Indiana Water Monitoring Council 
Maximizing resources through improved communication,
                  coordination, data sharing, and collaboration

Indiana water-resource issues: 

Flooding



According to the Federal Emergency Management Agency (FEMA), “Floods are one of the most common hazards in the United States. Flood effects can be local, impacting a neighborhood or community, or very large, affecting entire river basins and multiple states.” Some floods develop slowly, sometimes over a period of days. But flash floods can develop quickly, sometimes in just a few minutes and without any visible signs of rain. Flash floods often have a dangerous wall of roaring water that carries rocks, mud, and other debris and can sweep away most things in its path.  Flooding can occur behind levees and floodwalls when those structures are overtopped or breached, and dam failures can cause particularly devastating floods. Overland flooding from heavy rainfall can occur away from a stream or river, such as when road underpasses are flooded by torrential rains.  Floods cause human casualties and damage by inundating structures and roads, they can also cause substantial damage through bank erosion and movement of the stream channel – this particular hazard is called the “fluvial erosion hazard.”

In order to limit flood-related injuries and property damage, surface-water hydrologists study stream flow patterns and areas prone to flooding. You've probably heard someone refer to a 50-year or 100-year flood - these numbers called "recurrence intervals" indicate the statistical chance of a flood occurring in any one year. For example, a 100-year flood has a 1/100 or 1% chance of occurring in any year. People sometimes misunderstand this terminology, and think that once a 100-year flood has happened, another will not happen for 100 years - this is not true, and there are areas that have seen multiple 100-year or greater floods in the same year - sometimes, within a month of each other! The interval is based on a statistical analysis of streamflow data, which highlights the importance of maintaining gaging stations and establishing long-term data sets. Other flood-related information includes high-water marks that establish the elevations of flood waters. These records are used in conjunction with recurrence intervals to map floodplains that FEMA uses to administer the National Flood Insurance Program and that state and local agencies use to regulate development in floodplains. The information also helps developers and city planners to build structures in such a way that minimizes damages linked to flood events. The Indiana Department of Natural Resources has developed an online tool to disseminate floodplain mapping information, the Indiana Floodplain Information Portal (INFIP). 

Another proven way to help reduce damages and save lives is early flood warnings. The U.S. Geological Survey (USGS) maintains more than 220 streamgages across Indiana that provide emergency managers and the public with real-time water level data 24/7/365. The National Weather Service uses the streamgage data and advanced predictive techniques to provide flood forecasts at many streamgage stations. These forecasts can provide estimates of flood water levels up to 7 days in advance. The National Weather Service also has other ways of giving people "heads up" about flooding, such as issuing flood watches and warnings. 


Water-resource professionals in Indiana focusing on flooding and stream channels:

  • David Knipe (Indiana Dept. of Natural Resources)
  • Jeff Woods (U.S. Geological Survey)
  • Bob Barr (Indiana Univ. – Purdue Univ. Indianapolis)
  • Vankatesh Merwade (Purdue Univ.)


Related resources:

Federal Emergency Management Agency, 2014, Flood Map Service Center, accessed September 3, 2014 at: https://msc.fema.gov/portal.

Indiana Department of Natural Resources, 2014, Floodplain Mapping, accessed August 18, 2014 at: http://www.in.gov/dnr/water/2454.htm#flood%20plain%20mapping.

Indiana Department of Homeland Security, 2014, Floods, accessed August 18, 2014 at: http://www.in.gov/dhs/2791.htm.

Indiana Fluvial Erosion Hazard Program, 2014, home page accessed August 18, 2014 at: http://feh.iupui.edu/.

National Flood Insurance Program, 2014, home page accessed August 18, 2014 at: https://www.floodsmart.gov/floodsmart/.

National Weather Service, 2014, Significant River Flood Outlook, accessed August 18, 2014 at: http://www.hpc.ncep.noaa.gov/nationalfloodoutlook/. 

Purdue University GIS Services, 2014, Soil-based Natural Floodplain Maps, accessed August 20, 2014 at: http://mapsdev.lib.purdue.edu/floodmap/floodmap.htm.

U.S. Geological Survey, 2014, Indiana Daily Streamflow Conditions, accessed August 18, 2014 at: http://waterdata.usgs.gov/in/nwis/rt/.

 

This page written and maintained by Bryan Wallace from the City of Jeffersonville’s Engineering Department. 
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