Why Worry about Flooding in a Drought?

This morning, Harris County Meteorologist Jeff Lindner sent me an email that caused me to worry. It wasn’t about flooding. It was about our dismal rain chances for the next two weeks.

His email also contained a map of all the outdoor burn bans in effect across the state. Of 254 counties in Texas, 133 currently ban burns.

Texas’ drought monitor website shows that as of 6/15/22:

• 91.4% of the state is abnormally dry.
• 80% is in moderate drought.
• 64% is in severe drought.
• 42.5% is in extreme drought.
• 16.8% is in exceptional drought.
• Drought affects 19.3 million people in Texas.
• We’ve had the 8th driest year to date in the last 128 years.

So why worry about flooding now? Here are my top three reasons. You may have others.

Repetitive Cycles

Previously, Lindner sent a separate email comparing 2022 with 2011, the start of our last major drought. Within it, he said, “While it is easy to compare heat and drought to other instances in the past, our current heat and drought is far from what this region and state went through in 2011. Rainfall has been much more plentiful this spring than in 2011, and while some of the temperatures may be similar, the intensity of the heat thus far this year is not to the level of 2011. There are some similar comparisons to drought and heat of the summers of 1998, 1988, and 1980.”

The drought years caught my eye. I asked him if there was a reason for the relative regularity.

He replied, “Generally speaking … a lot of our heat/drought and floods correlate with El Niño and La Niña in the central and eastern Pacific. La Niña years tend to favor heat and drought in the southern plains, though not always. 2011 was one of the strongest La Niñas on record since 1950. On the other hand, El Niño tends to favor cooler and wetter periods. Many of our big floods have happened in El Nino years.”

Knowing that floods follow droughts in regular cycles (and that floods could happen at any time from a stray tropical storm), you never want to be lulled into a false sense of security about flooding.

Complacency

Droughts can create complacency about flooding. People forget the pain. Political pressure and attention shift to more pressing problems, such as crime or Covid. And after two years of lockdown, people are ready for vacation, even with $5/gallon gasoline! But like the parable of the Three Little Pigs, people who live in SE Texas can never become complacent about flood threats. Flooding is our #1 natural disaster.

After Harvey, flooding floated to the top of Houstonians’ concerns. We launched massive mitigation efforts. But do you know where they stand today?

• Many, but not all jurisdictions passed stricter development regulations. Do you know which still have to adopt new rules?
• We launched massive flood studies. But some counties are still working off flood map data from the 1980s.
• The TCEQ adopted new Best Management Practices for Sand Mines in the San Jacinto watershed. But they failed to include minimum setbacks from rivers for mines.
• The SJRA added two downstream directors to its board. Do you know how many downstream representatives remain?
• The Lake Houston Area had some of the worst flooding. But we currently have only 0.0008% of all the active flood-bond construction contracts.
• The San Jacinto Master River Basin Study identified 16 potential areas for upstream floodwater detention reservoirs costing an estimated $3.3 billion. But all had low benefit/cost ratios. So there’s no guarantee any will be funded. None has been yet.
• Adding additional floodgates to Lake Houston was originally intended to be a 3-year project. It started in August 2019. It’s still in engineering.
• Upstream developers continue to use hydrologic-timing studies and dubious soil tests that exaggerate the rate of infiltration to avoid building detention ponds.
• SJRA started a program of lowering Lake Conroe to reduce downstream flooding risk during the rainiest months of spring and hurricane season. But how many people know the policy was modified this year to raise the minimum levels?
• FEMA, HUD and the GLO sent billions of dollars to Houston And Harris County for disaster relief and flood mitigation. Do you know how much has actually helped people?

Apathy when we’re not flooding could sow the seeds of the next big flood. Vigilance is the price of freedom…from flooding, too.

Unintended Consequences

Most research on hydrological risks focuses either on flood risk or drought risk. However, floods and droughts are two extremes of the same hydrological cycle. They are inextricably linked. One follows the other like night follows day.

Strategies targeted at one may create unintended consequences for the other. So, it is important to consider interactions between these closely linked phenomena.

For instance, drought can decrease groundwater, kill ground cover, and increase erosion. Erosion can create sediment dams that contribute to flooding. We knew giant sand bars like the one below were likely to form in the headwaters of Lake Houston since the 1990s. But our mayors at the time refused to dredge. Even though there was no imminent threat, that turned out to be a costly decision.

I could list more examples. But you get the idea. Even though another Harvey is not lingering offshore at the moment, how much have we really learned? How much have actually improved conditions that increased flood risk during Harvey?

Please stay in the fight to make our homes, businesses and community safer.

Posted by Bob Rehak on 5/17/22

1753 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.