Floods

Houston Floods. It's that simple, and it floods here often in some places more than others . Customers can get two PDF files about the last major flood. There are also long periods of drought when the ground cracks from a lack of rain. There is no viable bedrock in this region and the soil is expansive due the high content of clay and "black mumbo"..

Flooding

Introduction

Floods kill people and destroy homes in many parts of the United States every year. Federal agencies estimate that an average of over 125 people die every year in the United States because of flooding, although losses vary widely from year to year. Property damage ranges into the billions each year, and has been rising in recent decades.

Of course the live video of a family clinging to their car in a swollen river as rescuers winch down from a helicopter is so compelling that few viewers can change channels. But flooding is also worth covering because if people are informed, they can make decisions which will save lives and reduce property loss.

Background and Context

As the deadliest and most damaging of U.S. weather hazards, floods have long been the focus of dreadful fascination by the public. Sometimes it is the scale that awes us—as in the legendary Mississippi River flood of 1927. Sometimes it is the sudden lethality—as in the 1889 Johnstown Flood that killed more than 2,209 people.

Flooding actually occurs from a range of causes and conditions—not always the ones that first come to mind. For example, few people appreciate that inland flooding has been the cause of more than half the deaths arising from hurricanes in the last three decades. Of the 56 people who died in 1999's Hurricane Floyd, 50 drowned from inland flooding. Torrential rains can accumulate when a storm becomes "stalled" in a certain location, even hundreds of miles from the coast.

Of course, river flooding is the kind we think of most commonly. Heavy rains or rapid snowmelt on upstream watersheds cause rivers to rise—more so at chokepoints or where tributaries converge.

Coastal flooding is also very common. In many places, coastal land is very close to sea level, and therefore vulnerable. During hurricanes or other large storms, waves may be much higher than normal, and super-low atmospheric pressure often forces sea level to rise a dozen feet or more above normal in a "storm surge." When violent surf and storm surge coincide with normal high tides, the results can be catastrophic.

Less often thought of are the floods that can result from the failure of dams, impoundments, or other regulatory systems. The Johnstown flood is an example. There are more than 76,000 dams in the National Inventory of Dams, and probably others uncounted.

FEMA, which runs the National Dam Safety Program, says there are 10,400 high-hazard and 13,300 significant-hazard dams in the United States FEMA says "Emergency Action Plans" are essential for all of these dams, but that so far some 70 percent still do not have them. According to the National Performance of Dams Program at Stanford University, "1,595 significant hazard dams are within one mile of a downstream city." To keep things in perspective, it is worth remembering that many dams offer major protection to the public from flood control.

Floods can be a concern even in arid and semi-desert parts of the country, such as those in the West. Flash floods there are more of a danger because people do not expect them. Arroyos and washes, or normally dry streambeds and gullies, can fill with water within minutes or seconds during an intense downpour. Because roads often follow their contours, they may present danger to people in cars.

A flash flood is really any sudden, severe flood event, and they can have a variety of causes—although large sudden downpours are the main ones. The effects of a downpour are worsened when terrain will not absorb water. Reasons vary: soil type (e.g. clay), lack of vegetation, steepness, extensive pavement (urban areas), frozen or ice-covered soil, or the saturation of soil by previous rains.

Another cause of flooding in some areas is ice jams. In colder northern areas, ice sheets form on the surface of a river during cold winter months of low flow. Warmer weather and higher flows cause the ice to break up into huge slabs that the current pushes downstream. When these slabs pile up against some obstacle, they form a dam that causes water to pool upstream—and flooding results.

Floods typically get the most headlines when waters are about to crest. But there are important post-flood stories that need telling as well. Members of a flood-stricken community need all kinds of information to avoid pitfalls and deal with problems. For example, failure of normal sewage and drinking water systems means people need advice about how to find safe drinking water. They need to avoid pumping out flooded basements too quickly to prevent water pressure from destroying foundations. They need to understand and address the problems of mold and mildew in waterlogged buildings. And of course they need advice on how to connect with disaster-aid agencies.

Issues

The federal government spends several billion dollars on disaster aid in any given year—a major share of it going to communities hit by flooding. Almost everybody agrees that people flooded out of their homes need immediate help.

But important issues arise over whether money is better spent preventing losses before-the-fact than compensating for them after-the-fact. And it is also an issue whether taxpayer money spent merely to compensate for flood loss does not encourage, even subsidize, people to remain in harm's way.

Federal disaster aid funds temporary housing for people while damaged homes are being repaired, money to help repair homes, grants for basic living expenses, etc., when these are not covered by insurance. There are also low-interest loans to families, farms, and businesses to help them repair or replace lost property—as well as unemployment aid, tax breaks, legal services, and crisis counseling. Another kind of aid goes to local governments, to help them clean up debris and restore facilities like roads, utilities, public buildings, and parks.

A different set of FEMA programs and funding are aimed at preventing and mitigating flood hazards. The most dramatic involves feds partly funding buyouts of flood-damaged property—to help people buy houses on dry land and the bought property reverting to uses like parks under ownership of local government. Other federal funds support measures like physically moving houses beyond the floodplain, elevating them on stilts, or floodproofing them.

The most important federal effort to address longer-term flood problems is the National Flood Insurance Program. People in flood-prone areas find it nearly impossible to get ordinary insurance against flooding—precisely because they are in flood-prone areas. The NFIP involves a bargain from which both sides benefit. Local communities must qualify by adopting and enforcing floodplain management ordinances (which might, for example, forbid building new houses in floodplains). This reduces future flood damage and federal liability for disaster aid. In return, the federal government backs flood insurance offered in these communities by participating private insurance companies. National Flood Insurance is offered in more than 19,000 U.S. communities.

Flood issues spur many policy and political debates at both the local and national levels. Although the NFIP insists that the program pays for itself, critics often charge that it is federally subsidized.

The debate is likely to emerge again as Congress and the President struggle with the 2002 budget. The Clinton administration, following the great Mississippi-Missouri flood of 1993, shifted a much greater emphasis in funding toward mitigation and buyouts, to the applause of environmentalists. President Bush's budget proposal would de-emphasize mitigation in favor of more direct (and politically popular) disaster aid.

National Weather Service Safety Brochures – Prediction, Floods, Covered Roadways

In August 2002, the National Safety Council partnered with the National Oceanic and Atmospheric Administration (NOAA) and National Weather Service (NWS) on safety and health initiatives surrounding the Advanced Hydrologic Prediction Service (AHPS). The result: a new AHPS brochure that increased awareness of the Weather Service’s improved river and flood forecasting capabilities and water information across America.

Since then, we’ve continued our partnership to produce:

Organizations

 

Click here to find additional information on storm proofing including wind forces.

Click here to View Flood Plane Maps from www.efloodmaps.coma division of Dodson and associates.
Harris County Montgomery County Fort Bend County

Also try these links:

Consequences of Land Subsidence

InSAR

InSAR-Detected Inland Subsidence, 1996

InSAR-Detected Coastal Subsidence, 1996–99

Integrated Monitoring in the 21st Century

Selected References

Figures

1. Map showing subsidence study area and extent of two satellite scenes, Houston-Galveston Bay area, Texas

2. Map showing extent of subsidence in the Houston-Galveston Bay area during 1906–95

3. Map and graphs showing that during 1978–95, subsidence in areas southeast of Houston essentially ceased as pumpage there decreased; and subsidence continued in areas northwest as pumpage there increased

4. Photograph showing land subsidence of 5 to 7 feet in a residential area in northern Houston exacerbated flooding in June 1989

5. Map showing areas of interferograms shown in figures 6–9

6. Wrapped and unwrapped interferograms for the western Houston area for the 11.5-month period January 13–December 29, 1996

7. Unwrapped interferogram for the Texas City area for the 31-month period August 27, 1996–March 29, 1999

8. Unwrapped interferogram for the Sagemeadow-Johnson Space Center area for the 31-month period August 27, 1996–March 29, 1999

9. Unwrapped interferogram for the Baytown area for the 31-month period August 27, 1996–March 29, 1999

    (Areas of Responsibility)             (Explanation of  Additional   hydrologic information
 for the area served by the NWS Forecast Office in Houston/Galveston 

Air Quality Problems Caused by Floods

How Are Floodwaters an Indoor Air Quality Problem?

During a flood cleanup, the indoor air quality in your home may appear to be the least of your problems. However, failure to remove contaminated materials and to reduce moisture and humidity can present serious long-term health risks. Standing water and wet materials in the home can become a breeding ground for microorganisms: bacteria, mold, and viruses. They can cause disease, trigger allergic reactions, and continue to damage materials long after the flood.

What Are the Health Effects?

Standing water is a breeding ground for microorganisms, which can become airborne and then can be inhaled. When floodwaters contain sewage or decaying animal carcasses, infectious disease is of concern. Even if the water appears clean, microorganisms can cause allergic reactions in sensitive individuals. For these health reasons, and also to lessen structural damage, all standing water should be removed as quickly as possible.

Excess moisture in the home is an indoor air quality concern in several ways:

How Can I Reduce the Moisture in My Home?

Drying out can take several weeks and microorganisms will continue to grow as long as the moisture and humidity levels are high and as long as there are damp items in the home. Materials such as carpet that cannot be adequately dried out should be discarded. Steps you can take to help reduce moisture in your home include the following:

What Indoor Air Problems Are Caused by Floodwaters?

Asbestos is a mineral fiber commonly used in the past in a variety of building construction materials for insulation and as a fire retardant. Some products that may contain asbestos are pipe and furnace insulation materials; asbestos and cement shingles, siding, and roofing; millboard; resilient floor tiles, the backing on vinyl sheet flooring, and floor tile adhesives; soundproofing or decorative material; patching and joint compound; certain fireproof gloves; and stove pads. However, most products made today and in the past do not contain asbestos. Asbestos can cause lung cancer, mesothelioma (a cancer of the chest and abdominal linings), and asbestosis (irreversible lung scarring that can be fatal). The risk of lung cancer increases with the number of fibers inhaled.

Asbestos, when damaged by a flood, should be repaired or removed by a professional. Repair usually means either covering or sealing the asbestos material. Covering involves placing a protective wrap over or around the material that contains asbestos thereby preventing the release of fibers. Sealing involves treating the material with a sealant that either binds the asbestos fibers together or coats the material so no fibers are released. Repair is usually cheaper than removal, but some repairs may make it more difficult to remove the asbestos later if the need arises.

Biological contaminants are or were living organisms. Common indoor biological contaminants are bacteria, molds, mildew, viruses, animal dander, house dust mites, cockroaches, and pollen. Nutrients and moisture are necessary to support biological growth. A flooded home can contain both of these conditions. Biological contaminants can trigger allergic reactions and asthma, and some can release disease-causing toxins that can damage the liver, central nervous system, digestive tract, and the immune system.

There are several ways to reduce your exposure to biological contaminants:

Carbon Monoxide is a colorless, odorless gas that is produced as a result of incomplete burning of carbon-containing fuels such as coal, wood, charcoal, natural gas, and fuel oil. When houses are flooded and occupants are without electricity, people sometimes attempt to use gasoline-powered generators, camp stoves, and lanterns indoors. Using these devices indoors poses serious safety risks and is strongly discouraged. Devices that are designed for outdoor use should never be used indoors. Using these devices can result in high levels of carbon monoxide, which can cause death.

Here are several ways to prevent carbon monoxide poisoning:

Lead

Approximately 64 million homes, or 83 percent of the privately owned housing units built before 1980 have lead-based paint somewhere in the building. Nearly one-fifth of these residences are home to families with children under the age of seven. Lead can also come from the solder or plumbing fixtures in the home, fishing lure weights, ceramics, and bullets. A flood in the home can expose the residents to lead from deteriorating paint, contaminated soil, and dust from peeling or chipping paint. Young children are especially vulnerable. Elevated lead levels can cause brain damage, stunt a child's growth, damage kidneys, impair hearing, cause vomiting and headaches, and cause learning and behavioral problems. In adults, elevated lead levels can increase blood pressure, nerve disorders, sleep problems, muscle and joint pain, and mood changes.

You can do several things to reduce your exposure to lead:

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