Retention of sediments and nutrients in floodplain areas provides critical ecosystem services to downstream communities. Lidar mapping, field data collection, and modeling were integrated to quantify the ecosystem service of sediment and nutrient retention that floodplains provide in the Delaware River watershed. The mapping component resulted in the development of the Floodplain and Channel Evaluation Toolkit (FACET) to identify features and calculate key metrics describing channel and floodplain geometry from high-resolution bare-earth elevation data in the Delaware River watershed. Field data collection employed dendrogeomorphic techniques to estimate rates of stream bank erosion and floodplain sediment deposition at fifteen sites in the watershed. These two datasets were combined to develop predictive models estimating sediment trapping and export for stream reaches within the non-tidal portion of Delaware River watershed.
Results/Conclusions
FACET was used to extract measurements of channel width, channel depth, and floodplain width for streams within the Delaware River watershed. Mapping indicated floodplain width, bank height, and cross-sectional area all increased with stream order. Floodplain width was widest in the coastal plain and narrower at sites in the piedmont, valley and ridge, and Appalachian plateau. Modeling indicted spatial variability in sediment fluxes with greater sediment trapping at coastal plain sites compared to Appalachian plateau sites. Both watershed attributes and stream geomorphic metrics were important in predicting sediment fluxes. Overall this assessment of floodplain sediment flux and associated ecosystem services can help identify areas for targeted management to maintain floodplains with high ecosystem service values, and to restore areas that could provide the most ecosystem service benefits.