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Yes, Pennsylvania, We Are All at Some Risk of Flooding

March 11, 2022 09:15 AM
By: PEMA

Rain with warning sign

​I don’t live in a flood zone. Why should I care about flooding? Am I at risk?

Yes. Anywhere it can rain, it can also flood. And we have a map that shows you that most flooding reported to the National Weather Service happened outside the 100-year flood zone!

March is a month of seasonal transition in Pennsylvania. The first day of spring is March 21, yet we are also still at risk of major snowstorms (Remember the blizzards in 1993 and 1997 and the nor'easter in 2018?). As a result, March is also when we begin shifting our attention to flooding risks. Rapid snow melt and heavy rain increases the risk of flooding in Pennsylvania. That risk isn’t just near those who live along a river, creek or stream. Everyone in Pennsylvania is at some risk of flooding which can have disastrous results. Take a look at this short video that describes a restaurant owner’s personal experience with unexpected flooding in 2018.

To understand who is at risk of flooding and where, we recently plotted all the locations of flood reports that were made to the National Weather Service from 1993 through 2021.

Then we color coded the locations to better understand where the flooding occurred:

  • Flood reports over one-half mile outside the FEMA 100-year floodplain area are marked red.
  • Flood reports falling within one-half mile of the FEMA 100-year floodplain are in green.

According to the map, approximately 90% of flooding in Pennsylvania that was reported to the National Weather Service occurred outside of the “FEMA 100-year flood plain”. The 100-year flood plain means there is a 1% chance of flooding in that area each year.  This map shows that 90% of the flooding reported, occurred in areas where there is less than a 1% chance of flooding each year.

How are there so many reports of flooding outside the high-risk flood areas?

There is risk of flooding anywhere there is excess water due to rain and/or snowmelt that accumulates faster than the ground can absorb it, or the drainage systems can carry it away.

Given that Pennsylvania has more than 83,000 miles of riverways, it makes sense that we are most familiar with “river flooding," and the risks associated with living near a body of water. Flooding along rivers, creeks, and streams occurs when heavy rains, rapid snow melt or erosion cause water levels to rise and overflow beyond the banks that contain them. But that’s only part of the story; in addition to river flooding, there is also coastal, flash, and urban flooding in Pennsylvania.

Flash and urban flooding is what puts so many additional red dots on that map.

About Flash and Urban Flooding

The National Weather Service explains that flash floods can be caused by extremely heavy rainfall from thunderstorms, dam or levee breaks or mudslides.

How quickly the flash flooding can occur depends on the intensity of the rainfall, land use and topography, vegetation types and how wet the ground is from prior rainfall or snowmelt.

Urban or populated areas are prone to flooding when impervious surfaces (parking lots, buildings, roads) do not allow water to infiltrate the ground or when storm drains and sewers overflow.  It can often show up in the form of wet basements and sewer backups. 

Flash and urban flooding is difficult to predict, very dangerous, and can cause costly damage.

Why flash and urban flooding can be so dangerous…

  • Just six inches of fast-moving water can knock you off your feet.
  • Six inches of water will reach the bottom of most cars causing loss of control and possible stalling.
  • A foot of water will float most vehicles.
  • Two feet of fast-moving water can carry away cars, SUVs and pick-ups trucks.

…And costly

  • Just one inch of water in a home can cost more than $25,000 in damage.
  • Most homeowner and renter insurance does not cover damages from flooding.

Rather than asking whether you are at risk, consider finding out the level of risk for where you live (or work) and what you can do to mitigate it.

How To Get Started with Mitigation

  1. Find out your level of risk. FEMA's flood map can help you determine your region's risk of flooding. Some regions are marked with color codes indicating the likelihood of flooding there.
  2. Lower your risk. Mitigating your flood risk not only protects your property against flood damage but can also help lower insurance costs.
    Learn about what you can do to reduce your risk.
  3. Prepare your home regardless of risk. Even if your region is listed as low to moderate risk, there are several ways to lessen the likelihood of flooding or mitigate the damage if you do have water in your home. Take a look at this tip sheet to learn more.

Flooding has shown Pennsylvania how devastating it can be. The more you learn, prepare for, and protect yourself and loved ones and your home against flooding, the easier your recovery. Download our Ready PA monthly newsletter for more helpful information to stay safe.


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