Horribly familiar scenes of flooding are playing tonight on the news: houses with water up to the eaves, submerged cars, people rescued by boat from their rooftops.  Soon will follow images of the cleanup, with piles of damaged possessions, appliances, and soaked construction materials at the curb, the losses mounting.  People will repeat a single phrase: it isn’t supposed to happen here.

These are words I myself have spoken.  It never flooded here before.  This site didn’t flood during the last 300 years of human settlement.

What changed?

Certainly, the warming climate is directly responsible for higher rainfall.  Warm air holds more moisture, so increasing temperatures create more intense rainfall and longer duration events.  Mitigating climate change, by tamping down carbon emissions, will reduce the accelerating effects of the climate.

Human modifications to the hydrological system are responsible, too.  We build in former wetlands and floodplains.  Impervious surfaces – concrete, asphalt, and roofs – cover 34% of the U.S.  These impermeable ground covers accelerate the flow of stormwater, preventing it from infiltrating and reducing transpiration through plant materials (incidentally starving aquifers of new supplies of water).  Every community upstream has a domino effect on those downriver, which is why places like Baton Rouge and Bridgeport, on the banks of river systems near the continental edge, are fraying along their waterfront edges.

There is another human pattern that affects the extent of flood damage, and that is hubris.  If we immediately build back “the way things were,” we shouldn’t expect different results.  If we turn to mechanical or structural solutions to flooding as evidence of human dominion over nature, we will continue to lose flood skirmishes… and the war.  We have made tremendous progress since Hurricanes Katrina and Sandy toward solutions that accommodate water in vulnerable cities, rather than attempting to build walls, or pump it out.  As long as we believe that we can “tame” the river or subdue the weather, we can continue to build where we like; but when these fantasies are exposed, we must find safe places for settlements.

The number of cities joining the list of vulnerable places is growing every day; cities that once had the capacity to handle unpredictable weather are now failing, and experiencing diminishing periods between catastrophic storms.  The best ways to reduce future flood losses are to mitigate the causes of climate change, restore permeability, and realign where we build to respect the genuine power of nature.  In the meantime, the scenes of damage and disbelief will continue to affect families, communities, and economies.