Delta T

I thought I should see if I could justify my Panglossian comment on Klaus Rohde’s blog that the Ganges Delta should be able to keep pace with sea level rise.

The historical vertical deposition rates quoted in this interesting paper of 5-8 mm/year seem adequate to keep pace to all but the most extreme rates of global warming-related sea level rise. This deposition rate should also increase with any increasing incursion of saline waters into the delta, since the stability of colloidal clay particles to aggregation is reduced markedly with increasing ionic strength of the solution.

However, I had not realised that the amount of sediment reaching the Ganges Delta has already been severely reduced by the construction of dams in India, and the effects of this on the western Ganges delta were already obvious by the time the paper was written at the end of the 1980s. Hopefully India will be moved to correct this problem out of self interest, as it puts many millions of its own citizens at risk.

It also appears that intensive human use of the most marginal coastal lands- where more than a million people died the day I was born, and where nobody ought to be living- contributes significant horizontal erosion, even if overall vertical deposition rates can keep up the level of the delta.