Flash flooding and other flood events, over the long term, kill more people in the United States than other types of severe weather. Floods can roll boulders the size of cars, tear out trees, destroy buildings and bridges, and pose a significant threat to human lives.
Flash flooding is a rapid rise of water along a stream or low-lying urban area. Most the deaths and damage from this type of flooding tends to occur in areas immediately adjacent to a stream and are a result of a combination of heavy rain, dam or levee failure, rapid snowmelt, or ice jams. Many times the risk associated with these floods is not taken seriously because they occur along small streams, which is why everyone who lives near any stream is encouraged to determine their risk by looking at the FEMA flood maps. FEMA flood maps can be accessed at https://msc.fema.gov/portal or through the Story County Flood Plain Management website at http://www.storycountyiowa.gov/index.aspx?nid=205. Residents are also encouraged to learn about possible risk upstream such as dams or levees.
Flash floods can be produced when slow moving or multiple thunderstorms occur over the same area and it generally occurs within 6 hours of the rain event. The flooding can be caused by rain falling several miles upstream which then moves downstream rapidly.
Densely populated areas also have a high risk for flash flooding as the construction of buildings, highways, driveways, and parking lots increases runoff by reducing the amount of rain absorbed by the ground. Another source of flooding may be storm drains which can become overwhelmed which flood roads and buildings. Contact your public works department if you notice blocked storm drains so they can be cleaned out and ready to accept a heavy rain.
Turn Around….Don’t Drown
Almost half of all flash flood fatalities occur in vehicles. Many people don’t realize two feet of water on a bridge or highway can float most vehicles. If the water is moving rapidly, cars, trucks, or SUVs can be swept off bridges and roads into the creek or downstream with the flowing water. Water can also erode the road bed, creating unsafe driving conditions.
Underpasses are another source of danger as they can fill rapidly with water, while the adjacent roadway remains clear. Driving into a flooded under-pass can quickly put you in five to six feet of water. The danger associated with flash floods is amplified at night when flooded roads are difficult to see. When you approach a flooded road, TURN AROUND, DON’T DROWN!
Flood Planning & Preparedness
· Be aware of the areas which flood around your community.
· Have a flood & evacuation plan which takes into account flood prone streets before the flooding comes. If you are advised to evacuate...evacuate!!
· Discuss flood plans with your family. Everyone in your family should know where to go if they have to leave.
· Have a three day supply of non-perishable food and water. It could take up to three days for help to come.
· Monitor your local National Weather Service for updates to the flooding situation. http://www.crh.noaa.gov/dmx/
· NEVER try to walk, swim, drive or play in flood water. You may not be able to see how fast the water is moving or see holes & submerged debris.
· Children should NEVER play around high water, storm drains, viaducts or arroyos. Six inches of water can knock you off your feet.
The NOAA Weather Radio is the best way to receive watches and warnings from the National Weather Service. The NOAA Weather Radio broadcasts the watches and warning, forecasts and other hazard information 24 hours a day. NOAA Weather radios can be purchased at most “big-box” stores.
Information on stream gauges and water levels throughout the State is available online through the National Weather Service Advanced Hydrologic Prediction Service (AHPS) at http://water.weather.gov/ahps2/index.php?wfo=DMX and the Iowa Flood Center’s, Iowa Flood Information System (IFIS) at http://ifis.iowafloodcenter.org/ifis/en/.
Information on assembling a disaster kit, making a plan and other Severe Weather Preparedness information can be located on the Story County website at www.storycountyiowa.gov/ema under Disaster & Emergency Preparedness. Story County Emergency Management can also be followed through Facebook at http://www.facebook.com/storycountyema which is being used for public education and Emergency Management activities.