Science-based Guidelines for Successful Roadside Ditch Management to Mitigate Floods, Droughts and Degraded Water Quality Rebecca Schneider Dept. Natural Resources Cornell University Dirt and Gravel Roads Conference September 22, 2009 1. Flooding – drivers i - climate change ii - watershed management 2. Ditch research project 3. Ditch management recommendations Talk Outline April 16, 2007, NY Albany Allegany Broome Catta raugus Cayug a Chautauqua Chemung Che nango Clinton Co lumbia Cortlan d Delaware Du tches s Erie Essex Franklin Fulton Genesee Greene Hamilton He rk i m e r Jefferson Lewis L i vingston Madison Monroe Montg. Nassau NY City Niagara Oneida Ono ndaga Ontario Orange Orleans Oswego Wayne Steuben Tioga Tompkins Schuyler Ulster Westchester Putnam Sullivan Rockland Suffolk Otsego Rensselaer Schenectady W as hi ngt on Schohari e St. Lawrence Warren Wyomin g Yates S e n e c a Sa ratoga 0x 1x 2x 3x 4x 6x 7x # FEMA Disaster Flood events per County from 1994-2006 Avg flood damage costs: ~$50 million/yr Flood damage estimates in U.S., 2002 R. Pielke, M. Downton, Z. Barnard-Miller Boulder, CO. www.flooddamagedata.org 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 Scientists http://www.northeastclimateimpacts.org
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Science-based Guidelines for
Successful Roadside Ditch Management to Mitigate Floods, Droughts and Degraded Water Quality
Goal: To provide some guidelines for better roadside ditch design and maintenance which accomplish the following:
1) Reduce work load and costs.
2) Keep stakeholders happy.
3) Prevent erosion, protect water, and maintaina healthy environment.
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 upslopethat 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.
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 #7
Communicate! Be part of the dialogue and provideleadership concerning stormwater management with landowners and town government.
Road drainage is a critical component of traffic safety
as well as flood prevention and water quality improvement !
Acknowledgments:Collaborators: T.Walter, D.Buckley, K. Falbo, J. Diaz-Robles, B.BuchananFunding: USDA CSREES, Cornell (funding); Cayuga Lake Watershed Network,Town of Candor, Cortland, Enfield Highway Depts., City of Ithaca Planning Dept.