Why Houston is prone to flooding
Houston is expected to receive historic amounts of rainfall.
— -- Hurricane Harvey has been downgraded to a tropical storm, but the system is still meandering over the Houston area, dumping torrential rains on Southeast Texas.
The result -- severe flooding that is expected to grow worse over the week.
Houston has dealt with floods before in recent years, but Harvey could lead to 50 inches of rainfall in spots by Wednesday, a historic level of flooding.
"This is a situation that Houstonians have dealt with before, because Houston is an area that is prone to flood about once a year like this," Texas Gov. Greg Abbott said Sunday on ABC News' "This Week." "But this is one of the worst, if not the worst, that Houston has suffered."
ABC News spoke with Texas A & M Professor Samuel Brody, who is an expert on flooding causes and consequences and is also the director of the Center for Texas Beaches and Shores.
What makes Houston prone to flooding
According to Brody, Houston is prone to flooding for a number of reasons.
The city is situated on a low-lying coastal plain with little topographic relief and the soils beneath it are clay-based, thwarting drainage.
"But I think the real driver for flood loss and impact in Houston is the built environment," Brody told ABC News in an interview Sunday. "This is a human-induced problem. Houston is a rapidly growing metropolitan area."
Because of all the rapid development in the city, the natural drainage patterns of the region have been changed.
"Instead of water seeping into the soil or running into the bayous, we're starting to see it run into people's homes," Brody said.
Houston uses bayous as its main drainage system, however the city has no major levee system in place.
But in trying to drain the water quickly from one place to another, you run the risk of harming another community downstream.
Brody added that Houston and the Harris County flood control district have "done amazing work" given the resources provided to them.
What can be done?
Brody argued that there needs to be a commitment to protect Houston because it is the fourth most populous city in the U.S.
"We've made some really good progress, but there's a lot more we can do in the future with time, funding, and commitment to make things happen," Brody said.
One of the issues that could improved, Brody said, is making local communities and its residents aware of flood risks.
"There's a real lack of awareness and messaging that reaches out to those neighborhood levels," Brody said.
Another way the local government could help be better equipped to deal with flooding is planning out how it's developing the city.
According to Brody, Houston also needs to focus not just on improving its physical infrastructure approach to flood mitigation, but thinking more widely of the surrounding communities.
What has been done?
In January, the city announced projects -- an estimate $130 million -- to expedite flood relief in areas surrounding the Brays, Hunting and White bayous.
"These projects will greatly reduce the flood threat for residents along these bayous and remove hundreds of properties out of the 100 year flood plain,” said Mayor Sylvester Turner said in a press release.
The action came just weeks after Turner authorized a Storm Water Action Team to replace sewer inlets and grates and other projects.
What happens if things stay the same?
It's the water and the inland flooding rather than the wind from a hurricane that's deadly.
"That's the number one cause for tropical storm-related fatalities," ABC News' chief meteorologist Rob Marciano said Sunday.
Although Houston was not in the direct path of Harvey hitting it as a hurricane, it's experiencing record level rainfall.
Brody also said that's it's not just Houston but other major cities like Miami, Chicago and New York that could deal with disastrous urban flooding in the future.
"As we continue to congregate in these urban areas, particularly in coastal regions, I think urban flooding is going to be a paramount issue moving forward for this country," Brody said.
Brody's hope is that there'll be greater leadership from the local and federal government to "genuinely start dealing with this flood issue."
"It's not a matter of will we get this again in some form? We absolutely will," Brody said. "The question is what is the cost of doing nothing or not doing enough going forward?"
Brody warned, "And every year we don't start thinking systematically about protection and mitigation for a lot of different areas, the price of tagging the next storm continues to go up."