Abstract:
Using daily discharge data from the US Geological Survey, we calculated 34 stream flow metrics for 150 watersheds (area<282 km2) within the Chesapeake Bay basin, and selected 17 of the metrics. We quantified the proportions of forest, agriculture, grassland, developed land, and impervious surface in each watershed. For each of the three physiographic provinces, we correlated the flow metrics with the land cover proportions to elucidate how different land cover types affect the flow regime. Higher proportions of forest increased stream flow in relatively dry winters or springs and reduced stream flow in comparatively rainy autumns. Higher forest proportions also reduced flooding, prolonged pulses of higher flow, and reduced flow variability. Higher proportions of agriculture reduced flow variability and prolonged pulses of higher flow in all physiographic provinces and reduced flooding in the highland physiographic provinces. Higher grassland proportions reduced flooding and flow variability and prolonged high flow pulses in all provinces. Higher proportions of developed land and impervious surface reduced infiltration, increased flooding and flow during high rainfall periods, intensified flow variability, and shortened high flow pulses; there are different hydrologic effects in different urbanized areas.
