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) Past and Present Distribution of SF Bay Wetlands
(from San Francisco Estuary Institute) 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 Theoretical Tidal Wetland Development
(from Williams and Orr 2002)
Theoretical Tidal Wetland Development
Accretion Rate Accretion
MLLW MTL MHHW Elevation Muzzi Marsh
Crissy Field
Island Ponds / A21
Pond A6 South Bay Salt Pond Restoration Project
Island Ponds / A21 Breached in March 2006
Pond A6 Breached in December 2010 100 m
Island Pond Sediment Accretion 250 Southern stations 200
150
100
50
0
Cumulative change in pin height (mm) height pin in change Cumulative 0 10 20 30 40 Time post-breach (months) Island Pond Sediment Accretion 250 Northern stations 200 Southern stations
150
100
50
0
Cumulative change in pin height (mm) height pin in change Cumulative 0 10 20 30 40 Time post-breach (months) Island Pond Sediment Accretion 250 Northern stations 200 Southern stations
150
100
50
0
Cumulative change in pin height (mm) height pin in change Cumulative 0 10 20 30 40 Time post-breach (months) 6 months
pre-restoration
36 months
24 months Photos © Cris Benton
http://steel.ced.berkeley.edu/research/hidden_ecologies/ Pond A6: Breached December 2010
200 m Pond A6 Sediment Accretion 300
250
200
150
100
50
0
Cumulative change in pin height (mm) height in pin change Cumulative 0 2 4 6 8 10 12 14 Time post-breach (months) Ponds A6 & A21 Sediment Accretion 300
250
200
150
100
50 Pond A21: Southern stations Pond A6 0
Cumulative change in pin height (mm) height pin in change Cumulative 0 10 20 30 40 Time post-breach (months) Muzzi Marsh
Crissy Field
Island Ponds / A21
Pond A6 Muzzi Marsh: Restored 1976
100 m SETs & Markers
Sedimentation Erosion Table (SET)
marsh surface
feldspar marker horizon Muzzi Marsh Sediment Accretion 12 Low Marsh 10 Mid Marsh High Marsh 8
6
4
2
0
Cumulative Sediment Accretion (mm) Accretion Sediment Cumulative 0 2 4 6 8 10 12 14 Cumulative change in pin height (mm) Crissy Field Marsh Restoration Project
(from Robert Campbell Photography) Crissy Field Marsh: Restored 1999
100 m
Transect #3
Transect #1
Transect #2 Crissy Field Marsh Sediment Accretion
80 HIGH STATIONS 40
0
-40
-80 80 MID STATIONS 40
0 Transect 1 Transect 2 -40 Transect 3 80 -80 LOW STATIONS 40
Cumulative change in elevation (mm)Cumulativein elevation change 0
-40
-80
2000 2001 2002 2003 2004 2005 2006 2007 2008
(from Kristen Ward, NPS) Petaluma River Marsh Coon Island Rush Ranch
China Camp
Browns Island Muzzi Marsh
Crissy Field
Whale’s Tail Marsh
Island Ponds
Greco Island Pond A6 210 137Cs Activity (dpm/g) Pb Activity (dpm/g)
0.0 0.2 0.4 0.6 0.8 1.0 1.2 0.0 0.5 1.0 1.5 2.0 2.5 3.0 0 0
-10 -10
-20 -20
-30 1963 -30
Depth (cm) Depth -40 -40
-50 -50 100 m Low station
Mid station
High station 1.0 137Cs 210 0.8 2 Browns Island Pb 0.6 2 2 Natural 0.4 2 2 1 0.2 1.0 0.0 0.8 Rush Ranch Wetland 0.6
0.4 2 2 2 2 2 2 0.2 Accretion Rates 0.0 1.0 3 Coon Island 0.8 0.6 3 0.4 3 4 2 • 37 dated cores using 2 0.2 1.0 0.0 both 137Cs and 210Pb (out 0.8 Petaluma River Marsh 0.6 of 48 cores collected)! 0.4 1 1 2 2 2 0.2 2 0.0 1.0 Accretion Rate (cm/yr) Rate Accretion • Very consistent rates of 0.8 2 China Camp 0.6 2 accretion in mid and 2 2 0.4 2 2 0.2 high marsh: ~0.3 cm/yr 1.0 0.0 0.8 2 Whales Tail 0.6 1 1 • Low marsh: four sites 0.4 1 1 0.2 ~0.6 cm/yr using 137Cs 0.0 Low Mid High Elevation (Callaway et al., in press) Marsh Marsh Suspended Sediment
Mean Suspended Sediment Concentration (mg/L) Concentrations
(J.Gagnon,USF)
Summary of Accretion Rates across Sites
Sites Range of accretion rates Pond A6 > 200 mm/yr
Island Ponds 10 to 100 mm/yr
Muzzi Marsh 3 to 10 mm/yr
Crissy Field -5 to 4 mm/yr
Low marsh (natural) Up to 6 mm/yr
Mid and high marsh (natural) 3 mm/yr
Theoretical Tidal Wetland Development
Accretion Rate Accretion
MLLW MTL MHHW Elevation Theoretical Tidal Wetland Development
A6 200 mm/yr
Island Ponds 100 mm/yr Natural Natural mid & low marsh high marsh Accretion Rate Accretion Lower 6 mm/yr 3 mm/yr Muzzi Marsh 10 mm/yr Elevation 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 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