Quasqueton Dam Rock Arch Rapids

Cardno’s hydrology and stream experts created a rock rapids at an existing dam structure to improve fish and mussel passage along the Wapsipinicon River in Buchanan County, Iowa, United States.

Services performed included the design, permitting, and construction oversight for the project. The creation of the rock rapids at the more than 80-year-old existing dam structure allowed for habitat connectivity for many migrating fish, amphibians, and mussels without increasing the flood stage over an existing eight-foot-low head dam.

To create the rock rapids structure, a 300-foot series of eight weirs were constructed to allow fish to pass over the existing dam. The weirs were spaced irregularly to give the completed rock rapids a more natural look.

This project offered a unique opportunity to address ecological impacts to the watershed by removing the source of the impediment to the movement of aquatic life and reconnecting a fragmented aquatic ecosystem.

By re-establishing fish passage and restoring aquatic habitat, downstream fish species can recolonize or be re-introduced upstream of the dam location. Bank grading with native vegetation also helped address bank erosion upstream of the dam.

The community was especially pleased with the rock rapid’s safety and aesthetic improvements to the Wapsipinicon River.