Will Restored Tidal Marshes Be Sustainable?

Orr, Michelle; Crooks, Stephen; Williams, Philip B.

doi:10.15447/sfews.2003v1iss1art5

Cited by 37 publications

(35 citation statements)

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“…Now that most of the hydraulic mining debris has likely been flushed from the system, local catchments draining directly to SF Bay may currently deliver more sediment to the SF Bay than the entire Sacramento-San Joaquin system [51]. If we consider the accelerated rates of SLR expected for the next centuries, the survivability of marshes could be in jeopardy [54,95], as their ability to keep pace with SLR through accretion is largely dependent on the suspended sediment load [96,97].…”

Section: The San Francisco Baymentioning

confidence: 99%

“…With water quality becoming less of a problem, the medium-to long-term strategies of dam removal, or at least the integration into existing dams of functional fish passages [71] and other measures, may in time allow the return or stabilization of anadromous fish stocks, and allow for a more sustainable sediment management [112,113]. This later aspect would likely be of crucial importance in enhancing wetland resilience in face of the increased rates of SLR, expected towards the end of the century, as the sustainability of wetlands appears to be strongly connected with the maintenance of a good sediment supply [54,58,90,91,[95][96][97].…”

Section: Environmental Protection Standards and The Concept Of "High mentioning

confidence: 99%

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Evolution of Two Urbanized Estuaries: Environmental Change, Legal Framework, and Implications for Sea-Level Rise Vulnerability

Pinto

Kondolf

2016

Water

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Abstract:The San Francisco Bay (CA, USA) and the Tagus Estuary (Lisbon, Portugal) share striking similarities in terms of morphology and urban development. A finer analysis of development patterns reveals crucial differences in the extent of shoreline alteration and types of land use that now encroach upon natural estuarine habitat. Through historical map analysis and prior stratigraphic and historical research, we reconstruct in GIS environment the evolution of both estuaries over the last millennia and the relative distribution of different classes of land cover. We also discuss the legal frameworks that accompanied this evolution, and how they have influenced the process of wetland reclamation and landfilling. We compared the legal history and synchronous patterns of development by compiling historical mapping information and resorting to GIS analysis to explore spatial patterns over time. This method was useful in isolating events and decisions that were unique to each of the case studies. The Tagus Estuary has experienced disruption of natural environments for over two millennia. Yet, the State has been able to keep estuarine lowlands under public control, even if vast areas have been transformed into farmland. Public control could allow wetland migration with rising seas and restoration efforts. The San Francisco Bay was affected by several decades of elevated sediment loads in the 19th century, which induced rapid wetland expansion, but virtual cutoff of sediment supply by dams in the 20th century now impairs their ability to accrete. Meanwhile, tidal wetlands were subject to extremely fast and poorly regulated development. Artificially filled and/or drained wetlands were transferred to local governments and private landowners, in violation of the Public Trust Doctrine. The transformation of wetlands into salt ponds, industrial zones and even residential neighborhoods created extensive developed areas at or below sea level, which are vulnerable to even modest rises in sea level. Remaining wetlands are now heavily encroached on their landward side by urban development, which prevents their landward migration. Different legal interpretations of comparable definitions of public trusts and jurisdictions over shorelines may have significant implications for the ability to adapt to sea-level rise.

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Section: The San Francisco Baymentioning

confidence: 99%

Section: Environmental Protection Standards and The Concept Of "High mentioning

confidence: 99%

Evolution of Two Urbanized Estuaries: Environmental Change, Legal Framework, and Implications for Sea-Level Rise Vulnerability

Pinto

Kondolf

2016

Water

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“…In San Francisco Bay, marsh stability has been reported to depend more on available suspended sediment for accretion processes (Stralberg et al 2011). It has been assumed that SPBNWR has the needed local suspended sediment supply from San Pablo Bay for vertical marsh accretion processes and has been projected to be sustainable under moderate SLR (Orr et al 2003;Stralberg et al 2011). However, our results indicated that there was widespread subsidence and low rates of accretion in the interior of the marsh indicating variability in biogeomorphic processes that may undermine its long-term sustainability.…”

Section: Elevation Changementioning

confidence: 99%

Importance of Biogeomorphic and Spatial Properties in Assessing a Tidal Salt Marsh Vulnerability to Sea-level Rise

Thorne

Elliott‐Fisk

Wylie

et al. 2013

Estuaries and Coasts

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We evaluated the biogeomorphic processes of a large (309 ha) tidal salt marsh and examined factors that influence its ability to keep pace with relative sea-level rise (SLR). Detailed elevation data from 1995 and 2008 were compared with digital elevation models (DEMs) to assess marsh surface elevation change during this time. Overall, 37 % (113 ha) of the marsh increased in elevation at a rate that exceeded SLR, whereas 63 % (196 ha) of the area did not keep pace with SLR. Of the total area, 55 % (169 ha) subsided during the study period, but subsidence varied spatially across the marsh surface. To determine which biogeomorphic and spatial factors contributed to measured elevation change, we collected soil cores and determined percent and origin of organic matter (OM), particle size, bulk density (BD), and distance to nearest bay edge, levee, and channel. We then used Akaike Information Criterion (AICc) model selection to assess those variables most important to determine measured elevation change. Soil stable isotope compositions were evaluated to assess the source of the OM. The samples had limited percent OM by weight (<5.5 %), with mean bulk densities of 0.58 g cm -3 , indicating that the soils had high mineral content with a relatively low proportion of pore space. The most parsimonious model with the highest AICc weight (0.53) included distance from bay's edge (i.e., lower intertidal) and distance from levee (i.e., upper intertidal). Close proximity to sediment source was the greatest factor in determining whether an area increased in elevation, whereas areas near landward levees experienced subsidence. Our study indicated that the ability of a marsh to keep pace with SLR varied across the surface, and assessing changes in elevation over time provides an alternative method to long-term accretion monitoring. SLR models that do not consider spatial variability of biogeomorphic and accretion processes may not correctly forecast marsh drowning rates, which may be especially true in modified and urbanized estuaries. In light of SLR, improving our understanding of elevation change in these dynamic marsh systems will play a crucial role in forecasting potential impacts to their sustainability and the survival of these ecosystems.

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“…Much of the previous modeling of marsh accretion processes in wetlands in the San Francisco Estuary focused primarily on inorganic processes (Krone 1985) and used a constant rate of organic accretion (Orr et al 2003;French 1993). In contrast, Callaway et al (1996) used a cohort accounting approach to more explicitly account for organic accretion processes and successfully simulate approximately 300 years of tidal-marsh accretion in the southeastern United States and England.…”

Section: Introductionmentioning

confidence: 99%

“…We used data described in Drexler et al (2009aDrexler et al ( , 2009b to simulate accretion on Franks Wetland during the last 4,700 years. We also analyzed data collected during the first 12 years in the Twitchell Island demonstration project and simulated vertical accretion and carbon accumulation rates.Much of the previous modeling of marsh accretion processes in wetlands in the San Francisco Estuary focused primarily on inorganic processes (Krone 1985) and used a constant rate of organic accretion (Orr et al 2003;French 1993). In contrast, Callaway et al (1996) used a cohort accounting approach to more explicitly account for organic accretion processes and successfully simulate approximately 300 years of tidal-marsh accretion in the southeastern United States and England.…”

mentioning

confidence: 99%

Impounded Marshes on Subsided Islands: Simulated Vertical Accretion, Processes, and Effects, Sacramento-San Joaquin Delta, CA USA

Deverel¹,

Ingrum²,

Lucero³

et al. 2014

SFEWS

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There is substantial interest in stopping and reversing the effects of subsidence in the Sacramento-San Joaquin Delta (Delta) where organic soils predominate. Also, the passage of California Assembly Bill 32 in 2006 created the potential to trade credits for carbon sequestered in wetlands on subsided Delta islands. The primary purpose of the work described here was to estimate future vertical accretion and understand processes that affect vertical accretion and carbon sequestration in impounded marshes on subsided Delta islands. Using a cohort-accounting model, we simulated vertical accretion from 4,700 calibrated years before present (BP) at a wetland area located within Franks Tract State Recreation Area (lat 38.059, long −121.611, hereafter, "Franks Wetland")-a small, relatively undisturbed marsh island-and at the Twitchell Island subsidencereversal demonstration project since 1997. We used physical and chemical data collected during the study as well as literature values for model inputs. Model results compared favorably with measured rates of vertical accretion, mass of carbon sequestered, bulk density and organic matter content.From 4,700 to model-estimated 350 years BP, the simulated rate of vertical accretion at Franks Wetland averaged about 0.12 cm yr -1 , which is within the range of rates in tidal wetlands worldwide. Our model results indicate that large sediment inputs during the last 150 to 200 years resulted in a higher accretion rate of 0.3 cm yr -1 . On Twitchell Island, greater organic inputs resulted in average vertical accretion rates as high as 9.2 cm yr -1 . Future simulations indicate that the managed impounded marsh will accrete highly organic material at rates of about 3 cm yr -1 . Model results coupled with GIS analysis indicate that large areas of the periphery of the Delta, if impounded and converted to freshwater marsh, could be restored to tidal elevations within 50 to 100 years. Most of the central Delta would require 50 to 250 years to be restored to projected mean sea level. A large portion of the western Delta could be restored to mean sea level within 50 to 150 years (large areas on Sherman, Jersey, and Bethel islands, and small areas on Bradford, Twitchell, and Brannan islands, and Webb Tract). We estimated that long-term carbon sequestration rates for impounded marshes such as the Twitchell Island demonstration ponds will range from 12 to 15 metric tons carbon ha -1 yr -1 . Creation of impounded marshes on Delta islands can substantially benefit levee stability as demonstrated by cumulative force and hydraulic gradient calculations.1 HydroFocus, Inc., Davis, CA USA 2 U.S. Geological Survey, California Water Science Center Sacramento, CA USA * Corresponding author: sdeverel@hydrofocus.com SAN FRANCISCO ESTUARY & WATERSHED SCIENCE 2 INTRODUCTIONThe 300,000-ha Sacramento-San Joaquin Delta is a critical natural resource, important agricultural region and the hub for California's water supply. Within an area of about 81,000 ha in the central Delta, an estimated 4.5 billion ...

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Will Restored Tidal Marshes Be Sustainable?

Cited by 37 publications

References 45 publications

Evolution of Two Urbanized Estuaries: Environmental Change, Legal Framework, and Implications for Sea-Level Rise Vulnerability

Evolution of Two Urbanized Estuaries: Environmental Change, Legal Framework, and Implications for Sea-Level Rise Vulnerability

Importance of Biogeomorphic and Spatial Properties in Assessing a Tidal Salt Marsh Vulnerability to Sea-level Rise

Impounded Marshes on Subsided Islands: Simulated Vertical Accretion, Processes, and Effects, Sacramento-San Joaquin Delta, CA USA

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