Why Harlingen’s storm drainage system worked


Staff Writer

HARLINGEN — As record-breaking rainfall goes, the series of storms which arrived two weeks ago conjured up nightmares of an early-season hurricane.

In 96 hours, 16.75 inches of rain fell on Harlingen, the convulsive rain bands coming and going, turning streets into mini-resacas and yards and parking lots into little reservoirs.

Yet despite day after day of this intense inundation, only a few homes in the city actually flooded. Outside of vehicles plowing through a foot or two of water on certain low-lying streets, a series of storms that might have caused major damage turned out to be little more than an inconvenience.

Because some things went right.

A little luck, sure

Carlos Sanchez, an assistant city manager, is also an engineer. He says some flooding of homes did occur but the city is still evaluating the total number and the damages they incurred.

But what can be determined is that parts of the city’s stormwater drainage system were not overwhelmed like during Hurricane Dolly in 2008 and Hurricane Alex in 2010.

Sanchez said there were significant differences between those rain events and the latest unnamed tropical system — like a “small hurricane,” he says — which came in from the gulf and blew through the Rio Grande Valley.

“There are a couple of factors that kind of play into it,” he said last week. “The way the storm came in and the amount of rain that we got, it seems like it came in bursts. Either it was late in the afternoon or early in the morning. That one event Wednesday, we got a heavy downpour, but prior to that it had been in the afternoons.”

The intermittently heavy rains allowed the city’s storm sewer system to recover when the rain stopped. Instead of water backing up and flooding significant areas of the city, the downtime between rain bands allowed the runoff to pour out of the city’s storm drains and exit via the Arroyo Colorado.

“That helped,” he added. “There was sometimes a 10-hour period or a 12-hour period between the heavy rains so that allowed the system to recover itself and be able to take on more water.”

No diversion into arroyo

Another significant factor that minimized flooding in the city was the International Boundary and Water Commission decision not to divert Mid-Valley floodwaters into the Arroyo Colorado at the time the heavy rain was occurring in Harlingen.

“The arroyo itself is one of the primary floodwater conveyance systems that we have,” Sanchez said. “We were advised by IBWC that they closed the gates — there’s a diversion structure up by the Mercedes area — which means no water was being diverted into the Arroyo Colorado.”

“That was a great help to our system because then it wasn’t competing with trying to drain (Harlingen runoff) into the arroyo and those other floodwaters that we saw in the past back in Dolly and even Hurricane Alex,” he said. “So that was a big help for our system, for the city, to be able to drain.”

Rio Grande behaved itself

Lori Kuczmanski, public information officer for the IBWC, said the Valley was fortunate that flooding was not having an impact on the region’s primary floodwater relief valve — the Rio Grande.

“I think the key thing here is that there was no flooding in the river so there was no reason to use the floodway for river flooding,” she said. “So we didn’t put water in the floodway from the Rio Grande.

“This situation you guys had the other day, it was handled by the local water municipalities versus the IBWC,” she added. “We did assist. We assisted Mercedes, the City of Santa Rosa to relieve some of the flooding in their areas. We were pumping water into the floodway to relieve some of that water.”

Areas of concern

Sanchez concedes the City of Harlingen and its residents were “lucky” in how the rain came down and when it fell. But in areas with localized flooding, it also served as a reminder that some spots need help.

“One was the area between 9th Street and 13th Street from Harrison to Washington,” he said. “It’s there by Boggus Stadium, the area to the west. That’s one of the areas that has been identified and actually has been partially funded for a drainage study by the Texas Department of Emergency Management, TDEM, to help us do the analysis from a hydraulics standpoint.

“If the study — which I feel will come back that we do have an issue there — then TDEM will help fund a $1.4 million project for that specific area,” he added.

That’s not the only place causing concern within the city, he said. The city’s Master Drainage Plan has identified around 30 projects which will require about $55 million to address.

“We’re not, in essence, out of the woods,” Sanchez said. “A large storm event within a shorter time span would really cause some issues for the city.”

Lessons re-learned

The fact storm drains in Harlingen functioned so well was due to city crews — as well as concerned neighborhood residents — making sure those drains were free of debris, which can clog them and make it impossible for water to make it into the storm runoff system.

“This is a good reminder for people to make sure that their ditches and stormwater drains are cleared out so water can get through,” said the IBWC’s Kuczmanski. “I know there was some backup and some drainage ditches that were obstructed, whether it was tires, coke cans or plastic bottles, et cetera. I know that needs to be something that’s addressed.”

For his part, Sanchez, who previously worked for the City of McAllen as public works director before coming to Harlingen two years ago, said the system worked.

“I think from my opinion as an engineer, and my work in McAllen, I feel that our storm sewer system functions efficiently,” he said. “I would say we did see localized flooding on the streets, and in some areas maybe going into private property, but the floodwaters receded within less than a 12- to 18-hour period, which is good.

“It means the system is functional, the system is being maintained, and so I think it’s a reflection of the maintenance of the existing infrastructure,” he added. “But we still need to continue making improvements to the storm sewer system.”