TheBurg

I t's one of Harrisburg's most treasured, beloved landmarks. e Susquehanna River is the longest river east of the Mississippi. Its basin—an immense 27,510 square miles—encompasses half of Pennsylvania, along with portions of New York and Maryland. It's an area that 4 million people call home, including those who live along its picturesque shores from Cooperstown, N.Y., to Havre de Grace, Md.— including Harrisburg's rocky riverbed stretching nearly a mile wide. "We are unique, in that we're a river city—and that has inherent issues," said Brian Enterline, Harrisburg Fire Bureau chief and head of emergency management. at's because the Susquehanna is considered one of the most flood-prone watersheds in the nation, averaging $150 million in flood damage annually—a fact that Ben Pratt thinks about daily. "I'm the point person here at the commission for all things related to flooding," said Pratt, a water resources engineer of 17 years with the Susquehanna River Basin Commission (SRBC). "So my day job is flooding. I get up every day concerned about flooding, and then climate change adds another level to it." As iconic as the Susquehanna is, what are the risks swirling within its basin amid climate change? What changes are we experiencing in Pennsylvania's weather and climate? And how are those changes connected to flooding? We set out to answer those questions from local, state and regional experts at top emergency management and environmental roles. A PERFECT STORM Geography and weather patterns provide the perfect storm of ingredients for the basin's flood-prone tendency, even before climate change enters into the mix. "We're always at risk for tropical storms and hurricanes in the summer seasons," Pratt said. "And with west-to-east weather patterns, we pick up moisture from the Great Lakes, which produces summer thunderstorms with heavy rain." Perhaps no one understands flood risks better than residents and businesses located in floodplains—areas designated to be most at-risk for flooding by the Federal Emergency Management Agency (FEMA). But weather events and climate change don't adhere to boundary lines drawn on maps. "e biggest concern with climate change is the heavy, extreme events, even to those who aren't in a floodplain," Pratt said. "You have to expand the area of concern, and frankly it's everyone now that has a flood risk of some sort. And that's a real challenge … it's an expansion of what we've known historically as the 100-year floodplain. It's pretty much everywhere now—not just along the rivers." Before we go further, let's explore flooding's connection to climate change. WARMING UP You've likely noticed changes—some of them extreme—in our weather. For example, Harrisburg has experienced little snowfall—even some 50-degree days—this winter. "It'll probably go down as one of the warmer winters we've had," said Jeff Jumper, Pennsylvania's state meteorologist working under the umbrella of the Pennsylvania Emergency Management Agency (PEMA). But changes in the weather don't exactly equal climate change. Weather is what happens on a daily basis. Climate is the big picture—a long-term average of weather over decades and centuries. Worldwide, the average global temperature—after being historically stable over the course of modern human civilization—began warming during the 1880s amid the Industrial Revolution, when the burning of fossil fuels accelerated. e earth has warmed 1.8 degrees Fahrenheit since 1900. "Harrisburg's annual average temperature went up .3 degrees per decade," said Jumper. "We're in the category of [temperatures] climbing at a rate we've never seen before." If we continue on this trajectory, the Department of Environmental Protection (DEP) estimates that Pennsylvania's temperatures will warm another 5.9 degrees by 2050. "e idea is the rate at which we're seeing those temperatures rise. How quickly are we going to lose winter? How quickly are we going to be more like Richmond?" Jumper said. IN THE ATMOSPHERE Changes in climate are being driven by the atmosphere. Scientists first noticed the greenhouse effect in the 1820s, and, today, more than 99.9% of all scientists who have published in the field agree that climate change is real, and human activity—primarily emissions from the burning of fossil fuels—is the cause. Carbon dioxide (CO2) is one of those greenhouse gases, so when experts talk about "de-carbonization," it refers to lowering CO2 emissions. And Pennsylvania is one of the leading emitters of CO2 in the nation. As one of the top three energy- producing states, the Keystone State is also the top electricity-exporting state, sharing 30% of its energy with neighboring states, according to DEP data. Pennsylvania is actually responsible for nearly 1% of total global emissions. Additionally, the state's industrial sector contributes about one-third of its greenhouse gas emissions, primarily due to processes used in manufacturing concrete and chemicals, along with mineral extraction. As greenhouse gases propel climate change and warmer temperatures, how does this tie into increased precipitation? Warmer air holds more water vapor, so when storms form, there's more water vapor available, compared to 50 or 100 years ago. "Our 2021 Climate Impacts Assessment found that currently our [Pennsylvania's] biggest hazard is flooding. Across the state, we have the second-most miles of streams in the U.S.," said Lindsay Byron, DEP environmental group manager. "And we can expect an 8% increase in precipitation by 2050." at's on top of an already-observed 10% to 20% increase in Pennsylvania's precipitation. e sum result? Pennsylvania's heightened risk of flooding. PEMA recently worked with each county's emergency management agency to identify their top three hazards—and the resulting map displays flood risks throughout the state (facing page). IN A FLASH "e other challenge is predicting flash flooding, and that can happen anywhere in the state," said Jumper, who points to 2018—Pennsylvania's wettest year on record. "We had no major snowstorm, no major A CHANGE IN THE WEATHER Pennsylvania's emergency management and environmental experts explain climate change: Why flooding is our top risk—and it's not the Susquehanna they're most worried about. But they are floating a number of solutions. BY KAREN HENDRICKS Image credit: DEP Jeff Jumper

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