USA – Catastrophic Flooding in Houston and South East Texas

Massive amounts of rain brought by Hurricane Harvey have caused catastrophic flooding in parts of south eastern Texas, including Fort Bend, Brazoria and Galveston Counties, as well as Harris County and wide areas of Houston.

Five people have reportedly died in the storm, including at least 2 in flooding in the Houston area. President Trump has issued a Major Disaster Declaration for the state of Texas

The National Weather Service said:

“The breadth and intensity of this rainfall are beyond anything experienced before. Catastrophic flooding is now underway and expected to continue for days.”

River levels in south eastern Texas have already broken previous record highs in at least 6 locations, with more record highs likely to follow.

Local flood control authorities estimated that thousands of homes have been flooded across the Harris county, which includes most of Houston.

Levels of the Addicks and Barker dams near Houston are dangerously high. The Army Corps of Engineers said it is releasing water to ease the situation. A spokesman for the Corps said “This flood event will exceed the 2016 tax day flood elevations.”

The torrential rain is expected to continue and spread eastwards, threatening flooding in parts of Louisiana.

US Coast Guard – flooding in Greater Houston 27 August 2017. Photo: USCG

 

US Coast Guard – flooding in Greater Houston 27 August 2017. Photo: USCG

Rainfall

Since making landfall on the Texas coast late on 25 August, Harvey has dumped historical levels of rainfall across parts of Houston and south eastern Texas.

On Social Media, Jeff Lindner of the Harris County Flood Control District, described the rainfall totals as “insane” and “staggering”.

Harris County Flood Control District (HCFCD), responsible for flood control in the Houston area, said on 27 August that rainfall across Harris County has continued to intensify, “with rainfall totals in the last three to six hours that have greatly exceeded our 500-year rainfall levels”.

More than 20 locations in south eastern Texas recorded 20 inches of rain or more in a 24 hour period between 26 and 27 August. According to National Weather Service Houston, 26.76 inches of rain was recorded in parts of Brazoria County, and 27.45 inches was recorded in Dayton, Liberty County.

Nearly all of HCFCD’s rainfall gauges around Houston recorded more than 20 inches of rain in 48 hours to early 28 August. Clear Creek Village (30.72 inches), Baytown (33.08), and a gauge near Mont Belvieu (31.76) all recorded more than 30 inches during this period.

Rainfall totals in south east Texas, 26 to 27 August. Image; NWS / NOAA

Rivers

On 27 August HCFCD said that all but a few watersheds were experiencing devastating flooding. HCFCD added that areas around the watersheds not currently flooded – Cedar Bayou, Carpenters Bayou, Sims Bayou, and White Oak Bayou – were still likely to see some flooding from the heavy rain.

Rivers and creeks have exceeded major flood stage at 26 points across south eastern Texas as of 28 August. Rivers have exceeded previous record highs at 6 locations:

  • Greens Bayou at Houston (current level, as of 28 August: 39.51 feet / Previous record: 39.4 feet)
  • Cypress Creek near Cypress (128.11 / 127.6)
  • Cypress Creek near Westfield (96.06 / 94.3)
  • Navidad River at Sublime (36.23 / 34)
  • Navidad River near Speaks (29.44 / 28.2)
  • Buffalo Bayou at Piney Point Village (67.46 / 61.23)

Greens Bayou at Houston jumped almost 40 feet in the space of 48 hours. River levels are predicted to exceed previous record highs in numerous other locations.

Levels of Greens Bayou near Houston. Image: NWS / NOAA

Evacuations

Over the last few days evacuation orders have been issued for several areas of south eastern Texas, initially in coastal areas where Harvey made landfall, and later areas near the San Bernard and Brazos rivers due to threat of flooding, among others. However, the total number of those displaced is as yet unclear.

Thousands of people in the Houston area are thought to have moved to higher ground. In some cases residents of flooded homes have taken refuge on rooftops. Emergency management officials requested that people escaping flood waters as a last resort do not stay in the attic, adding “If (the) highest floor of your home becomes dangerous, get on the roof.

Red Cross shelters have been opened in the Houston area to house those forced from their homes. Houston City Multi Service Centers and some libraries have also been opened for shelters, as well as churches and community centers.

Rescues

Federal, state, and local search and rescue teams are operating 24/7 to reach those stranded in flooded areas. Emergency services have received thousand of appeals for rescues.

Houston Police reported that police personnel have completed 90 flood rescue missions resulting in over 1,100 community members being brought to safety.

Thousands of state and national guard troops have been deployed to affected areas.

The Coast Guard has over 400 personnel conducting operations in south Texas, with 16 helicopters in the air and 8 more inbound. As of the afternoon 27 August, the Coast Guard had confirmed rescues of more than 2,000 multi-person cases in the Houston-Galveston area. The Coast Guard also has an additional nine teams onsite for shallow water rescues.

Federal Emergency Management Agency (FEMA) had more than 400 Urban Search and Rescue (US&R) personnel working to save lives in south Texas, with another 500-plus personnel who were expected to be joining operations by late 27 August.

Dam Releases

The U.S. Army Corps of Engineers Galveston District is set to release water from Addicks and Barker dams after levels in the reservoirs increased dramatically.

“Residents adjacent to the reservoirs need to be vigilant because the water in the reservoirs is rising rapidly,” said Col. Lars Zetterstrom, Galveston District commander. “Both reservoirs are rising more than half a foot per hour.”

“If we don’t begin releasing now (early 28 August), the volume of uncontrolled water around the dams will be higher and have a greater impact on the surrounding communities,” said Zetterstrom. “We are coordinating floodwater releases from Addicks and Barker with the Harris County Flood Control District so they can make informed decisions for the communities they support.” 

“This flood event will exceed the 2016 tax day flood elevations,” Zetterstrom added.

State and Federal Disaster Declarations

Gregg Abbott, Governor of the State of Texas, issued State Disaster Proclamation on 23 August, 2017, initially for 30 counties in anticipation of the threat posed by Harvey. More areas have since been included and as of late Sunday 27 August, 54 counties in Texas had been declared state disaster areas.

On 25 August, President Trump issued a Major Disaster Declaration for the state of Texas, making federal funding available for emergency work and to affected individuals and businesses owners who sustain damage as a result of the storm.

About Hurricane Harvey

Storm Harvey was thought to have all but died around a week ago. However, NASA observations noted on 23 August that Harvey had regenerated and was now a tropical depression in the Gulf of Mexico.

The National Hurricane Center (NHC) issued hurricane and storm surge watches for portions of the Texas coast as Harvey was expected to strengthen. NHC also warned that the storm was likely to bring massive amounts of rainfall.

Landfall

Harvey made landfall as a Category 4 hurricane near Rockport, in Aransas County, Texas, late (local time) on 25 August, 2017.

Harvey is the first major hurricane to make landfall in USA since Hurricane Wilma in 2005 and the first Category 4 hurricane to make landfall in USA since Hurricane Charley in 2004.

Storm Surge and Wind Damage

Harvey caused some storm surge floods in coastal areas during the early hours of 26 August.

A National Ocean Service tide gauge at Port Lavaca, Texas, reported a water level of 5.9 ft above Mean Higher High Water, early on 26 August, 2017. A NOAA tide gauge at Port Lavaca, Texas, recently measured a water level of 6.4 feet above Mean Higher High Water. Another NOAA tide gauge at Seadrift, Texas, recently measured a water level of 5.3 feet above Mean Higher High Water.

Winds of up to 130mph (215 km/h) caused major damages and power cuts affecting up to 100,000 people in Corpus Christi. One death was reported in Rockport after storm damage caused a house fire.

Mandatory evacuation orders were issued in seven counties on the Texas coast from Corpus Christi to the western end of Galveston Island. Residents have been warned not to return to Aransas County until emergency and disaster management services have completed their work.

Flood Summary

Last updated: September 6, 2017
Event
Hurricane Harvey, USA, August 2017
Date
August 26, 2017
Type
Urban flood, River flood, Storm surge
Cause
Storm surge, Extreme rainfall

Locations

A - Cypress
B - Spring
C - Katy
D - Barker Dam
E - Addicks Dam
F - Alvin
G - Atascocita
H - South Houston
I - Houston
J - Mont Belvieu
K - Clear Creek Village
L - Baytown
M - Rockport
N - Port Arthur
O - Beaumont
P - Lake Charles, Louisiana

Magnitude

Rainfall level
680 mm in 24 hours
Pearland, Brazoria County - August 26 to August 27, 2017
Rainfall level
584 mm in 24 hours
Alvin, Brazoria County - August 26 to August 27, 2017
Rainfall level
697.23 mm in 24 hours
Dayton, Liberty County - August 26 to August 27, 2017
Rainfall level
558 mm in 24 hours
South Houston - August 26 to August 27, 2017
Rainfall level
622.3 mm in 24 hours
Santa Fe, Galveston County - August 26 to August 27, 2017
Rainfall level
511 mm in 24 hours
Mount Houston - August 26 to August 27, 2017
Rainfall level
604 mm in 24 hours
Bacliff, Galveston County - August 26 to August 27, 2017
River level
12.04 metres
Greens Bayou at Houston - August 28 to August 28, 2017
level as of 28 August: 39.51 feet / Previous record: 39.4 feet
River level
39.05 metres
Cypress Creek near Cypress - August 28 to August 28, 2017
level as of 28 August: 128.11 feet / Previous record: 127.6 feet
River level
29.27 metres
Cypress Creek near Westfield - August 28 to August 28, 2017
level as of 28 August: 96.06 feet / Previous record: 94.3 feet
River level
11.04 metres
Navidad River at Sublime - August 28 to August 28, 2017
level as of 28 August: 36.23 feet / Previous record: 34 feet
River level
8.97 metres
Navidad River near Speaks - August 28 to August 28, 2017
level as of 28 August: 29.44 feet / Previous record: 28.2 feet
River level
20.56 metres
Buffalo Bayou at Piney Point Village - August 28 to August 28, 2017
level as of 28 August: 67.46 feet / Previous record: 61.23 feet

Damages

Evacuated
35,000
August 26 to August 31, 2017
35,000 people were evacuated and staying in over 200 shelters. According to media reports, over 1 million people were displaced overall: in Texas: 779,000 mandatory evacuations; 980,000 voluntary evacuations. In Louisiana: 7,000 mandatory evacuations; 133,000 voluntary evacuations (source: Reuters)
Fatalities
44 people
August 26 to August 31, 2017
According to media reports
Buildings destroyed
7,000
August 26 to August 31, 2017

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