Severe Weather Awareness Week: River Flooding

Posted on 4/25/2019 8:41:19 AM

2019 Severe Weather Awareness week for Pennsylvania is April 22–26. Plan ahead and stay weather aware for safe spring!

Our severe weather and weather safety topic for today is “River Flooding and River Flood Safety.”

Pennsylvania has an extensive river system that is scenic and beautiful. Most of the towns and cities were founded on the banks of a river or large creek. This means that when river levels rise, many people will be affected at the same time. The rising river waters can become destructive, and even deadly. Significant, widespread river floods have occurred in Pennsylvania almost every year.

The great Johnstown flood of 1889 is considered the third worst flood in American history, after the catastrophic failure of the South Fork Dam on the Little Conemaugh River.

johnstown flood

The scale of the flood is hard to image. Here is a list of some of the most descriptive facts about the Johnstown flood:

  • 2,209 people died.
  • 99 entire families died, including 396 children
  • More than 750 victims were never identified and rest in the Plot of the Unknown in Grandview Cemetery
  • Bodies were found as far away as Cincinnati, and as late as 1911
  • 1,600 homes were destroyed
  • Flood lines were found as high as 89 feet above river level
  • The great wave measured 35–40 feet high and hit Johnstown at 40 miles per hour

What causes river floods?

Generally, river floods happen due to prolonged periods of widespread heavy rainfall.

Our rivers can flood any time of the year. In spring and summer, complexes of slow-moving thunderstorms can cause the rivers to flood. During late summer and fall, heavy rain from tropical storms and hurricanes are the biggest cause of river flooding.

Sometimes, an extensive snow melt occurs at the same time as heavy rain. This is especially true in late winter and early spring when the snow pack of the previous winter melts away. The destructive winter flooding of January 1996 was one such situation where snow melt and heavy rain combined to push river levels even higher.

River flooding can result in widespread property damage and may result in loss of life. More than 50 percent of the deaths associated with flooding are automobile related.

What does a River Flood Warning mean?

A River Flood Warning means that river levels will exceed flood stage at certain points along our larger rivers, like the Susquehanna and Juniata rivers.

Because river floods take longer to develop than flash flooding does, river floods may not pose as much of a threat to life, but river floods can take a much larger toll on property and infrastructure.

What should you do when a River Flood Warning is issued?

Gather all necessary items, including medicine and clothing, if you cannot return home for several days. Decide to protect your property by moving your valuables to higher ground or to an upper level of your home.

Obey evacuation orders from emergency management or local law enforcement officials, avoiding any roads that are or may be covered with water.

This message is brought to you by the IUP Emergency Management Office.