Editor’s pickHas heavy rainfall become the new norm?

11-09-2017

Floodwaters from Hurricane Harvey inundating residences in Houston, Texas, U.S. Image credit: Marcus Yam/Los Angeles Times

Looking back, Hurricane Harvey, the incredibly destructive storm that just swept through Houston, Texas, United States (U.S.), is certainly not the first of its kind. In fact, it is Houston’s third “500-year” flood in three years. It should not even have been a surprise – after all, climate scientists have cautioned again and again over a number of years that intense rainfall from the warming earth should be expected. But that begs another question: How can cities all over the world prepare themselves for such extremes weather occurrences that can no longer be considered rare?

The evidence is not exactly hidden, either.

Damage done by the flash floods near Boulder, in Colorado, U.S. Image credit: Tim Rasmussen/The Denver Post

 

Villagers displaced by the floods in Gauhati, Assam, India. Image credit: Anupam Nath/Associated Press

Floods in Bangladesh, India, and Nepal, triggered by severe monsoon rains, have left more than 1,200 dead, with a building in Mumbai crumbling under the strain of the floodwaters. In 2016, a “thousand year” storm flooded Baton Rouge, Louisiana, U.S., along with several other parishes, killing 13 and wrecking damage on 92,000 homes. In 2013, an entire year’s worth of rain was dumped on Colorado’s Front Range mountains in five days, sparking flash floods that took the lives of ten people.

While it is true that Houston is situated right at the Gulf of Mexico and vulnerable to hurricanes, it does not take away from the fact that intense rains can wreck colossal damage anywhere and everywhere, no matter if the climate in the location is wet or dry. And to top it off, few communities are prepared for the destruction.

“Every location on the planet is at risk in this regard,” Michael Wehner, a senior staff scientist at the Department of Energy’s Lawrence Berkeley National Laboratory in California, U.S., said to National Geographic. “The important thing in my mind is to raise awareness that everybody should expect more extreme storms no matter where they live. A key question for Houston’s urban planner is ‘Just how rare an event do you design for?’”

Houston’s answer may be hard to come by as costs continue to rise and political debates move over to the fact that cities do not absorb more than 1.2 metres of rain over a period of several days before flooding. But New Orleans recovered after Hurricane Katrina hit them in 2005, as did New York in Hurricane Sandy’s aftermath in 2012.

But that does not answer the main question – what can, and what should, cities do as severe rainfall becomes more normal and less rare?

The flooding following Hurricane Harvey’s wake did set records for rainfall, but it is still the third “500-year” flood Houston has been subjected to in three years. And “500-year” floods are floods with a one in 500 chance of happening any given year – unless, of course, global warming is added to the equation.

There is, after all, little doubt left that climate change is affecting the Earth.

 

Source: National Geographic