Author Topic: On this day in history 2200 people die in a massive Pennsylvania flood (May 31) 😳  (Read 50 times)

Michael Caswell

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Read all about this tragedy here - https://en.wikipedia.org/wiki/Johnstown_Flood

2209 people DEAD!


This Johnstown flood ranks as the worst flood event in US History, and sadly conditions exist along the Erie Canal that can cause a repeat here in NY State. Mainly because people still refuse to learn from their mistakes, and history can easily be repeated, due to ignorance of dam safety by the public at large.

https://abcnews.go.com/2020/story?id=2918360&page=1
« Last Edit: June 17, 2022, 07:57:39 am by Doug K »

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Doug K

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Re: On this day (May 31)
« Reply #1 on: May 31, 2022, 03:15:09 pm »
That's quite a bit of water, big dam.

Now imagine a smaller version, along the Erie Canal, with only about 200,000 tons of water crushing everything in its path.  But the real issue in a flood is drowning and according to the soon to be released Earthen Embankment Integrity Program SEQR package, that's about 340 million gallons of water to deal with. And that water will spill out of a 150' long tear, in the side of a canal navigation dam, and flow for 90 minutes until the water can be stopped by floodgates and coffer dams.

It's all right here->
https://www.canals.ny.gov/Earthen_Embankment/DGEIS/NYSCC_EEIP_Draft_GEIS_3-12-2021_Combined.pdf

The words are on page 3-16 and describes the "do nothing approach" to the overgrown earthen embankments, which will lead to failure.


3.2.3 Potential Impact of Alternatives
Under the Null or No-Action Alternative, any earthen embankments would be left to fail. Prior to
any such failure, there would be no measurable impact to land use within the canal right-of-way
or at adjacent property. At such time that the embankments would fail, water contained within
the canal prism would be rapidly released. The risks associated with such an event are described
in Appendix B. Depending on the location of the breach, the surrounding area would be
inundated to various depths depending on topography.

A breach in a canal or feeder embankment having a water depth of 12 feet is estimated to occur
over 1 hours, enlarge to 150 feet wide and discharge a peak flow of between 5,000 and 10,000 cfs.

The resulting flood wave would seriously impact existing land uses for the inundated terrain outside
the canal limits. In addition to potential loss of life and damage to infrastructure, most of the flooded
lands would be rendered unusable until restoration projects were completed. Lack of financial
capability to fund restoration work could leave some areas unusable for an extended period of
time.


Engineers get paid to do calculations, which is how those figures above were found. 5000 to 10000 cubic feet of water per second is a lot. Use the middle point, 7500, and thats for 90 minutes, or 5400 seconds. The numbers get large fast. Cubic feet to gallons of water is a internet calculator, along with the weight of 340 million gallons of water. 2000 lbs per ton is a standard number, known by most... you do the math.


Now add height to the equation, is the impounded water 15 feet overhead or is it 50 feet? Higher creates a bigger debris field, according to another "potential impact" of leaving trees growing on Erie Canal Embankments. Don't be deceived by Facebook discussions, this is a potential for disaster and should drive a bit more public awareness.

https://rochesterbeacon.com/2019/07/02/trees-on-dams-are-a-high-risk-danger/#comment-64553

« Last Edit: May 31, 2022, 03:16:51 pm by Doug K »