In April, Harris County Commissioners directed the County Engineer and Executive Director of the Flood Control District to recommend minimum drainage standards for all communities in Harris County. The idea: to protect the County’s $2.5 billion flood bond investment. Lax standards in one place could undermine mitigation projects in another.
In May, the two executives came back to Commissioners Court. Here is what they recommended. These ideas apply to all cities within Harris County as well as those outside the county, but which drain into Harris County.
The recommendations must be adopted within municipal boundaries AND extraterritorial jurisdictions by December 31, 2020, IF the municipalities in question wish to partner with the county on any flood bond projects. That’s a $2.5 billion stick the county wields and that’s a powerful incentive.
Here are the recommendations:
- Use Atlas 14 rainfall rates for sizing storm water conveyance and detention systems.
- Require a minimum detention rate of 0.55 acre feet per acre of detention for any7 new development on tracts one acre or larger in size. However a single family residential structure and accessory buildings proposed on an existing lot is except from providing detention.
- Prohibit the use of hydrographic timing as a substitution for detention on any project, unless it directly outfalls into Galveston Bay.
- Require no net fill in the current mapped 500-year flood plain, except in areas identified as coastal zones only.
- Require the minimum Finished Floor Elevation (FFE) of new habitable structures be established at or waterproofed to the 500-year flood elevation as shown on the effective Flood Insurance Study.
County Has Hired Engineering Firm to Identify Specific Changes
These are higher-level recommendations than those the County asked the City of Houston to make as a condition for the purchase of the Woodridge Village property in Montgomery County. The reason: The list provided to the City pertained to actual regulations that needed to change as a result of these high-level directives.
The County has hired an engineering firm, EHRA Engineering, to assist communities in evaluating and updating their policies and ordinances at no cost to the community.
To help ensure participation, no partnership projects, including flood control or county roadway projects, will be constructed after December 31, 2020, in communities that have failed to implement these minimum standards. Projects started before that date may be continued only if communities are actively working to update their criteria.
Fix Flooding First Initiative About to Be Unveiled
The letter, signed by John Blount, Harris County Engineer, and Russ Poppe, Executive Director of Harris County Flood Control, also hints at something called a “Fix Flooding First” Initiative scheduled for roll out later this month. A Google search for “Fix Flooding First” turned up an initiative in Charleston, SC, but nothing in Harris County yet. Stay tuned.
Exact Text of Language Approved by Commissioners
Below is the exact text of the language in the two page letter unanimously approved by Commissioners and the County Judge.
Reference to Hydrograph Timing Explained
The reference to hydrograph timing in the letter above refers to the Beat-the-Peak exemptions that Montgomery County offers to developers as an alternative to detention ponds. If developers can prove that their runoff will reach a river or stream BEFORE the peak of a flood, they can avoid building detention. The theory is that they aren’t adding to the peak.
Of course, that only encourages developers to get water to a river faster in a flood. That reduces the time of accumulation and adds to flooding downstream. It’s the exact opposite of what should happen to reduce flooding.
Using Beat the Peak, the 2200-acre Artavia development near the West Fork San Jacinto got away without building any detention ponds. Look out below!
Posted by Bob Rehak on 6/8/2020
1014 Days after Hurricane Harvey