Rapid rise in Effective Sea-Level in southwest Bangladesh: Its causes and contemporary rates

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    Evidence is presented from three estuarine tide gauges located in the
    Sundarban area of southwest Bangladesh of relative sea level rise
    substantially in excess of the generally accepted rates from altimetry, as
    well as previous tide-gauge analyses. It is proposed that the difference
    arises from the use of relative mean sea level (RMSL) to characterise the
    present and future coastal flood hazard, since RMSL can be misleading in
    estuaries in which tidal range is changing. Three tide gauges, one located in
    the uninhabited mangrove forested area (Sundarban) of southwest
    Bangladesh, the others in the densely populated polder zone north of the
    present Sundarban, show rates of increase in RMSL ranging from 2.8 mm
    a-1 to 8.8 mm a-1. However, these trends in RMSL disguise the fact that high
    water levels in the polder zone have been increasing at an average rate of
    15.9 mm a-1 and a maximum of 17.2 mm a-1. In an area experiencing tidal
    range amplification, RMSL will always underestimate the rise in high water
    levels; consequently, as an alternative to RMSL, the use of trends in high
    water maxima or ‘Effective Sea Level Rise’ (ESLR) is adopted as a more
    strategic parameter to characterise the flooding hazard potential. The rate
    of increase in ESLR is shown to be due to a combination of deltaic
    subsidence, including sediment compaction, and eustatic sea level rise, but
    principally as a result of increased tidal range in estuary channels recently
    constricted by embankments. These increases in ESLR have been partially
    offset by decreases in fresh water discharge in those estuaries connected
    to the Ganges. The recognition of increases of the effective sea level in the
    Bangladesh Sundarban, which are substantially greater than increases in
    mean sea level, is of the utmost importance to flood management in this
    low-lying and densely populated area.
    Original languageEnglish
    Number of pages9
    Pages (from-to)237–245
    JournalGlobal and Planetary Change
    Journal publication dateDec 2013
    Early online date07 Oct 2013
    Publication statusPublished - Dec 2013

      Research areas

    • Sundarbans, effective sea-level rise, tidal range amplification, embankments

    ID: 5487571