As search and recovery efforts remain ongoing in Kerr County, residents of Maverick County on the border are now dealing with dangerous flooding.
Officials issued a mandatory evacuation Monday evening for some areas because of an imminent flooding risk, including parts of Eagle Pass along the Rio Grande. Residents downstream are keeping an eye on the river. The National Weather Service also issued a flood warning for the Rio Grande in Laredo through Thursday evening.
Laredo officials are coordinating their response with authorities in Mexico. Minor flooding could affect some of the international bridges in that area.
In Central Texas, at least 132 people have died from catastrophic flooding in Kerr County. The number of missing is at about 100. Authorities say it’s hard to get an exact count because so many were visitors celebrating the Fourth of July holiday along the Guadalupe River.
During that same week, there were four major rare rainfall events in several other parts of the United States.
John Nielsen-Gammon, the Texas state climatologist, said it is not unheard of to have multiple “100-year floods” or “1,000-year floods” in the same year.
“We certainly expect more than one in a given year because those odds refer to individual locations and so, you know, separate storms will trigger that threshold in different locations,” he said. “But we also have seen a trend in extreme rainfall intensity across basically the eastern two-thirds of the United States. And because of that, the odds are probably about twice as high as the official statistics would indicate.”
Those terms — 100-year flood or 100-year floodplain — refer to the probability that flooding will occur in any given year, Nielsen-Gammon said.
“A 100-year flood would be a flood that has a 1 in 100 chance of happening in a given year,” he said. “Same thing for 100-year rainfall amounts and so forth.”
» MORE: Expert cautions on rebuilding within Guadalupe River floodplain
Nielsen-Gammon said climate change isn’t the only factor causing these floods, but it is making them more extreme.
“We’ve seen catastrophic flooding in the Hill Country without climate change, so it’s definitely not being caused by climate change,” he said. “Climate change is more of an enhancement factor at this point, making intense rainfall maybe 10 to 15% greater in magnitude than it would have been otherwise.
“But the rainfall itself was basically a combination of factors. We had remnants from one tropical storm. We had moisture from another hurricane. And everything was set up to allow for heavy rain to fall in just one spot for several hours. Unfortunately, that spot was the headwaters of the Guadalupe River.”
Nielsen-Gammon said he is working on an analysis right now to come up with more realistic floodplains based on the current climate.
“We’re doing an analysis sponsored by the State of Texas right now to look at those extreme rainfall trends within Texas and come up with numbers that are more realistic for the present-day climate,” he said. “And also make it possible to look forward into the future climate to ensure that if you want to, you can build things that are going to be robust and not flood for several decades as conditions potentially become more extreme as the climate warms.”
» MORE: Complete coverage of deadly flooding in the Texas Hill Country
It is also possible for people to prepare for flooding and make a safety plan if their area experiences a flash flood.
“If you don’t know where your floodplain is nearby, you should look it up. That information’s available on the FEMA website,” he said. “You can zoom in on the floodplain maps of your own location, see where the floodway is, 100-year floodplain, 500-year floodplain … those are underestimates of the actual risk of flooding.
“Make sure if you’re in danger, you know a route away from danger that doesn’t involve crossing the floodplain. You can take a lot of action to ensure your own personal safety.”
You can search your address on the FEMA floodplain map here.
