Catfish are blocked from living in hundreds of miles of rivers, and other fish could likely be more successful if it weren't for a legacy of small dams on Iowa's major rivers, according to analysis conducted for a new statewide plan for dam mitigation.
"Our radio tagging data indicate that channel catfish move to deep water habitat for over-wintering," said Greg Gelwicks, interior streams research biologist for the Iowa DNR. "If they move downstream of dams, in some cases they are unable to return upriver."
Dozens of communities are currently evaluating whether maintaining their dams are worthwhile. Solving Dam Problems: Iowa DNR's 2010 Plan for Dam Mitigation, released on the DNR web site last month, offers alternatives ranging from structural modification to dam removal on a case-by-case basis. These approaches can be more cost effective than reconstruction.
Dams can also block navigation, and "roller" currents can cause injury or death. Many dams are literally falling apart, and the cost to replace a dam's gates or the main structure can be high. While a handful of dams are for flood control, the fact that some dams actually contribute to flooding has led to reconsideration of dams in their present form. An array of alternatives to dams can preserve existing functions by converting a dam to a rock rapids, or can result in removing dams and river restoration.
"The Iowa DNR rivers team receives requests each year for assistance to determine what to do next at dam sites," said Nate Hoogeveen, the Iowa DNR river programs coordinator. "A lot of this infrastructure dates back to the 1930s and earlier. Mitigation funding has provided a good alternative for cash-strapped communities, while offering the statewide benefits of safer, more navigable rivers and improved conditions for fish and fishing."
The statewide dam mitigation plan helps guide and prioritize that work. It lays out a process that respects and listens to local stakeholders while seeking solutions.
Dams researched for the plan included a variety of structures on navigable-sized rivers. The plan includes findings developed through surveys of dam owners, boaters, anglers and the broader public. Solutions are geared to help solve problems for local interests while providing statewide benefits.
"We've learned that dams have effects far beyond their location," Hoogeveen said. "As a new generation learns to fish and boat on rivers, what we do with these dams nearing the end of their life cycle is important."
The dams plan is available on the DNR web site at www.iowadnr.gov/riverprograms/ under the dam mitigation link.