Which type of drainage basin has the greatest effect on surface runoff?
Long, narrow drainage basins generally display the most dramatic effects of surface runoff. These drainage basins have straight stream channels and short tributaries. Storm waters reach the main channels far more rapidly in long narrow basins than in other types of basins. Flash floods are common in long, narrow drainage basins, resulting in greater erosion potential. Topography (relief) and slope (gradient) are additional factors affecting water velocity, infiltration rate, and overland flow rate. Water velocity, infiltration rate and overland flow rate affect surface and subsurface runoff rates. Climate is also important. Precipitation (type, duration, and intensity) is the key climatic factor. Infrequent torrential downpours easily erode sediment-laden topography, while soft drizzly rain infiltrates the soil. Vegetation aids in slope stability. Removal of vegetation by fire, clear-cutting (logging), or animal grazing often results in soil erosion. The eroded material is washed into
