survey information. The use of the valley cross section method to analyze the relationship between soil and engineering based flood hazard areas is recom- mended. Although the results from this method do not indicate the degree of correlation between flood hazard areas obtained by the method of areal measurement, the cross sectional method entails much less measurement and calculation. If this method is used for analysis of areas having published soil survey maps, enlargements of the soil maps will be necessary to insure accurate measurements. 2. Increased investigation and research are greatly needed to provide better techniques for identifying and classifying soils derived from alluvium or soils having 151 recent surface deposits of alluvium. The present soil taxonomy does not provide sufficient criteria to enable field soil scientists fo map with a high degree of accuracy those alluvial soil areas not marked by distinctive land- scape features and to identify relic alluvial soils, soils that have not been subject to flooding for a con- siderable period of time. 3. The Soil Conservation Service's flood hazard ‘ ' I‘m-XLAI’“ It analysis program should be continued and expanded. It is the only flood hazard analysis program that provides both soil and engineering information for planning and manage- ment of flood hazard areas. 4. Interpretations of soil maps for delineating flood hazard areas should be done only by an experienced soil scientist. In interpreting soil maps, he should also make use of other available sources of data. It is imperative that he make a field review of the area under consideration to locate and assess recent disturbed areas, especially in urbanizing watersheds. 5. The difficulties in using source material from different agencies strongly emphasizes the need for improved coordination between federal agencies and between federal agencies and other units of government engaged in flood hazard analysis studies. The type