A study has shown that one dollar spent on avoiding damages can save five dollars later on flood mitigation. So, as we focus on flood mitigation, we must not forget flood prevention.
Almost half the watersheds in Harris County originate in surrounding counties.
If upstream communities do not implement regulations that help prevent flooding, downstream communities will face increased flood risk regardless of how much money they spend on flood mitigation.
Loopholes and Omissions in Regs that Increase Flooding
In my research, I’ve discovered loopholes or omissions in regulations that, if addressed, could help reduce flooding. These will be controversial. But they deserve debate.
- Require permits for clearing and grubbing land. And require wetlands determinations before issuing these permits. Not all jurisdictions do. So, unscrupulous developers can clear land and fill wetlands. Then, when a developer applies for a construction permit, there’s no proof during the environmental inspection that wetlands ever existed.
- Going forward, require storm sewers large enough to prevent rainfall from going higher than the tops of curbs. Many places already do to reduce street flooding and home damage.
- Maintain ditches. Get surrounding counties to maintain ditches, i.e., HCFCD. Many don’t have organizations to do that. Some even give adjoining property owners the responsibility – something clearly beyond their capability. We also need to create dedicated funding streams for maintenance that cannot be diverted. Finally, create an online map that shows what maintenance will happen when and where, so citizens can report problems when they see them.
- Follow the Association of State Floodplain Managers’ recommendations for documenting “No Adverse Impact” in drainage studies. They’re more stringent than most local regs. They address topics such as water quality, erosion and sedimentation, not just water levels.
- Analyze “depressions lost” through development, i.e., ponds. Require mitigation of that lost detention capacity. Again, since most counties do not require permits or inspections for clearing and grading land, there’s often no way to account for these in drainage impact analyses.
- Require drainage analyses to examine impacts on upstream and downstream properties. Don’t just estimate the amount of runoff within a parcel’s boundaries before and after development. High detention pond walls can push water onto adjoining properties.
- Make factors in flood studies such as Manning’s Roughness Coeffcients and soil curve numbers less subjective. Require engineering documents to show how coefficients were selected. Establish minimum values that force developers to plan for worst case scenarios. Require a sensitivity analysis that prohibits fudging the numbers.
- Prohibit the outsourcing of the County or City Engineer function to companies that also do other business within the jurisdiction. It’s a conflict of interest. We have seen examples of companies investigating themselves after hundreds of homes flood.
- Require mitigation to be constructed before any structures are permitted. Parallel development can increase runoff before ponds are ready to accept it.
- Encourage the use of nature-based flood mitigation, i.e., bio-swales and the use of vegetation in ponds that encourages infiltration. The Corps, ASFPM and FEMA already do this.
- Break up counties into at least four Atlas-14 zones. Montgomery County uses one average for the entire county. But an average increases costs on areas that receive less rain than the average rainfall. It also increases risks in areas that receive more than the average.
- Include “erosion” when proving “No Adverse Impact“. Require field visits that document pre-existing erosion. Developers must ensure they will not increase erosion potential and that and no new erosion areas will be created. Erosion increases sediment build up that can decrease conveyance downstream. It also decreases water quality and maintenance intervals; and increases mitigation costs such as dredging. ASFPM says, “An adverse impact can be measured by an increase in flood stages, flood velocity, flows, the potential for erosion and sedimentation, degradation of water quality, or increased cost of public services.”
- Adopt new post-Harvey flood maps. Some areas have fought Allison maps for 15 years. Other areas still base their maps on data from the 1980s. This benefits builders and harms buyers. People don’t see their true flood risk. Commissioners sometimes fight updates because they fear it will harm growth.
- Avoid competing for new development with lax regulation or enforcement. It will raise mitigation costs for everyone in the long run.
A Matter of Self-Preservation
No matter how much money we spend on flood mitigation, if the amount of inbound water constantly increases, we won’t reduce flooding. It’s like trying to go up the down escalator.
But what’s in it for upstream communities? The answer is simple. Many are already starting to flood. Everybody lives downstream from somebody else. Without common sense flood regulations, even those that aren’t flooding yet will flood soon enough. This isn’t about increasing costs, though some will argue that. It’s about self-preservation.
Posted by Bob Rehak on 1/22/2022
1607 Days since Hurricane Harvey
The thoughts expressed in this post represent opinions on matters of public concern and safety. They are protected by the First Amendment of the US Constitution and the Anti-SLAPP Statute of the Great State of Texas.