Historic Sediment Accretion Rates in a Louisiana Coastal Marsh and Implications for Sustainability PDF Download
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Author: Rebekah Perkins Smith
Publisher:
ISBN:
Category : Marshes
Languages : en
Pages : 69
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Book Description
Deltaic marshes of the Mississippi River in Louisiana disappeared at a rate of 88 km2 annually from 1956 to 2000 (Barras et al. 2003) as marshes become inundated by sea water. Marsh surface elevation varies spatially and temporally due to fluvial sediment deposition, resuspension, erosion, compaction, sea level rise, and organic matter accumulation and decomposition. If net accretion from sediment deposition and/or peat production is insufficient, marshes respond to sea level rise by migrating landward. Since human development prevents landward migration of marsh in Breton Sound Basin, Louisiana, marsh sustainability can only be achieved if vertical accretion keeps pace with a relative sea level rise of 10 mm/yr so that marsh surface elevation is maintained within the tidal range. Measurement time scale and changing influences on marsh sediment were considered in an assessment of the long-term sustainability of Breton Sound marsh based on comparison of the rate of relative sea level rise to measured accretion rates. Six cores (~4 m long each) were collected in Breton Sound and a combination of three radioisotopes, as well as stratigraphic analysis were used to measure accretion rates and identify evidence of historical river effects and storms. Net accretion rates over recent short-term (decadal) and long-term (centennial/millennial) time scales were measured using 210Pb, 137Cs, and 14C dating. Long-term mean accretion based on 14C dating was highly variable (3.5 mm/yr, [sigma]=4.5). Three 210Pb rates were recovered, averaging 4.3 mm/yr ([sigma]=1.9). Accretion rates measured using 137Cs averaged 7.7 mm/yr ([sigma]=2.3). Rates of sediment accretion are ultimately insufficient to offset relative sea level rise, especially after allowing for sediment volume reduction encountered over the long term. The combined effects of reduced fluvial input, rising sea level, and prevention of landward marsh migration create an environment that is inherently unstable.
Author: Rebekah Perkins Smith
Publisher:
ISBN:
Category : Marshes
Languages : en
Pages : 69
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Book Description
Deltaic marshes of the Mississippi River in Louisiana disappeared at a rate of 88 km2 annually from 1956 to 2000 (Barras et al. 2003) as marshes become inundated by sea water. Marsh surface elevation varies spatially and temporally due to fluvial sediment deposition, resuspension, erosion, compaction, sea level rise, and organic matter accumulation and decomposition. If net accretion from sediment deposition and/or peat production is insufficient, marshes respond to sea level rise by migrating landward. Since human development prevents landward migration of marsh in Breton Sound Basin, Louisiana, marsh sustainability can only be achieved if vertical accretion keeps pace with a relative sea level rise of 10 mm/yr so that marsh surface elevation is maintained within the tidal range. Measurement time scale and changing influences on marsh sediment were considered in an assessment of the long-term sustainability of Breton Sound marsh based on comparison of the rate of relative sea level rise to measured accretion rates. Six cores (~4 m long each) were collected in Breton Sound and a combination of three radioisotopes, as well as stratigraphic analysis were used to measure accretion rates and identify evidence of historical river effects and storms. Net accretion rates over recent short-term (decadal) and long-term (centennial/millennial) time scales were measured using 210Pb, 137Cs, and 14C dating. Long-term mean accretion based on 14C dating was highly variable (3.5 mm/yr, [sigma]=4.5). Three 210Pb rates were recovered, averaging 4.3 mm/yr ([sigma]=1.9). Accretion rates measured using 137Cs averaged 7.7 mm/yr ([sigma]=2.3). Rates of sediment accretion are ultimately insufficient to offset relative sea level rise, especially after allowing for sediment volume reduction encountered over the long term. The combined effects of reduced fluvial input, rising sea level, and prevention of landward marsh migration create an environment that is inherently unstable.
Author: Jos T.A. Verhoeven
Publisher: Springer Science & Business Media
ISBN: 3540331875
Category : Science
Languages : en
Pages : 365
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Book Description
This book provides a broad and well-integrated overview of recent major scientific results in wetland science and their applications in natural resource management issues. The contributors, internationally known experts, summarize the state of the art on an array of topics, divided into four broad areas: The Role of Wetlands for Integrated Water Resources Management: Putting Theory into Practice; Wetland Science for Environmental Management; Wetland Biogeochemistry; Wetlands and Climate Change Worldwide.
Author: National Research Council
Publisher: National Academies Press
ISBN: 0309164907
Category : Science
Languages : en
Pages : 204
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Book Description
During the past 50 years, coastal Louisiana has suffered catastrophic land loss due to both natural and human causes. This loss has increased storm vulnerability and amplified risks to lives, property, and economies-a fact underscored by Hurricanes Katrina and Rita. Drawing Louisiana's New Map reviews a restoration plan proposed by the U.S. Army Corps of Engineers and the State of Louisiana, finding that, although the individual projects in the study are scientifically sound, there should be more and larger scale projects that provide a comprehensive approach to addressing land loss over such a large area. More importantly, the study should be guided by a detailed map of the expected future landscape of coastal Louisiana that is developed from agreed upon goals for the region and the nation.
Author: Lauren Nicole Brown
Publisher:
ISBN:
Category :
Languages : en
Pages : 38
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Book Description
Coastal marshes are complex ecogeomorphic feedback systems that require further investigation on the Southern California coast to understand potential responses to sea level rise (SLR). Long-term accretion rates - deposition and erosion of mineral and organic matter - form a basis of understanding processes in the marsh related to SLR responses. From sediment cores, I reconstruct the net accretion rates of three marshes using radiocarbon dating methods and analyze loss on ignition (LOI) data to understand the physical properties of the sedimentary record in the three marshes. Average net accretion rates for Tijuana Estuary are 1.0 ± 0.94 mm yr¬-1, for Upper Newport Bay are 1.0 ± 0.4 mm yr-1, and for Morro Bay are 8.0 ± 8.3 mm yr-1. Over the past 2000 cal YBP, all net accretion rates kept pace or exceed rates of SLR (when compared to historic SLR of 0.6 to 2 mm yr-1); however, only Morro Bay exhibits historic net accretion rates high enough to compare to possible rates of SLR associated with projected sea level gains of 0.3 to 1.6 m on the Pacific coast through 2100. Core stratigraphies indicate marsh conditions change frequently and the current Spartina spp. and Salicornia spp. marsh vegetation communities are geologically recent features in their present locations, existing from 700 to 1000 cal YBP. The future under continued human modification of coastal systems, climate change, and accelerated SLR merit continued research into the dynamics of coastal salt marsh systems on the California coast.
Author: Douglas Arthur Wolfe
Publisher:
ISBN:
Category : Science
Languages : en
Pages : 536
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Book Description
Author: Kathryn E. L. Smith
Publisher:
ISBN:
Category :
Languages : en
Pages : 203
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Book Description
Combined paleoecological and geochronological analyses can provide a critical tool for understanding coastal marsh development and ecological response to perturbations, such as sea-level rise and tropical storms, particularly in regions like coastal Louisiana, where high rates of wetland loss threaten an ecologically and economically important ecosystem. Analysis of sediment cores from Rockefeller Wildlife Refuge identify sediment deposition from storm surge and show that diatom assemblage of hurricane sediments are dissimilar from non-storm sediments and have the potential for examining historical frequency of storms. Chronology and vertical accretion rates calculated from 210Pb radioisotope using the constant flux : constant sedimentation method provided the best match to an independent tracer (137Cs), and indicate that marsh rates of vertical accretion are generally lower than regional estimates of mean sea-level rise, despite recent hurricane deposition. Contemporary diatom samples from 46 sites located throughout the Chenier plain were examined to test the relationship between diatom assemblage and environmental parameters.
Author: Glenn A. Richard
Publisher:
ISBN:
Category : Salt marshes
Languages : en
Pages : 176
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Book Description
Author: Duncan M. FitzGerald
Publisher: Cambridge University Press
ISBN: 1107186285
Category : Nature
Languages : en
Pages : 499
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Book Description
A multidisciplinary review of salt marshes, describing how they function and respond to external pressures such as sea-level rise.
Author: John W. Day
Publisher: Springer
ISBN: 9401787336
Category : Technology & Engineering
Languages : en
Pages : 203
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Book Description
Human impacts and emerging mega-trends such as climate change and energy scarcity will impact natural resource management in this century. This is especially true for deltas because of their ecological and economic importance and their sensitivity to climate change. The Mississippi delta is one of the largest in the world and has been strongly impacted by human activities. Currently there is an ambitious plan for restoration of the delta. This book, by a renown group of delta experts, provides an overview of the challenges facing the delta and charts - a way forward to sustainable management.
Author: James G. Gosselink
Publisher:
ISBN:
Category : Coastal ecology
Languages : en
Pages : 156
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Book Description
Tracings: 99.29.
