5.1.8 Direct Runoff
5.1.8 Direct Runoff
Direct runoff is water not absorbed by soil or that does not soak into the soil but flows into surface waters. Geology, slope, and topography are the most controlling factors of runoff and area, actual evapotranspiration/ rainfall and vegetation cover least control runoff. In general, low rainfall, high evapotranspiration, gentle slope, very permeable volcanic falls and disappearing drainage pattern can confirm the lowest runoff.
Direct runoff is that part of the precipitation, snow melt, or irrigation water that appears in uncontrolled surface streams, rivers, drains or sewers. And it consists of precipitation that neither evaporates, transpires nor penetrates the surface to become groundwater. It occurs when the rate of
rainfall on a surface exceeds the rate at which water can infiltrate the ground, and any depression storage has already been filled. This more commonly occurs in arid and semi-arid regions, where rainfall intensities are high and the soil infiltration capacity is reduced because of surface sealing, or in paved areas. The runoff efficiency
(volume of runoff per unit of area) increases with the decreasing size of the catchment i.e. the larger the size of the catchment the larger the time of concentration and the smaller the runoff efficiency.
Direct runoff is water not absorbed by soil or that does not soak into the soil but flows into surface waters. Geology, slope, and topography are the most controlling factors of runoff and area, actual evapotranspiration/ rainfall and vegetation cover least control runoff. In general, low rainfall, high evapotranspiration, gentle slope, very permeable volcanic falls and disappearing drainage pattern can confirm the lowest runoff.
Direct runoff is that part of the precipitation, snow melt, or irrigation water that appears in uncontrolled surface streams, rivers, drains or sewers. And it consists of precipitation that neither evaporates, transpires nor penetrates the surface to become groundwater. It occurs when the rate of
rainfall on a surface exceeds the rate at which water can infiltrate the ground, and any depression storage has already been filled. This more commonly occurs in arid and semi-arid regions, where rainfall intensities are high and the soil infiltration capacity is reduced because of surface sealing, or in paved areas. The runoff efficiency
(volume of runoff per unit of area) increases with the decreasing size of the catchment i.e. the larger the size of the catchment the larger the time of concentration and the smaller the runoff efficiency.