Marsh Loss and Tidal Habitat Degradation

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Felix Madsen
5 år siden
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1 Marsh Loss and Tidal Habitat Degradation

2 Alternative 2: New Ocean Inlet Data: PWA

3 Alternative 3: Highway 1 Sill Data: PWA

4 Alternative 4: Parsons Slough Data: PWA

5 Alternative 2 Detailed Cost Subtotal: $69,600,000 Contingency (35%): $24,400,000 TOTAL: $94,000,000 Alternative 3 Detailed Cost Sill: $ 5,000,000 Sediment: $15,000,000 Subtotal: $20,000,000 Contingency (35%): $ 7,000,000 TOTAL: $27,000,000

6 Water Level vs. Velocity Year EBB FLOOD 2 Water Level (m, NAVD) MSL, Existing Alt. 1 No Action Velocity (m/s) Data: PWA

7 Water Level vs. Velocity Year EBB FLOOD 2 Water Level (m, NAVD) MSL, Existing 1943 Alt. 1 No Action 0 Alt. 2 New Inlet Alt. 3a Low Sill Alt. 3b High Sill Alt. 4 Parsons Velocity (m/s) Data: PWA

8 Annual erosion rates (thousands m 3 /yr) Years 0-10 Years Alternative 1 No action Alternative 2 New inlet Alternative 3a Low sill Alternative 3b High sill Alternative 4 Parsons Slough Data: PWA

9 Predicted Tidal Prism Scenario Year 0 Mm No Action New Inlet Low Sill High Sill Parsons Slough Data: PWA

10 Marsh plain viability Water Level vs. Percent Exceeded Year Alt. 1 No Action Water level (m NAVD) Marsh plain % time exceeded Data: PWA

11 Marsh plain viability Water Level vs. Percent Exceeded Year Alt. 1 No Action Water level (m NAVD) Marsh plain % time exceeded Data: PWA

12 Some alternatives reduce the inundation of the marsh plain, allowing revegetation Water level (m NAVD) Marsh plain 1943 Alt. 1 No Action Alt 2. New Inlet Alt 3a. Low Sill Alt. 3b High Sill Alt. 4 Parsons % time exceeded Data: PWA

13 What about the sediment and sea level rise?

14 At Year 50, without accretion of the marsh plain, 30 cm of sea level rise drowns the marsh Water level (m NAVD) Alt. 1 No Action Alt 2. New Inlet Alt 3a. Low Sill Alt. 3b High Sill Alt. 4 Parsons Marsh plain % time exceeded Data: PWA

15 Sediment accretion measurements: the marsh surface is accreting Feldspar markers October 2006 April 2008 Eight sites (all salt marsh) Two measurement dates Accretion rate: 4.4+/-0.9 mm Data: ESNERR

16 Sediment Supply and Demand: marsh building and channel erosion metric tons/year 100,000 80,000 60,000 40,000 20,000 marsh building channel erosion streams 0 measured ( ) no action Parsons project low sill new inlet high sill Carneros Creek Analysis: PWA

17 Sediment Supply and Demand: fluvial sediment sources 3,000,000 metric tons per year 2,500,000 2,000,000 1,500,000 1,000, ,000 marsh building channel erosion streams 0 measured ( ) no action Carneros Creek Pajaro River Salinas river Analysis: PWA

18 Sediment Supply and Demand: accumulated sediment deficit 5,000,000 4,500,000 4,000,000 3,500,000 3,000,000 2,500,000 2,000,000 subsidence marsh building channel erosion streams 1,500,000 1,000, ,000 0 Parsons project Pajaro River Salinas river Subsidence in Parsons Slough wide subsidence Analysis: PWA and ESNERR

19 Sediment Supply and Demand: will there be enough? metric tons/year 100,000 80,000 60,000 40,000 20,000 marsh building channel erosion streams 0 measured ( ) no action Parsons project low sill new inlet high sill Carneros Creek Analysis: PWA

20 Sediment Supply and Demand: paying off the debt 5,000,000 4,500,000 4,000,000 3,500,000 3,000,000 2,500,000 marsh building channel erosion streams subsidence additions 2,000,000 1,500,000 1,000, ,000 0 no action Parsons project Pajaro River Subsidence in Parsons Slough wide subsidence Graniterock Analysis: PWA and ESNERR

21 Long term sediment supplies Carneros Creek Channel restoration Pajaro River Flood control Persistent organic pollutants Salinas River Salinas River Lagoon breach management

22 Project Tasks Parsons Slough Project Timeline Establish Goals complete Quality Assurance Plan complete Draft Existing Conditions Report complete Draft Sediment Additions Report complete Restoration Options Meeting May 7, 2008 Draft Restoration Options May 30, 2008 Comments on Restoration Options June 20, 2008 Final Restoration Options June 30, 2008 Draft Restoration Plan Aug 29, 2008 Restoration Plan Meeting October, 2008 Final Restoration Plan Dec 12, 2008

Partner Investigations Countdown to Decision 2008 Tide Stations ongoing Marsh Sediment Monitoring ongoing Community Involvement ongoing Oxygen & Nutrient

25 Partner Investigations Countdown to Decision 2008 Tide Stations ongoing Marsh Sediment Monitoring ongoing Community Involvement ongoing Oxygen & Nutrient Dynamics 6/2008 Responses of Key Species 8/2008 Economic Values 10/2008 Legal and Policy Factors 10/2008 DECISION whether to pursue a project November-December 2008

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