What is the 100-Year Floodplain? |
The 100-year floodplain is a geographic region in which all locations have an annual flood exceedance probability of 1% or higher (or return period of 100 yrs or less). Here, the exceedance flood value is at least the ground elevation. Because probabilities vary by location, many locations within the floodplain have greater than a 1% chance of flooding to at least ground elevation.
A line on a map typically marks floodplains, where homes on one side of the line are in the floodplain and homes on the other are not. Yet, there is large uncertainty in estimating flood probabilities. So, it is likely that homes on either side of the floodplain line have very similar flood exposure. |
Flood return periods included in the 100-year floodplain.
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Acknowledgements & Credits: This material is based upon work supported by the Texas Department of Public Safety's Division of Emergency Management. Background photo courtesy of Mark Moran (Creative Commons license CC BY 2.0)
© 2019 Jennifer L. Irish & Steven M. Quiring. All rights reserved.
© 2019 Jennifer L. Irish & Steven M. Quiring. All rights reserved.