Hunker Down

Has Houston Always Flooded?

Space City Weather's Eric Berger and Matt Lanza answer your most pressing questions about our city's weather and how it's changing.

By Eric Berger and Matt Lanza July 18, 2017 Published in the August 2017 issue of Houstonia Magazine

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Space City Weather's Eric Berger (left) and Matt Lanza (right)

Image: Matty Newton

You've got weather questions, they've got answers.

Eric Berger is a meteorologist who worked at the Houston Chronicle for nearly two decades before starting Space City Weather to provide Gulf Coast residents with simple, sensible forecasts. Matt Lanza is a forecast meteorologist in Houston's energy sector. He contributes forecasts and writes about Houston's weather history for Space City Weather.

Below, the questions these forecasters encounter most frequently:

Have we seen more flooding events than usual recently?

Arguably, the spring of 2015 through the summer of 2016 was the wettest period in Houston’s history. From March 1, 2015, through August 31, 2016, Houston received a total of 119.77 inches of rain, according to the National Weather Service. This annihilated the previous total by about a foot—prior to then, Houston’s wettest consecutive 18 months had yielded a total of 106.68 inches. The totals were bolstered by six historic rainfall events, including the Memorial Day Floods (2015), Halloween rains (2015) and Tax Day floods (2016). During this period, nearly every single bayou and river in the Houston area saw waters rise above banks at least once.

Why was traffic so bad during the Hurricane Rita evacuation?

Anyone who lived in Houston in 2005 remembers Rita, and the nightmarish evacuation that took place in the days before it came ashore. There were several reasons for the terrible traffic jam that occurred as everyone tried to get out of town at the same time. First, Rita arrived just three weeks after Hurricane Katrina, so images from a flooded New Orleans were fresh in our minds. Second, three days before landfall, Rita truly was a menacing storm, with Category 5 winds and a projected path that would have brought an immense storm surge into Houston (in, the end, it turned right, hitting the Texas-Louisiana border before landfall). Third, there was poor planning on the part of local and state officials, who had no system in place for implementing contraflow traffic lanes or staging evacuations from the area’s most vulnerable residents to the least. When Hurricane Ike hit three years later, officials seemed to have learned some of those lessons.

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A snowfall in 1940 covered downtown Houston, with City Hall at left and the former Sam Houston Coliseum, demolished in 1998, at center.

Why doesn’t it snow very often in Houston?

Rarely do we get the right combination of cold and ample moisture to deliver a snowstorm this far south. But in a few instances, most notably Valentine’s Day 1895 and Christmas Eve 2004, circumstances do come together. You need very cold air to plunge down the Plains, deep into Texas, as well as some sort of storm system to deliver moisture off the Gulf, over the top of that cold air. The 1895 event was a great example, and it remains Houston’s biggest snowstorm, delivering an estimated 20-plus inches across most of the Houston, and 15-plus in Galveston. The 2004 event saw the heaviest distribution south of here, with areas from Victoria into Brazoria County seeing over a foot of snow.

Does a warm winter mean a more active hurricane season?

This is a natural question to ask after one of the warmest winters in the region’s history. Part of the reason for our recent warm winter was that the Gulf of Mexico never really got cool, and this meant that any time winds blew onshore, Houston warmed up quickly. In fact, for the first time on record, during the winter of 2016-17, the Gulf’s daily average surface temperature never fell below 73 degrees Fahrenheit. Still, that’s unlikely to have much influence on the current hurricane season. Why? Because whether or not the Gulf is warm in the winter, by summertime, the temperature is always at least 80 degrees—high enough to support hurricanes. The more important variables to watch are wind shear (changing wind speed) and moisture levels in the atmosphere.

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Unfortunately, sights like this—a flooded Addicks Reservoir in 2015—will become only more common in the future.

Image: Shutterstock

How do El Niño and La Niña typically impact Houston’s weather?

Unlike some other parts of the United States, Houston typically doesn’t see major effects from either of these climatological patterns, the periodic warming (El Niño) and cooling (La Niña) of the equatorial Pacific Ocean. A strong El Niño usually leads to a bit more rain and a few degrees lower temperatures during Texas's late fall and winter, whereas La Niña’s effects are the opposite. Both patterns also affect hurricane season. El Niño tends to increase wind shear over the Atlantic Ocean, limiting hurricane activity. La Niña, on the other hand, has historically led to somewhat more active hurricane seasons in the Atlantic. This year a weak or non-existent El Niño is unlikely to have a significant effect on hurricane season.

Is Houston more flood-prone than other major U.S. cities?

The Gulf Coast clocks some of the highest annual rainfall totals of any region in the country. And according to the Federal Emergency Management Agency (FEMA), Texas sees some of the highest frequencies of flooding events in the country. Dallas, Fort Worth and San Antonio have a slight edge on Houston in the flash-flooding department, but it’s not by a wide margin, and Houston is catching up, as our area is seeing an increase in flash-flood events. Another cheerful thought: Our risk of storm-surge flooding from a hurricane is one of the highest in America in terms of damage potential.

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A series of strong thunderstorms in November 1978 flooded downtown Houston.

Are droughts and flood events getting worse?

Houston’s economic success has its downside. As our area has grown, more and more prairies that used to absorb water are being paved over. This means that when rain falls, it has fewer places to go, so street flooding in the metro area is likely becoming more frequent. Flooding will always occur in Houston, of course, but managing our land use better can help mitigate it somewhat. Additionally, climate-change research has shown that a paradox will emerge in Texas. The dry periods will likely get drier, and the stormy periods will likely get stormier. So across Texas, global warming could lead to both harsher droughts and more rainy periods with worse floods.

Why doesn’t Houston get more large tornadoes?

Believe it or not, Harris County has seen the second highest number of tornadoes (over 215) of any U.S. county since 1950. This is likely due to our population and size. More than 80 percent of our tornadoes are EF-0 or EF-1—the scale runs up to EF-5, the highest intensity—and those can still be very serious. Still, we’ve only had one EF-4, which took place in November 1992 in Channelview, and no EF-5 tornadoes. Why? Our geography likely helps us. We’re far south, so mid-latitude storms develop, and usually track, far enough north to keep the strongest wind shear—the biggest ingredient needed for strong tornadoes—away from our area. Occasionally, as happened back in 1992, we do get an outlier setup, in which a storm will track across south or central Texas, bringing us ample wind shear and allowing for more powerful tornadoes. But the vast majority of the time, they stay north and move north.

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Sears moved its main department store from Buffalo Parkway (now called Allen Parkway) in the 1940s, because nearby Buffalo Bayou kept flooding it. This 1947 storm would cause it to flood once again at its new location on Main Street at Richmond.

Is Houston prepared for the next big hurricane?

Probably not. While it’s true that local officials learned some evacuation lessons from Hurricane Rita, we did not learn much from Hurricane Ike. Although Ike produced a devastating surge, and there’s been a lot of talk about surge prevention in the nine years since, the coast is no more well-prepared today. In fact, the region is considerably more vulnerable, given all of the development between Houston and Galveston since 2008. Wind is another issue. Few in Houston even remember our last significant wind storm, which took place in 1961, when Hurricane Carla made landfall down the coast. Given the mixed bag of building codes implemented across the region in the decades since, it’s not clear how well our housing stock would fare against major hurricane-force winds today.

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