River mouth bars, such as those of the Pinnebog River along Lake Huron’s Saginaw Bay, are dynamic landforms shaped by both fluvial and coastal processes. Although they are prominent features in coastal settings, their influence on coastal geomorphology is poorly understood. These river mouth bars are ecologically important barriers that thwart storm waves from impacting upstream habitats. Given the frequent changes, studying these features and their impacts requires high temporal resolution geomorphic and hydrodynamic data sets. Using high-temporal resolution satellite imagery from Planet Labs, we documented the geomorphic evolution of the river mouth bar and adjacent shoreline over an 8-year period (2016-2023) including the effects of the rise and fall of Lake Huron water level. Wave data USACE hindcast were integrated with NOAA lake level and precipitation data to document the hydrodynamic processes driving the geomorphic behaviors at the river mouth. These satellite and hydrodynamic data indicated river mouth bars are highly responsive to fluctuating lake levels, river discharge and wave events, which alter location of the bar within the nearshore. Former mouths of the Pinnebog River, suggesting over annual periods these river mouth processes exert a measurable influence on nearshore depositional patterns. High temporal satellite images combined with a series of data reveal a highly mobile and dynamic bar affected by lake level, wave conditions and river discharge.
Read
