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Watershed Structures Prevent Flooding Damages

The Swan Creek Watershed in southeast Nebraska has experienced heavy rainfall events during the spring and summer of 2013. June storms dumped over nine inches of rain in some areas last week, and storms in early August produced nearly 5 inches of rain in the same watershed. Although there were many people affected by flood damages, flooding could have been much worse if not for the watershed control structures in Gage and Saline counties, according to the USDA Natural Resources Conservation Service (NRCS).

NRCS, with assistance from the Lower Big Blue Natural Resources District, has constructed many flood control structures in Gage and Saline counties through the Watershed Protection and Flood Prevention Act. These funds authorized NRCS to provide assistance with the planning and installation of flood control structures like small dams and grade stabilization structures, and in applying conservation practices like no-till, terraces and waterways.

The Lower Big Blue NRD sponsored the project and purchased the land rights in order to build the flood control structures. NRCS provided engineering expertise and over $18 million to construct the 165 floodwater control structures throughout watersheds in Gage and Saline counties.

Flood control structures may easily go unnoticed across the landscape. But after a heavy rain event, like what was recently experienced in southeast Nebraska, these structures spring into action.  They capture rushing flood water and hold the water back allowing it to be slowly released downstream.  Slowing the water down and allowing it to be gradually released reduces damage to roads, bridges, fences, cropland and other property.

According to NRCS Hydraulic Engineer Arlis Plummer, the existing flood control structures in Gage and Saline counties helped prevent over $11 million in flood damages from the recent storms.

“With big rain events like these, we really see the benefit of flood control structures.  They work together with conservation practices to prevent damage to infrastructure.  When things like roads and bridges are spared from damages, then we’re talking about a lot of dollars saved,” Plummer said. 

Kelli Evans, NRCS District Conservationist in the Beatrice USDA Service Center surveyed the effects of the heavy rainfall.  She saw first-hand how the flood control structures and conservation practices have worked together to lessen the damage from the heavy rainfall.

“Even though several county roads received flash flood water damage, it could have been much worse if these flood control structures had not been in place,” Evans said.

With nearly 900 watershed dams constructed statewide the Watershed Protection and Flood Prevention Act has benefited over 1.6 million acres in Nebraska.  Benefits include significant savings in soil erosion, water conservation, road and bridge damage reduction, wetland/upland wildlife habitat creation and most importantly, saved lives and property.  The total benefits to Nebraska exceed $37 million each year according to NRCS.

The recent heavy rain events have also demonstrated the importance of good soil conservation practices. According to NRCS Agronomist Corey Brubaker, conservation practices like no-till, terraces, waterways and buffer strips protected fields from significant erosion.

“Heavily tilled fields with no terraces or waterways have seen a lot of soil erosion. The fields where conservation practices were in place fared much better. This is because terraces and waterways help slow rainwater down reducing damages from heavy rains. No-till fields also saw less erosion since no-till helps protect the soil with last year’s crop residue. This residue helps capture the rainwater before it can run off fields, allowing it to soak in to the soil,” Brubaker said.

Conservation tillage can make a major difference in the way a field handles a rain event. No-till is the most effective tillage practice to reduce runoff, according to Brubaker.

"The 70 percent to 90 percent residue cover that continuous no-till provides will decrease soil erosion by 95 percent and increase water infiltration by 200 percent to 400 percent. The increased water infiltration provided by long term continuous no-till is a result of residue cover and improved soil structure. The residue cover deflects and dissipates the impact of raindrops preventing compaction of the soil surface and allowing the rainfall to soak in," said Brubaker.

For more information on installing conservation practices on your land to help prevent erosion and reduce flooding, contact your local Natural Resources Conservation Service office located in the USDA Service Center.