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.