John Metcalfe was CityLab’s Bay Area bureau chief, covering climate change and the science of cities.
New research reveals the changing nature of storms.
The storms of today are not like those that wetted our ancestors. They’re throwing out quicker, more-sodden punches, with short periods of intense rainfall perfect for swamping urban areas.
So says a research team from the University of New South Wales that’s been examining three decades of rainfall patterns in Australia. After sifting through nearly 40,000 historical storms, they found that greater amounts of precipitation are being squeezed into ever-smaller bursts. To use a rough analogy: If a storm a century ago was like slowly pouring out a glass of water, one today is grabbing a Big Gulp and dumping it out all at once.
The forceful downpours, which the researchers say are tied to the warming atmosphere, are likely to ratchet up the risks from flash flooding. They calculate a rise in temperature of 9 degrees Fahrenheit—which could conceivably happen in some cities by 2100—will heighten flood peaks in drainage areas by as much as 20 percent. That means “people in Australia can expect to see intensification in the magnitude of flash flooding in smaller catchments, particularly in urban or residential areas," says engineering professor Ashish Sharma in a press release.
Here’s more on the findings, published today in Nature Geoscience:
“These more intense patterns are leading to more destructive storms, which can significantly influence the severity of flood flows,” says lead author and PhD candidate Conrad Wasko, from the UNSW School of Civil and Environmental Engineering. “The climate zones we studied in Australia are representative of most global climates, so it’s very likely these same trends will be observed around the world.”…
“The fact that these increases represent changes only in the intensity of rainfall within storms, and not the total volume of rain—which will also increase as temperatures warm—is concerning,” says Professor Sharma. “These results highlight the need for local councils to think about redesigning sewage and road infrastructure, and updating guidelines about where it’s safe to build homes.”
The Aussie’s conclusions on the changing nature of storms echo those of the 2009 National Climate Assessment, which predicted increasingly frequent outbursts of heavy rain. In the U.S. that will mean more days of trudging along in heavy downpours in the Pacific Northwest, Midwest, and Northeast. This NOAA map shows the places likely to get an extra day or two of “extreme rainfall” each year from 2041 to 2070, should emissions increase unfettered:
“Depending on how resilient a natural or manmade landscape is,” write the folks at NOAA, “heavier rain could exacerbate floods that disrupt traffic and transportation, overburden stormwater and runoff systems, damage property and infrastructure, and reduce crop yields due to excess water or field flooding, among other impacts.”