USGS - Science for a changing world

Flood Outlook 2012: Hoping for the Best, Preparing for the Worst

This Science Feature can be found at: http://www.usgs.gov/blogs/features/usgs_top_story/flood-outlook-2012-hoping-for-the-best-preparing-for-the-worst/

It’s difficult to forget the epic flooding along the Mississippi, Missouri, and many other rivers throughout 2011. Of course, the memory of these floods is especially vivid for those living in cities like Minot, N.D., where 12,000 people had to evacuate their homes and where record flooding caused an estimated $1 billion in damage; or in Cairo, Ill., where officials had to make complex decisions about whether to divert flood waters onto farmland in order to save the city.

Looking east at Burdick Expressway as the Souris River rises in Minot, North Dakota. Photo taken by USGS personnel during a FEMA Flood Inundation Mapping Project.

Throughout the last century in the United States, on average, floods have caused more lives lost and more economic damage than any other natural hazard. According to forecasts, severe flooding in 2012 will likely be far less widespread than last year. However, scientists cannot predict weather and water patterns with 100 percent accuracy, and there is always the potential for severe flooding somewhere in the country.

When it comes to flooding, preparation is key for saving lives and protecting property. USGS scientists and hydrologic technicians are specially trained and standing by. As soon as water starts to rise, they are measuring water levels, river velocities, and high water marks. All of this information is crucial for National Weather Service flood forecasts, for decisions by the U.S. Army Corps of Engineers to operate spillways and levees, and for the planning of Federal, State, and local emergency managers, first responders, and many other groups.

In preparation for flood events, the USGS continues to invest in and update equipment like the acoustic Doppler current profiler, which measures water velocity, as well as rapidly deployable streamgages, which measure river heights in areas that do not have a permanent gage or where a gage has been damaged by fast-moving water.

Perhaps most importantly, the USGS is constantly refining, innovating, and updating its ability to deliver river information to emergency managers, first responders, and other Federal agencies before, during, and after a flood. The USGS offers an increasing number of resources to help these organizations, as well as you and your family, better prepare for flood hazards.

Flood Inundation Mapping

When the water starts to rise, how do you know if you’re going to get wet?

Right now, if you want to see areas where river levels are higher than normal, you can go to USGS WaterWatch and view a map of the thousands of real-time streamgages that constantly monitor the Nation’s rivers and streams. But how do you put that number in context? If the current stage is forecasted to go above flood stage, does that mean water will be barely spilling over the banks? Or does it mean that your house might be underwater? At what stage is the river going to spill over onto a roadway and affect traffic? Are you and your family in danger?

River stage measurements can be confusing, and they are not always a great indicator of the actual scope and impacts of the flooding. To reduce this ambiguity, the USGS and the National Weather Service are working together to create visual products, called flood inundation map libraries, that show you estimates of where the water will be — what roads, yards, and buildings will be affected — when a river or stream reaches a certain stage.

For example, in Findlay, Ohio, the flood inundation map shows that when the stream stage is around 11 feet, only the roads closest to the river are underwater, but the rest of the town is out of danger. However, when you use the tool to map out a flood stage of 18 feet, streets as far as 15 blocks away from the river’s banks are underwater, as are a few parks, a cemetery, and almost the entire Findlay Country Club.

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 strategy goal of reducing the vulnerability of the people and areas most at risk from natural hazards. Flood inundation maps have been created for cities on the map indicated by a black triangle (Iowa City, IA, Marshall, MI, Ottawa, OH, Findlay, OH, Peach Creek, near Atlanta, GA, Albany, GA, Trenton, NJ St. John River, near Fort Kent, ME, and Scituate, MA).

In Iowa City, Iowa, the flood inundation map shows that when the stream stage is at 17 feet, the river is barely out of the channel, and most of the town is out of danger. But when you map out a flood stage of 25 feet, parks and local areas designed to hold floodwaters are submerged. At 30 feet, several neighborhoods and much of the University of Iowa are flooded. On this map, you can click anywhere in the flooded area to see the estimated water depth for any location at any stage. Damage estimation models, which are based on FEMA’s Hazus tool, are also available for each flood stage on the map. All of these features allow emergency managers to see what areas and how many people need to be evacuated, and to estimate the cost of potential flood damages.

This new tool is especially useful to emergency managers responsible for keeping people safe on the roads. In fact, over half of all flood-related deaths are the result of people driving their cars onto submerged roadways. These new, interactive flood maps allow emergency managers to see what roads will be submerged at a forecasted flood level, so that the roads can be closed long before waters start to rise.

Flood inundation maps have already been produced for nine areas in the United States. The USGS plans to produce over 40 more of these maps within the next year, including for Terra Haute, Ind., Sweetwater Creek, Ga., and Hattiesburg, Miss. The USGS hopes to eventually have flood inundation map libraries available for many other areas across the country.

You can see what areas have already been mapped by using the tool.

WaterAlert

Smartphones let you know when the river is rising

If you’re on the USGS site and reading this, chances are you probably have a favorite outdoor spot, a favorite river, and perhaps a favorite streamgage that you check on a regular basis. Did you know that you can get automatic notifications from that streamgage sent straight to you as an email or text message? The USGS provides a service called WaterAlert that can text or email you when water levels at a streamgage of interest exceed certain thresholds.

This means that you can keep tabs on a river without having to repeatedly check the USGS website. And if waters start to suddenly rise, you will be alerted, allowing you to put necessary precautions in place to keep yourself, your family, and your property safe.

USGS scientists take streamflow and water quality measurements downstream of the Bonnet Carre Spillway near Norco, La. The Army Corps of Engineers uses USGS streamflow data to help them manage flood control structures.

Sign up for WaterAlert by selecting a State, checking the “surface water” box, and clicking on your streamgage of choice. You can also subscribe to WaterAlert from the flood inundation interactive map. If you live in a community covered by a flood inundation library, use the flood inundation map to discover what flood stage puts you at risk, then click the link in the “Services and Data tab” to sign up to receive a text or email when the water approaches, reaches, or exceeds that stage!

Links:

Flood Inundation Interactive Mapper: http://wim.usgs.gov/FIMI/FloodInundationMapper.html

Additional information about Flood Inundation Mapping: http://water.usgs.gov/osw/flood_inundation/

WaterAlert: http://water.usgs.gov/wateralert/

Main USGS Flood Site: http://water.usgs.gov/floods

News Release: Smart Phones Know When Rivers Rise…with USGS WaterAlert: http://www.usgs.gov/newsroom/article.asp?ID=2919

News Release: Instant Information about Water Conditions: Ask the River to Text You a WaterAlert: http://www.usgs.gov/newsroom/article.asp?ID=2464