Recent St Louis flooding made worse by human changes to landscape

Humans put considerable effort into controlling river flood water. We build dams to hold the water back, levees to keep it in the river channel, and floodways to divert it from protected areas if the first two reach their limit. The great irony of levees, though, is that the more of them you build, the more dangerous the river becomes. Whatever volume of water comes down the river has to go somewhere. Wall off part of the river’s natural floodplain, and it will have to take up extra space somewhere else.

Climate change looks to be responsible for greater flooding risk in some places, as extreme rainfall becomes more common or weather patterns shift. But greenhouse gas emissions are not the only way we bring more flood damage on ourselves. We also manipulate river systems and construct new developments in risky places.