Rebecca Schneider, Nancy Trautmann, & Linda Wagenet
Cornell University
Roadside Ditches: A Watershed Curriculum Module
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
Lake and stream health are linked to adjacent land uses and human
activities.
Watersheddivide
Watershed:The total area above a specific point on a stream or river from which water drains toward the stream.
Photo: Y. Arthus Bertrand
Water Cycle: Balance between precipitation, evapotranspiration, infiltration, and runoff
Credit: http://www.nrcs.usda.gov/technical/stream_restoration/chap2.html
Stream order - classifies stream segments according to the number of tributaries
2nd Order
5th Order
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
Rain
Baseflow (from groundwater)
High flowButtermilk Falls,NYNatural stream flow patterns
Runoff
Low flow
Impervious Surfaces: Rooftops Parking lots DrivewaysCompacted Soils: Lawns Crop fields
Impacts of Land Use on Runoff
Credit: http://www.nrcs.usda.gov/technical/stream_restoration/chap30002.html
time (hrs/days/weeks)
streamheight
post-development
pre-development
Impervious surfaces impact the natural patterns of flow:
frequency and magnitude of floods
summer droughts (due to lower baseflow)
15% impervioussurface
Impervious surfaces impact stream health:
• increased flooding and drought
• increased erosion
• degraded water quality
• loss of diversity of fish and aquatic organisms
Roadside Ditches – a neglected but critical factor in protection of water resources
After
Before
Ditches are managed by highway staff to prevent flooding of roads and buildings…and rarely linked to watershed management
Downstream Impacts
Credit: http://www.nrcs.usda.gov/technical/stream_restoration/scrhimage.htm
Watershed: 56 km 2
Stream Length: 88 km Roads: 87 kmDitches: 142 km
70% linked to stream
Increased drainage density 1.6 km-1 4.1 km-1
Enfield Creek
Road Stream Divide
• Total water flow• Suspended sediment• Dissolved chemicals • Bedload sediment
8 ReplicateSampling Stations + Creek
Research
Doolittle, Enfield, 6-Mile Creeks
Total Bedload Sediment Collected by Ditch Type per event
0
500
1000
1500
2000
2500
Gra
ms
Bare Dirt
Grassy
Gravel
Weedy
bare grassy weedy
Enfield Creek – Preliminary Findings
Ditch Type
gravel
Downstream erosion?
Roadside Ditch Impacts:
• mechanism for increased land-water linkages
• conduit for rapid runoff
• internal source of sediment and other contaminants
Scraped, exposed
Concrete, hardened
Recommended Ditch Management Strategies
Hydro-seeded
Rock-lined
Mowed grass
Recommendation: Disconnect ditches from streams. Use infiltration basins & detention ponds to capture water and allow it to recharge groundwater
Recommendation: Use permeable paving to reduce runoff
EPA Phase II Stormwater Regulations:Small towns/ designated MS4communities must develop
stormwater management plansby 2008.
Current guidelines focus on construction activities.