Where can I find flood maps?

FEMA is the official public source for flood maps for insurance purposes:

NOAA is responsible for producing flood forecast maps that combine precipitation data with USGS streamflow data:

USGS flood map products include:

  • USGS Flood Information: Maps and resources for current and historical floods
  • Flood Inundation Mapper: Shows where flooding might occur over a range of water levels. Only available for a few areas.
  • Flood Event Viewer: Provides access to additional data (such as rapid-deployment gages, temporary sensors, and high-water marks) collected during large, short-term flood events like hurricanes and multi-state storms.

Related Content

Filter Total Items: 5

What is a 1,000-year flood?

The term “1,000-year flood” means that, statistically speaking, a flood of that magnitude (or greater) has a 1 in 1,000 chance of occurring in any given year. In terms of probability, the 1,000-year flood has a 0.1% chance of happening in any given year. These statistical values are based on observed data.

Does an increase in the 100-year flood estimate originate from climate or land-use change?

Climate variability (dry cycles to wet cycles) and land-use change play a significant role, but there is a large amount of uncertainty around the flood quantile estimates (the value of discharge corresponding to the 100-year flood), particularly if there isn’t a long record of observed data at a stream location. Learn more: Flood recurrence...

We had a "100-year flood" two years in a row. How can that be?

The term "100-year flood" is used to describe the recurrence interval of floods. The 100-year recurrence interval means that a flood of that magnitude has a one percent chance of occurring in any given year. In other words, the chances that a river will flow as high as the 100-year flood stage this year is 1 in 100. Statistically, each year begins...

How are floods predicted?

Flood predictions require several types of data: The amount of rainfall occurring on a realtime basis. The rate of change in river stage on a realtime basis, which can help indicate the severity and immediacy of the threat. Knowledge about the type of storm producing the moisture, such as duration, intensity and areal extent, which can be valuable...

What are the two types of floods?

There are two basic types of floods: flash floods and the more widespread river floods. 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 causes a rapid rise in the water height (stage) of a stream or normally-dry channel. Flash...
Filter Total Items: 4
Date published: September 18, 2018

USGS Science – Leading the Way for Preparedness

Learn About USGS Hazards Science and More About National Preparedness Month: The very nature of natural hazards means that they have the potential to impact a majority of Americans every year.  USGS science provides part of the foundation for emergency preparedness whenever and wherever disaster strikes.

Date published: February 22, 2017

Stormy weather: How the USGS goes to work monitoring its effects

Atmospheric rivers are a global weather phenomenon that can bring large amounts of rain or snow to the U.S. West Coast each year. These rivers of wet air form over the Pacific Ocean near Hawaiʻi and pick up large amounts of moisture from the tropics and on their way to the West Coast. This moisture is carried in narrow bands across the Pacific Ocean to California, Oregon, Washington and Nevada.

Attribution: Natural Hazards, Pacific
Date published: August 22, 2016

Fighting the Floods

The USGS response to the Louisiana floods is part of the larger USGS flood science mission...

Date published: January 14, 2011

ARkStorm: California’s other "Big One"

For emergency planning purposes, scientists unveiled a hypothetical California scenario that describes a storm that could produce up to 10 feet of rain, cause extensive flooding (in many cases overwhelming the state’s flood-protection system) and result in more than $300 billion in damage.

Filter Total Items: 8
June 30, 2018

Understanding Floods | Long-term Streamflow Data Collection

The USGS is developing methods to improve data collection during floods to gain new insight into the rise and fall of flood waters. In the past, the only data left behind after a flood was how high the water got, or the peak of the flood. This video presents the methodology that hydrologists are using to set up a Continuous Slope-area Reach in remote areas that are

Flood inundation mapping - Use an interactive tool to view flooded landscape at variable river heights.
December 14, 2016

Flood inundation mapping - Interactive floodplain mapping tool.

The USGS Flood Inundation Mapper

Floods are the leading cause of natural-disaster losses in the United States. Although the amount of fatalities has declined due to improved early warning systems, economic losses have continued to rise with increased urbanization in flood-hazard areas. The USGS

screenshot of the flood inundation mapper web tool
April 14, 2016

Flood Inundation Mapper

The recent (3/18/16) real-time report from the USGS Flood Inundation Mapper for Petersburg, IN, showed that the moderate flood would continue to decline in the hours ahead.

Image: Flood Inundation Mapper
March 7, 2012

Flood Inundation Mapper

A powerful new tool for flood response and mitigation are digital geospatial flood-inundation maps that show flood water extent and depth on the land surface. Because floods are the leading cause of natural-disaster losses, the U.S. Geological Survey (USGS) is actively involved in the development of flood inundation mapping across the Nation pursuant to its major science

flood sign
January 11, 2012

Flood Sign in Tualatin River, OR

Peak flood height of 1996 flood, as observed in the Tualatin River, OR.