Why Houston is prone to flooding

The news came as officials warned the death toll from the flooding could soar once the water receded from one of America's most sprawling metropolitan centres. In a rescue effort that recalled the aftermath of Hurricane Katrina, helicopters landed near flooded freeways, airboats buzzed across submerged neighborhoods and high-water vehicles plowed through water-logged intersections.

In Brazoria County a levee breached at Columbia Lakes some 60 miles south of Houston, prompting officials to tell residents: "Get out now!"

A mandatory evacuation was ordered for the low-lying Houston suburb of Dickinson, home to 20,000, and questions swirled in Houston itself about why the mayor did not issue a similar evacuation order.

The overflow is expected to continue until September 20.

A major dam in Houston has spilled over for the first time in history after Harvey's rains inundated its reservoir, a federal official said.

Harvey has been dumping torrential rain on Texas since Sunday, causing catastrophic flooding across the state and in particular on Houston and the surrounding area. Addicks Reservoir is already slightly above the levels seen during the Tax Day floods in 2016, Lindner said. Engineers started the process earlier than announced after water levels increased beyond expectations. Dam releases are expected to occur for several months following this storm event.

"It's going to be better to release the water through the gates directly into Buffalo Bayou as opposed to letting it go around the end and through additional neighborhoods and ultimately into the bayou", he said.

With at least six inches still possible in Houston on Monday, the Buffalo Bayou could rise another six feet. New freeways are built to handle 100-year floods, but we've already exceeded the conditions that define a 100-year flood at in many spots with the flooding from Harvey. One area of the city hit particularly hard is around Addicks Reservoir.

Initially, the water release from Addicks reservoir was planned to begin at 2 a.m. CT on Monday, with Barker to follow 24 hours later. The water will endanger more homes and add to the flooding that has crippled the area.

The reservoirs were built after catastrophic floods in 1929 and 1925 and were created to contain water until it could be released downstream at a controlled rate, according to the Associated Press. The U.S. Army Corps of Engineers owns and operates the reservoirs.

But where those waters will travel has been misunderstood, according to Simon VanDyk, public information officer for Harris County Emergency Services District No. 48, which includes the reservoirs.

Residents living near the Addicks and Barker reservoirs - that were created to prevent flooding in downtown Houston - were warned Sunday that a controlled release from both reservoirs would cause additional street flooding that could spill into homes. There was, he said, simply a higher amount of water flowing into the reservoirs from its feeder creeks in Waller, Fort Bend and western Harris counties.

  • Kyle Peterson