MONITORING STREAM FLASHINESS IN THE WEST BRANCH OF THE ROCKY RIVER

In populated areas of the piedmont of North Carolina, human development has a significant impact on stream pollution, discharge, and morphology. In particular, the clay rich soils and soft saprolite streambeds of the area mean small changes in surface flow may have significant implications for stream morphology. In order to determine the effect of modern discharge regimes on highly sensitive headwater streams, we have compared discharge between three 1^st order streams in Davidson, North Carolina. Each drainage basin is characterized by substantial differences in land use— the Ecological Preserve (EP) stream (drainage basin area = 0.924 km²) is nearly completely forested, the Patterson Court (PC) stream (drainage basin area = 0.657 km²) is a suburban-like mix of impervious surfaces and lawns, and the Baker Sports Complex (BS) stream (drainage basin area = 0.370 km²) is mainly impervious surfaces. To measure how each stream responded to precipitation events, water level sensors were installed near the mouth of each of the three streams to measure water level every 15 minutes. Water level was converted into discharge using ratings curves created for each site. Our results indicate that headwater streams in the region are extremely sensitive to changes in land use. For instance, during precipitation events, streams in drainage basins containing significant impervious surface area peak rapidly, and at high discharges, when compared with more natural streams. In fact, the PC stream often returns to base flow before the EP stream begins to rise. Numerically, lag time and the Richards-Baker Flashiness Index were used to quantify flashiness. Differences in lag time confirmed that the stream with a higher percentage of impervious surface coverage exhibited flashier behavior. The Richards-Baker Flashiness Index returned the opposite result, ranking the more natural stream (EP) as more flashy. Despite the result of this index, lag time and anecdotal evidence support the concept that streams with more traditionally suburban land use in the catchment exhibit flashier behavior. These results likely have significant implications for geomorphic and ecologic variations in streams regionally.