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The runoff curve number (also called a curve number or simply CN) is an empirical parameter used in hydrology for predicting direct runoff or infiltration from rainfall excess. [1] The curve number method was developed by the USDA Natural Resources Conservation Service , which was formerly called the Soil Conservation Service or SCS — the ...
A runoff models or rainfall-runoff model describes how rainfall is converted into runoff in a drainage basin (catchment area or watershed). More precisely, it produces a surface runoff hydrograph in response to a rainfall event, represented by and input as a hyetograph. Rainfall-runoff models need to be calibrated before they can be used.
capture and retention of rainfall/runoff with various types of low impact development (LID) practices. SWMM also contains a flexible set of hydraulic modeling capabilities used to route runoff and external inflows through the drainage system network of pipes, channels, storage/treatment units and diversion structures. These include the ability to:
Unimpaired runoff calculations are used extensively in western United States states such as California for water resources management applications, particularly in the calculation of water year classifications and river indexes. The following is a list of some examples of use of unimpaired runoff calculations:
Correspondingly, the runoff footprint allows someone to calculate their baseline annual runoff and assess what the impact of ideal stormwater green solutions would be for their site. Since the passage of the Clean Water Act in 1972, the EPA has monitored and regulated stormwater issues in urban areas. Municipalities across the United States are ...
The infiltration capacity decreases as the soil moisture content of soils surface layers increases. If the precipitation rate exceeds the infiltration rate, runoff will usually occur unless there is some physical barrier. Infiltrometers, parameters and rainfall simulators are all devices that can be used to measure infiltration rates. [2]
Runoff routing is a procedure to calculate a surface runoff hydrograph from rainfall. Losses are removed from rainfall to determine the rainfall excess which is then converted to a hydrograph and routed through conceptual storages that represent the storage discharge behaviour of overland and channel flow. [23] [24]
The TWI has been used to study spatial scale effects on hydrological processes. The topographic wetness index (TWI) was developed by Beven and Kirkby [3] within the runoff model TOPMODEL. Although the topographic wetness index is not a unitless number, it is sufficiently approximate that its interpretation doesn't rely on its physical units.