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Watershed Processes

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IIHR researchers are studying various aspects of sediment transport and deposition processes to resolve critical engineering challenges. A thorough understanding of sediment transport is key to improving Iowa’s water and soil quality. Soil erosion in the agricultural Midwest not only decreases the value and productivity of farmland, but also causes problems downstream. Fertilizer runoff contributes excess nutrients (nitrogen and phosphorus) to the watershed, impacting water quality and contributing to the “Dead Zone” in the Gulf of Mexico.

Iowa Nutrient Research Center

IIHR is a key partner in the Iowa Nutrient Research Center (INRC), which brings together researchers from Iowa’s three public universities and several government agencies to better understand how nutrients move through the landscape.

A woman in jeans and waders cleans mud out of the housing of a water-quality sensor, while a man also in waders looks on. Both stand in the shallow water of a stream.

Researchers adjust the level of a water-quality sensor within an in-stream structure.

IIHR established a network of water-quality sensors deployed throughout Eastern Iowa. The remote sensors measure nitrates, turbidity (cloudiness), dissolved oxygen, temperature, specific conductance, pH, and chlorophyll A, which is an assessment of how much algae-type “greenery” is in the water. The near real-time data relay back to the center every 15 minutes. With this data, researchers are able to better describe the system dynamics and hydrology.

The INRC funded 10 research projects for 2014–15, ranging from an investigation of farming practices and stream nitrate trends to a pilot study of nutrient trading in a small watershed. Four of the 10 projects involve UI researchers:

Iowa Watersheds Project

A group of people, mixed in age and gender, pose with a sign for the Otter Creek Watershed. The scene is green and leafy.

IIHR faculty, students, and staff pose with community members from the Otter Creek watershed.

The U.S. Department of Housing and Urban Development (HUD) awarded funds to the Iowa Flood Center and IIHR to develop watershed mitigation projects to reduce flood damage in select Iowa watersheds.

Through the Iowa Watersheds Project, researchers have analyzed the movement of water in the selected watersheds. With landowner participation and leadership, construction of the improvement projects (including farm ponds, wetlands, floodplain easements, and more) will begin in spring 2015.

The following subwatersheds have been selected to receive $1.5M to fund the construction of small-scale flood mitigation projects:

This map of Iowa shows the watersheds chosen for the Iowa Watersheds Project. They are: Beaver Creek on the Upper Cedar River, Otter Creek on the Turkey River, and South Chequest on Soap/Chequest Creek.

Iowa Watersheds Project selected watersheds are shown in light green; areas selected for construction of improvements are darker green.

Researchers deployed a dense instrumentation network to monitor stream stage, precipitation, soil moisture, soil temperature, and water quality in each of the pilot watersheds. They will assess and analyze the improvements’ impacts on water movement in the watershed to better understand what works and which strategies can be scaled up for implementation across the state.

Sediment Transport and Fate

Flow in and around manmade structures such as culverts, dams, and bridge piers can lead to erosion of the streambed, exposing the foundations and weakening the structure. Several IIHR researchers focus their attention on sediments and their interaction with flow. For example, IIHR Research Engineer Marian Muste leads a team that designed a self-cleaning culvert that flushes out sediment deposits using the power of the stream flow. Sedimentation and vegetation often block Iowa culverts, obstructing the flow and potentially causing the culvert to overtop during storms, producing local flooding and property damage. Clean-up can be frequent and costly.

Muste’s new design uses fabric-formed concrete to shape the floor of the culvert to slope toward the stream center, bringing the site back to its original shape. The culvert directs sediment toward the central channel, where the flow is strongest, preventing sediments from settling in the low-velocity areas at the stream’s edges.

The study of sediment transport is central to many other research efforts at IIHR:

 

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Last modified on August 11th, 2017
Posted on April 4th, 2011

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