Novel Applications in Wetland Soils Mapping on the Delmarva Coastal Plain

Abstract

On the Delmarva Peninsula, depressional wetlands provide a range of ecosystem services, including water purification, groundwater recharge, provision of critical habitat, and carbon storage. Concern for the health of the Chesapeake Bay and the establishment of the Bay Total Maximum Daily Load have led to growing interest in restoring depressional and other wetland types to mitigate agricultural nitrogen inputs. The ability of natural resource managers to implement wetland restoration to address nonpoint source pollution is constrained by limited spatial information on hydrogeologic and soil conditions favoring nitrogen removal. The goal of this study was to explore the potential of new digital soil mapping techniques to improve identification of wetland soils and map soil properties to improve assessment of wetland ecosystem services, including removing excess nitrogen, and inform natural resource decision making. Previous research on digital soil mapping has focused largely on the development of medium to low-resolution general purpose soil maps in areas of heterogeneous topography and geomorphology. This study was unique in its focus on mapping wetland soils to support wetland restoration decisions in a low relief landscape. A digital soil mapping approach involving the spatial disaggregation of soil data map units was used to create maps of natural soil drainage and texture class. The study was conducted in the upper part of the Choptank River Watershed on central Delmarva, where depressional wetlands occur in high densities and historical loss of wetlands is estimated to be high compared to similar Maryland watersheds. The soil disaggregation techniques developed in this study were successful in creating a more refined representation of natural soil drainage and texture class in forested depressional wetlands. Comparison of the disaggregated soils map with recently developed time-series inundation maps of the region demonstrate the need for further research to understand how indicators of historic and current hydrologic conditions can guide operational soils and wetland mapping and inform wetland restoration decisions.