Beyond the Surface: How NRCS Engineers Help Plan and Maintain Iowa Watersheds

by Jolene Bopp, Public Affairs Specialist, USDA-NRCS, Des Moines, Iowa

In early May, engineers with USDA's Natural Resources Conservation Service (NRCS) launched a boat into a body of water held by one of the Badger Creek Watershed structures in Madison County, Iowa. Instead of bait and tackle, the boat carried a survey rod and a GPS unit to help determine how well the structure is functioning, and what may need to be done to keep it working in the future.

Although this structure is over 50 years old, it continues to help manage 300 acres of upstream drainage by reducing flood risk, controlling gully erosion and trapping sediment before it reaches Badger Creek Lake. NRCS worked closely with local sponsors to design and implement solutions to protect the land and improve water quality. Thanks to good stewardship and strong partnerships it continues to do just that.

The project was a collaborative effort between NRCS and local sponsors including the Dallas, Madison and Warren County Soil and Water Conservation Districts and Madison County. The watershed plan was signed in 1960. The structure was completed in 1973 under Public Law 566, now known as the Watershed and Flood Prevention Operations (WFPO) Program.

"This might have been an equipment test run, but the information we gathered is valuable and usable right now," said Hayes Durbin, civil engineering technician with the NRCS in Iowa. "We can start assessing whether this site needs repairs, rehabilitation or if it's still operating as designed."

Durbin and NRCS State Technology Engineer Tim Mensing are preparing for a large bathymetric survey later this month. Typically, they use a remote-controlled bathymetric boat with survey equipment already built in. Due to the large scale of the next site, they are utilizing a manned boat they will equip with the survey rod and computer.

At the bottom of the rod is the transducer, which sends out and receives the sonar signals that detect the bottom of the pond, stream or wetland. On the top of the rod is a Trimble R12i receiver, a GPS unit which collects the latitude, longitude, and elevation data. This data is key to understanding sediment buildup and changes in water storage over time.

Combined, this data allows engineers to create a 3D map that gives them the ability to track sediment buildup and long-term capacity changes. Over time, sediment builds up in watershed structures, decreasing water and sediment storage capacity. Sediment runoff reduces water quality and contributes to erosion or infrastructure damage during high-flow events. If the dam is silted full it will continue to provide the same flood control benefits.

Why Iowa's Watersheds Matter

Watersheds are interconnected, impacting every community. They provide resources for all living things to survive. Watershed dams are built through federal, state and local partnerships. They were designed to protect property, farmland and infrastructure from erosion and flooding. The technical expertise of NRCS engineers becomes especially critical when these structures start approaching or exceeding their expected design life which is typically 50 to 100 years.

Since 2005, watershed structures have provided approximately $435 million in flood and non-flood benefits statewide. NRCS engineers work closely with local watershed boards, soil and water conservation districts, and landowners to address resource concerns and issues like failing embankments, unstable streambanks, and grade stabilization.

"Collaboration is key," NRCS State Conservation Engineer Christian Osborne added. "We're not here to just design and walk away. We stay involved, help monitor, and make sure these investments continue to pay off for farmers and rural communities."

In this case, the surveyed structure is nearing the end of its lifespan, prompting conversations between NRCS and local partners about what's next. The data collected will play a key role in those discussions.

Engineers Behind the Scenes

While people may know NRCS for its financial assistance programs like the Environmental Quality Initiatives Program (EQIP) or Conservation Stewardship Program (CSP), NRCS roots are grounded in the technical services they provide. NRCS engineers and technicians design terraces, grassed waterways, grade stabilization structures, and water and sediment control basins. They inspect and evaluate infrastructure that might be decades old.

Iowa NRCS has built 2,695 structures through all four of the NRCS Small Watershed Programs offered over time. The first structure was built in 1948, and most structures are still in place today providing the benefits they were intended for.

In 2024, NRCS engineers assisted Iowa communities with about 20 watershed structures. The importance of functioning watershed infrastructure may go unnoticed unless something goes wrong. Thanks to the work of NRCS engineers and partners, many of those risks are managed long before they become emergencies.

Learn More

Through NRCS watershed programs, staff provide free technical and financial assistance to help project sponsors address watershed resource concerns in local communities. Assistance in Iowa is available through:

• Emergency Watershed Protection (EWP) Program assists communities in recovering from natural disasters and sudden watershed impairments.
• Watershed and Flood Prevention Operations (WFPO) Program focuses on reducing flood risks, conserving natural resources, and improving water quality.

To learn more about NRCS technical and financial assistance, contact your local service center: farmers.gov/service-center-locator or visit: https://www.nrcs.usda.gov/GetStarted.