HydroCAD® Stormwater Modeling - Since 1986
Modeling Check Dams
What are Check-Dams?
Check-dams are partial blockages constructed across a channel, commonly constructed of broken rock. They can be used to reduce the flow velocity (in order to reduce erosion) or to create pooling (to enhance water quality.)
How are check-dams modeled?
The best approach to modeling check dams will depend on the prevailing flow regime within the channel:
Modeling check-dams as ponds
Like any pond, you need to specify storage and discharge characteristics for each check-dam:
Setting-up multiple check-dams
Before creating the ponds for additional check-dams, check the routing results for a single check-dam to make sure you're satisfied with the results. In most cases, you should start with the first (upstream) check-dam. You can then create clones of the first pond without having to re-enter all the data!
To create the first clone, drag the existing pond while holding down the Ctrl key. This sequence will create a second check-dam that is an exact duplicate of the selected node, but with a new node number. With HydroCAD 8.0 (and later) you can also also Copy the node to the clipboard and use Paste to create each clone.
To set the correct (lower) elevation for the cloned check-dam, right-click the new pond and select Raise/Lower from the menu. Enter a negative value indicating the elevation difference from the first to second check-dam. This will lower all the elevation values within the pond by the specified amount.
Finally, drag the primary outflow handle from the first pond to the clone, so that the flow will be routed to the second check-dam.
Repeat this process for each subsequent check-dam as required.
Handling tailwater effects
HydroCAD will issue a warning message if a potential tailwater dependency is detected between the ponds. If this occurs, you may need to select a tailwater-sensitive routing procedure, such as the Dynamic Storage-Indication method. In the absence of a tailwater warning, you should be able to use the default Storage-Indication procedure for pond routing.
Assessing the results
As always, remember to use the simplest model that will address your specific objectives. Although check-dams can be modeled in great detail, this may or may not have a significant effect on the overall results of your model. If in doubt, do a trial study to determine the effects and plan your model accordingly. Although properly constructed check-dams can be useful in controlling erosion, their effect on hydrograph routing may be minimal for all but the smallest rainfall events. For further details please see the general modeling tips.
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