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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 x,y coordinate file is only necessary if there are not existing x, y coordinates on the D1 line of the SWMM 4 Extran input data[ set. The command File=>Define Ini File can be used to define the location of the ini file. The ini file will save the conversion project input data files and directories. The SWMMM3 and SWMM 3.5 files are fixed ...
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 Hydrologic Modeling System (HEC-HMS) is designed to simulate the precipitation-runoff processes of dendritic drainage basins.It is designed to be applicable in a wide range of geographic areas for solving the widest possible range of problems.
The five output files that are created for every model run are the output documentation, highway-runoff quality, annual highway runoff, precipitation events, and stormflow file. If the Stream Basin or Stream and Lake Basin output options are selected, then the prestorm streamflow and dilution factor files also are created.
Example 1 The linear-reservoir model (or Nash model) is widely used for rainfall-runoff analysis. The model uses a cascade of linear reservoirs along with a constant first-order storage coefficient, K , to predict the outflow from each reservoir (which is then used as the input to the next in the series).
Analysis of the relationship between precipitation intensity and duration and the response of the stream discharge are aided by the concept of the unit hydrograph, which represents the response of stream discharge over time to the application of a hypothetical "unit" amount and duration of rainfall (e.g., half an inch over one hour). The amount ...
Plotted on a graph, these data from the unit hydrograph for that storm, which represents the runoff added to the pre-storm baseflow. To forecast the flows in a large drainage basin using the unit hydrograph method would be difficult because in a large basin geographic conditions may vary significantly from one part of the basin to another. This ...