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
      StatePublished - Dec 2013

        Research areas

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

      ID: 5487571