August 29, 2017

Special Report

Executive Summary

A long-duration, catastrophic flood event is ongoing in the Greater Houston area in Texas following the landfall of Hurricane Harvey. As of Aug. 28, some areas had received more than 76 cm (30 inches) since Harvey came onshore Aug. 25, and another 38-63 cm (15-25 inches) of precipitation is possible through Sept. 1. Some waterways have risen to, or exceeded, 500-year flood levels, and record flooding has occurred in many locations. Water levels in rivers, creeks, and bayous throughout the region could remain above flood stage into early September; areal flooding will continue for weeks.

Key Judgments

• The main threat from Harvey will continue to be torrential rainfall and catastrophic flooding. As of the evening of Aug. 28, widespread accumulations of 50-76 cm (20-30 inches) have been reported across much of southeastern Texas.

• Health risks in the area are likely to become more severe due to the threat posed by floodwaters and the increased potential for disease transmission at emergency shelters, which may house more than 30,000 people by the end of the week.

• The storm and associated flooding have brought business operations and transportation to a halt; disruptions are likely over at least several weeks, as floodwaters recede and recovery efforts begin.

Tropical Storm Harvey will continue to bring life-threatening weather conditions to southeastern Texas and southern Louisiana through at least Aug. 31. As of Aug. 28, at least eight deaths linked to Harvey have been confirmed. The flooding will probably expand into southwestern Louisiana as Harvey makes its second landfall.

The main threat from Harvey will continue to be torrential rainfall. As of midday Aug. 28, officials report widespread accumulations of 50-76 cm (20-30 inches) across much of southeastern Texas. In Dayton, Texas, officials recorded nearly 101 cm (40 inches) of rainfall since Aug. 25. Persistent onshore flow will direct rain bands into parts of southeastern Texas and Louisiana through Aug. 30. Additional accumulations of 38-63 cm (15-25 inches) are possible through Sept. 1 in the Houston, Galveston, and Beaumont/Port Arthur areas, as well as southwestern Louisiana.

Flash and areal flooding will occur along roadways, bayous, creeks, and rivers throughout southeastern Texas, including the Atascosa, Brazos, Calcasieu, Colorado, Frio, Navidad, Neches, Nueces, Sabine, San Antonio, San Bernard, San Jacinto, and Trinity rivers. As of midday Aug. 28, fifty-five water gauges along creeks, bayous, and rivers in Texas and Louisiana were at major or moderate flood stage. This number will likely rise in the coming days as runoff drains toward the Gulf of Mexico. Many of these bodies of water will probably remain above flood stage into early September.

In addition to the historic rainfall, storm surge continues to inundate parts of the Gulf Coast. Between 0.3-0.9 meters (1-3 feet) of surge is possible between Port Aransas to Morgan City, including Galveston Bay. Rough seas, coastal flooding, and dangerous rip currents will be possible along the Texas and Louisiana coast through at least Aug. 30. Persistent onshore winds and storm surge through Aug. 30 will make it difficult for floodwaters to empty into the Gulf of Mexico; water will likely back up in Galveston Bay and the Houston Ship Channel. Flood control systems throughout the region will be stressed by the water volumes, and some protection measures - such as levees and dikes - will probably fail.

Houston Situation

The Greater Houston area's drainage system is overwhelmed, some dams have been overtopped, and Buffalo Bayou has flooded portions of downtown Houston. On Aug. 28, authorities initiated controlled releases of the Addicks and Barker reservoirs in West Houston to prevent possible levee failures and major loss of life in downstream areas. Rapidly rising water has also forced thousands of people to evacuate their homes or move to elevated locations in multiple parts of the metropolitan area. Police have urged stranded people to climb onto roofs rather than move to attics, which can become flooded without warning, and to hang sheets or towels outside of residences so rescue teams can locate stranded individuals. Flooding has forced the closure of numerous roads throughout Greater Houston, including multiple locations along I-10, I-45, I-69, I-610, Beltway 8, the Hardy Toll Road, and the Sam Houston Tollway.

Emergency responders have conducted thousands of rescues, and are generally overwhelmed. Response times will be delayed in even the best circumstances. Emergency staging areas have been established throughout the city, but first responders have had difficulty reaching some of these sites due to high water and streets blocked by stranded vehicles. Helicopter and boat rescues generally do not take place during darkness hours, to reduce the danger from submerged hazards. The US Coast Guard is assisting with water rescues, and has provided several hotlines to call for those in distress.

Transportation and Utilities

Harvey will continue to cause ground, air, and maritime transport disruptions throughout the affected area through at least Aug. 31. Traffic and commercial trucking delays are highly likely on regional highways in the US, including along portions of the I-10, I-20, I-35, I-37, I-45, I-49, and I-69 corridors. Secondary and low-lying roads will be inundated by floodwaters; authorities will likely close roads and bridges to traffic, especially those along the coast or in frequently flooded locations of urban areas. Flooding could wash away roads and bridges, and repairs could take several weeks to complete. Standing water will probably block some low-lying roads for several days following Harvey's dissipation. Strong winds will pose a hazard to high-profile vehicles.

Additional flight delays and cancellations are likely at regional airports, including those serving Austin (AUS), Dallas (DFW, DAL), Houston (HOU, IAH), New Orleans (MSY), and San Antonio (SAT) during the severe weather period. As of midday Aug. 28, flight operations remain suspended at HOU and IAH due to flooding. Officials reopened Corpus Christi (CRP) terminals for flights the morning of Aug. 28. Several major airlines have waived change fees and are offering flexible rebooking policies for regional flights. American Airlines (AA), Delta Airlines (DL), Frontier (F9), JetBlue (B6), Southwest (WN), Spirit (NK), and United Airlines (UA) have initiated such policies for their flights.

Temporary port closures have occurred in Corpus Christi, Ingleside, Aransas Pass, Harbor Island, Point Comfort, Freeport, Galveston, Texas City, and Houston. On Aug. 25, the US Coast Guard set Port Condition "Zulu" - which suspends all inbound and outbound traffic - for the ports of Houston, Texas City, Galveston, Freeport, and Corpus Christi. The Port of Corpus Christi increased their hurricane readiness status to Port Condition 1, and the port is officially closed to vessels. Container terminals and general cargo facilities will remain closed at Port Houston through Aug. 29; officials will determine if conditions are safe to resume operations Aug. 30.

Widespread power and utility outages are almost certain in southeastern Texas and southern Louisiana, and could persist for several days. Outages can be expected in the Entergy service areas in Texas and Louisiana, as well as the CenterPoint Energy, TNMP, and AEP Texas service areas. Estimates indicate that more than 308,000 customers are without power in southeastern Texas as of Aug. 28.

Regionwide Government Response

Coordinated federal, state, and local rescue and recovery efforts are ongoing to deal with the life-threatening effects of Harvey in Texas, particularly the ongoing catastrophic flooding situation in Houston. Texas Gov. Greg Abbott has declared a state of disaster in 50 counties, and at least 18 of these have also been declared federal disaster areas. These decrees have allowed for the rapid deployment of state and federal resources, including thousands of personnel. Over 2,500 Texas Army National Guard members have been mobilized and sent to affected areas, including Corpus Christi, Houston, and Victoria. Thousands more are likely to be mobilized, as Abbott has ordered the activation of the entire Texas guard force, which includes nearly 12,000 members. More than 400 Humvees and high-water vehicles have been deployed, and at least 16 military aircraft are conducting search and rescue missions.

Nearly 2,000 Federal Emergency Management Agency (FEMA) personnel and more than 400 US Coast Guard (USCG) members are also supporting operations. The USCG has deployed nine shallow-water rescue teams and at least 15 helicopters in the region to conduct rescues. Mobile medical teams and equipment - including air ambulances - have been sent to the region, as some local hospitals have been forced to close due to flooding. Police and first responders in Houston have responded to tens of thousands of emergency calls and conducted hundreds of water rescues; however, the city lacks boats capable of conducting night-time rescues. Dozens of aid-group and government-operated shelters have been opened in the Greater Houston area and other localities impacted by the storm. Authorities have also asked the public to assist in recovery efforts - including participating in search-and-rescue operations and clearing debris - as long as it is safe to do so.

Disaster preparations have been underway in southern Louisiana, as heavy rainfall from Harvey is expected to cause destructive flooding in these areas as well in the coming days. At the request of Louisiana Gov. John Bel Edwards, the federal government has pre-emptively declared five parishes - Beauregard, Calcasieu, Cameron, Jefferson Davis, and Vermillion - as emergency disaster areas; additional declarations could be issued as conditions worsen. These measures will allow FEMA to coordinate relief efforts in these localities. Due to the extent and severity of the flooding, local, state, and federal recovery efforts will likely persist for months or years, following the passage of the storm.

Health Concerns

Avoid immersion in floodwaters, if possible. The floodwaters have increased threats from mosquito-borne disease and water-borne contaminants, especially from vehicles and industrial sites that have been inundated. Floodwaters also become vectors for the spread of disease. Take precautions to avoid mosquito bites; the threat from insect-borne disease will increase as waters recede.

Rapidly Moving Water

Even water that appears shallow or slow moving may have swift undercurrents or very deep segments due to erosion or missing manhole covers. Never attempt to cross standing water. If you cannot see the road or its line markings, do not drive through the water. As little as 30 cm (1 foot) of water can move most cars off the road, and as little as 15 cm (6 in) of fast-moving water can sweep a person off of his or her feet.


Prolonged exposure to cold or cool water or mud can lead to hypothermia and decreased survival time even in temperatures as high as 27 C (80 F). Between 21-27 C (7-80 F), survival time is estimated to be as little as 3 hours for some, with exhaustion and unconsciousness occurring between 3 and 12 hours' time. In areas where the water temperature is between 4-15 C (40- 60 F), the survival time is reduced to 1 to 6 hours. Keeping dry is very important to surviving in most flood prone environments.

Mechanical Hazards

Floodwaters are very strong and can displace large structures, breaking them apart in the process of washing them away. Hidden in murky waters may be exposed glass and metal that can cause serious injury, as well as nails and other sharp objects. Continually shifting waters may cause entrapment by large moving objects unexpectedly pinning a victim. Additionally, electrical lines may be broken, and charged power lines may remain in flood waters, causing electrical hazards. Until the power is turned off at the main breaker, assume the lines are still active. This includes flooded basements and dwellings.

Toxic Spills

Flooding may occur near industrial sites, raising concerns of toxic chemicals and hazards being released in an uncontrolled manner into the environment and contaminating the surrounding ecosystems. Poisonings caused by the release of above or underground chemicals that may combine inadvertently may occur immediately or may take months following exposure. Avoiding contaminated floodwaters and using personal protective clothing and equipment to prevent contact with water are the best means of preventing illness and injury.


Food can be contaminated easily by floodwater contact; contaminants with pathogens and chemicals may cause illness. Any food that has been in contact with floodwaters should be treated as if it is contaminated. All food should be cooked thoroughly. Food may only be salvaged if it is in a commercially canned metal or rigid sealed plastic container and can be washed in a solution of warm clean water and detergent. The entire container should then be sanitized by soaking in a solution of one tablespoon of bleach in a gallon of clean water. Products should be relabeled with any information from the original label. Even cans with "easy open" tops should be considered unsafe and discarded, as bacteria may enter at the seams.


Sealed and bottled water is preferred for consumption as drinking water. There are several methods to treat water if sealed and bottled water is not available. Add 8 drops of sodium hypochlorite (bleach) to clear water or 16 drops to turbid water in a one gallon, standard sized container and agitate. Wait 30 minutes before drinking. You can also treat clear water with water purification tablets per manufacturer's directions.

• Take care when considering boiling water for disinfection. Remember that if the water is chemically contaminated, boiling will merely concentrate the toxic chemicals, not eliminate them.

• Add 5 drops of a 2-percent iodine solution to one liter of water and let stand at least 30 minutes, or longer if colder than 25 C (77 F). Do not use iodine if there is an allergy, if pregnant, or if thyroid disease is present.

• Use portable water filters per manufacturer's directions. These do not filter all chemicals and viruses. Check the manufacturer's guide.

Disease Threats

Disease hazards following a flood will vary depending upon location. The most common threats will be due to waterborne disease risks from bacteria or viruses carried from poor sanitation and agricultural disruption. Illnesses such as Campylobacter, Giardia, and Cryptosporidia are possible pathogens to be found. Tetanus, normally occurring in the soil and on debris, is also a high risk. In temperate climates, mosquito-borne threats are a problem several weeks following floods when waters recede and standing pools have yet to be absorbed into the soil, yielding plentiful breeding grounds for disease vectors. Dengue, Zika, and chikungunya may present in this area, although as reported cases of these diseases were negligible prior to the event, it is unlikely they will pose a risk. West Nile virus and other vector-borne disease may pose a greater threat, and care should still be taken against mosquito and tick bites. It is important in any case to maintain a good sense of personal hygiene, wash hands frequently, use mosquito repellent and insect-treated nets when unable to stay indoors, and ensure that all immunizations are up to date. Seek medical attention promptly for any fever, general symptoms or gastric illness lasting longer than several days, despite treatment.

Other Potential Hazards

Combustible or Poisonous Gases: Hurricanes can damage natural gas and fuel lines. As a result, explosive gas vapors may be present in buildings. Methane gas may also accumulate due to decaying materials. Open all windows upon entering a building. If you smell gas, leave the building immediately, and notify authorities. Do not smoke or use electrical equipment or telephones (including mobile phones) while in any building in which a gas smell is present. Do not use gasoline or other fuel burning equipment within buildings, or within 3 meters (10 feet) of doors, windows or air intakes (operating fuel burning equipment within a building will cause poisonous carbon monoxide to accumulate, even if doors and windows are open and fans are running).

Safe Use of Electrical Equipment: Electrical equipment that has been exposed to salt water will be unreliable even if it seems to be working properly. Be sure equipment is properly grounded and connected to a ground break-equipped electrical source.

Mold, Bacteria, and other Microorganisms: Floodwaters contain many infectious organisms, some of which can become airborne. The greatest respiratory risk is probably due to mold, and people with asthma or chronic lung disease are most likely to be affected. Mold can survive in structures that appear completely dry; complete drying of a building may require removal of ceilings, walls, insulation, flooring, and other materials. Wear rubber gloves and boots, goggles, an N95 respirator (if available), or a dust mask for protection during cleanup.


Weather/Road Conditions

National Hurricane Center:

National Weather Service:

National Meteorological Service (Spanish):

Louisiana Road Conditions:

Texas Road Conditions:

City of Houston Office of Emergency Management:

Houston Emergency Operations Center:

Harris County Flood Information:

FEMA Asset List:

US Coast Guard emergency telephone numbers: 281-464-4851; 281-464-4852; 281-464-4853; 281-464-4854; 281-464-4855


Austin-Bergstrom International Airport:

Corpus Christi International Airport:

Dallas Love Field Airport:

Dallas/Fort Worth International Airport:

Houston Airports:

Louis Armstrong New Orleans International Airport:

San Antonio International Airport:


CenterPoint Energy:


AEP Texas:


Related Advice: How to prepare for a hurricane/tropical cyclone/typhoon

Related Advice: How to prepare for thunderstorms and cope with them safely

Related Advice: What to do before, during, and after a flood

Related Advice: How to prepare for and survive a tornado