Flooding is less significant in these more natural conditions because some of the runoff during a storm is absorbed into the ground, thus lessening the amount of runoff into a stream during the storm.
Farmers rely on topsoil to grow crops. Sediment-filled rivers are dumping tremendous amounts of suspended sediment into the Atlantic Ocean.
Typically snowmelt will peak in the spring and glacier melt in the summer, leading to pronounced flow maxima in rivers affected by them.
A significant time interval occurs between the start of rain and the beginning of the main rise in discharge on the hydrograph.
Types of runoff
Other computer models have been developed such as the DSSAM Model that allow surface runoff to be tracked through a river course as reactive water pollutants. Generation[ edit ] Surface runoff from a hillside after soil is saturated Surface runoff can be generated either by rainfall, snowfall or by the melting of snow, or glaciers. Condensation is the process of water vapor turning back into liquid water, with the best example being those big, fluffy clouds floating over your head. Montgomery County , Maryland implemented the first local government sediment control program in , and this was followed by a statewide program in Maryland in The resulting contaminated runoff represents not only a waste of agricultural chemicals, but also an environmental threat to downstream ecosystems. As it flows, the amount of runoff may be reduced in a number of possible ways: a small portion of it may evapotranspire ; water may become temporarily stored in microtopographic depressions; and a portion of it may infiltrate as it flows overland. Transient Factors - are those factors associated with precipitation input - size of storm, intensity, duration of rainfall, etc. Blair Stormwater Runoff Stormwater runoff is the runoff drained into creeks, bays, and other water sources after a storm. When the cloud droplets combine to form heavier cloud drops which can no longer "float" in the surrounding air, it can start to rain, snow, and hail And if your street was surrounded by houses with yards sloping uphill, then all the runoff from those yards and driveways would collect in a lake at the bottom of the street. Once the soil is saturated, runoff occurs. Antecedent soil moisture[ edit ] Soil retains a degree of moisture after a rainfall. In areas where there is no snow, runoff will come from rainfall. This result occurs when chemical use is excessive or poorly timed with respect to high precipitation.
Splash erosion is the result of mechanical collision of raindrops with the soil surface: soil particles which are dislodged by the impact then move with the surface runoff.
In this case the surface runoff may be considered to be a line source of water pollution to the receiving waters.
An example land use control program can be seen in the city of Santa Monica, California.
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