Far be it from me to be critical, but if Bangledesh is really drowning, why don't they use all this sand to build up their own country?

Bangladeshi sand to save Maldives | Asian Tribune

With huge amount of naturally flown sand from the Himalayas being deposited in Bangladeshi rivers, the flood-prone country sees sand as a new potential for export –-and the Maldives in dire need of defences against rising sea levels, appears a ready buyer.
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“A huge amount of sediment is naturally deposited in Bangladesh from the Himalayas by the river network spread over the country.

The quantity of sediment is around one billion cubic metres, which is one of the main reasons the country’s rivers are losing their navigability,” it reported.