Beyond “Flood Zones:” Time to Personally Floodproof Homes and Businesses

“We’ve had heavy back-to-back rainfalls before. So I don’t think it’s the new normal. When you talk about a 1 percent chance of happening [in a given year], it can happen. You can flip a coin and have it come up heads 10 times in a row. It’s just, statistically, it shouldn’t happen, but it can.”

— Mike Talbot,  then Executive Director of the Harris County Flood Control District (2016)

“Floodproofing needs to be routine for Houston area property owners based on their individual perception of risk. Each property owner would consider their elevation in the landscape, distance from nearby bayous and channels that can overflow, and whether their home or business sits on concrete pads or pier-and-beam foundations.”

— Barry Klein (below)

I live in a 100-year old house in Houston. I avoided the recent flood (and those before Hurricane Harvey) thanks to my higher elevation north of Buffalo Bayou and two-foot piers under my house. So not only location, but floodproofing, can be a first line of defense to keep the first responders away.

In the months after Allison, which was called a 500-year flood, brought massive flooding to Houston in 2001, the Harris County Flood Control District released a booklet of more than 30 pages, Off the Charts, to explain to stunned Harris County citizens why their taxes had bought them so little flood protection. It is actually an excellent primer.

On the penultimate page, we find this statement:

“It’s impossible to control the extraordinary forces of nature.”

Since then the county has spent hundreds of millions of dollars more trying to control flooding, or at least reduce the risks of it. But big flood events continue. Some are calling Harvey a thousand-year event. The District is very much under scrutiny.

Mike Talbot’s View

Mike Talbot, quoted above (interview) made several enlightening statements. Since it was published, Talbot has retired from the Harris County Flood Control District. He spoke twice to my group, the Houston Property Rights Association, a talk I remember well.

Talbot, who seems to be a straight-shooter, described a flood protection system based on the so-called 100-year flood event, which can happen often. And he speaks of “extreme rainfall events” that we get occasionally.

So flooding is a given. What Talbot does not make clear is that the risk will vary depending on where you live on the landscape (which is not flat), how close you live to a bayou, and the particular characteristics of an individual storm, which are never predictable.

Talbot notes that developers have to comply with “two inch thick” criteria manuals. So development is not “unchecked”. Of course, sometimes the manuals are not followed. But, in any event, the system is not designed to stop all flooding.

On the Prairies

The following is an important statement from Talbot that needs to be investigated. He implies that the prairies cannot absorb much water. Elsewhere, I have seen him refer to a report by his agency that concluded the clay and sand mixture in our prairie soil does not allow for much absorption:

A lot of the ink that has gone down after [the Tax Day flood] has been given to critics with an agenda. When somebody wants to claim that, “well, it’s because we’re paving over all the wetlands and these magic sponges out in the prairie would have absorbed all that water,” [that’s] absurd.

[During the recent floods], the heaviest rain fell on the prairie, and the prairie did some good, but then it flowed off of the prairie, and all the runoff from the prairie is what flooded that development.

Some people assert that the prairie, once covered with high grass with 10-foot-long roots, would be absorbing the storm waters if it had not been replaced by impervious development. But we have clayey soils in our area. At least one report by settlers traveling inland spoke of walking for days through west Harris County with water to their knees after major rains. So, the absorbent qualities of the Gulf Coast prairie is probably exaggerated.

More Government Planning?

Many people, such as the editorial board at the Houston Chronicle, are pointing to global warming and climate change to argue that higher taxes are needed for expanded infrastructure to accelerate drainage, and that planners should not look just at past flooding to determine flood zones. They argue that local governments need to draw vastly bigger flood zones, in which development would be banned to accommodate the projected bigger, wetter storms.

I personally am dubious that wider, deeper bayous, combined with flood zones designed to accommodate the yet unseen 2,000- or 5,000-year flood (how big are we talking here?), will protect us from flooding. It would all be based on computer modeling, which is subjective and should never be trusted. (The “spaghetti models” shown on TV during the run-ups to Harvey and Irma are evidence of that. Each strand of spaghetti is the product of a team of modelers making hundreds of assumptions which result in different scenarios.)

Floodproofing

In recent months I have decided that floodproofing needs to be routine for Houston area property owners based on their individual perception of risk. Each property owner would consider their elevation in the landscape, distance from nearby bayous and channels that can overflow, and whether their home or business sits on concrete pads or pier-and-beam foundations.

The new routine for gulf coast dwellers would include sealers and waterproof paint, flood bags and flood gates, all combined with back up pumps that can protect from moderate flooding (often times flooding is only a few inches of water). Additionally I am hopeful that temporary exterior structures can be devised that would deal with hydrostatic and hydrodynamic pressure on windows and exterior walls of homes when water gets above the level of a foot or two. Renters can look for units above the ground floor and may have to pay a premium for the extra measure of safety. Flood insurance too should be part of everyone’s plan. 

The flood control district can help people decide their level of risk by erecting poles around the county showing the level of flooding in our landmark storms. I have it on good authority that The Clear Lake area had such a pole a few years ago until members of the real estate industry succeeded in having it removed.

This firm is in the business of making flood proofing products.

Better Next Time

A few county buildings downtown were flooded by Harvey. Why did the county not use its superior knowledge of the risks of flooding to take extra precautions, such as having more “submarine doors” in the tunnel system to contain the flooding? I recently walked several of those tunnels and found only one such door, which surprised me. The Med Center has them, as well as other kinds of flood barriers now, and so do many commercial buildings in the downtown.

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Related Links

Off the Charts

Don’t blame sprawl for Houston’s floods.

Mike Talbot explains Houston drainage and flooding (note the videos):

http://www.houstonchronicle.com/news/houston-texas/houston/article/After-35-years-Mike-Talbott-leaves-flood-control-9179726.php

http://www.houstonchronicle.com/local/explainer/article/The-trouble-with-living-in-a-swamp-Houston-7954514.php?t=4ee936dcd1438d9cbb

Soil Survey of Harris County

See especially page 5: The soil is “moderately permeable to slow permeable”

What lessons will Houston-area officials learn from Harvey? History gives us a clue.