Streambank erosion, floodplain importance topics of new publications

Billy Beck
Iowa State University Extension
Tall, bare, near-vertical streambanks are a common sight along many of Iowa’s river and stream corridors.

Two new Iowa State University Extension and Outreach forestry publications are available for free on the Iowa State Extension Store. The releases highlight the results of research done at Walnut Creek watershed in central Iowa and discuss the mechanics and implications of sediment erosion in streams and rivers.

The releases were written by Billy Beck, assistant professor and extension forestry specialist at Iowa State University, and Melissa Irish, undergraduate research assistant in the Department of Natural Resources Ecology and Management.

The first publication, Streambank Alluvial Units, explains how layers within sediment along streambanks can be used to study erosion over time. These sediments are referred to as alluvium.

By studying the sediment making up Iowa’s streambanks, researchers hope to learn more about weathering processes in Iowa, and how these processes can be slowed to avoid an overabundance of sediment and phosphorus in Iowa waters. Excessive amounts of sediment and phosphorus in streams can have negative implications for water quality and may cause a loss of valuable crop ground.

“Streambanks should be recognized as a potentially significant source of sediment and phosphorus delivery to waterways,” Beck concluded.

The second publication, Floodplain Connectivity, also explains and discusses research from Walnut Creek watershed. As Beck explains, floodplains are relatively flat areas bordering rivers and streams that help to clean and contain floodwaters when rivers and streams overtop their banks. Floodplain vegetation can trap excess nutrients, slow flood velocity and retain floodwaters, which can enhance stream water quality and reduce downstream flooding impacts.

However, Iowa’s floodplains have become disconnected from their respective rivers and streams due to river straightening and land conversion. A loss of the connection between rivers or streams and floodplains represents a loss of their ecological benefits, according to Beck.

“Loss of trapping and retention opportunities may lead to increased levels of contaminants in stream water, as well as intensified downstream flooding,” he added.

For more information, Beck can be reached at 515-294-8837 or wjbeck@iastate.edu.