restoring ditched salt marshes: acting today, preparing for the next 100 years

Restoring Ditched Salt Marshes: Acting Today,

Preparing for the Next 100 years

S.C. Adamowicz, Ph.D.; US FWSB. Argow, Ph.D.; Wesley College

Z. Hughes, Ph.D.; Boston UniversityJ. Franklin, Dalhousie University

E. Hazelton, Utah State UniversityJ. Kramer, US FWS

Overview

• Introduction• Concepts• Ditch types & history• Predicted Future Conditions• Previous Restoration Efforts• New Techniques

Unditched Marshes:Nauset Marsh, MA

Fisherman’s Island, VA

Webhannet Marsh, Wells, ME

Introduction• Salt marshes

– Are extensive ecosystems dominated by halophytic grasses

– Are a highly productive– Provide important ecosystem services

• Fish & wildlife habitat• Storm surge protection• Nutrient cycling• Flood attenuation• Shoreline protection• Marine fishery nurseries• C-sequestration

Important Concepts

• Resilience• Salt marsh capital• Self-sustaining processes

Ecosystems possessinghigh resilience can be pushed to extremes without reorganizing into a different form of stable state.

Systems lacking resilience can be “pushed” into an alternative stable state, of which there may be more than one.

Resilience

Concepts cont

• Salt Marsh Capital

MSL

S. A

ltern

iflor

aGr

owth

zone

Concepts cont

• Salt Marsh Capital

MSL

S. A

ltern

iflor

aGr

owth

zone

Concepts cont• Self-sustaining ecosystem processes

Ditching History

• Colonial Times• Public Works Administration• OMWM• Other misc (boat access, pipelines, etc)

Colonial Ditching

• Purpose- salt hay production, pasturing• Characteristics –

– “step across” x 1 ft deep– Boundary ditches 3 ft deep– Spacing: “able to turn a horse” ~60 ft

• Methods of construction– Hand digging

Recipe to make Manure.

Take the Soil and Mud, which you cutt up and throw out when you dig Ditches in a Salt Marsh, and put 20 Load of it in a heap. (John Adams, 1771) John Adams by John Trumbull;

wikitree.com

Salt marsh haystack; M. J. Heade1863

Public Works Ditching

• Purpose – mosquito control

• Characteristics- – 1- many feet deep– 1- many feet wide

• Methods: see subsequent slides

• Bourn & Cottam 1950By mid-century ~90% of salt marshes from Maine to Virginia had been ditched

Botsford Spade

Photos Courtesy CT DEP: Paul Capitosto

Hay knife CrewHay knife

Westbrook method of piling peat

Hammonasett State Park, CTClogged ditch

Scavel Plow

Ditch cleaning at Hammonasett

Hammonasett State Park, CT

90 ft spacing

Bombay Hook NWR

Parker River NWR

Prime Hook NWR

150 ft spacing

Stewart B. McKinney NWR

100 ft spacing

Rumstick Point, RI

90-130 ft spacing

Stewart B. McKinney NWR

Effects of Ditches: Drainage• Redfield 1972:“The general effect of ditching is to

reduce the natural drainage system by providing an alternate route for the flow of water.”

y = -0.4671x + 146.96R2 = 0.5673 p<9E-6

0

50

100

150

200

250

300

350

400

0 50 100 150 200 250 300 350 400

Ditch Length (m/ ha)

Cre

ek L

engt

h (m

/ha)

Linear (Creek length (m) /ha)

Adamowicz 2002

Ditch Effects: Elevation & Sedimentation

• LeMay (2007) – Natural marsh: creeks fill first then sheet flow covers

the marsh– Ditched marsh: interior fills first & remains flooded

for longer period of time– Increased ditch length within a given area correlated

with decreased elevation– Reduced elevation and increased inundation did not more sedimentation• Ditched marshes were net erosive environments

Ditch Effects: ElevationTotal elevation and accretion reduced at ditched sites

May-00Jul-00

Sep-00

Nov-00

Jan-01

Mar-01

May-01Jul-01

Sep-01

Nov-01

Jan-02

Mar-02

May-02Jul-02

Sep-0

2

Nov-02

Jan-03

Mar-03

May-03Jul-03

Sep-03

-0.2

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

Total Elevation Change vs Accretion of Non-Ditched Sites in Abscecon State Management Area, NJ

SET_NDFeldspar_NDSET_D

Chan

ge (c

m)

Erwin et al. unpublished data

Ditch Effects: Biodiversity

• Corman (2011):

– natural creeks have higher species richness– No change in density BUT:

• Mummichogs preferred upper creeks but lower ditches

• Clarke et al. (1984):– Shorebirds, wading birds, terns, swallows & crows

deprived of foraging areas (inadequate foraging areas)

OMWM: Open Marsh Water Management Ditches

• Open Marsh Water Management– Construct shallow ditches and pools to link fish

reservoirs to mosquito breeding areas– Keep fish on the marsh in between tides– Use natural control mechanisms (fish, water

regulation) to reduce mosquito production

Wertheim NWR

Parker River OMWM

Prime Hook OMWM Site

East Coast Sea Level Changes

• Sea Levels Onlinehttp://tidesandcurrents.noaa.gov/sltrends/sltrends.html

Mean Sea Level Trend8534720 Atlantic City, New Jersey

http://tidesandcurrents.noaa.gov/sltrends/sltrends_station.shtml?stnid=8534720

The mean sea level trend is 3.99 millimeters/year with a 95% confidenceinterval of +/- 0.18 mm/yr based on monthly mean sea level data from 1911 to 2006 which is equivalent to a change of 1.31 feet in 100 years.

Mean Sea Level Trend8557380 Lewes, Delaware

The mean sea level trend is 3.20 millimeters/year with a 95% confidence interval of +/- 0.28 mm/yr based on monthly mean sea level data from 1919 to 2006 which is equivalent to a change of 1.05 feet in 100 years.

http://tidesandcurrents.noaa.gov/sltrends/sltrends_station.shtml?stnid=8557380

Mean Sea Level Trend8443970 Boston, Massachusetts

The mean sea level trend is 2.63 millimeters/year with a 95% confidenceinterval of +/- 0.18 mm/yr based on monthly mean sea level data from 1921 to 2006 which is equivalent to a change of 0.86 feet in 100 years

http://tidesandcurrents.noaa.gov/sltrends/sltrends_station.shtml?stnid=8443970

Mean Sea Level Trend8418150 Portland, Maine

http://tidesandcurrents.noaa.gov/sltrends/sltrends_station.shtml?stnid=8418150

The mean sea level trend is 1.82 millimeters/year with a 95% confidenceinterval of +/- 0.17 mm/yr based on monthly mean sea level data from 1912 to 2006 which is equivalent to a change of 0.60 feet in 100 years.

Summary: Future Conditions

• Different rates of SLR versus….

– Marsh capital– Sediment supply– Growth rate (increased CO2 increased Growth rate)

Effects of Previous Management Efforts

• Ditch plugging• Ditch filling• OMWM/closed systems

-20

-15

-10

-5

0

5

10

150 5 10 15 20 30 40 45 50 52

Groundwater ResultsMoody Normal Transect

bd

a

b,cb,c b,c,d

b,c

c,de

ePluggedDitch

OpenDitch

Distance (m)

Dept

h to

gro

undw

ater

(cm

)

Peat Study Site Locations(Age of plugs)

Granite Point 10

Moody 10

Parker River A 15Parker River B2 6

Westbrook 16

Hammonasset State Park 24+

Ditch Plugging 2005: Groundwater Levels

HM MO PKR A PKR B2

-25

-20

-15

-10

-5

0

5

Average groundwater depths 2005***

OpenPlugged

Grou

ndw

ater

dep

th cm

Groundwater 2009: Creek, Ditch, Plugged Ditch

2006 HR 2006 MO 2009 HR 2009 MO 2010 HR 2010 MO

-16

-14

-12

-10

-8

-6

-4

-2

0

2

4

Average groundwater depths***

CreekOpenPlugged

Grou

ndw

ater

dep

th cm

Soil Bulk Density 2009

HR MO PKR_A PKR_B2 WB0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

Average bulk density

CreekOpenPlugged

g/cm

3

*********

SignificantTreatment Effectsp<0.01 -0.001

**

% Organic Matter 2009

HR MO PKR_A PKR_B2 WB0

10

20

30

40

50

60

70

80

90

100

% Organic matter

CreekOpenPlugged

% O

M

*** *** *****

Significant Treatment Effectp<0.01 - 0.001

Soil Pore Water 2009: H2S

HR MO PKR A PKR B2 WB0

500

1000

1500

2000

2500

3000

3500

4000

Average pore water H2S***

CreekOpenPlugged

Conc

entr

ation

H2S

uM

Treatment Effectp<0.001

Seliskar et al. 2004

0

20

40

60

80

100

120

Perc

ent C

over

Average Percent Cover of Species Contributing Most to Dissimilarities Between Plugged and Open Ditched Sites 2005

Plugged

Ditched

Creek vs. Moody Open, Plugged 2009 SIMPER Results

HR Creek MO Open MO Plugged0

10

20

30

40

50

60

70

80

90

100

Average of Spa_pateAverage of Spa_alteAverage of Bare GroundAverage of WaterAverage of Dis_spicAverage of Pla_mariAverage of Puc_mariAverage of Tri_mari

% C

over

Species accounting for differences between groups

Creek vs. PKR B2 Open, Plugged 2009 SIMPER Results

HR Creek PKR_B2 Open PKR_B2 Plugged0

10

20

30

40

50

60

70

80

90

100

Average of Spa_pateAverage of Spa_alteAverage of WaterAverage of Dis_spicAverage of Jun_GerAverage of Gla_mari

% C

over

Species accounting for differences between groups

New Restoration Approaches & Techniques

• Objectives– Restore marshes in ways that increase resilience to

sea level rise• Remove sediment sinks• Increase marsh accretion• Increase marsh capital

– Be self-sustaining– Easily used at multiple sites– Remove ditch hydrology/ replace tidal channel

hydrology

Dike Removal

• Objectives– Restore tidal flow– Increase sedimentation– Increase site elevation – Increase plant

productivity– Increase marsh capital

Mousam River Dike Removal Feb 15, 2011

Other Dikes

Furbish Rd, Wells, ME

Patriots’ Day Storm 2007

Ditch Remediation & Tidal Channel Restoration

• New Techniques Need to:– Be self-sustaining– Easily used at multiple sites– Remove ditch hydrology/ replace tidal channel

hydrology

Thin Layer Deposition at Gateway NP

Sediment from adjacent channel Planted following Spring

Ditch Remediation

Project Area 1a

Project Area 1b

No change

Ditch 6: roll

Ditch 1: roll

Ditch 4: roll

Ditch 2: meander

Ditch 5: meander

Ditch 8: roll

No change

Mow & Roll

Cut salt grass in ditch

Sediment trapSeed trapRooting medium

Objective: Fill ditch with living roots, incorporate into surrounding peat

Expected Results

• Increase sedimentation within ditches• Increase sedimentation on adjacent marsh

surface• Increase number and density of plants

growing within ditches• Increase sheet flow

Tidal Channel Restoration

• Imperative to link tidal channel restoration to prevent waterlogging the site (recall Redfield quote)…not enough just to remove ditches

Ditches are not Creeks

Hughes unpublished data

Self-similarity of Natural Channels

Stratford, CT Mandelbrot Diagram

Average Contractor Channel Designs

Created Channel Mandelbrot Diagram

Call in the Numbers Guys

Jonathan FranklinEric Hazelton

Modeling Natural Tidal Channels

GIS to Python Model

Purpose: Provide channel design parameters to contractors

Final Goal

Increase Resilience• Increase marsh capital• Restore natural hydrology• Increase biotic diversity

Harbor Rd., Wells, ME

Thank you• Brit Argow• Zoe Hughes

• R5 LMRD Funds• NAWCA grant to DU

– Ray Whittemore– Craig Ferris

• Jordan Kramer• Jonathan Franklin• Eric Hazelton