Development of hydrologic modification indicators to support watershed-based restoration of shellfish resources impacted by fecal coliform contamination

The Jump Run Creek Project in North Carolina is a multidisciplinary, multi-agency, watershed-based restoration project that combines in-column water quality data, stormwater quality data, storm and stream flow measures, with spatial analysis, and community involvement to investigate causes and solutions of bacterial loading contributing to shellfish closure management. Preliminary project efforts were reported at ISCR '98. Hilton Head showing data indicating that increased volume and velocity of stormwater flows may be the primary transport vector. However, the impervious surface area in this watershed is less than 5% - well below the threshold of 12%-25% cited in the literature as the level at which nutrient loading causes water quality degradation. Very little investigation has been conducted to review the effects of land use modification on bacterial loading. This effort reports on one approach to measure impacts to watershed hydrology indicating conditions contributing to excessive bacterial loading and bed closure. Using scanned images of aerial photos of the watershed from the 1960s through the 1990s, overlain with current parcel data, and linked to GIS classification ranks are assigned to each parcel indicating the degree of hydrologic modification. Parameters being used are vegetative cover, ditching, and impervious surface area. Using regression techniques, spatial and temporal models of hydro-modification will be regressed against thirty years of bacterial data collected by North Carolina Division of Environmental Health - Shellfish Sanitation Branch to investigate relationships. The aerial and GIS have been completed. The hydro-modification database is currently under construction. Regression analysis will be conducted during the summer months; so that a report on the results can be made to the conference in September. Over the coming year, this information will be used in two ways: 1) to help watershed citizens understand land use activities that contribute to bacterial loading; and 2) in conjunction with watershed citizens, to design and locate BMPs for mitigation and restoration.