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Iowa State University--Becoming the Best

Water Quality in Rathbun Lake: On-Road Structure Training and Demonstration


Principal investigator:

Project status


Start date: 08/21/00
End date: 08/21/02


Sponsor(s): Wayne County Soil & Conservation District

About the research

Abstract: The project tasks were development of curriculum materials for a workshop on design of on-road impoundment structures and then teaching several three-day workshops on hydrologic design of on-road impoundment structures. One of the principal causes of decreased water quality in Rathbun Reservoir and other streams and lakes in Iowa is sediment. An issue faced by counties throughout Iowa is the cost associated with replacement of obsolete bridges on many of the secondary roads across Iowa. An on-road structure is essentially an embankment dam constructed on the centerline or alignment of an existing, or proposed, road. If a bridge is involved, it is replaced with the impoundment structure, creating a permanent reservoir upstream of the road. The attenuation of downstream peak flow rates during storm events decreases downstream channel erosion and movement of sediment within the watershed. Sediment trapped in the on-road structure will also tend to reduce movement of nutrient loads downstream. There is an additional benefit to the adjacent landowners through livestock and recreational use of the pond that is created.