Flooding persists as Harvey downgraded to tropical depression

The downpour has stopped in Houston, which was inundated for days by record-setting rain and floodwaters from the aftermath of Hurricane Harvey.

But Harvey, now a tropical depression, is still dumping extraordinary amounts of rain as it travels northeast through Louisiana.

The Southeast Texas city of Beaumont, home to many huge oil refineries, had recorded nearly four feet of rain by Wednesday morning, according to the National Weather Service.

Mayor Derrick Freeman of Port Arthur, Tex., posted on Facebook that “our whole city is underwater right now.” Motiva shut down its Port Arthur plant, the country’s largest refinery, as the storm flooded the city.

Lake Charles, La., had more than a foot of rain, and storm surge threatened areas along the coast. The National Weather Service warned Wednesday of “catastrophic and life-threatening flooding” that would continue from west of Houston into southwest Louisiana for the rest of the week. Vulnerable New Orleans is not in Harvey’s path, but the right-side rain bands will drench the city.

Drainage and flooding are perennial worries along the Texas-Louisiana Gulf Coast, and huge storms can overwhelm the two major cities.

The National Weather Service monitors four regions along the Gulf Coast, each with its own series of flood gauges.

Weather service gauges in the Houston/Galveston region reported the highest levels of flooding over the weekend as the storm slammed into the city starts and started its path northeast this week.

Low-lying Houston is drained by a network of bayous that flow into one outlet, the Houston Ship Channel, a busy shipping port lined with some of the biggest oil refineries in the United States.

As the city’s population grew, developers built structures over large chunks of wetlands, leaving the vulnerable land with less natural drainage. The impermeable surfaces — asphalt and concrete — reduced the area’s ability to absorb excess water. Roads that were built to carry off water in an emergency were filled, hampering travel, evacuation and rescue efforts.

New Orleans, which was devastated 12 years ago by Hurricane Katrina, had flooding earlier this month and problems with the huge pumping system that is supposed to get rid of the water.

Three key elements combined to create such a rain-laden storm as Harvey: the warm waters of the Gulf of Mexico, strong hurricane winds and a weak late-summer jetstream.

The result was a slow-moving storm that churned near Houston for days before meandering east, continuously dumping rain from the strong bands on its right side.

When Harvey returned to the warm gulf, it picked up more moisture to pour onto land. It is expected to continue creeping northeast until it dissipates later in the week, according to the National Hurricane Center.

The map below depicts flood waters detected by satellite imagery. This data is preliminary and does not show all of the flooded areas due to cloud cover.

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