Search results
Results from the WOW.Com Content Network
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 ...
Input parameters required by this method include the maximum and minimum infiltration rates, a decay coefficient that describes how fast the rate decreases over time, and the time it takes a fully saturated soil to completely dry (used to compute the recovery of infiltration rate during dry periods). Figure 2. SWMM 5's QA/QC Master Example Network.
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.
[1] [13] [30] [31] Structural BMPs are defined as the components of the drainage pathway between the source of runoff and a stormwater discharge location that affect the volume, timing, or quality of runoff. SELDM uses a simple stochastic statistical model of BMP performance to develop planning-level estimates of runoff-event characteristics.
[8] The runoff coefficients for different surface types on a site can be multiplied with the area for each surface along with the annual precipitation to generate a rough runoff footprint. If the runoff coefficient and areas of proposed stormwater green solutions like rain gardens and bioswales for the site are known, the reduction in overall ...
It is based on the percentage runoff equation: P R = 0.829 P I M P + 25 S O I L + 0.078 U C W I − 20.7 {\displaystyle PR=0.829PIMP+25SOIL+0.078UCWI-20.7} where PR is percentage runoff, PIMP is percentage imperviousness of the catchment, SOIL is the soil index and UCWI is urban catchment wetness index.
The rational planning model is a model of the planning process involving a number of rational actions or steps. Taylor (1998) outlines five steps, as follows: [ 1 ] Definition of the problems and/or goals;
Surface runoff is defined as precipitation (rain, snow, sleet, or hail [5]) that reaches a surface stream without ever passing below the soil surface. [6] It is distinct from direct runoff, which is runoff that reaches surface streams immediately after rainfall or melting snowfall and excludes runoff generated by the melting of snowpack or ...