modeling a house deck

[RogerL]

I have a steady-state RAS project where in a river there is a house with a deck that extends into the cross-section about 10 feet (maybe 10% of the section width). Since the deck is elevated the water only hits the deck at the upper end of the channel flow range so I cant use obstructions since they fill in the section from below.

I can use a cross-section LID and only have it extend a little into the flow, is that an acceptable use of a cross-section Lid? I did try it and the velocity seemed to go up which may just represent the narrowing of the section but I wanted to see if using a lid was an acceptable solution. I could just regrade the actual cross-section data to include the deck but that is more work. Wondering about the pros and cons of these (or other) options in RAS.

Thanks, R

[Chris G.]

Roger-

I think a cross section lid is a good way to simulate the effects of the deck. You could also try using a bridge, which would allow you to add in deck piers (if you have them) but make sure you use the energy equation for your high flow modeling approach. Either method (lids or bridge with energy method) should give similar results. The best way to gage the effect is to see what kind of rise in water surface elevation you get just upstream of the deck for both existing and proposed conditions. Good Luck.
Chris
@RASModel

[Anonymous]

Thanks Chris.

Is there a specific way to specify the energy equation for my high flow modeling approach? i.e. is there a window in the model menu somewhere that I need to click to specify? and for both lids and bridges or just normal cross-sections?

thanks, Roger

[huesmann]

When you enter your bridge data, click on the Bridge Modeling Approach button on the left and select Energy (Standard Step). (This applies only to modeling it as a bridge.)

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