Evaluating a Two-Stage Roadside Ditch Design to Improve Environmental Performance

Conventional trapezoidal roadside ditches are designed to rapidly deliver runoff, sediment and nutrients to downstream surface water but they can be impacted from erosional downcutting and excessive sedimentation. In agricultural regions, ditches have been modified with a two-stage design that involves modifying the conventional trapezoidal ditch into one that better replicates the features of a natural stream through the addition of adjacent benches. The two-stage design reduces bank slumping and undercutting during high flows while improving water quality by trapping and treating runoff water flowing through them. The objectives of this project are to evaluate the performance of a two-stage roadside ditch constructed along a selected roadway and evaluate its stability and long-term maintenance requirements in Iowa conditions. In this project, the team will work closely with DOT and a Technical Advisory Committee (TAC) to select, model, design, construct, and monitor a two-stage ditch prototype. The monitoring protocols will be adapted for the conditions at the prototype construction site and include treatment-control scenarios either as upstream-downstream or paired designs. Continuous discharge and turbidity measurements will be used to capture stormwater runoff loads whereas regular grab samples will be collected and analyzed for baseflow changes in water quality parameters including nutrients and sediment. Stability and maintenance will be assessed through annual field evaluations and drone surveys. At the conclusion of the project the research team will present the research in a final report that evaluates the performance of a new design for roadside ditches, based flow conveyance, stability of the road infrastructure, and capacity to retain sediment and improve downstream water quality. A series of practical recommendations will be provided that summarizes the major findings of the study on the performance and efficiency of the proposed two-stage design and illustrates the lifecycle cost benefits resulting from the new design implementation.


  • English


  • Status: Active
  • Funding: $446118
  • Contract Numbers:


  • Sponsor Organizations:

    Iowa Department of Transportation

    800 Lincoln Way
    Ames, IA  United States  50010
  • Managing Organizations:

    Iowa Department of Transportation

    800 Lincoln Way
    Ames, IA  United States  50010
  • Project Managers:

    Clute, Khyle

  • Performing Organizations:

    University of Iowa, Mechanical and Industrial Engineering

    3100 Seamans Center for the Engineering Arts and Sciences
    Iowa City, Iowa  United States  52242
  • Principal Investigators:

    Schilling, Keith

    Muste, Marian

  • Start Date: 20191101
  • Expected Completion Date: 20260321
  • Actual Completion Date: 0

Subject/Index Terms

Filing Info

  • Accession Number: 01910384
  • Record Type: Research project
  • Source Agency: Iowa Department of Transportation
  • Contract Numbers: 20-SPR1-002
  • Files: RIP, STATEDOT
  • Created Date: Feb 28 2024 5:38PM