Win3 ! Basic Guidelines for Successful Roadside Ditch … · Goal: To provide some guidelines for...
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Win 3 ! Basic Guidelines for Successful Roadside Ditch Management Rebecca Schneider Dept. Natural Resources Cornell University Cornell Local Roads Conference June 2, 2008
Transcript of Win3 ! Basic Guidelines for Successful Roadside Ditch … · Goal: To provide some guidelines for...
Win3 ! Basic Guidelines forSuccessful Roadside Ditch
Management
Rebecca SchneiderDept. Natural Resources
Cornell University
Cornell Local Roads Conference
June 2, 2008
• Potholes and road resurfacing
• New roads
• Shoulder maintenance
• De-icing and clearing
• Drainage and ditch management
• Personnel, budgets, facilities …..
Town Highway Staff Responsibilities
• Potholes and road resurfacing
• New roads
• Shoulder maintenance
• De-icing and clearing
• Drainage and ditch management
• Personnel, budgets, facilities …..
Town Highway Staff Responsibilities
Road drainage is a critical component of traffic safety !
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 maintaina healthy environment.
Roadside Ditches –the unrecognized factor
in stormwaterrunoff management
Balance between precipitation, runoff , infiltration , and evapo-transpiration
Cross-section of a watershed
2) Monitor:• Total water flow• Suspended sediment• Dissolved chemicals
• Bedload sediment
On-going Researchon ditch networks
1) Map:• ditch lengths,• mgmt types• connections
to streams
Ditches intercept ~1/4 ofthe surface runoff in
our watersheds and shunt it downstream
where it is injected as high flow
into the streams.
Ditch drainagebasins
Stream
Road ditches
Ditch outflows
April 16, 2007, NY
Ditches increase the volume and velocity of runoffentering streams and therefore contribute to floods.
Ditches are a sourceof sediment and
associatedcontaminants to
downstreamwaters, especially
when scraped.
Large quantities of gravel, rocks and other bedload move out of ditches and form deltas in the streams.
Meander induced by ditch-formed delta
Ditch and delta
Stream bank erosioncreated by re-directed stream flow.
A broader perspective -Precipitation has been increasing in NY and the Northeast
http://yosemite.epa.gov/oar/globalwarming.nsf/content/us-newyork.html
Northeastern U.S. Climate –Future directions
2006 Union of Concerned Scientistshttp://www.northeastclimateimpacts.org
What floods cost in New York annually.
In thousands of current dollars
1
10
100
1,000
10,000
100,000
1,000,000
‘55 ‘65 ‘75 ‘85 ‘95 ‘03
Flood damage estimates in U.S., 2002R. Pielke, M. Downton, Z. Barnard-MillerBoulder, CO. www.flooddamagedata.org
2006 – $54.8 million
YEAR
E.P.A. Phase II Stormwater Regulations 2003For 450 towns in New York –
Municipal Separate Storm Sewer Systems
The Regulatory Framework
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
Don’t overditch – 18 -24 inches depth is plenty deep enough to carry
away stormwater
Avoid the V-shaped ditch -the bottom is easily
incised and starts the erosion process.
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.
Wherever possible, mowditches regularly instead of scraping.
Guideline #3
• 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 itin patches withvegetated stripsleft downslopeto capture sediments.
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.
Guideline #4:Minimize erosion of gravel and rocks that move as bedload into streams.
Use permeable pavements or vegetation along road shoulders.
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.
Guideline #5
Guideline #6Reduce transfer of runoff
from land to ditches. • Increase infiltration of rain
water on land associated with houses, parking lots, and farms.
Guideline #7Communicate! Be part of the dialogue and provideleadership concerning stormwater management with landowners and town government.
New Directions:Ditches as conduits of
Ag pathogens todownstream
drinking waterreservoirs
Sampling to monitor for fecal coliforms and pathogens in ditches.
Continue the conversation –suggestions are welcome!
Acknowledgments:USDA CSREES, Cornell (funding); Cayuga Lake Watershed Network,Town of Candor, Cortland, Enfield Highway Depts., City of Ithaca Planning Dept.
Questions ?
