Perched atop a tree, Nur Islam watched the waters rise, breach the mud embankments and smash down the wall of his home in the Sundarbans when Cyclone Yaas hit India's east coast last month.

A month later, Islam still has not repaired the wall because of a high tidal-wave alert issued for later this week.

"How many times can I fix a broken house?" he asked over the phone from his village in the heart of the low-lying Sundarbans delta in South 24 Parganas district of West Bengal state.