Large river ecosystems are an important functional part of the landscape in the southeastern United States. The extent and condition of large river floodplains greatly affect the quality of fish and wildlife habitat and the supply of important ecosystem goods and services. To better understand patterns of floodplain inundation, scientists used 1,334 Landsat images over 51 Landsat scenes collected under a variety of hydrologic conditions from 1983 to 2011. Each image was classified into categories of wet and dry, and then composited all images to develop a measure of relative floodplain inundation frequency for each Landsat scene (15–40 images per Landsat scene). Scientists developed an analytical methodology to link inundation frequency with gage measurement to develop measures of flood return frequency that may be tailored to the specific requirements of an individual species. Results were merged from all 51 scenes to form a regional landscape mosaic of relative floodplain inundation frequency. These datasets have been used to determine optimal alligator gar--a giant freshwater fish--spawning locations along the lower Mississippi, Arkansas, and Trinity Rivers. This regional mosaic has also been used to inform land conservation prioritization in the Atchafalaya Basin and Mississippi Alluvial Valley, to estimate denitrification capacity within the Atchafalaya Basin, and to identify suitable environmental conditions for lidar acquisition.
Example of floodplain inundation frequency results at the confluence of the Ohio and Wabash Rivers.
Example of inundation frequency results within a single Landsat scene translated into inundation return frequencies in the spring (April, May, June) based on long-term gaging data from Natchez, Mississippi. Areas outside of the direct influence of the Mississippi River are shaded grey as they are primarily driven by hydrologic conditions from other than the Mississippi River.