FLOODS/FLASH FLOODS

Flash Floods:

Flash floods are short-fuse weather events, typically lasting on the order of 6 hours or less. Usually, flash floods occur within a few minutes or hours following an excessive rainfall event. They can also be caused by a man-made event, such as a dam or levee failure. Flash floods cause most of the fatalities associated with flooding events. Usually, less warning lead time is provided for flash flooding which requires quick action on the part of the public.

Urban Floods:

Flash flooding is most severe in urban areas like the Houston metropolitan area. Urbanization increases runoff by 2 to 6 times over what would occur in natural terrain. Flood waters can fill streets, freeway underpasses, and parking lots and can sweep away cars.

River Flood:

Heavy rainfall falling over a widespread area (such as a large portion of a watershed) over a prolonged period (like several days) can cause river flooding. Typically, river flooding begins as a high crest on the upper part of a watershed that takes several days to move downstream. Due to the slow nature of river flooding, ample advanced warning is provided to evacuate people or property in the path of the flooding.

June 2001:

Tropical Storm Allison devastated a large portion of Southeast Texas with an incredible amount of rain as she meandered around Southeast Texas for over five days. Between the 5th and the 10th, much of Houston and the surrounding areas to the north, east and south received between 15 and 35 inches of rain which caused devastating flooding and flash flooding. The largest amount fell over a 6 to 12 hour period on the 8th and 9th resulting in 22 deaths in the Houston area. More than 48000 homes were damaged (11000 with major damage and 3600 completely destroyed). More than 70000 automobiles were flooded during the storm. In Harris County alone, an estimated 300 billion gallons of water fell. This amount was enough to fill the Astrodome more than 5600 times! Allison ended up being the costliest tropical storm ever (>$5 billion) for the state of Texas and for the United States.

September 1998:

Tropical Storm Frances made landfall along the upper Texas coast on September 11th. As the storm moved inland, widespread heavy rainfall occurred in the Houston metropolitan area. Rainfall amounts of up to 16 inches were reported in the downtown Houston area. Frances caused extensive flooding along White Oak Bayou and flooded several major roads and freeways in the Houston area.

October 17-21, 1994:

This was perhaps the worst flooding to impact southeast Texas on record. Lake Livingston recorded a record height on the 17th and a record flow of 110,000 cfs. Liberty recorded 30 inches of rainfall in less than 48 hours, and much of the city went underwater due to a failed levee system. Spring Creek and Lake Houston set new flood crest records. Several major highways into and out of Houston were flooded including I-45 north of Houston and US 59 northeast of Houston. Four fuel pipelines ruptured on the San Jacinto River, causing a massive fuel spill and widespread fires. An estimated 22,000 homes were flooded across southeast Texas during this event, with $900 million in damage reported. Seventeen fatalities resulted from the floods.

March 3-4, 1992:

Heavy rainfall associated with a stationary line of thunderstorms produced major flash flooding in the metro Houston area. Both I-10 and I-45 near White Oak Bayou were covered with several feet of water bringing traffic to a standstill for several hours. An estimated 2000 homes and 4000 automobiles were flooded. One fatality was attributed to the storm.

• FLOOD WATCH
  Means that conditions in the watch area will be favorable for flooding during the specified period. Usually heavy rainfall is expected following a long period of wet weather.
• FLASH FLOOD WARNING
  Flash flooding is reported or is imminent in the counties specified in the warning. Take immediate precautions.
• URBAN AND SMALL STREAM FLOOD ADVISORY
  Flooding of streets, low-lying areas like underpasses and storm drains, and small streams is expected. Caution should be taken while traveling.
• FLASH FLOOD STATEMENT
  Follow-up information on a Flood Watch or a Flash Flood Warning.
• RIVER FLOOD OUTLOOK
  Indicates potential for flooding along rivers and streams.

1. Know the flood risk at your place of home or business and its elevation above flood stage.
2. Store drinking water in clean bathtubs or containers. This is very important as flood waters will contaminate the drinking water supply in your area.
3. Stock non-perishable food items requiring little cooking and no refrigeration.
4. Keep first aid supplies on hand.
5. Keep NOAA Weather Radio, battery-powered portable radio, emergency cooking equipment, and flashlights in working order.
6. Install check valves in sewer traps to prevent flood waters from backing into your home.

first aid kit

canned food/can opener

bottled water

rubber boots/gloves

NOAA Weather Radio

battery-powered radio/batteries

flashlight

1. If advised to evacuate, do so immediately!!
2. Move to a safe area...not cut off by flood waters.
3. Avoid areas you know are subject to flooding.
4. Do NOT attempt to drive over a flooded roadway. Do not drive into barricaded areas, the barricades are there for a reason!
5. Children should never play around storm drains, creeks, streams, or rivers, or in flooded streets.

1. Boil drinking water before using. Do not use tap water without boiling it!
2. Seek necessary medical care at the nearest hospital. Clothing, food and shelter are available at the nearest Red Cross.
3. Do not visit disaster areas. You may hamper rescue and emergency operations.
4. Electrical equipment should be checked or dried before being returned to service. Make sure to wear rubber gloves and rubber boots when working with electrical equipment.
5. Report broken utility lines to the proper authorities.

Flood Events (by county)

Flood Events (by month)

Flood Events (by time)