Before You Watch

In this lecture, we will do additional evaluations with HEC-RAS exploring the effects of channel lengths and resolution in the channel on water surface profiles. We will also look at evaluating a mixed flow regime problem with HEC-RAS and look at how HEC-RAS develops a hydraulic jump in the water surface profile for these types of problems. Lastly, we will cover information on flood frequency and how to determine the return periods associated with different flows using statistical methods.

How does the channel length and channel resolution affect the water surface profiles for an M2?
How do we obtain a hydraulic jump in HEC-RAS with a mixed flow regime?
How do we determine the return periods and flow rates from given USGS data for a flood study?

Video

Download/print PDF lecture slides: flood_frequency_hecras.pdf

Key Takeaways

Now, revisit the above questions with the lecture material and your assigned reading. In this week, you should know how to use HEC-RAS to see: 1) how different resolutions affect water surface profiles; 2) the effects of channel resolution on the water surface profiles; and 3) the effects of the mixed flow regime in a water surface profile. Lastly, you should know how to use the lognormal distribution to find flow rates based on the return period of a storm.