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

Details

• Creators:
  Schilling, Keith ; Muste, Marian ; Amado, Antonio Arenas ; Anderson, Elliot ; Honings, Joseph ; Meisson, Justin ; Cintura, Ingrid ; Eustice, Betret ; Arenas-Amado, Antonio
• Corporate Creators:
  Iowa Geological Survey ; University of Iowa. IIHR - Hydroscience & Engineering
• Corporate Contributors:
  Iowa. Department of Transportation ; United States. Department of Transportation. Federal Highway Administration
• Subject/TRT Terms:
  • Roadside
  • Ditches
  • Water quality
  • Floods
  • Monitoring
  • Vegetation
  • Phosphorus
  • Sediment discharge
• Resource Type:
  Tech Report
• Geographical Coverage:
  United States ; Iowa
• Edition:
  Final Report
• Corporate Publisher:
  Iowa Department of Transportation
• Abstract:
  Roadside ditches are integral components of watershed-scale hydrologic processes that are designed to rapidly convey surface runoff from roads to receiving streams. In this project, a two-stage roadside ditch was constructed during expansion of Highway 30 in east-central Iowa. Pre-construction monitoring and development of a preliminary design was conducted in 2020 and 2021, and between January to April 2021, the two-stage roadside ditch was graded, seeded and finalized. Post-construction monitoring was originally slated for 2021-2023, but monitoring efforts were compromised on several occasions and the monitoring period extended into 2024. Performance monitoring of the two-stage ditch site focused on vegetation conditions, hydraulic changes and water quality improvements. Native vegetation was established successfully and seeding densities increased while invasive species were reduced. Hydraulic modeling for design storms indicated the two-stage ditch reduced peak flow rates, total water volume and maximum velocities relative to a standard single stage configuration. Water quality monitoring conducted upstream and downstream of the two-stage ditch included stage, turbidity and dissolved constituents. Turbidity measurements revealed a statistically significant impact of the two-stage ditch on daily mean turbidity with the difference in turbidity between the upstream and downstream monitoring sites increasing following construction. Using siting criteria established for the project, 314roadside ditches were identified across Iowa that could be converted to a two-stage design, potentially reducing particulate phosphorus and organic nitrogen loads. Overall, the construction and monitoring results of the two-stage roadside ditch were encouraging for reducing flood risks and improving water quality across the State of Iowa.
• Format:
  PDF
• Funding:
  20-SPR1-002
• Download URL:
  https://rosap.ntl.bts.gov/view/dot/93175/dot_93175_DS1.pdf
• File Type:
  [PDF - 3.51 MB]
• Collection(s):
  US Transportation Collection
• Main Document Checksum:
  urn:sha-512:405b15a1cf13475a9b74494b3f35650aab43db19bea53fc7667ab08007acfcba92da4fb58017627b2ef7eeeda6d8f6d1e05662fedd42b84135c8561384091a06