An analysis has been made of the effects of urbanization and highway con¬struction on run-off, erosion and siltation on the Anacostia watershed. The analysis is based on changes in land use patterns as determined from aerial photographs as well as geologic and hydrologic data for the region.nTwo selected subwatersheds of Indian Creek and one of Little Paint Branch of the Northeast Branch of the Anacostia were studied in terms of three hypo¬thetical storms of different magnitudes. It was determined that an approximately 10 percent increase in impervious surface could bring about a 12 percent increase in the peak discharge for storms of the magnitude of tropical storm Agnes, a 20 percent increase in peak discharge for 10 hours storm and as much as a 150 percent increase in peak discharge for a typical thunderstorm.
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