THE SKINNY ON ASSESSING RISK IN A LONG NARROW PARK; EVALUATING POTENTIAL IMPACTS TO RARE, THREATENED AND ENDANGERED SPECIES ASSOCIATED WITH THE KARST FEATURES AT THE C&O CANAL NHP

The Chesapeake and Ohio Canal National Historical Park is a critical preserve for the protection of rare, threatened, and endangered (RTE) subterranean macroinvertebrates in Maryland. The park is located along the north bank of the Potomac River and is approximately 280 km long with an average width of 265 m. The identified RTE species live in the 110 km of the park underlain by carbonate rocks. A previous inventory of the carbonate areas in the park identified 23 caves, 9 springs, 2 areas of tufa deposits, and 3 abandoned carbonate-rock mines. Over 10 RTE macroinvertebrate species have been identified in these and nearby features. Evaluating the potential impacts to water quality and the RTE species is complicated due to (1) the narrow footprint of the park; (2) the number of sites across hundreds of km; (3) difficulty in obtaining access to recharge areas outside of park boundaries; (4) the region’s ongoing conversion from rural to suburban land use; (5) the likelihood that small, independent basins recharge the features; and, (6) the lack or intermittent nature of flow in many features. Instead of conducting a traditional hydrogeological study, we are evaluating risk by defining the magnitude and likelihood of potential impacts and comparing them in a “risk vulnerability matrix” which plots risk-magnitude against risk-likelihood. Risk-magnitude is defined by the RTE species: e.g., a high magnitude of impact would be defined as adverse impact to a cave with many listed or endangered RTEs. Risk-likelihood is summed from factors that define possible adverse influences: e.g., caves with flowing water have a higher likelihood of contamination from upstream than do dry caves. Each site is given a score for both magnitude and likelihood and plotted on a four-by-four matrix that can then be used by park as a resource management tool to compare and prioritize sites for future protection and research. Each factor is weighted based on its importance to park management. The risk matrix model allows park managers to readily incorporate new sites, to alter the weighting on individual factors if park priorities change, and to conduct sensitivity analyses of the impact from individual factors.