Definitions

A 100-year floodplain is a flood elevation area that has a one percent chance of being equaled or exceeded by the elevation of water each year. This doesn't mean that a flood will happen only once in 100 years. Even if a flood happens in one year, there is still a one percent chance of flood the next year. The 100-year floodplain, which is the standard used by most federal and state agencies, is used by the National Flood Insurance Program as the standard for floodplain management and for determining the need for flood insurance.

A 500-year floodplain is an area that has a 0.2 percent chance of flooding in any given year.  This standard is not used for determining the need for flood insurance.

For most waterways, a floodway is where the water is likely to be deepest and fastest. It is the area of the floodplain that should be kept free of obstructions to allow floodwaters to move downstream. Your community has restrictions on constructing new buildings or placing any fill in a floodway and may have requirements for any structures already located in a floodway. Before any construction or development can occur in a floodway, the City of Vassar requires an engineering analysis of impacts and a Flood Elevation Letter. The letter can be requested on this website after you do an analysis of site locations in the floodplain.