Heavy Rain Events and Flooding are the New Norm

Have you noticed that there has been an increase in heavy rain events and flooding in the past couple of years? I’ve noticed it too! These extreme weather events are just one more anomaly to get used to. Not only will these events continue, they will get worse and increase in frequency.

For each degree Celsius that the earth warms the atmosphere’s water vapor increases by about 7%. Warmer air holds more moisture than cooler air. These climate changes also alter the normal characteristics and patterns of weather and storm systems. These human-induced changes will lead to increased heavy downpours, more damaging and dangerous storm surges from sea-level rise, and more rapid spring snowmelt.

These changes have different impacts on different regions. Increased urbanization means more impermeable surfaces, excess runoff and increased flash flooding. Urban areas are at an extreme risk of flash flooding meanwhile areas downstream are more susceptible to riverine flooding. Coastal cities will be ravaged by sea-level rise and subsequent storm-surge from violent coastal storms that will increase in frequency.

Imagine that two inches of rain per hour is enough to overwhelm most drainage infrastructure and turn streets into rivers. If you watch the news lets take a look back:

  • June 2016: 8-10 inches of rain fell within 12 hours in West Virginia resulting in a 1,000 year flooding event.
  • May 26-27, 2016: 19-22 inches of rain reported in the Houston area in just 24 hours. There was a report of a river cresting nearly 13 feet over major flood stage.
  • June 1, 2016: Lubbock, TX experienced up to 3 inches of rain in an hour.
  • August 11-13, 2016: 24 inches of rain fell in 48 hours over the East Baton Rouge area of Louisiana,
  • August 2016: Elliott City, MD saw 6.5 inches of rain fall in only 3 hours. 5.5 of the total fell in 90 minutes.

Just in case you were thinking on a much larger scale, perhaps globally:

  • August 2016: Skopje, Macedonia saw 20 inches of rain fall in 2.5 hours.
  • December 26, 2016: Uluru National Park saw 9 inches of rain in 24 hours.

North Carolina just experienced a heavy rainfall event a week ago. There were urban flooding impacts but of course those areas have been mitigated and there was not a large housing/residential impact. We all know that water rolls downstream and those riverine communities have been heavily impacted. In fact almost a week later we are still waiting on the rivers to recede.

We can’t grind the downward spiral to a halt in an instant. It took us many years to wear this weary planet down and it will take many years to repair. The issue here is how do we prepare or mitigate for these heavy flooding events that are just going to get worse and increase in frequency? Our environment and culture tells us its every man (woman and child) for themselves. I’m not trying to be an alarmist. I’m not saying you should run out and float your house like a pontoon and fill it with goods to survive the “big one”.  I think more people should visit their leadership and approach this from a top down urban city and land use perspective. I recently learned that many communities on the Mississippi and Missouri River have gone to great lengths with urban planning. They strategically farm on land that serves as a reservoir for flood waters so there is a loss of crops but not a loss of homes. The farmland is deliberately lower in elevation than the urban land for channeling the flood waters. I would take it a step further. Communities have to start looking into increasing stormwater and drainage capacity. Increase the use of permeable road surfaces that allow for the proper drainage and collection of water to route to flowing waterways and away from heavily populated areas. It’s time to start seeing the bigger picture. Stop thinking of recovery in terms of the “current” event and focus on preparing for not only the next event but all the others to come.

EPA
Global Change
Hot Gulf Mexico Hurls Rain Bombs at Florida and the U.S. Gulf Coast

One thought on “Heavy Rain Events and Flooding are the New Norm

  1. Great post – the 10,50, 100 and 500-year events become much less meaningful in the set-up you described, Maybe if we all start at the 500-year event as our new baseline a lot of communities will be better able to adapt to our new normal.

    Like

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