Flood and Flash Flood Safety
Perhaps the biggest cause of flood-related deaths and injuries is lack of public understanding of the severity and danger involved in floods and flash floods. Many people are killed by driving or walking on roads or bridges that are covered by water. Even though the water might look only inches deep, it could be much deeper and contain very strong currents. It only takes two feet of water to carry away most vehicles; six inches of swiftly moving water will sweep a person off his/her feet. Nearly half of all flash flood related deaths are auto related.
Here is the science of it...Water weighs 62.4 lbs. per cubic foot and typically flows downstream at 6 to 12 miles an hour. When a vehicle stalls in the water, the water's momentum is transferred to the car. For each foot the water rises, 500 lbs. of lateral force are applied to the car. But the biggest factor is buoyancy. Buoyancy is the tendency of an object to remain afloat. For each foot the water rises up the side of the car, the car displaces 1500 lbs. of water. In effect, the care weighs 1500 lbs. less for each foot the water rises. Therefore, about 2 feet of water will carry away most automobiles. If you are approaching a flooded roadway, turn around and take an alternate route, even though vehicles in front of you have passed through the high water, you may not be as lucky. If your car stalls or becomes trapped, get out immediately and move to higher ground. Many deaths have resulted from attempts to move stalled vehicles. Most trucks, four-wheel drive, and sport utility vehicles also are susceptible to being swept away by high water. Such vehicles often give motorists a false sense of security, believing the vehicles are save under any conditions. Be extra careful at night when it's harder to see flood dangers. Seventy-five percent of flash flood fatalities occur at night. This makes sense because you cannot see the rising water after dark, plus, evening thunderstorms dump most of their rain close to or after nightfall.
Never let children play near creeks or storm drains when the water is rising or high. Every year, deaths or injuries occur as a result of people getting swept away, with the most frequent victims being children. Flooded streams and rivers are not safe for recreational boating. Many canoeists and kayakers have had to be rescued from dangerous rapids in flood-swollen streams and rivers. Never set up a tent or camper on the bank of a river or stream. It is best to allow some distance between the campsite and water so if a flash flood does occur, you will have more time to move to higher ground. If you live in a low-lying area or near a creek, pay close attention to the water level during heavy rain events. Water levels rise rapidly during flash flood, often surprising victims. Heavy rainfall upstream can cause a river or stream to rise quickly, even if it is not raining near you. Central Texas is no stranger to flooding.
On September 9-10, 1921, South Central Texas saw a flood event that still holds the national 24 hour rainfall record. At Thrall, Texas, in eastern Williamson County, 32.0 inches of rain fell in 12 hours. 38.3 inches fell in 24 hours ending at 7:00am September 10, 1921. The storm began brewing in the western Gulf of Mexico September 6th. It quickly formed into a hurricane then made landfall near Tampico, Mexico on September 7th. The storm fell to tropical storms status and headed northward to Texas. As it crossed the Rio Grande its winds had decreased to tropical depression intensity. The remnants moved into South Texas where the northern part of San Antonio received very intense rainfall on the evening of the ninth. Up to 18 inches of rain had fallen by 11:00pm. A flood wave slammed through downtown San Antonio between 1 and 2 am on Sept. 10th. The downtown area was under 12 feet of water as creeks overflowed their banks. Cars, trees, and buildings made debris dams at all the street bridges. Many people evacuated vertically by climbing to upper floors of buildings during the rapidly rising flood. Unfortunately, during the early morning hours, fifty-one people had perished. By 7am, Williamson County, south of Temple, had received disastrous rainfall. Eighty-seven people drowned in and near Taylor, TX as 19.65 inches of rain fell in just 12 hours ending at daybreak. 23.11 inches fell there in 24 hours. Nearby Thrall received 32 inches in 12 hours and the record setting 39.3 inches in 24 hours. Two hundred fifteen people drowned in Texas with ninety-three of those in Williamson County alone. This remains the deadliest flood in Texas history.
Be prepared to move quickly to higher ground if water levels begin rising. Quickly responding to an evacuation order can save your life. If advised to evacuate, do so immediately and follow recommended evacuation routes. Watch NewsChannel 25 or 25Weather Now to see if your county is under a flash flood watch or flash flood warning. A flash flood watch means a flash flood is possible within or near the designated watch area. A watch is usually issued to cover many counties. A flash flood warning means a flash flood has been reported or is immanent. Flash flood warnings are issued by county. Take necessary precautions immediately if your county is under a flash flood warning. If a watch or warning is issued for any county in Central Texas, the counties affected will be displayed on NewsChannel 25 and 25Weather Now so you can stay informed.