Wednesday, February 24, 2010

Wind-induced waves in reservoirs.

Written by Chris Goodell, P.E., D. WRE | WEST Consultants
Copyright © RASModel.com. 2010. All rights reserved.

Though HEC-RAS has no function for computing wave heights, its a fairly simply procedure that can be done external to RAS and incorporated into your design, or breach assumptions.

There are equations for wave heights and run up as a function of wind speed, reservoir depth, and fetch length. You simply gather some historical wind data that you can assign probabilities to. Assign a wind direction (to be conservative, you can assume the longest fetch length, unless the wind never blows that way), then compute wave heights and run up for different frequencies of wind magnitudes. Which frequency you design to (100-year, 50-year, etc) is up to you and your client.

Here’s a good place to start:

http://140.194.76.129/publications/eng-manuals/em1110-2-1420/c-15.pdf

Here are some other interesting links that might lead to additional information:

http://wave.oregonstate.edu/

http://www.wldelft.nl/cons/area/wds/im/wave-dynamic-structure.pdf

2 comments:

  1. How about if you are doing operational forecasting?

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    1. I guess you'd have to make some assumptions based on time of day/month/year to factor into your forecast predictions. But wind-induced waves may be too variable and uncertain to adequately include in a long term forecasting analysis. Just offering a guess, since I don't regularly do operational forecasts. What do you think?

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