Sediment Dynamics in Restored Tidal Wetlands of San Francisco Bay

Transcription

1 Sediment Dynamics in Restored Tidal Wetlands of San Francisco Bay John Callaway & Jennifer Gagnon (USF) Lisa Schile (UC Berkeley) Evyan Borgnis & Tom Parker (SFSU) Donna Ball (HT Harvey & Assoc.) Gene Turner & Charlie Milan (LSU)

2 Past and Present Distribution of SF Bay Wetlands (from San Francisco Estuary Institute)

3 Huge interest in restoration in SF Bay, but many potential restoration sites (including former salt ponds) have subsided substantially and need to increase elevation to reach threshold elevations for vegetation establishment David Sanger

4 Theoretical Tidal Wetland Development (from Williams and Orr 2002)

5 Accretion Rate Theoretical Tidal Wetland Development MLLW MTL MHHW Elevation

6 Muzzi Marsh Crissy Field Island Ponds / A21 Pond A6

7 South Bay Salt Pond Restoration Project Island Ponds / A21 Breached in March 2006 Pond A6 Breached in December 2010

8 100 m

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11 Cumulative change in pin height (mm) Island Pond Sediment Accretion Southern stations Time post-breach (months)

12 Cumulative change in pin height (mm) Island Pond Sediment Accretion Northern stations Southern stations Time post-breach (months)

13 Cumulative change in pin height (mm) Island Pond Sediment Accretion Northern stations Southern stations Time post-breach (months)

14 6 months pre-restoration 36 months 24 months

15 Photos Cris Benton

16 Pond A6: Breached December m

17 Cumulative change in pin height (mm) Pond A6 Sediment Accretion Time post-breach (months)

18 Cumulative change in pin height (mm) Ponds A6 & A21 Sediment Accretion Pond A21: Southern stations Pond A Time post-breach (months)

19 Muzzi Marsh Crissy Field Island Ponds / A21 Pond A6

20 Muzzi Marsh: Restored m

21 SETs & Markers Sedimentation Erosion Table (SET) marsh surface feldspar marker horizon

22 Cumulative Sediment Accretion (mm) Muzzi Marsh Sediment Accretion Low Marsh Mid Marsh High Marsh Cumulative change in pin height (mm)

23 Crissy Field Marsh Restoration Project (from Robert Campbell Photography)

24 Crissy Field Marsh: Restored m Transect #3 Transect #2 Transect #1

25 Crissy Field Marsh Sediment Accretion HIGH STATIONS Cumulative change in elevation (mm) MID STATIONS Transect 1 Transect 2 Transect 3 LOW STATIONS

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27 (from Kristen Ward, NPS)

28 Petaluma River Marsh Coon Island Rush Ranch China Camp Muzzi Marsh Browns Island Crissy Field Whale s Tail Marsh Island Ponds Greco Island Pond A6

29 137 Cs Activity (dpm/g) Pb Activity (dpm/g) Depth (cm)

30 Low station 100 m Mid station High station

31 Accretion Rate (cm/yr) Browns Island Rush Ranch Coon Island Petaluma River Marsh China Camp Whales Tail Low Mid High 137 Cs 210 Pb Natural Wetland Accretion Rates 37 dated cores using both 137 Cs and 210 Pb (out of 48 cores collected)! Very consistent rates of accretion in mid and high marsh: ~0.3 cm/yr Low marsh: four sites ~0.6 cm/yr using 137 Cs Elevation (Callaway et al., in press)

32 Mean Suspended Sediment Concentration (mg/l) Marsh Suspended Sediment Concentrations (J. Gagnon, USF)

33 Summary of Accretion Rates across Sites Sites Pond A6 Island Ponds Muzzi Marsh Crissy Field Low marsh (natural) Mid and high marsh (natural) Range of accretion rates > 200 mm/yr 10 to 100 mm/yr 3 to 10 mm/yr -5 to 4 mm/yr Up to 6 mm/yr 3 mm/yr

34 Accretion Rate Theoretical Tidal Wetland Development MLLW MTL MHHW Elevation

35 Accretion Rate Theoretical Tidal Wetland Development A6 200 mm/yr Island Ponds 100 mm/yr Lower Muzzi Marsh 10 mm/yr Natural low marsh 6 mm/yr Natural mid & high marsh 3 mm/yr Elevation

36 Conclusions Rapid sediment accumulation at low elevations in most restored marshes Results closely match expectations of marsh development over time Natural wetlands are keeping pace with current rates of SLR High suspended sediment concentrations within SF Bay marshes

37 Acknowledgments Gordon and Betty Moore Foundation South Bay Salt Pond Project & the Resources Legacy Fund San Francisco Bay Conservation and Development Commission & US EPA Coastal Conservancy Association USF Faculty Development Fund Many USF and SFSU students