Science-based Guidelines for

Successful Roadside Ditch Management to Mitigate Floods, Droughts and Degraded Water Quality

Rebecca SchneiderDept. Natural Resources

Cornell University

Dirt and Gravel RoadsConference

September 22, 2009

1. Flooding – driversi - climate changeii - watershed management

2. Ditch research project

3. Ditch management recommendations

Talk Outline

April 16, 2007, NY

Albany

AlleganyBroomeCa

ttaraugus

Cayug

aChautauqua

Chemung

Chenango

Clinton

ColumbiaCortland

Delaware

Dutchess

Erie

Essex

Franklin

FultonGenesee

Greene

Hamilton

Herkimer

Jefferson

Lewis

Livingston

Madison

Monroe

Montg.

Nassau

NY City

Niagara OneidaOnondagaOntario

Orange

Orleans

Oswego

Wayne

Steuben

Tioga

Tompkins

Schuyler

Ulster

Westchester

Putnam

Sullivan

RocklandSuffolk

Otsego Rensselaer

SchenectadyWashington

Schohari

e

St. Lawrence

Warren

Wyoming

Yates Seneca

Saratoga

0x

1x

2x

3x

4x

6x

7x

# FEMA Disaster Flood events per County from1994-2006

Avg flood damagecosts: ~$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

Watershed: all of the area which captures rainfall and contributes to stream flow,i.e. the “bowl”.

Poor Watershed Management

Watershed

divide

Balance between precipitation, runoff , infiltration , and evapo-transpiration

Cross-section of a watershed

Overland runoff

via stream channel

networks

Watershed

divide

Stream numbering

Photo: Y. Arthus Bertrand

rain

Groundwater

contribution –

base flow

Natural stream flow patterns

High flow

Low flow

ImperviousSurfaces:RooftopsParking lotsDriveways

Compacted Soils:Lawns,Crop fields

time (hrs/days/weeks)

stream

height

post-development

pre-development

• in frequency and magnitude of floods

• in summer droughts

• degraded water quality – erosion

• loss of diversity of fish and aquatic animals

Impervious surfaces impact the natural patterns of flow:

Talk Outline

1. Flooding –i - climate changeii - watershed management

2. Ditch research project

3. Ditch management recommendations

Roadside Ditches –the unrecognized factor

in stormwaterrunoff management

What role do they playin flooding, droughts,and pollution?

Managed by highway staff to preventroad flooding and traffic accidents

rarely linked to watershed mgmt issues

2) Monitor:• Total water flow• Suspended sediment• Dissolved chemicals

• Bedload sediment

On-going Research

on ditch networks

1) Map:• ditch lengths,• mgmt types• connectionsto streams

Without Ditches

With Ditches

Paine’s Creek Watershed,Lansing, NY

GPS and GIS mapping of the ditch networks relative to natural stream channel systems in 6 watersheds.

Ditches intercept ~1/4 ofthe surface runoff inour watersheds and shunt it rapidly

downstreamwhere it is injected

as high flowinto the streams.

Ditch drainage

basins

Stream

Road ditches

Ditch outflows

Mean Peak conc. by Percent of exposed substrate at the bottom

y = 0.0316e0.0413x

R2 = 0.7413

0

1

2

3

4

5

6

7

0 20 40 60 80 100 120

% exposed substrate at the bottom

Mean Peak conc. (kg/m^3)

Ditch 4

Ditch 2

Ditch 7

Ditch 3 (incised)

Ditch 8

Ditch 6

Ditch 5 old

Ditch 1

Ditch 5 new

Ditch 3 (scraped)

Regression

BAREVEGETATED

Ditches are a sourceof sediment and associated

contaminants to downstream

waters, especiallywhen scraped.

Nutrients

Element Total load (kg)

Ortho-Phosphates 1.43

Total P 83.43

NO3-+ NO

2- 21.43

Trace

Metals

Al 22.64

Mn 1.48

Fe 52.27

Ni 6.39

Cu 1.28

Pb 0.25

Cr 3.79

Zn 2.90

Cations

Na+ 11,100.58

Mg2+ 737.39

K+ 75.78

Ca2+ 3,205.36

Anions As3- 0.16

Summary of Chemicals Transported in Ditches

Dissolved Chemical Loads

A diversity of chemicals

dissolved in thewater and

adsorbed on the sediment particles are transported by

ditches downstream.

De-icers

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

Current Research: Potential influence on stream erosion.

Ditch influence on

erosion?

Moose River, Adirondacks

Current research:Ditches as conduits of

human pathogens to downstreamdrinking waterreservoirs

MethodsE. coli Quantification

Positive for Total Coliforms

Positive for E. coli

Idexx’s Colilert/Quantitray Method ™

EPAStd.

Talk Outline

1. Flooding –i - climate changeii - watershed management

2. Ditch research project

3. Ditch management recommendations

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.

Questions ?

B. Hecht