ADJUSTMENTS OF STREAM CHANNEL MORPHOLOGY TO LAND USE IN BUFFALO CREEK TRIBUTARIES, CENTRAL PENNSYLVANIA

The Buffalo Creek watershed, a tributary of the Susquehanna River, drains approximately 134 square miles in central Pennsylvania. The watershed has a history of nearly 300 years of anthropogenic alterations. Currently the upstream half of the watershed is forested while most of the remainder is agricultural and low density dwellings. Significant land use changes occurred in the past century when all of the now forested area was clear cut. During the Summer of 2006, data on stream morphology, dendrochronology, and stream geometry was collected in Spruce Run and Rapid Run, two of the main tributaries of Buffalo Creek. Observations included point bar sedimentology, surveying channel cross-sections to evaluate width-to-depth ratios moving downstream, and coring trees to ascertain ages and estimate surface ages to establish timing of late Holocene channel-floodplain adjustments. Data suggests that both streams are currently in states of disequilibria and adjustment to changes in sediment yield. In Spruce Run, the clast sizes in active point bars decrease moving downstream, whereas the volume of the point bars increases. Two specific aggradational zones and a reach of markedly episodic aggradation occur along Spruce Run, indicating that the stream is experiencing significant channel adjustments. A distinctive low surface occurs in Spruce Run dated at between 77 and 137 years based on age bracketing by trees buried by this unit and trees established on its surface. This surface appears to relate to increased sediment yield from the logging era. Rapid Run appears to have one large aggradational pulse located in the lower 6 km of the watershed in the process of moving downstream and an aggradational surfaced between 82 and 115 years related to the logging era. This project further verifies the regional phenomenon of channel adjustment in response to land use changes that is occurring in the Northeastern United States and provides a greater understanding of the Buffalo Creek watershed in the event that stream remediation is desired in the future.