Our office ran into an unusual modeling situation recently. Here is a description of the situation: The project is a dam breach model, and the spillway for the dam diverts water to an adjacent basin. The spillway is actually more like a canal (the spillway reach) that runs about a mile until it empties into the adjacent […]
Just ran into an interesting phenomenon. I was running a dam breach model with fairly typical breach parameters and piping failure mode. After the peak of the breach hydrograph, there appeared a mysterious “spike” as shown in the figure below. This happens to be right at the same time the flow through the developing breach […]
This is a common question. It’s often desirable to have a table of timing for peak stages and flows for dam breach models. This allows you to track the arrival of the flood wave at all locations downstream of the dam. However, the typical output plots in HEC-RAS are not very helpful in providing this […]
Last Friday, Condit Dam, on the White Salmon River was intentionally breached by blowing a hole in the spillway as part of a plan to remove the dam and restore the river to its natural state. Although the actual breaching of the dam was not all that spectacular (i.e. the dam itself wasn’t destroyed-only a […]
I was recently asked my opinion on a good way to model the following dam breach event: “I …recently completed three consulting projects where I simulated the breach of three proposed coal slurry impoundments. The permitting agency required a RAS model of an “instantaneous” hypothetical breach (over full depth, almost 80 ft for one of […]
By using the Mixed Flow Regime option for Unsteady Flow Analysis, RAS can better handle transitions from subcritical to supercritical flow. This option should be utilized only after determining that a mixed flow situation exists, which requires judgment from the modeler. One application where this could be particularly useful is dam breach modeling, or any […]
Written by Chris Goodell, P.E., D. WRE | WEST ConsultantsCopyright © RASModel.com. 2010. All rights reserved.I would appreciate any feedback from you all on this topic. It’s something I’ve been thinking about for a while now. My biggest concern with the current practice of dam breach modeling is the overwhelming uncertainty associated with dam breach […]
Written by Chris Goodell, P.E., D. WRE | WEST ConsultantsCopyright © RASModel.com. 2010. All rights reserved.This is a summary from a paper (Goodell,Christopher;Wahlin, Brian. “Dynamic and Level Pool Reservoir Drawdown: A Practical Comparison for Dam Breach Modeling.” 33rd IAHR Congress Proceedings, Vancouver Canada, 2009) on level pool versus dynamic reservoir drawdown for dam breach modeling. […]
Written by Chris Goodell, P.E., D. WRE | WEST ConsultantsCopyright © RASModel.com. 2010. All rights reserved.Some questions and answers related to dam breach modeling in HEC-RAS… Question. The Sunny Day model has a consistent water surface elevation from the very start of the model – it only decreases once the breach occurs. How is HEC-RAS […]