Rebecca Schneider Dept. Natural Resources Cornell University, NY

Ditches – Improving management to reduce flooding,

water pollution, and in-stream erosion

and habitat degradation

“Re-plumbing” Roadside Ditch Networks

PA Dirt and Gravel Roads Conference April 2017

Precipitation = Runoff + Groundwater + Evaporation/transpiration

Watersheds determine the quantity and quality of water available

rain

Groundwater contribution –

base flow

Groundwater - Low flow Runoff - High flow

Naturally dynamic

stream flow patterns

Runoff

PRE-development

POST-development

Center for Watershed Protection 1995

time (hrs/days/weeks)

stream height

POST-development

PRE-development

• increase in frequency and magnitude of floods

• increase in stream dry out, water table decline

Human activities have shifted the balance

Roadside Drainage Networks

What role do they play in:

Floods? Droughts? Water pollution? Stream ecosystem health?

Faculty: D. Orr, Cornell Local Roads Program T. Walter, Dept. Biological and Environmental Engineering D. Buckley, P. Bergholz, Dept. Crops and Soils R. Marino, R. Howarth, K. Sparks, Dept. Ecology S. Allred (Dept. Natural Resources) Graduate Students: K. Falbo, B. Buchanan, J. Diaz-Robles, J. Archibald, L. McPhillips, S. Davis, W. Pluer, T. Johnson, J. Kimchi

Roadside Ditch Team

Study Sites

NY

PA

Approaches

(2) MONITORING Total water flow Suspended sediment Dissolved chemicals Bedload Fecal coliforms

(1) GPS and ARC-GIS MAPPING Ditch lengths Connections to streams Management types

vegetated exposed, scraped

Ditch Study Sites

Watershed area Road length Roadside ditch length* Total ditch length connected to strms Total # of direct connections to strms % road surface area of wtshd Area of basins draining to ditches % of watershed draining to ditches Stream channel length (no ditches) Stream channel density w/o ditches Stream channel density with ditches

42.3 km2 (16.3 sq. mi) 54.3 km 81.4 km 51.0 km (31.7 miles) 94 0.69 % 8.1 km2 (3.1 sq. mi) 22.0 % 66.0 km 1.55 (km/km2) 2.73 (km/km2)

Characteristic Average value

Results - Drainage Mapping

* 23% is exposed – scraped or eroded

Ditch drainage basins potentially intercept ~22 % of the surface runoff and

shallow groundwater from each watershed and

rapidly shunt it to the nearest stream.

Ditch drainage basins Stream Road ditches Ditch outflows

Results – Drainage Mapping

Results – Hydrology

Doolittle Creek Watershed 8 ditch monitoring stations and Doolittle Crk 10 storms 2005-2006; 1.3 – 12.9 cm total rain/event Each ditch captured avg of 51% of rainfall in the ditch’s basin

Diaz-Robles 2007

Methods

Runoff

INPUTS:

Slope Soils Land use

Routing

Methods – Hydrologic Model

Buchanan et al. 2012

Results – Hydrologic Model

Entire Modeled Ditch Drainage Networks: Doolittle: transported 45,400 m3 water / storm =

3.6% (+/- 1.4%) of incoming precipitation and 19.5% (+/- 9.7%) of total stream flow measured in each storm

Paine’s Creek: 22% of total stream flow in spring storm event and 29% of total stream flow in a summer storm event.

Results - Hydrology

Buchanan et al. 2012

7 ditches 34 storms 2.5 – 40 mm rain April – Dec. 2009

Paine’s Creek Watershed

Results – Hydrology

Ditch discharges contribute to increased peak flows (avg 78%) and total flows (avg 57%) in streams. Buchanan et al. 2012

spring summer

time (hrs/days/weeks)

stream height

Ditches

No ditches

Results: Ditches alter the Natural Flow Regime, Aka Environmental Flows

Ditches are a source of sediment and

associated contaminants to

downstream waters, especially

when scraped.

Photo Bill Hecht

Results – Sediment

0.00E+00

1.00E-03

2.00E-03

3.00E-03

4.00E-03

5.00E-03

6.00E-03

0.00

2.27

4.27

7.95

21.67

22.17

22.67

24.67

45.95

47.95

0

0.005

0.01

0.015

0.02

0.025

0.03

Dis

char

ge (m

^3/s

ec)

Disc

harg

e ( TSS concentrationDischarge

Diaz-Robles, 2007 Duration of storm (hrs)

TSS

conc

entr

atio

n

Dis

char

ge (m

3/se

c)

Nutrients

Element Total load (kg)

Ortho-Phosphates 1.43

Total P 83.43

NO3- + NO2

- 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

Dissolved Chemical

Loads over 10 storms

A diversity of chemicals

dissolved in the

water and adsorbed on the sediment particles are

transported by ditches

downstream. De-icers

Results – Nutrients, Cations

Diaz-Robles 2007

Positive for Total Coliforms

Positive for E. coli

Idexx’s Colilert/Quantitray Method ™

Methods - Microbes E. coli quantification

Manure spread on farm fields

Falbo et al. 2012

Manure spreading, livestock pasturing … microbes move via tile drains to roadside ditches

Results - Microbes

7/08 8/08 9/08 10/08 11/08 12/08 1/09 2/09 3/09 4/09 5/09 6/09 7/09

E. c

oli c

once

ntra

tions

(MPN

/100

mL)

0

5000

10000

15000

20000

25000

Manure spreading

Manure spreading

EPA STD

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

Results – Bedload

Moose River, Adirondacks

Results – Bedload + Discharge Stream Geomorphology

High velocity discharges, bedload deltas

impact stream at ~94 locations in each watershed.

Upstream

Ditch

Downstream

Flow direction

30 m

30 m

Average Bankfull Width (m)

0

2

4

6

8

10

12

14

1 2 3 4 5 6

Stream Number

Wid

th (m

)

UpstreamDownstream

Average Grain Size Distribution

0

5

10

15

20

25

30

35

40

45

50

<2 2--4 4--8 8--16 16--32 32--64 64--128 128--256 256--512

Grain Size (mm)

%To

tal UpstreamDownstream

Results – Hydraulic Radius and Substrate

Kimchi 2010

upstream

downstream

Streams are in chronic disequilibrium with a storm-driven geomorphology

N2O ~50 ug/m2-hr

NO3 ~20 mg/l

Groundwater Exchange

On-going Research: Conduits/ filters of Nitrogen from manure ?

NO3 900 kg/ 6 mo Marino 2017 in prep

Summary – Roadside Ditch Impacts

Intercept, capture and shunt ~20% of watershed runoff to streams

Contribute to flooding in streams Contribute to headwater stream dry-outs and probably lowering of water table Rapid conduit, and source, of sediments, pathogens, de-icers and nutrients Contribute to in-stream erosion and stream ecosystem degradation

Extension Program on Re-plumbing Ditches

Presentations to ~2,800 town highway staff – Cornell Local Roads Highway School, Town govts Chesapeake Bay Watershed Conference and Report 2016

Strategies to Reduce Flooding /Droughts Disconnect ditches from streams. Use infiltration basins, constructed wetlands, or

detention ponds that allow for groundwater recharge.

“Re-plumb” our watersheds to reduce floods, droughts and pollution

Catch and save the rain to buffer the impacts of

climate change!

Mow ditches, instead of scraping.

Strategies to Reduce Pollution

Hydroseed immediately after ditching.

Ditches as opportunity for a watershed-wide filtration system.

Questions?

www.SustainbleWaterResourceManagement.info