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Re: (erielack) Flooding at Del Water Gap station



If you get into the statistics of floods, a 100 year flood is actually that
flood which has a 1% chance of occurrence. Since any 100 year period both
begins now and ends now, that 1% chance of occurrence is the same today as
it was yesterday, or tomorrow. The probability of occurrence is a constant.
I suspect the current flooding should cause a close look at the records to
see if these recent data points alter the flow vs frequency curves for this
reach of the Delaware.

The DL&W line through the Gap was built in the 1850s?? or there abouts.  At
that time I don't believe anyone had the data to predict any particular
flood stage, including a 1% flood.  I suspect the actual location along any
river was based on getting the highest, firmest piece of ground with the
least amount of rock blasting to achieve the desired grade. I also think
local "old timers" would have been questioned on high water levels, and the
engineer in charge of the project would have used that info in his final
decision. And, since a steam engine on a firm roadbed can move through
several feet of water, the need for a "constantly high & dry" track didn't
exist, so some degree of flooding could have been acceptable. That line was
originally built in a very different time.

RICH CHAPIN, P.E.
ELHS #3129


- ----- Original Message ----- 
From: "Tom Beckett" <tabeckett_@_stny.rr.com>
To: "EL List" <erielack_@_lists.railfan.net>
Sent: Thursday, April 07, 2005 12:44 PM
Subject: (erielack) Flooding at Del Water Gap station


> The other thing to keep in mind is that the "100 year flood" is a
> statistical average. You will have a flood of that magnitude, on average,
> once every 100 years. In the real world, it may occur twice in 7 months,
> then not again for 300 years. But it is true that development has
increased
> the runoff significantly versus undeveloped forest, increasing the
> likelihood and severity of any flooding resulting from large amounts of
> rainfall. For the most part, the railroads took this into account when
> locating their lines. I notice that the Erie line here in the Binghamton
> area has not been affected by any of the flooding I have seen in the last
17
> years, even though adjacent roads have been closed due to high water on a
> number of occasions, including this past weekend.
>
> Tom B
> ----- Original Message ----- 
> From: "Chris Lee" <leesome1226_@_yahoo.com>
> To: "EL List" <erielack_@_lists.railfan.net>
> Sent: Thursday, April 07, 2005 10:17 AM
> Subject: RE: (erielack) FW: Flooding at Del Water Gap station
>
>
> > It would not have made sense for the DL&W to spend the
> > extra money at the time to build their tracks away
> > from the river. Let's look at the stats for the flood
> > based on Easton numbers.
> >
> > Flood this past week: Crested at 36.8 ft in Easton.
> > 3rd largest flood on record
> > Flood in Sept: Crested at 33.45 ft in Easton. Was the
> > 3rd largest flood on record at the time and is now the
> > 4th.
> >
> > Dr. David Brandes here at Lafayette College figured
> > that the Sept storm to be the 100 year flood, aka, a
> > storm that comes every 100 years to a region. Dr.
> > Roger Ruggles, PE, figured this past storm to be
> > either the 250 or 300 year flood. However, according
> > to his data this does not make sense. He said that
> > historically 100 year floods generally occur with 7
> > inches of rain. We only got about 4.5 inches during
> > the storm. He believes that the larger flooding with
> > less rain is due to all the development in the
> > Poconos. The runoff from these new developments is
> > going into the river and not into the ground as it
> > used to. Therefore, it takes much less water to do
> > more damage.
> >
> > The DL&W clearly had great Civil Engineers. It would
> > have been impractical to move their tracks when they
> > were only getting the 100 year flood every 100 years.
> > Today we are getting a 100 year flood and an even
> > larger one in the span of 7 months. Flooding of this
> > magnitude was a rare occurance for the DL&W back then
> > but according to Professor Ruggles is something that
> > we will see happen more often in the future.
> >
> > Chris Lee
> > BSCE 2007
> > Lafayette College
>
>
>
>

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