In order to create a HEC-HMS model and compute a model analysis, the following project modeling stages must be completed:
Collect and organize data
The first step is to collect and organize the required data for analysis, such as rainfall data, stream gauge data, land use data, soil data, and topographical data. It is important to ensure that the data is accurate, consistent, and in the correct format.
Next, the user needs to set up the project in HEC-HMS by defining the watershed boundary, specifying the units of measurement, and setting the time interval for the simulation.
Define basin characteristics
The user then needs to define the physical characteristics of the watershed, such as land use, soil type, and topography. This information is used to calculate the runoff, which is a critical input for the model.
Create hydrologic model
The next step is to create the hydrologic model, which involves selecting the appropriate hydrologic method and defining the parameters of the model. Some of the supported hydrologic methods are SCS Curve Number, Green-Ampt, etc.
After creating the hydrologic model, it is important to calibrate the model using observed streamflow data.
Once the model has been calibrated, the user can compute the model analysis to generate the predicted hydrological response of the watershed. The output of the model includes a range of hydrological variables, such as rainfall, runoff, etc.
In GeoHECHMS, the Compute Analysis command is used to simulate the analysis for single or multiple scenarios (plan) of the model.
Follow the steps below to compute the analysis of the current scenario:
From the Analysis ribbon menu, click the Compute Analysis dropdown menu and then select the Current Scenario option. Alternatively, press the [F5] key.
The Compute Analysis – Current Scenario dialog box will be displayed.
The name of the scenario selected for analysis is displayed in the Scenario being analyzed read-only field. Once the analysis is performed, the elapsed analysis time will be displayed in the Elapsed analysis time read-only field.
Click the [Compute] button to start the analysis.
Once the analysis is done, the completion status will be displayed in the Analysis Progress read-only field as the Exit status. Note: If the Exit status is equal to 0, it means the analysis is successful. If the Exit status is equal to -1, it means the analysis has failed, and the corresponding modeling error(s)/warning(s) will be displayed under the Analysis Progress read-only field.
The user can click the [Copy to Clipboard] button to copy the computed analysis progress into the clipboard.
Similarly, the Multiple Scenarios command can be used to perform computations of multiple plans sequentially (one immediately after the other). Refer to this article in our knowledge base to learn more about multiple plan analysis.
Once the analysis is computed successfully, the user can evaluate the results of the simulation to ensure that they are reasonable and consistent with the observed hydrological conditions.
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