Pros, Cons of Strategies to Reduce Flood Damage
Last week, I published a three-part series on the root causes of flooding. Some readers immediately started leaping to solutions. But different mitigation strategies each have pros and cons. That prompted the idea for this post. Flood control experts say that there are only three things you can do with excess stormwater:
- Store it.
- Convey it.
- Avoid it.
Within each of these high-level strategies, a range of tactical alternatives exists. Let’s look at them and their pros and cons.
Storage
Storage alternatives include detention basins, reservoirs and levees. They can trap excess water during storms and release it slowly after the storm passes.
PROS
- Can be multi-use. Dry detention basins can double as parks or sports fields. Large reservoirs can supply water and recreation.
- Can develop new habitat for fish. Plants and other filters can improve stormwater quality.
- Can be a community amenity or economic feature.
- Easy for public to understand how they work.
CONS
- Requires extensive rights-of-way, which can be costly, time consuming and politically difficult
- Usually involves destruction of the original habitat/land cover, and sometimes even whole neighborhoods
- Requires constant maintenance in perpetuity
- Expensive and difficult to retrofit and/or repair, as we’re seeing with the Lake Houston Dam gates.
Conveyance
Increasing conveyance usually involves: channel widening/modifications; concrete-lining to accelerate throughput; straightening channels to reduce travel time; or creating new, supplementary pathways such as storm tunnels.
PROS
- Proven to be very effective.
- Relatively simple concept and easy to understand.
CONS
- Can require extensive right-of-way acquisition and relocations of homes/businesses.
- Can destroy habitat along channel banks.
- In urban areas, modifying bridge crossings and moving utility lines adds significant expense. For instance, since 2000, we have spent approximately half a billion dollars to widen Brays Bayou and rebuild 30 bridges across it.
- Can move the flooding problem from one location to another.
Avoidance
The avoidance strategy involves several different strategies: building on high ground far from rivers; elevating structures; conserving floodplains; implementing better building codes and more.
PROS
- Prevention is always less expensive than correction and usually the least expensive option.
- Floodplain conservation can result in dual-use opportunities (i.e., parks/trails). From a developer’s point of view, homes near green space usually fetch higher prices.
- Floodplain preservation is low/no maintenance. Nature heals itself.
- Structure elevation can significantly reduce risk of flooding, but it’s much harder and more costly after flood damage than during original construction.
CONS
- New regulations/building codes can be difficult to get approved. FEMA estimates that adoption of hazard-resistant building codes saved $32 billion during the last 20 years and could save another $132 billion by 2040. But Texas hasn’t updated its building codes since 2012.
- Floodplain acquisition can be very expensive. And doing it before surrounding land is developed means the Benefit/Cost Ratio probably won’t qualify for federal assistance.
- Pier-and-beam foundations are not as popular as slab-on-grade foundation for single-family, residential development. They’re also usually more expensive.
Finding the Best Alternative
No one answer exists for every situation. To find the optimal solution, engineers study multiple alternatives and weigh their costs against the benefits. Then comes the hard part – finding the money to build them. No one budgets for disasters. We typically deal with disasters after the fact.
Altogether, projects such as these can take a decade or more to develop. And during that time, flood risk can be a shifting target because of upstream development and revisions to rainfall probability statistics. Personally, I’m a big advocate of caution when it comes to living near water. Your best bet is to avoid flooding.
Posted by Bob Rehak on 12/5/2023 based on information from leading hydrologists
2289 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.