Processes of formation and degradation of marshes along the Louisiana Gulf Coast

R.D. DeLaune

    Research output: Thesisexternal PhD, WU

    Abstract

    <p>Processes governing the stability of Louisiana's rapidly deteriorating Gulf coast marsh were investigated. Vertical marsh accretion determined from 137 <sub>Cs</sub> dating were compared to water level increase obtained from tide gauge data. In subsiding coastal environments the continued existence of marsh habitat is dependent on the ability of marsh to maintain elevation through vertical marsh accretion (mineral sediment and organic matter accumulation). Coast-wide average vertical accretion was 0.60 to 0.80 as compared to water level increase of over 1 cm year. Rapid water level increase, attributed primarily to subsidence, was 3 to 5 times greater than eustatic sea level changes reported to be 0.23 cm yr<SUp>-1</SUp></p><p>The measured accretionary deficits (difference between water level increase and vertical marsh accretion) parallels reported marsh disappearance of over 100 km2 yr <sup>-1</SUP>Organic matter accumulation was identified as an important component of marsh aggradation in response to changes in water level. A appreciable amount of organic production of marsh macrophytes remains on the marsh as peat or is decomposed to carbon dioxide or methane. Organic matter on a dry weight basis constituted an increasing fraction of soil solids as its marine influence diminishes inland from the coast. Organic matter is of greatest structural significance in low density, fresh, and brackish marsh environments. However, on a unit volume basis, the organic matter occupies the same volumes in fresh, brackish, and salt marshes.</p><p>Louisiana Gulf coast marsh will likely continue disappearing at a rapid rate unless means are implemented for distributing Mississippi River sediment to the marshes. The combined effect of rapid subsidence, eustatic sea level rise and accompanying salt water intrusion will likely destroy much of these marshes. Results presented may represent future conditions for many coastal regions of the world, which may experience a rapid rise in water level as a result of the predicted "greenhouse" warming and resultant accelerated worldwide sea level rise.</p>
    Original languageEnglish
    QualificationDoctor of Philosophy
    Awarding Institution
    Supervisors/Advisors
    • van Breemen, N., Promotor
    Award date3 Jun 1988
    Place of PublicationS.l.
    Publisher
    Publication statusPublished - 1988

    Keywords

    • beaches
    • climate
    • floods
    • landscape
    • louisiana
    • marine sediments
    • morphology
    • salt marshes
    • soil formation
    • weathering

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