Houston flooding eased in most areas Wednesday, as the largest rainstorm the continental United States has ever seen moved east to the Texas-Louisiana border.

Water remained high near the reservoirs and along the large creeks north and south of the city, but the number of overflowing drainage channels dropped by half from the Monday morning peak. Many residents began returning to homes and businesses that had been flooded, but nearly 35,000 people were in shelters.

Saturday, August 26

Sunday

Monday

Tuesday

Wednesday

A five-day view of the ebb and flow of Brays

Bayou, with the Texas Medical Center in the

background. (Kevin Sullivan/

The Washington Post)

Saturday, Aug. 26

Sunday

Monday

Tuesday

Wednesday

A five-day view of the ebb and flow of Brays Bayou, with the Texas Medical Center in the

background. (Kevin Sullivan/The Washington Post)

Saturday, August 26

Sunday

Monday

Tuesday

Wednesday

A five-day view of the ebb and flow of Brays Bayou, with the Texas Medical Center in the background. (Kevin Sullivan/The Washington Post)

The Houston region’s flood control channels withstood the rains on Saturday, with only 3 out of 150 gauges flooded when the sun went down. But by sunrise Sunday, a majority of the 150 stations were underwater. Flooding worsened all day Sunday until the predawn peak Monday when more than two-thirds of the flood channels were under sheets of rainwater.

Harris County strategically placed gauge station channels — ranging from two to 40 feet deep — to measure water levels from rainfall and hurricanes. Arrow heights indicate water levels exceed the top of the channel and circles represent the peak flood level of a channel.

Friday, Aug. 25 1 a.m. EDT

North and West

Downtown Northwest

Northeast

Downtown South

South

The northwest section of downtown suffered less flooding and drained more quickly. At worst, half of the channel measurements showed flooding on bayous flowing east toward Lake Houston. By late Wednesday, the only flooding in that area was at Addicks Reservoir. Further north Cypress and Spring creeks had 10 to 20 feet of floodwater from Sunday through Tuesday. Only on Wednesday did half of the measurements show water contained within the channels. Some measurements in that sprawling region of 1.5 million people are hazy, however, because gauges were damaged by the flooding and are stuck at the greatest depths.

On Monday evening, every channel in the northeast section of Houston showed flooding from portions of Greens Bayou, Hunting Bayou and the San Jacinto River. The neighborhoods are not as dense as other portions of the city but house a greater share of the African American and immigrant communities. By Wednesday, all water downtown was contained in the drainage channels.

The south sections of downtown have been consistently flooded by Buffalo Bayou with several feet of floodwater Wednesday night.  The growing portion of the city has about 1.4 million people including a mix of upscale and inexpensive housing. Flooding further south along Brays Bayou dropped on Tuesday and was within the channel on Wednesday. Further south along Clear Creek in Brazoria County, floodwaters remained several feet deep Wednesday afternoon in the region of about 1.2 million people.

Measuring the storm

As of Tuesday, agencies such as the National Weather Service provided estimates for total rainfall and flooding, and local agencies such as Houston TranStar provided data on road closures. Yet the volatile and ongoing nature of the storm makes it difficult to map the extent of flooding in the region.

This map shows   gauge station sites where water had topped channel banks and high water locations along roads. It also includes flooding observed from satellite imagery.  Arrow heights indicate water level in feet over the top of the channel. The following shows data as of 9 a.m. Eastern time on Aug. 29.

19 ft. over

top of channel

20 ft. over

10 MILES

Note: Data as of 9 a.m. Eastern time on August 29

10 MILES

7 feet over

top of

channel

20 feet over

top of channel

19 feet over

top of channel

Dayton

Lake

Houston

8

HOUSTON

Baytown

Downtown

8

610

8

Rosenberg

Note: Data as of 9 a.m. Eastern time on August 29

7 feet over

top of channel

20 feet over

top of channel

10 MILES

19 feet over

top of channel

Dayton

Lake

Houston

George Bush

Intercontinental Airport

8

HOUSTON

610

Downtown

Baytown

8

610

Hobby

Airport

8

NASA Johnson Space Center

Rosenberg

Note: Data as of 9 a.m. Eastern time on August 29

Affected populations

In the most densely populated areas, to the west and southwest along Interstate 610, sensors recorded water levels almost eight feet higher than canal banks in some places. On the north side, particularly along Spring Creek, not far from George Bush Intercontinental Airport, water topped channel banks by more than 10 feet.

Detail

Population density

Less dense

More dense

5 MILES

8

HOUSTON

12 ft. over

top of

channel

3 ft.

over

610

8

Population density

Detail

Less dense

More dense

8

7 ft. over

top of channel

HOUSTON

8

Addicks

Reservoir

610

12 ft. over

top of channel

Downtown

Texas

Med. Center

610

8

Hobby

Airport

5 MILES

8

Population density

Detail

Less dense

More dense

8

4 feet over

top of channel

17 feet over

top of channel

HOUSTON

8

Addicks

Reservoir

610

12 feet over

top of channel

8

Barker

Reservoir

Downtown

Texas

Med. Center

610

Hobby

Airport

5 MILES

8

Several areas in Houston with significant flooding reported include neighborhoods where people don't speak English, poor communities and residents who don't own cars. Taken together, a Washington Post analysis found, hundreds of thousands of the city's residents could be at greater risk when heeding evacuation orders, calling for help or escaping to high ground.

Details on how many of the city's 850,000 homes were flooded are not yet available. A Catholic Charities representative told The Post it's too early to assess who is in the most need because the group’s staff can't safely travel around the city.

Share of households with no cars

Less

More

5 MILES

12 ft. over

top of

channel

3 ft.

over

Share of households with no cars

Less

More

7 ft. over

top of channel

12 ft. over

top of channel

5 MILES

Share of households with no cars

Less

More

7 ft. over

top of channel

12 ft. over

top of channel

5 MILES

The county has about 430,000 residents older than 64, including those in about 367 assisted-living facilities and nursing homes.  Many of the facilities are in the areas west of downtown along portions of Buffalo Bayou, where waters Tuesday afternoon were about eight feet above channels.  Those areas may be subject to additional flooding when water is released from the Addicks and Barker reservoirs to the west.

Share of population over 65

Less

More

Nursing home or assisted living facility

5 MILES

HOUSTON

12 ft. over

top of

channel

3 ft.

over

Share of population over 65

Less

More

Nursing home or assisted living facility

7 ft. over

top of channel

12 ft. over

top of channel

5 MILES

Share of population over 65

Less

More

Nursing home or assisted living facility

7 ft. over

top of channel

12 ft. over

top of channel

5 MILES

For undocumented immigrants and communities who don't speak English, the disaster could bring an added challenge: Residents can struggle with official flood warnings, evacuation plans and shelter information. Some undocumented immigrants were already afraid to go to shelters days before a state law cracking down on sanctuary cities was scheduled to take effect on Friday. U.S. District Judge Orlando Garcia temporarily blocked the law Wednesday evening.

The greatest concentration of non-English speakers is north of the city, outside I-610 and along the Hardy Toll Road, where water has overflowed nearby bayous by as much as six feet. Meanwhile, The Post found, the north and east sides of Houston — which have the densest concentrations of Hispanic residents — have seen bayous overflow as much as 11 feet above the canals.

Share of population that does not speak

English well

Less

More

5 MILES

12 ft. over

top of

channel

3 ft.

over

Share of population that does not speak English well

More

Less

7 ft. over

top of channel

12 ft. over

top of channel

5 MILES

Share of population that does not speak English well

More

Less

7 ft. over

top of channel

12 ft. over

top of channel

5 MILES

The greatest share of black residents live on the south side of Houston inside Beltway 8 along the South Freeway, where flooding has been reported in areas along Clear Creek. To the northeast of the city, waters are more than 12 feet above the San Jacinto River, adjoining other black neighborhoods.

More than a third of children in Houston live in poverty. Such poverty is concentrated mostly in the eastern and northern areas of the city, and flooding along Greens Bayou, Halls Bayou and elsewhere was recorded as much as six feet above the canals.

Share of population in poverty

Less

More

5 MILES

12 ft. over

top of

channel

3 ft.

over

Share of population in poverty

More

Less

7 ft. over

top of channel

12 ft. over

top of channel

5 MILES

Share of population in poverty

More

Less

7 ft. over

top of channel

12 ft. over

top of channel

5 MILES

[As Harvey submerges Houston, local officials defend their calls not to evacuate]

As of Tuesday morning, water was higher than channel walls at 72 of the more than 150 gauge sites in the Harris County region. In a few places, water overflowed the channel banks by more than 15 feet — and was still rising.

Record levels of rainfall in Houston

Record cumulative

precipitation

(1900)

80

inches

72.86

70.82

70

Cumulative

precipitation

since Jan. 1, 2017

60

50

40

30

Normal

cumulative

precipitation

(1981-2010

average)

20

10

0

JAN

DEC

Note: As of 8:30 a.m. Aug. 30,

George Bush Intercontinental Airport

Record cumulative

precipitation

(1900)

Cumulative precipitation

since Jan. 1, 2017

80

inches

72.86

70.82

70

60

50

40

30

20

Normal cumulative

precipitation

(1981-2010

average)

10

0

JAN

FEB

MAR

APR

MAY

JUN

JULY

AUG

SEP

OCT

NOV

DEC

Note: As of 8:30 a.m. Aug. 30, George Bush Intercontinental Airport

Record cumulative

precipitation

(1900)

Cumulative precipitation

since Jan. 1, 2017

80

inches

72.86

70.82

70

60

50

40

30

20

Normal cumulative

precipitation

(1981-2010 average)

10

0

JAN

FEB

MAR

APR

MAY

JUN

JULY

AUG

SEP

OCT

NOV

DEC

Note: As of 8:30 a.m. Aug. 30, George Bush Intercontinental Airport

Shelter locations

Houston Mayor Sylvester Turner has announced that all city of Houston multi-service centers and some other designated city and nonprofit facilities will be opened for those who may need immediate shelter from floodwaters. The city has also partnered with the Red Cross to provide shelter.

Convention Center

Capacity:

5,000 people

10 MILES

Lake

Houston

Baytown

Convention

Center

Capacity: 5,000 people

Rosenberg

10 MILES

Lake

Houston

8

610

Baytown

8

Convention

Center

Capacity:

5,000 people

10 MILES

Rosenberg

One of the largest shelters, the downtown George R. Brown Convention Center, had reached its 5,000-person capacity by Monday night but was still accepting people, according to the Houston Chronicle.

Darla Cameron, Bonnie Berkowitz and Aaron Steckelberg contributed to this report.

About this story

Traffic and road closure data provided by Houston TranStar. Flood gauge data provided by the Harris County Flood Warning System. Nursing homes and assisted living from Texas Health and Human Services Commission. Preliminary observed flooding data from the Dartmouth Flood Observatory. Demographic information from the U.S. Census Bureau. Rainfall data from National Weather Service.

Originally published Aug. 28, 2017.

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