Click on a pin on the map to see more information. Flash floods are the most dangerous kind of floods, because they combine the destructive power of a flood with incredible speed. National Disaster Education Coalition, 1999, Talking about disaster: Guide for standard messages: Produced by the National Disaster Education Coalition, Washington, D.C., p. 63-64. If your place is located in any of these areas, then you should be ready for possible damage caused by floods, – Location is at the bottom of an elevated area like a hill. One example is when water mains break such as the one that occurred in July of 2014 on the UCLA campus in the United States that caused water to gush out into the surrounding area at 75,000 gallons per minute. 100-Year Flood-It's All About Chance; 2010; GIP; 106; Holmes, Robert R., Jr.; Dinicola, Karen. Floods caused by heavy rainfall or a water source overflowing with the effect of melting snow. Thanks for sharing your thoughts about cause. As water flows downstream from point "A" to point "B" and the drainage area (of the watershed) increases, the volume of streamflow increases. It can happen with steady rainfall over several days or it can happen because of a short and intense period of rainfall. The effects of development (conversion of land from forested or agricultural uses to commercial, residential, or industrial uses) on peak flows is generally much greater for low-recurrence interval floods than for high-recurrence interval floods, such as 25-, 50-, or 100-year floods.

This question points out the importance of proper terminology. The following topics provide background on some of the scientific issues regarding floods.

In these cases, streamflow will remain elevated for a longer period of time. Estimates of peak flows, which are outside the range of the established rating curve, may be made by an extrapolation of the rating curve to the peak stage. Flooding occurs in known floodplains when prolonged rainfall over several days, intense rainfall over a short period of time, or a debris jam causes a river or stream to overflow and flood the surrounding area. The USGS and other agencies often refer to the percent chance of occurrence as an Annual Exceedance Probability or AEP. Floods are a powerful force on our planet. •  Water Science School HOME  •  Surface Water topics  •. At locations where the stream channel widens or may contain heavy vegetation, the water velocity may decrease. The purpose of this manual is to provide a comprehensive description of state-of-the-art standardized stream-gaging procedures, within the scope described below. In natural ecosystems, there is a lot of resiliency to the majority of flood events. Snowmelt also causes inland floods, although rainfall is a more common cause. During periods of urban flooding, streets can become swift moving rivers and can be dangerous for drivers.
Recurrence-interval terminology tends to be more understandable for flood intensity comparisons. Effects of August 1995 and July 1997 Storms in the City of Charlotte and Mecklenburg County, North Carolina; 1998; FS; 036-98; Hazell, William F.; Robinson, Jerald B.; Young, Wendi S. Geographic Names Information System (GNIS), Mapping, Remote Sensing, and Geospatial Data. Given this, it may seem reasonable to think that peak flows would increase in the same manner, but this is not necessarily true. In the U.S., losses average close to $8 billion a … Your email address will not be published. Greentumble is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com. Climate changes cause a sudden temperature increase. However, that is not as threatening when a damn may burst and cause strong and heavy flooding. These and other factors determine whether or not a 100-year storm will produce a 100-year flood. Ices at the top of the mountains melt when the temperature rises. When we engage in development, our development must incorporate permeable surfaces that allow water to recharge groundwater supplies, instead of simply allowing precipitation to runoff and flood vulnerable areas. This information is from the U.S. Geological Survey Fact Sheet FS-036-98.
When a major flood occurs, you might have heard that the stream stage reached the "100-year flood level". When large amounts of rain falls on these impermeable surfaces, the water can accumulate and lead to flooding in low-lying areas if it is not directed properly. Can two "100-year floods" occur within several years or even within the same year?