Floods and Droughts

Floods are a dangerous hazard throughout the world. On average in the United States, about 165 people are killed and about $2 billion of damage occurs each year. Most people underestimate the power and destructiveness of flood waters.Learn more:USGS map...
Most currently available flood maps are used to assist planners in identifying and preparing for flooding scenarios. These maps portray statistics based on long-term historical records to estimate and forecast an approaching weather system. For more...
There are two basic kinds of floods, flash floods and the more widespread river flooding. Flash floods generally cause greater loss of life and river floods generally cause greater loss of property.A flash flood occurs when runoff from excessive rainfall...
Several types of data can be collected to assist hydrologists predict when and where floods might occur:Monitoring the amount of rainfall occurring on a realtime basisMonitoring the rate of change in river stage on a realtime basis, which can help...
Several kinds of flood maps are available from USGS and other sources.Online USGS map showing real-time flood conditionsUSGS Web site to track flooding in your areaOnline USGS current and past flood mapsNational Oceanic and Atmospheric Administration...
A drought is a period of drier-than-normal conditions that results in water-related problems. Precipitation (either rain or snow) falls in uneven patterns across the country. The amount of precipitation at a particular location varies from year to year,...
The beginning of a drought is difficult to determine. Several weeks, months, or even years may pass before people know that a drought is occurring. The end of a drought can occur as gradually as it began. Dry periods can last for 10 years or more. During...
A period of below-normal rainfall does not necessarily result in drought conditions. Some rain returns to the air as water vapor when water evaporates from water surfaces and from moist soil. Plant roots draw some of the moisture from the soil and return...
To view the USGS streamflow information on drought go to Drought Watch. This map shows below normal 7-day average streamflow compared to historical streamflow for the day of the year (United States). 
Rainfall in any form will provide some drought relief. A good analogy might be how medicine and illness relate to each other. A single dose of medicine can alleviate symptoms of illness, but it usually takes a sustained program of medication to cure an...