Scenario Management with HEC-RAS


In this tutorial, we’re going to learn how to
perform scenario management in GeoHECRAS. One of the powerful features of the
Army Corps’ HEC-RAS software is its ability to support multiple
geometry files as well as multiple flow files. The software does this through
its use of plans. What GeoHECRAS has done is made management of multiple plans much simpler for the user to perform. It makes it much easier for
the user to switch between different plans. In this project, there is both an
existing conditions plan and another plan containing a new bridge for a
proposed roadway crossing. From the left side on input ribbon menu we can switch the plan which contains
the proposed roadway crossing if we look at the Scenario Manager
dialog box we can see that we can make copies of
existing geometries and flows. In addition, we can create new plans or what GeoHECRAS refers to as scenarios by selecting the geometry and flow files to use. All this allows us to manage multiple plans more easily. Let’s take a look at an example exercise
utilizing this. For these two plans or scenarios we are going to analyze both
of them and then compare their results. To do that switch to the Analysis ribbon menu. Then, from the Compute Steady menu item select the dropdown menu and
choose multiple scenarios. This will display a dialog box allowing us to select which multiple plans to
simultaneously analyzed using HEC-RAS. From this dialog box, we will
choose to analyze both the Existing Geometry and Proposed
Roadway Crossing plans. To analyze these plans
Click the Compute button. The HEC-RAS computations
will then run twice once for each plan After the computations have completed,
click on the Close button to close the dialog box. Next, switch to the Results ribbon menu. From there, select Profile
Plot menu command. This will display the profile plot results
window for the current plan. Click on the Profiles dropdown entry
and turn off the 25-year and 500-year flows so that we are only
looking at the 100-year flow. Now, right-click on the profile plot and
from the displayed context menu select select Land Marks and then River Stationing. This will display the cross section
locations on the profile plot Next, we’re going to turn off some
of the profile plot output allowing us to get a clearer
view of the results. Again, right click on the profile plot and from the displayed context
menu select variables. This displays a dialog box that allows us to control which variables
are to be displayed on the profile plot. In this dialog box, we are
going to uncheck the Filled-in Water Surface and
Energy Grade Elevation options. Keep in mind, though, you typically want
the Energy Grade Elevation option turned on when doing a bridge analysis. We are also going to uncheck the
Critical Depth Elevation option. Next, click OK to close the dialog box. And, just like that, we can now see the
100-year water surface profile for the proposed roadway crossing. Next, we are going to display the results for the existing conditions scenario in order to compare the results. To do this, right-click the profile plot window and from the displayed context menu select plans This will display a plan
selection dialog box. Select the Existing Geometry plan and
then click OK. Now, we can see both plans in the Profile Plot. To better identify which plan
each profile line corresponds to click on the profile item listed
in the plot legend. When we do that, the selected profile is
highlighted on the profile plot Taking a look at this profile plot comparison we can see that the proposed roadway
crossing bridge opening is not sized significantly large enough to
handle the 100 year flow We will have to go back and reiterate
the bridge opening design design to handle this flow. We can see from this tutorial how to use
Scenario Manager to manage multiple plans or what GeoHECRAS refers to as scenarios for doing HEC-RAS comparison analysis.

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