flooding in a Tompkins County community
photo courtesy The Ithaca Journal
Flooding used to be a regular occurrence in Tompkins County. With the large number of streams, lakes, gorges, and other waterways, flooding was a constant threat. Due to great efforts, however, the most flood-prone streams and creeks have had flood-control dams installed. Six Mile Creek in Ithaca is a prime example, with a series of flood-control dams; Dryden fairly recently installed the Crispell dam in Fall Creek to prevent flooding.
Some historic floods:
There are two main categories of floods: flash floods and slow-rising floods.
Flash floods come with little or no warning, and are caused by a number of factors. The mostly likely cause of a flash flood in Tompkins County would be a dam break.
Slow-rising floods usually come with more warning. A long period of heavy rains or a spring thaw can cause rivers and streams to swell above their normal banks. The water then flows into what is referred to as a floodplain -- generally a flat, open area near the stream. A prime example in Tompkins County is the large shopping plaza in downtown Ithaca, home to Wegmans, Tops, K-Mart, Home Depot, and other stores. These stores were built on a floodplain for Cayuga Lake Inlet. If the inlet ever floods, these stores will likely be under some water.
Check the Tompkins County Planning Department National Resource Inventory and click on the link for "Interactive Mapping" to see where the recognized floodplains are in this county.
NOTE: a 100-year flood does NOT mean one flood every 100 years! It means, statistically, there is a 1% (1 in 100) chance each year of a flood to that level. Likewise, a 500-year flood is a statistical analysis. It is possible to have two 500-year floods in the same year -- although it would be extremely unlikely.
National Disaster Education Coalition - Guide to floods and flash floods.
National Flood Insurance Program - See if your community is eligible!
FloodSmart - A government resource for information on flood safety, preparedness, and more.
American Red Cross - advice on flood safety and preparedness.