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This article is for the HEC-RAS Model. This model is no longer included in SMS.

The HEC-RAS model is now part of WMS – Watershed Modeling System.

HEC-RAS is a one-dimensional model for computing water surface profiles for steady state or gradually varied flow. HEC-RAS supports networks of channels and is capable of modeling subcritical, supercritical, and mixed flow regime profiles. HEC-RAS is able to model obstructions in the flow path.

The SMS interface to HEC-RAS includes tools for setting up the river networks and cross-sections as well as post-processing capabilities. SMS reads and writes the HEC-GeoRAS GIS import format.

The first step to using HEC-RAS with SMS is to setup the river schematic. For information on the tools and processes to setup a river schematic, see the 1D River Hydraulic Module. Specific attributes for a HEC-RAS simulation include:


  • Delete Simulation – The link SMS maintains to the current HEC-RAS simulation project file is deleted.
  • Material Properties... – SMS uses an Area Property coverage to map the roughness line properties to segments of a cross section. The cross sections store the material property ID's and in order for SMS to correctly associate a material ID with an actual roughness they must be defined using the Material Properties dialog.
  • Model Control...

Assigning Materials

Roughness values for HEC-RAS are tied to materials in SMS which must be assigned as line properties inside the cross-section database. To assign roughness values to the materials, choose HEC-RAS | Material Properties. Also, the property type that is being used for the material values must be specified in the model control dialog. This dialog is accessed by selecting HEC-RAS | Model Control from the menu.

Running HEC-RAS

Before loading the data into HEC-RAS, the simulation needs to be saved in HEC-RAS GIS export format. This is done by using File | Save As and changing the type to HEC-RAS GIS export format. The file can then be loaded into HEC-RAS by choosing File | Import From GIS Format inside the geometry editor. See HEC-RAS documentation for information about setting up boundary conditions and running the model.

Once the solution has been generated the data may be used in SMS for post-processing. The data must first be exported to GIS format from within HEC-RAS (Under File Menu choose Export GIS format). This file can be opened inside of SMS. Once this solution data has been loaded into SMS, plots can be generated from the solution. For information on how to use the post-processing tools that are found in SMS, see the 1D hydraulic Module document.

HEC-RAS Model Control

The HEC-RAS Model Control dialog allows applying roughness to a cross section databases. A list of available cross section databases will be on the left. On the right, the user can select if roughness will or will not be applied to a database.

Hec-Ras Model Control dialog

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