EFFECT OF RIPARIAN ZONES ON TURBIDITY IN URBAN STREAMS

Riparian zones influence the health of streams by increasing bank stability and promoting nutrient transformations through biogeochemical and hydrological processes. Urban development is often associated with channel incision and disconnection from riparian areas in response to increases in impervious surface areas and altered drainage patterns. Stream restoration and stormwater control measures seek to improve riparian function by increasing channel complexity, reconnecting incised channels, re-establishing riparian vegetation, and enhancing infiltration; however, the effectiveness of these techniques is poorly understood. This project compares the turbidity signals from storm events in the Tookany Creek and its tributary, Mill Run, in the suburbs of Philadelphia, PA. Turbidity is defined as the optical clarity of the water and can be used as a proxy for total suspended sediment. YSI 600 OMS data loggers were installed longitudinally along 30 to 100 m intervals for two stream reaches with varying connectivity and vegetation in buffer zones. The turbidity of the stream was recorded at 15 minute intervals to determine how stream characteristics influence sediment input into the stream during storm events. Several parameters were evaluated along the reaches including riparian vegetation, embeddedness of the stream channel, proximity to large woody debris, and channel morphology. Stream cross sections and bank pins were also used to assess erosion. The storm signals on the Tookany Creek are consistent, with seven out of nine storm events in June 2015 following the same turbidity pattern. Alternatively, within the same timeframe no repeatable pattern was present at Mill Run. It is hypothesized limited stream embeddedness and large woody debris contribute much of the variability into the turbidity signals at Mill Run as vegetation and channel morphology were controlled for in logger placement. In neither stream did the turbidity increase consistently downstream. By studying turbidity signals longitudinally along urban streams we hope to increase understanding of the effectiveness of riparian vegetation on urban stream health and water quality.