Documenting the geomorphic impacts of high lake level on freshwater coastal wetlands using topobathymetric surveys : a case study from saginaw bay in Lake Huron

There has been extensive research connecting vegetative processes in coastal freshwater wetlands and water level fluctuations. However, there is little work on changes to wetland geomorphology, what those transformations may be, and how they impact the wetland. This paper aims to identify changes in wetland geomorphology and decern any correlation between water level and vegetation extents. Data for this study spans from 2012 to 2021, capturing the most recent period of rising water levels. Vegetation extent imagery and topobathymetric data were collected during field excursions in the summer of 2021 and compared to NAIP imagery acquired from USGS Earth Explorer and topobathymetric LiDAR data from NOAA Data Access Viewer. Imagery from 2021 was collected using a DJI Phantom 4 Pro quadcopter drone and 2021 topobathymetric data utilized an RTK-GPS antenna and Seafloor Systems SonarMite single-beam echosounder to conduct boating, kayaking, and wading surveys at each study site. Studies took place at Wigwam Bay and Quanicassee State Wildlife Areas located in Saginaw Bay of Lake Huron. Findings show water level had a variable impact on vegetation extent and suggest that erosion of sediment occurred during high water levels at both sites. Results show observable changes in geomorphology adjacent to the wetlands. Changes to geomorphology could potentially impact the size, health, and ecosystem services of coastal wetlands. This initial study has limitations due to the nature of available historical data but is intended as a first step towards further understanding the role of geomorphology in coastal freshwater wetland systems.