Old ways of thinking about Delaware River Basin flooding no longer apply

The last record-setting floods in the Delaware River Basin are inadequate baselines to prepare for the extreme weather to come as the old rules of resiliency planning no longer apply in a time of climate change, a keynote speaker at a forum on flooding said on Friday.

Planners have to expect inundation that is 15 to 25 percent greater than the last record-breaking floods, said the speaker, Glenn Schwartz, who retired last year as chief meteorologist for WCAU-TV in Philadelphia after a lengthy career.

Schwartz offered a sobering assessment of floods to come and the effects of climate change at the conference, sponsored by the Water Resources Association of the Delaware River Basin.

In a presentation that included photos from the catastrophic fatal flooding that was wrought by back-to-back Hurricanes Connie and Diane in 1955, Schwartz said the Delaware River Basin had not seen flooding like that in decades. And then came so-called once-in-one-hundred-year-floods that struck in three consecutive years: 2004, 2005 and 2006.

People will wake up to climate change at different times and have their “a-ha” or “uh-oh” moments after they have experienced it firsthand in the form of flooding or devastation brought by extreme weather, he said.

“That will convince you more than any book or article you will read,” he said.

That climate change is real and manmade and that temperatures and sea levels are rising is no longer in dispute. “It’s just a fact – one-hundred-point-zero percent,” he said. “It’s as sure as gravity.”

Wearing a red bowtie with snowflakes to honor this past snowless winter, Schwartz was one of 10 speakers who addressed the daylong conference, which was titled, “Take Action: Using Science & Collaboration to Manage Flooding and Climate Change Risks.” The conference was held at the Nurture Nature Center in Easton, Pa.

He said that some refer to the extreme weather disasters that regularly now make headlines – atmospheric rivers bringing flooding to California, powerful wildfires, tornadoes and hurricanes – as the “new normal,” but he corrected that perception.

“It’s not the new normal,” he said. “It’s the new normal — for now.”

If resiliency planners build mitigation measures based on the most recent record-setting flooding, the efforts are bound to fail. “We can’t plan for what the story is now,” he said. “We have to plan for what’s coming.”

Rainfall records are being set and broken, with one leapfrogging ahead of the last, at a rapid pace. Climate change causes these extreme weather events to be more frequent and more damaging, Schwartz said.

All of it points to more intense rainfalls, flooding and extreme heat that could also lead to droughts and less snowfall.

In Philadelphia alone, the number of heavy downpours has increased 360 percent since the 1950s. Rain events of three inches or more per day in Philadelphia have accelerated over the past 20 years, he said, with the city setting records for the wettest hour, day and year since 2010 alone. And by the end of the century, the city could be besieged by flooding during every high tide – and that does not even include times of heavy rainfalls, he said. 

“The old rules no longer apply,” warned Schwartz, who is also a disaster preparedness meteorologist for the National Weather Service.

Steps need to be taken to minimize the potential dangers to humans because the best that can be hoped for now is that climate change levels off or slows down.

“It will cost more to do nothing,” he said, adding, “We have no choice because there is no ‘Planet B.’ We have only one planet. We cannot afford to screw up.”

Challenges of communicating to the public

Other speakers (from the Delaware River Basin Commission, the Federal Emergency Management Agency, the Philadelphia Water Department and other organizations) spoke of the importance of risk messaging – conveying information clearly to a lay audience about the hazards of pending extreme weather.

Kathryn Semmens, the science director at the Nurture Nature Center, said one of the challenges is effectively displaying scientific data in a way that allows the public to make sound decisions.

“We found the issue is there is a lot of data out there,” she said, adding some feedback from focus groups is that some data-driven graphics can cause eyes to glaze over.

Mathy Stanislaus, the executive director of the Drexel Environmental Collaboratory, said people are scared about how to best prepare themselves against the next flood, especially if they’ve been affected before.

Stanislaus, a former assistant administrator for the Environmental Protection Agency’s Office of Land and Emergency Management in the Obama administration, said every natural disaster raises political, technical and communications issues.

“While there are different ways to communicate, people all want to be protected,” he said.