Assessing riparian functioning condition for improved ecosystem services: A case study of the Back Creek watershed...

Riparian functioning condition refers to a rating and description of the current ecological status of a reach of a riparian ecosystem in consideration of its potential hydrology, vegetation, and geomorphology. Reach rating options are Proper Functioning Condition (PFC), Functional-At-Risk (FAR), Non-Functional, and apparent or monitored trends. We assessed the functioning condition of flowing riverbank areas of Back Creek located in Virginia (USA) following a PFC protocol developed by the U.S. Department of the Interior and the U.S. Department of Agriculture. The PFC protocol involves 17 qualitative assessment items that address three categories of attributes (hydrology, vegetation, and geomorphology); each is answered as "yes", "no," or "not applicable" with an explanation. We discussed key PFC items driving stream water quality contextualizing the previously modeled riparian buffer zones and ecosystem services tradeoffs in the Back Creek watershed published by U.S. Environmental Protection Agency. Using the remote sensing data in the Geographic Information System, we delineated and characterized 26 Back Creek reaches of 41.1 km length. We also analyzed the 38-year (1981-2018) daily datasets of the precipitation, surface runoff, temperature, soil moisture pattern, and vegetation types for the watershed. Then, we conducted the PFC assessments using field reconnaissance of 10 reaches, 19.3 km of the Back Creek. The field assessments concluded that 52% of the assessed length of Back Creek was in PFC, attributed to diverse vegetation, maintained channel characteristics, floodplain accessibility (where appropriate), and balanced water and sediment loading supplied by individual headwater streams to the Back Creek. 48% of the assessed length was in FAR condition due to land use changes and urban road network. This study provides an exemplar of nonpoint source (diffused pollution generated by land runoff) methodology for identifying key riparian functioning issues and assessing effectiveness of the non-point source best management practice programs.