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A unit hydrograph (UH) is the hypothetical unit response of a watershed (in terms of runoff volume and timing) to a unit input of rainfall. It can be defined as the direct runoff hydrograph (DRH) resulting from one unit (e.g., one cm or one inch) of effective rainfall occurring uniformly over that watershed at a uniform rate over a unit period ...
The SWMM 5.0.001 to 5.1.022 main components are rain gages, watersheds, LID controls or BMP features such as Wet and Dry Ponds, nodes, links, pollutants, landuses, time patterns, curves, time series, controls, transects, aquifers, unit hydrographs, snowmelt and shapes (Table 3). Other related objects are the types of Nodes and the Link Shapes.
Computing the total hydrograph Provided the value of A is known, the total hydrograph can be obtained using a successive number of time steps and computing, with the runoff equation, the runoff at the end of each time step from the runoff at the end of the previous time step. Unit hydrograph The discharge may also be expressed as: Q = − dS/dT .
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]
Building on the work of Horton, the unit hydrograph theory was developed by Dooge in 1959. [18] It required the presence of the National Environmental Policy Act and kindred other national legislation to provide the impetus to integrate water chemistry to hydrology model protocols.
A hydrograph is a graph showing the rate of flow (discharge) versus time past a specific point in a river, channel, or conduit carrying flow. The rate of flow is typically expressed in units of cubic meters per second (m³/s) or cubic feet per second (cfs). Hydrographs often relate changes of precipitation to changes in discharge over time. [3]
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The SELDM BMP-treatment module has provisions for stochastic modeling of three stormwater treatments: volume reduction, hydrograph extension, and water-quality treatment. In SELDM, these three treatment variables are modeled by using the trapezoidal distribution [ 32 ] and the rank correlation [ 33 ] with the associated highway-runoff variables.