Win 3! Basic Guidelines for Successful Roadside Ditch Management

Transcription

1 Win 3! Basic Guidelines for Successful Roadside Ditch Management Rebecca Schneider Dept. Natural Resources Cornell University Cornell Local Roads Conference June 2, 2008

2 Town Highway Staff Responsibilities Potholes and road resurfacing New roads Shoulder maintenance De-icing and clearing Drainage and ditch management Personnel, budgets, facilities..

3 Town Highway Staff Responsibilities Potholes and road resurfacing New roads Shoulder maintenance De-icing and clearing Drainage and ditch management Personnel, budgets, facilities..

4 Road drainage is a critical component of traffic safety!

5 Goal: To provide some guidelines for better roadside ditch design and maintenance which accomplish the following: 1) Reduce your work load and your costs. 2) Keep your stakeholders happy. 3) Prevent erosion, protect water, and maintain a healthy environment.

6 Roadside Ditches the unrecognized factor in stormwater runoff management

7 Balance between precipitation, runoff, infiltration, and evapo-transpiration Cross-section of a watershed

8 On-going Research on ditch networks 1) Map: ditch lengths, mgmt types connections to streams 2) Monitor: Total water flow Suspended sediment Dissolved chemicals Bedload sediment

9 Ditches intercept ~1/4 of the surface runoff in our watersheds and shunt it downstream where it is injected as high flow into the streams. Ditch drainage basins Stream Road ditches Ditch outflows

10 April 16, 2007, NY Ditches increase the volume and velocity of runoff entering streams and therefore contribute to floods.

11 Ditches are a source of sediment and associated contaminants to downstream waters, especially when scraped.

12 Large quantities of gravel, rocks and other bedload move out of ditches and form deltas in the streams.

13 Ditch and delta Meander induced by ditch-formed delta Stream bank erosion created by re-directed stream flow.

14 A broader perspective - Precipitation has been increasing in NY and the Northeast us-newyork.html

15 Northeastern U.S. Climate Future directions 2006 Union of Concerned Scientists

16 What floods cost in New York annually. In thousands of current dollars 1,000, ,000 10,000 1, YEAR 2006 $54.8 million Flood damage estimates in U.S., 2002 R. Pielke, M. Downton, Z. Barnard-Miller Boulder, CO.

17 E.P.A. Phase II Stormwater Regulations 2003 For 450 towns in New York Municipal Separate Storm Sewer Systems The Regulatory Framework

18 Guideline #1: Create and maintain a shallow, gently sloping ditch. easier to maintain by mowing many landowners will do it themselves safer for traffic less likely to erode

19 Don t overditch inches depth is plenty deep enough to carry away stormwater

20 Avoid the V-shaped ditch - the bottom is easily incised and starts the erosion process.

21 Guideline #2: Plan ahead to prevent erosive water flows. Consider drainage areas upslope that may contribute to erosive flows. Use check-dams to slow velocities.

22 Guideline #3 Wherever possible, mow ditches regularly instead of scraping.

23 Use hydroseeding immediately after ditching Hydroseed early in the season to allow sufficient growing time, and not immediately before rain. If scraping is necessary, do it in patches with vegetated strips left downslope to capture sediments.

24 Pros and cons of using rocks: Pros: reduces velocities, non-erosive, some filtering Cons: expensive, trap and transmit heat that impacts streams and fish, eventually fill w/sediment and need replacement.

25 Guideline #4: Minimize erosion of gravel and rocks that move as bedload into streams.

26 Use permeable pavements or vegetation along road shoulders.

27 Guideline #5 Disconnect ditches from streams. Use infiltration basins or detention ponds that allow for groundwater recharge. Use multiple, under-road culverts to spread out the flow.

28 Guideline #6 Reduce transfer of runoff from land to ditches. Increase infiltration of rain water on land associated with houses, parking lots, and farms.

29 Guideline #7 Communicate! Be part of the dialogue and provide leadership concerning stormwater management with landowners and town government.

30 New Directions: Ditches as conduits of Ag pathogens to downstream drinking water reservoirs

31 Sampling to monitor for fecal coliforms and pathogens in ditches.

32 Continue the conversation suggestions are welcome!

33 Questions? Acknowledgments: USDA CSREES, Cornell (funding); Cayuga Lake Watershed Network, Town of Candor, Cortland, Enfield Highway Depts., City of Ithaca Planning Dept.