Silt from the centre of the US runs down the Mississippi river to the sea
Gerald Herbert/ AP / Alamy
The Mississippi river flows past New Orleans, Louisiana, at an average rate of about 150,000 cubic metres per second, carrying more than a hundred million tonnes of sediment from the middle of the US into the Gulf of Mexico each year. Standing along its shore on land made of such sediment, I watch the silt spin in brown eddies in the river. That mud might soon be put to use.
A construction team not far…