Marsh Accretion with Sea Level Rise

Steve Crooks, Matt Brennan,Justin Vandever, Jeremy Lowe, PWA

John Callaway, USF

Diane Stralberg, PRBO

RSM Science WorkshopApril 14, 2010

Sensitivity of bird habitat to sea level rise

Long term habitat evolution and sustainability of restored habitats

Quantification of carbon sequestration with sea level rise

Marsh Elevation

Marsh elevation response to: initial bed elevation, suspended sediment concentration, organic material accumulation, rate of sea level rise, and subsidence and compaction

Marsh98

Based on mass balance calculations described by Krone (1987)

Accretion rate depends on: availability of suspended sediment depth and period of inundation

As marsh aggrades, frequency and duration of flooding decreases and accretion rate decreases.

Sedimentation in tidal wetlands

Mineral sedimentation model

Vegetation colonization elevation

Natural Marshplain Elevation in 2100(relative to rising tidal waters)

Dry density of carbon: 500 kg m3Initial marsh elevation: MHHW

Orr, Crooks and Williams 2003 Will Restored Tidal Marshes Be Sustainable?San Francisco Estuary and Watershed Science. Vol. 1, Issue 1 (2003), Article 5.

Vegetation die-back

Restored Marshplain Elevation in 2100(relative to rising tidal waters)

Dry density of carbon: 500 kg m3Initial marsh elevation: -0.5m MHHW

Orr, Crooks and Williams 2003 Will Restored Tidal Marshes Be Sustainable?San Francisco Estuary and Watershed Science. Vol. 1, Issue 1 (2003), Article 5.

Vegetation die-back

Model Revisions

Allows acceleration of rate of sea level rise NRC-I (0.5m rise) NRC-III (1.5m rise)

Organic matter added directly to bed elevation

ASA/GSFC/METI/ERSDAC/JAROS,

and U.S./Japan ASTER Science Team

March 3, 2000

Richardson Bay

Petaluma Estuary

San Pablo Bay

Approach

Bio-geomorphic units

Sediment supply Organic

accumulation Sea level rise 100 year time

frame

Model Runs

Initial Bed Elevation Colonization elevation (+1.3m MLLW) MHHW (+1.8m MLLW) Subtidal, minimal waves (-0.6m MLLW)

SSC 25, 50, 100, 150, 300 mg/l

Organic Matter 0, 1, 2, 3 mm/yr

Rate of Sea Level Rise NRC-I, NRC-III

Low sediment availabilityConverts to mudflat

SLR Scenario: NRC-IIISuspended Sediment Conc: 25 mg/LOrganic sedimentation rate: 1.0 mm/yr

Medium sediment availabilityTracks colonization elevation

SLR Scenario: NRC-IIISuspended Sediment Conc: 150 mg/LOrganic sedimentation rate: 1.0 mm/yr

High sediment availabilityKeeps pace with SLR

SLR Scenario: NRC-IIISuspended Sediment Conc: 300 mg/LOrganic sedimentation rate: 1.0 mm/yr

High initial elevation has larger net change in elevation as less frequently inundated and receives less sediment.

Higher organic accretion raises bed elevations and reduces inundation period and inorganic accretion rate.

25mg/l – unlikely to sustain marshes

50mg/l – sustain marshes only under most favorable conditions (high initial elevation and organic accumulation)

100-150mg/l – sustain marshes for particular combinations

Next Steps

Influence of waves

Compaction and subsidence

Integration in SLAMM-type model