BASELINE ASSESSMENT OF STREAM HEALTH AFTER RESTORATION, VALLEY CREEK WATERSHED, PA

Urbanization tends to reduce the number and diversity of aquatic species in watersheds. The effect of stream restoration on the ecosystem is less well understood. This issue was examined at Crabby Creek, a stream located in Valley Creek watershed in southeastern PA. In the summer of 2008, a portion of the stream was moved and reconstructed because it was corroding a sewage line. Restoration structures were constructed along the stream to create stability and reduce erosion along the banks. The structures included J-Hooks, cross vanes and cross logs and also helped to create riffle, run and pool stream environments.

Certain species of aquatic macroinvertebrates are more tolerant of pollution than others. Based upon tolerance levels, as well as the variety and quantity of taxon, macroinvertebrates can be used to determine the health of a stream’s ecosystem and its water quality. In spring 2009, samples were collected using a Surber sampler from nine randomly chosen sites, including riffle, run and pool habitats. The Surber sampled a 1 ft square area. Samples were picked using a dissecting scope then sorted and identified to genus when possible. These data were compared with macroinvertebrate counts before reconstruction.

To date, the samples have shown little diversity and low abundance of species. Only 4-6 taxon per site were observed in spring 2009 compared to 15 in the pre-restoration count. Total counts were low, on the order of 100 individuals per site, where typical prerestoration numbers are closer to 1000 per site. The macroinvertebrates observed were also very small in size compared to average macroinvertebrates. The low counts may be the result of the dynamic nature of the new streambed which has undergone a lot of sediment redistribution. This study provided a baseline macroinvertebrate assessment, which can be compared to future studies to determine the rate of restoration of the stream’s ecosystem health.