Flood Safety Awareness Week - Types of Flooding
Your National Weather Service (NWS) invites your participation in the annual Flood Safety Awareness Week, March 16-20, 2009.
Today's theme is flooding. Floods occur nationwide and are the deadliest weather related killer in the United States.
Northern Illinois and northwest Indiana have experienced several episodes of major to record flooding over the last year. Some of the flooding types experienced over the last few years included:
Urban Flooding - Heavy rainfall over urbanized areas like Chicago or Rockford can result in rapid rises in water levels on small creeks and ditches. Intersections and viaducts can be flooded in a matter of minutes. Impermeable surfaces, roadways, and storm drainage networks decrease the time from peak rainfall to peak runoff. Flash flooding over the Keith Creek basin in southeast Rockford resulted in significant damage in September 2006 and again in August 2007.
Ice Jam Flooding - When an ice cover begins to break and move downstream it can jam at a constriction in the channel such as a bridge, where a change in the slope of the river bed exists, or an obstruction in the river like an island. In 2008, flash flooding from ice jams occurred on portions of the Fox, Rock, and Kankakee rivers in Illinois.
River Flooding - Remnants of two tropical systems in September of 2008 resulted in torrential rainfall of nearly half the annual amount during the first 15 days of the month. Widespread river flooding occurred throughout northern Illinois and northwest Indiana. New crests of record were established at several river forecast points including the Illinois River at Morris and La Salle. Monitor the latest river levels and river forecasts at our Advanced Hydrologic Prediction Service page.
Here are some terms we use to inform you of the flood threat.
- Flood Watch or Flash Flood Watch indicates that conditions are favorable for flooding to happen.
- Flood Warning or Flash Flood Warning means flooding is occurring or imminent.
- Minor Flooding - minimal or no property damage is expected to occur, but the flooding could possibly cause some public threat or inconvenience.
- Moderate Flooding - inundation of structures and roads near streams will occur. Some evacuations of people and/or a transfer of property to hitcher elevations are necessary.
- Major Flooding - extensive inundation of structures and roads along with possible significant evacuations of people and/or transfer of property to higher elevations.
Additional information about flood safety awareness week is available at: www.weather.gov/floodsafety
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