PA Environment Digest

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Chesapeake Bay Foundation: New Report - Extreme Rainfall In Pennsylvania To Increase

By B.J. Small, Chesapeake Bay Foundation

A new report suggests that the devastation from extreme rain events that claim lives, cause billions of dollars in damage, and pollute local waters, will become more severe in Pennsylvania if left unchecked, thanks to climate change.

The report “Extreme Precipitation in a Warming Climate,” by the science communication group Climate Central, predicts that on average, U.S. counties are likely to experience a 17 percent increase in extreme rainfall on the heaviest 1 percent of days.

Much of the data in the report is from the U.S. Global Change Research Program’s Fifth National Climate Assessment.

For every 1°F of warming, the air can hold an extra 4 percent moisture, according to the report.

The Chesapeake Bay Foundation notes that one inch of rain falling on an acre of hardened surface, such as streets and parking lots, produces 27,000 gallons of runoff. Stormwater passing over impervious surfaces often picks up oil, grease, dirt, and nutrients (nitrogen and phosphorus) and flows into nearby waterways.

According to the state’s latest report on impaired waters, 3,828 miles of Pennsylvania’s rivers and streams do not meet water quality standards because of polluted urban stormwater runoff and storm sewers-- the third leading source of impairment.

The report details how much more rainfall is likely to fall in each Pennsylvania county during severe storms if the climate warms by 3.6 °F (2 °C).

That includes Bucks County, 23.9 percent; Philadelphia, 22.5 percent; Centre County, 30.0 percent; Allegheny County, 17.4 percent; Lancaster County, 16.9; and Luzerne County, 15.8.

The Climate Central report notes that as the climate warmed between 1958 and 2021, the heaviest storms now drop 60 percent more rain in the Northeast (including Pennsylvania, Maryland, the District of Columbia, New York, and West Virginia) and 37 percent in the Southeast (including Virginia).

This increases the chances of heavier downpours that contribute to flash floods like those that killed seven people in Southeastern Pennsylvania last summer.

A grandmother, mother, and her two children were swept away by rushing waters after nearly 7 inches of rain fell on Bucks County in 45 minutes last July.

The mother and 2-year-old daughter perished and the search for the 9-month-old son was called off. The father, a 4-year-old son, and the grandmother survived.

Four other people died in Bucks County floodwaters that day.

Climate Central reported that flood damage costs in Pennsylvania totaled roughly $2.8 billion in 2020 and that figure could go up by 8 percent by 2050 as global temperatures continue to rise.

Harry Campbell, CBF Science Policy and Advocacy Director for Pennsylvania, issued the following statement--

“The impacts of climate change go well beyond warmer summertime highs.

“The Susquehanna River is already one of the most flood prone in the nation, and coupled with Pennsylvania’s aging infrastructure in many towns, costly flooding events are likely to increase in the coming years.

“The intense precipitation is also likely to increase the amounts of polluted runoff flowing into our lakes, rivers, and streams.

“When rainfall lands on a hot surface, like a parking lot, the solar energy is transferred to the cooler rainfall as it makes its way to the nearest waterbody. This superheated stormwater runoff can be so hot that it can critically harm critters that rely on clean, cool water to survive, like brook trout and the eastern hellbender.

“Because hotter water holds less dissolved oxygen than cold water, many critters will find it harder to breathe. If it doesn’t kill them, it can render them susceptible pathogens and diseases. To make matters worse, some pollutants can become more toxic in warmer waters.

“There’s one thing nearly every homeowner, community, and business can do to mitigate these negative impacts. Planting and preserving native trees, shrubs, and other vegetation alongside streams, streets, and other sensitive areas helps slow down, spread out, and soak in precipitation, filter out pollutants, and cools runoff.”

Click Here for the complete announcement.

For more on Chesapeake Bay-related issues in Pennsylvania, visit the Chesapeake Bay Foundation-PA webpage. Click Here to sign up for Pennsylvania updates (bottom of left column). Click Here to support their work.

Also visit the Keystone 10 Million Trees Partnership to learn how you can help clean water grow on trees.

CBF has over 275,000 members in Bay Watershed.

How Clean Is Your Stream?

The draft 2024 report has an interactive report viewer that allows you to zoom in to your own address to see if the streams near you are impaired and why.

Click Here to check out your streams. Click Here for a tutorial on using the viewer.

Visit DEP’s Chesapeake Bay Watershed webpage to learn more about cleaning up rivers and streams in Pennsylvania's portion of the Chesapeake Bay Watershed. Click Here to sign up for regular updates on Pennsylvania’s progress.

NewsClips:

-- WHYY: Flood Risk Is Increasing In Philly Region, Here’s What You Need To Know

-- WESA: ReImagine Appalachia Report Proposes Policy Recommendations To Increase Flood Resilience In Appalachia

Resource Links:

-- PA Will Experience 42% More Days Of Extremely Heavy Precipitation By 2050 Due To Climate Change [PaEN]

-- 71% Increase In Very Heavy Precipitation Events In Last 54 Years In PA [PaEN]

-- DEP Now Accepting Applications For Act 167 County Stormwater Management Planning [PaEN]

-- PEMA Publishes Updated Guidance For Disaster Recovery Assistance Program For Individuals [PaEN]

-- Delaware River Basin Commission, PEMA, Other Partners Make Available Flood Loss Reduction Assistance Resources For Local Officials [PaEN]

-- Delaware River Basin Commission Releases New Tool To Help Communities Understand Local Impacts Of Extreme Precipitation Events [PaEN]

-- US Geological Survey Hosts May 9 Webinar On New USGS Base Streamflow Forecasting Web Tool [PaEN]

-- First Street Foundation Releases New Tool Showing Mid-Atlantic States Will See Wind Gusts In Storms Increase 37 MPH, Wind Damage To Property Increase Over 50% In Next 30 Years [PaEN]