You wrote: “Having practiced drainage engineering in the Houston region for 43 years , I feel free to discuss floods...”
In Katrina, the dikes failed, flooding New Orleans, as I understand it.
What about Houston? Is it just a case of too much rain for any system to handle, or were there ways to keep the city from flooding that weren’t implemented in the past?
Just curious what insights you might have. I’m not trying to stir the pot. I actually suspect it’s just too flat and large an area to be able to shed that much rain without flood damage occurring, but am wondering if that’s the case.
And city with the word Bayou written within city limits can flood easily.
Yeah, but the dikes failed because the people living immediately behind them didn't allow the dikes to be built as the Corps of Engineers wanted.
The original design was the concrete wall, which was supposed to be backed by an earthen berm. The folks whose property would have been condemned to build the berm pissed and moaned enough that the CoE just built the concrete part.
When the hurricane tide began to splash over the top, it washed out the footing behind the concrete wall, which then collapsed "inwards".
If the earth berm had been present, the oversplash would have simply flowed smoothly down the slope of the berm, dissipating the gravitational energy that caused the washout.
The standard design for development requires finish floor slab elevations to be 18-inches above the FEMA designated 100-year frequency storm water surface elevation.
New development requires the developer to provide storm water detention volume equal to one acre-feet for each acre of development. The 100 year frequency rainfall per 24-hours is 12 inches. Parts of Harris County had 30-inches of rainfall in only two days!
This approaches likely a 500 year frequency event (catastrophe)!!