The Dam Facts

Image of hydroelectric dam


Why Dams?

Dams were built for many reasons, but the more common ones include flood control, hydroelectric power generation, municipal water supplies, recreation and navigation. Some dams serve a useful purpose, but many dams are obsolete and have outlived their purpose. Some are in serious disrepair.

There are more than 200 dams on Iowa's rivers and streams.


Low head dam warning sign with animated hydraulic


Why Are Low Head Dams So Dangerous?
When water flows over the top of a dam and hits the water below, it creates a backwash or boil that re-circulates surface water back against the dam. Anything that floats gets trapped, pushed down to the bottom, pulled up and back to start the process over again. A life vest will not help you and even the strongest swimmers will drown in these currents. Typical low head dams also have concrete side walls that prevent escape at the sides of the dam.


Fisherman wading in river


Aren't Dams Good Places To Fish?
Typically fishing is better, because fish will bunch up at dams while attempting to migrate upstream. Unfortunately studies show that dams contribute to the decrease of game fish and mussel populations and the increase of pollution tolerant fish populations such as carp. Dams block fish spawning migrations, and the buildup of sediment above the dams degrades spawning habitats for miles upstream.


Views of Vernon Springs dam before and after modification


What Are The Solutions To Dams That Are Dangerous And Serve No Useful Purpose?

Each dam is unique and requires an alternatives analysis or feasibility study to see what options are available. Removal is usually the least expensive option that not only makes the river safer, but also contributes to the river's overall environmental health. However removal tends to be controversial, because dams often have historical significance and tend to be better places to fish. Modification or retrofitting of dams may be expensive, but such projects do reduce the hazard at dams and often allow fish passage which improves the watershed's fishery overall. Some modifications remove blockage of the natural movement of sediment downstream. Some dams can be converted into whitewater courses that allow for varying forms of exhilarating recreation and economic development.