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South Williamson Floodwall– Constructed 1991
Living in the Ohio River Basin – What does this mean?
The Corps of Engineers operates 78 reservoirs, 5 dry dams and over 95 local protection projects known as “LPP’s” include levees, floodwalls, stream diversions and channel modifications within the Ohio River Basin. This basin system has been under development since the late 1930’s and early 1940’s.
Dewey Dam– Constructed 1949
The Corps owned dams and reservoirs are designed to retain excess rainfall and snowmelt runoff based upon historic and projected flooding events within each watershed. Retention of those excess flows reduces the heights of flooding downstream and the retained water is released in a controlled manner over a period of days. LPP’s, as is the case with reservoirs, are designed to protect communities and facilities from a certain historic or projected flood event. Interior drainage and pumping systems at LPP’s control rainfall runoff within the protected area. As a combined basin-wide system these projects have prevented over $19.0 billion in flood damages over a 70-year period.
So, if you live close to one of these structures does this mean that you will not get flooded? Absolutely not.
Mississinewa Dam Repairs – Constructed 1967
Over the many years that flood control measures have been constructed, the Basin has seen dramatic changes. Significant portions of the basin once dedicated to forest and agriculture have been replaced by residential, commercial and industrial uses. These new uses, uses that generate far greater amounts of stormwater runoff than the previous land uses have contributed to more frequent and larger flood events in the basin.
All levees and reservoirs are designed to provide certain levels of protection. In the event that rainfall or snowmelt events exceed that designed protection level, flooding can still occur within a protected area. Both dams and LPP’s require regular maintenance to maintain their original protection purpose. Being constructed out of degradable materials (soil, rock, and concrete) and operating daily, levee and reservoir structures can deteriorate over time and maintenance can become a serious challenge. Should a levee or reservoir fail, they fail catastrophically, the flood damage may be more significant than if the levee or reservoir was not there.Â
Mohawk Dam – Constructed 1936
For these reasons, people who live near or are protected by levees or reservoir need to understand the flood risks they face and what they can do to address them. That is why the Ohio River Basin Comprehensive Plan is important – it takes a holistic, regional view of the flood risk reduction capabilities of the existing system of dams and LPP’s to determine what investments may be required in the future to maintain a reliable and safe protection system.