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Understanding Roadside Ditches for Watershed Management

This module aims to educate students on the impact of roadside ditches on stream ecosystem health and watershed management. It covers topics such as watershed divides, water cycles, stream orders, land use impacts, and recommended ditch management strategies.

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Understanding Roadside Ditches for Watershed Management

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  1. Roadside Ditches: A Watershed Curriculum Module Rebecca Schneider, Nancy Trautmann, & Linda Wagenet Cornell University

  2. Goals: • To help students understand connections between watershed land uses and stream ecosystem health • To demonstrate connections between ditch runoff and streams • To engage students through use of Global Positioning Systems (GPS) technology

  3. Lake and stream health are linked to adjacent land uses and human activities.

  4. Watershed divide Watershed: The total area above a specific point on a stream or river from which water drains toward the stream.

  5. Photo: Y. Arthus Bertrand

  6. Water Cycle: Balance between precipitation, evapotranspiration, infiltration, and runoff Credit: http://www.nrcs.usda.gov/technical/stream_restoration/chap2.html

  7. Stream order - classifies stream segments according to the number of tributaries 2nd Order 5th Order

  8. Measuring discharge: • Volume of water flowing past a fixed location at any given point in time • Measured in units of ft3/sec or m3/sec

  9. High flow Buttermilk Falls,NY Rain Runoff Baseflow (from groundwater) Low flow Natural stream flow patterns

  10. Impacts of Land Use on Runoff Impervious Surfaces: Rooftops Parking lots Driveways Compacted Soils: Lawns Crop fields

  11. Credit: http://www.nrcs.usda.gov/technical/stream_restoration/chap30002.html

  12. post-development stream height pre-development time (hrs/days/weeks) Impervious surfaces impact the natural patterns of flow: frequency and magnitude of floods summer droughts (due to lower baseflow) 15% impervious surface

  13. Impervious surfaces impact stream health: • increased flooding and drought • increased erosion • degraded water quality • loss of diversity of fish and aquatic organisms

  14. Roadside Ditches – a neglected but critical factor in protection of water resources

  15. Ditches are managed by highway staff to prevent flooding of roads and buildings… andrarely linked to watershed management Before After

  16. Downstream Impacts Credit: http://www.nrcs.usda.gov/technical/stream_restoration/scrhimage.htm

  17. Road Stream Divide Enfield Creek Watershed: 56 km 2 Stream Length: 88 km Roads: 87 km Ditches: 142 km 70% linked to stream Increased drainage density 1.6 km-1 4.1 km-1

  18. Research Doolittle, Enfield, 6-Mile Creeks 8 Replicate Sampling Stations + Creek • Total water flow • Suspended sediment • Dissolved chemicals • Bedloadsediment

  19. Enfield Creek – Preliminary Findings Total Bedload Sediment Collected by Ditch Type per event 2500 2000 Bare Dirt 1500 Grassy Grams Gravel 1000 Weedy 500 0 bare gravel grassy weedy Ditch Type

  20. Downstream erosion?

  21. Roadside Ditch Impacts: • mechanism for increased land-water linkages • conduit for rapid runoff • internal source of sediment and other contaminants

  22. Recommended Ditch Management Strategies Scraped, exposed Hydro-seeded Mowed grass Concrete, hardened Rock-lined

  23. Recommendation: Disconnect ditches from streams. Use infiltration basins & detention ponds to capture water and allow it to recharge groundwater

  24. Recommendation: Use permeable paving to reduce runoff

  25. EPA Phase II Stormwater Regulations: Small towns/ designated MS4 communities must develop stormwater management plans by 2008. Current guidelines focus on construction activities.

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