Where it rains, it can flood. But water runs downhill, so it is possible to anticipate the highest risk areas.

Local Flood Hazards

Local Flood Hazards: Where Will it Flood?

Special Flood Hazard Areas

Areas with a 1% or greater probability of flooding in any given year have been mapped by the Federal Emergency Management Agency (FEMA) for many rivers, streams, and lakes (also called the 100-year floodplain). Development activities within this “special flood hazard area” area require a floodplain development permit from the municipality. Flood insurance may be required for a mortgage. In addition to this regulated floodplain, some FEMA Flood Insurance Rate maps also show a floodway—high risk part of the floodplain that should be kept open to allow for the flow of water—and the moderate risk 0.2% probability (500-year) floodplain.

FEMA Flood Map Service Center

The “official” effective Flood Insurance Rate Maps for STC counties are paper maps maintained in municipal and county planning offices. Scanned images and any subsequent revisions or amendments are also available at the FEMA Flood Map Service Center website.
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Online mapping tools

STC and counties maintain online mapping information that includes approximate boundaries from the FEMA maps. These approximate flood zones can be viewed with aerial photography and other information.
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Flood hazards occur near every waterbody

Flash floods, which develop quickly, send torrents of water down streams and ditches and often cause extensive erosion damage. High runoff from developed areas can overwhelmed stormwater systems and flood urban areas, particularly in the fall when leaves clog the storm drains. Ice, debris, watershed development, or altered drainage patterns can result in flooding of areas that have not previously flooded or been mapped as high risk areas.

It is prudent to assume that any site near a river, stream, lake, wetland, or drainageway may be subject to flooding or erosion hazards. Soil characteristics and other analyses may provide additional clues about where these risks are highest.

Web Soil Survey

Web Soil Survey by the USDA Natural Resources Conservation Service provides mapping and descriptions of soils, including an indication of whether it is poorly drained or subject to frequent flooding.
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Flood Smart Communities Mapping of the Cohocton River Watershed

Flood Smart Communities Mapping of the Cohocton River Watershed includes “Community Planning Floodplains” mapped by the Nature Conservancy
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Levees reduce — but do not eliminate — flood risks

Even though the design, construction, operation, and maintenance of the region’s levees may be exemplary, there is still a possibility that they will be overtopped or fail.

STC Levee Maps

Shows the area protected by each levee system.
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National Levee Database

U.S. Army Corps of Engineers website provides levee maps and data.
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Guidelines for Levee-Protected Areas

Handout
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So, You Live Behind a Levee! What you should know to protect your home and loved ones from floods

(American Society of Civil Engineers)
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If it has flooded before, it can flood again

Mother Nature doesn’t look at the flood map and flood risks are increasing. Learn about past flooding from neighbors, historical societies, and local governments.

Historic Flood Information Map

Map of the STC region shows floods of record (highest recorded at a gauge) and historic water levels for major events.
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Planning in Water’s Way online mapper

Includes delineation of areas inundated by river flooding during the 1972 Tropical Storm Agnes Flood (as documented by the U.S. Geological Survey) for the Elmira-Corning area.
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Historic Floods in the STC Region

A surprisingly long list that includes a couple of Pumpkin Floods (when fall flooding of farm fields washed pumpkins downstream), a Great Inundation, a Tremendous Flood, a couple of Big Floods, and many more.
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Additional Resources

Before Buying or Building: Flood Risk Identification in Steuben County

Brochure provides suggestions to help identify potential flooding issues before buying or building a home.
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