Estimating Benefits of Hydrologic Restoration and Freshwater

Introduction Projects in Coastal Wetlands

Ron Boustany USDA/Natural Resources Conservation Service

Lafayette, LA

CEER 2014

Area

(Spa

tial)

Time (Temporal)

Progradation Degradation

Delta Cycle

High River Influence High O2 High Mineral/Sediment High Nutrient Availability Low Plant Competition Mineral Soils High Bulk Density Geologically Driven

Low River Influence Low O2 Low Mineral/Sediment Low Nutrient Availability High Plant Competition Organic Soils Low Bulk Density Biologically Driven

Based on O’Neil 1949, Gosselink 1984, Sasser 1994, Swarzenski et al. 2008

Input > Output

Input = Output

Input < Output

+1.0%

+0.5%

+0.25%

-0.25%

-0.5%

TIME

AREA

Annual Land Change Rates

0%

-1.0%

Prograding (Land Gain)

Degrading (Land Loss)

Input > Output

Input = Output

Input < Output

+2.0%

-2.0%

Inputs = organic + mineral accretion; Ouputs = subsidence + erosion + SLR

Organic Fraction

Mineral Fraction

Wetland Soil Nutrients

Plant Production

Sediment

Export

(-)

(-) (+)

(+)

(-)

(+)

Salinity

NSED2 Model: Calculates a benefit from nutrient and sediment introduction. SPROD2 Model: Calculates benefit from reduction in salinity.

Nutrients In situ Organic Production

Organic soil fraction

Export Denitrification

Burial (Immobilization)

Decomposition Export

Salinity Reduction

Sediment Mineral soil

fraction

Export

SPROD2

NSED2

Gosselink et al. 1984

Patterns Consistency Predictability Model “remarkably constant”

* Nyman et al. 1990, Hatton et al. 1983 ** Faulkner and Poach 1996

About 0.026 g cm-3 organic carbon in all soils

32.5%

16.3%

10.0%

3.0%0.08

0.160.24

0.835

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

0.0%

5.0%

10.0%

15.0%

20.0%

25.0%

30.0%

35.0%

Fresh/Intermediate Brackish Saline New Delta

% Organic C Bulk Density

Bulk Density = 0.16 g cm-3 (Brackish Marsh)

% Organic = 16.25% Organic Fraction = BD * % Organic Organic Fraction = 0.16 * 0.1625 = 0.026 g cm-3

Production Rate (PR) = 2653 g m-2 y-1

= 0.2653 g cm-2 y-1

= 0.2653 g cm-3 y-1 (at 1 cm depth) % of Production in BD = (Organic Fraction)/(PR) (0.16 g cm-3)*(0.1625) ÷ (0.2653 g cm-3) = 9.8%

1 cm

Organic Fraction Calculation (NSED2 & SPROD2)

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

1 2 3 4 5 6 7 8 9 1011121314151617181920212223242526272829303132333435Salinity (ppt)

% Maximum Productivity

Fresh

Intermediate

Brackish

Saline

Reproduced from Snedden and Swenson 2012

Central Terrebonne Freshwater Enhancement Project (TE-66)

Project Area – 48,446 acres 19,421 acres wetland 29,025 acres water

Loss Rate = -0.46%/y

(89.3 acres/y)

Problem: Expanded breach in historic ridge that allows for more direct transfer of higher saline gulf marine waters to penetrate deep into the upper Central Terrebonne fresh and intermediate marshes. Goals: Reestablish historic hydrologic and salinity conditions by reducing the intrusion of gulf marine waters via the Grand Pass into the Central Terrebonne marshes. Solution: Construction of rock barge bay in pass to reduce 900 ft wide x 37 ft deep opening by 90% to 150 ft x 16 ft. Model: SPROD2 (STELLA 10.0.4)

SPROD2 Model – Calculates the benefits of salinity reduction from freshwater introduction and/or structural features

Module 1- Salinity Dilution Box Model Calculates the percent difference in salinity with the project.

SPROD2 Salinity/Production Model

1:10 PM Wed, Jul 09, 2014

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2:

2:

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-1

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5

0

15

30

1: Tide Level 2: Tide Sal

1

11

12 2

2

2

1:18 PM Wed, Jul 09, 2014

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15

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-2

-1

1

1: Tide Sal 2: Salinity 3: Percent Salinity Diff

1

1

1

12 22

2

3 3 3 3

Module 2 – Marsh production factor calculator Calculates the percent difference in production within each marsh zone.

SPROD2 Salinity/Production Model

1:36 PM Wed, Jul 09, 2014

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Hours

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1:

1:

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2:

0

15

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-1

0

1

1: B Init Sal 2: B Diff%

1

1

1

1

2 2 2 2

Example of brackish marsh results.

Module 3-Land Change Calculators Calculates the acres of land benefit within each marsh zone based upon the increase in organic production from salinity reduction.

SPROD2 Salinity/Production Model

1:40 PM Wed, Jul 09, 2014

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-0.02

-0.004

0.012

0

15

30

1: I Acres 2: B Acres 3: S Acres 4: Salinity

1 1 1 122

2 23 3 3 3

4

4

44

Annual Land Loss Reduction Percent Calculator

Annual Net Change Calculator

SPROD2 Salinity/Production Model

14.3% reduction in land loss rate

Land Loss Spreadsheet

233 net acres in 20 yrs 1:10 PM Wed, Jul 09, 2014

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19090

19295

19500

0

0

0

0

10

20

1: FWOP 2: FWP 3: ANNUAL LLR PERCENT 4: ANNUAL NET CHANGE

1

1

1

1

2

2

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3

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4

4

4

4

Cameron-Creole Freshwater Introduction Project (CS-49)

Project Area = 22,240 acres 7,659 acres wetland 14,581 acres water

Loss Rate = -0.76%/y

(58.2 acres/y)

Problem: Experiencing increased tidal exchange, saltwater intrusion, and reduced freshwater retention associated with the Calcasieu Ship Channel and the GIWW. Also recently impacted by hurricanes. Goals: The project would restore the function, value, and sustainability to approximately 22,247 acres of marsh and open water. Solution: Construction of ten 48-inch culverts in the bank of the GIWW to establish freshwater flow from the GIWW into the Cameron-Creole marshes. Model: NSED2 (STELLA 10.0.4)

NSED2 Nutrient/Sediment Model

NSED2 Nutrient/Sediment Model

Nutrient Module: calculates the acres of benefit from increase in nutrients.

NSED2 Nutrient/Sediment Model

Sediment Module: calculates the acres of benefit from increase in sediments.

Annual Net Change and Land Loss Reduction Percent Calculators

NSED2 Nutrient/Sediment Model Marsh Fill Calculator

156 net acres in 20 yrs

Conclusions

• Desktop modeling has allowed us to quantify benefits of introducing nutrients, sediments and lowering salinities in a way that allows equitable comparison to all project types.

• By quantifying the benefits of nutrient, sediment and salinity reduction, we are able to provide estimates of cost/benefit to allow decision makers to make more informed decisions in selecting projects for funding.

Questions?

Weeds or Organic Production?