Initial assessments in Galveston County have not found widespread road damage from Hurricane Harvey, but problems caused by the extreme flooding could appear later, engineers and city officials familiar with major floods said.
Massive floods can weaken the durability of streets in the long-run, said Amit Bhasin, an associate professor of civil engineering at the University of Texas at Austin.
“It’s not something that you would see right away,” Bhasin said. “You’re looking at, perhaps, something that could shave off a couple of years of the pavement’s life.”
The effects of flooding and the post-storm influx of heavy vehicles can cause road problems long after the event, officials with the city of News Orleans, which was flooded by Hurricane Katrina, said.
Hurricane Harvey made landfall Aug. 25 in Rockport, Texas, about 200 miles south of the county. The storm traveled along the coast and dumped more than 50 inches of rain in some areas, overflowing rivers and creeks and causing destructive flooding across the region. Roads all over the county were under water for days.
Since the storm, structural engineers and city public works department crews have looked for immediate problems, including potholes, deterioration of bridges and weakened road bases, officials said.
In most places, the roads are in fairly good shape, officials said.
In League City, Friendswood and on state highways across the county, where flooding was severe, the resulting damage was manageable, officials said.
On state highways in the county, potholes were the main damage, said Danny Perez, Houston-area spokesman for the Texas Department of Transportation.
“There are very minimal impacts,” Perez said. “We’re able to get those fixed fast.”
No apparent undermining of road integrity has occurred in League City, Assistant City Manager Ogden “Bo” Bass said.
“We have found a couple of places where some marginal areas of asphalt paving and potholes have formed,” Bass said.
In Dickinson, however, damage to roads was much worse, Director of Public Works Paul Booth said.
“We have several roads that are pretty severely damaged,” Booth said. “All of the roads in Dickinson are currently passable. However, we’re starting to see some deterioration of those roads.
“We’ve got a lot of pothole issues, we’ve got some road base damage that is going to require some rebuilding.”
Many roads are asphalt structures that sit on a stone base above natural soil, Bhasin said. When flooding occurs, water gets into the natural soil and can leak into the roads, he said.
“There are three things that are extremely important for good pavement,” Bhasin said. “The three things are drainage, drainage and drainage. You don’t want water in your pavement structure, and you design it to keep it out in every possible way.”
Water in road structures weakens the foundation, making it more susceptible to damage over time, Bhasin said.
“When you have a weak foundation and you drive a truck over, it’s going to deflect and deform more,” Bhasin said.
Even the increased presence of recovery effort vehicles, like trucks pulling debris off roads, can contribute to a weakened road structure, Bhasin said.
“All of those things are going to make the situation worse,” Bhasin said. “You have unusually heavy traffic when the roads are unusually weak.”
Twelve years after Hurricane Katrina, the city of New Orleans is still dealing with the effects floodwater had on its streets, said Tyronne Walker, director of communications for Mayor Mitch Landrieu.
“After millions of pounds of water saturated and stressed streets for weeks, massive heavy equipment and commercial vehicles further damaged subsurface infrastructure as part of the recovery, demolition and debris removal operations,” Walker said.
“Engineering studies have shown how this damage reduced the service level, life span and structural capacity of New Orleans’ streets and subsurface infrastructure.”
To date, New Orleans has completed 305 road projects totaling $490 million, Walker said.
Bhasin said city roads would be more likely than state roads to sustain long-term damage from flooding, because state roads are built to tighter standards.
State highways in the county don’t seem to have any deep structural damage, although the state is continuing to monitor them, Perez said. Part of that could be because the water didn’t sit on the highways for longer than five days or so, Perez said.
“A lot of our roads and freeways were impacted by water,” Perez said. “What you don’t want is for them to marinate in that for days and days.”
City officials in Friendswood, Dickinson and League City are still conducting final assessments on the status of city roads, they said.
“If the water takes a long time to leave, it’s going to keep the pavement structure in weak condition,” Bhasin said. “These kinds of things would shave off a year or two, who knows, of pavement life.”