[PRCo] About that 1936 flood level...

[robert netzlof]

On 1 Mar 2004 at 10:53, Jim Holland wrote:

> 	"""On St.Patrick's day in 1936 Pgh. suffered one
> of its most devastating floods.    On Monday, March 16,
> the waters rose to 21.7-feet; two days later they
> had risen to 46-feet.......       ."""
> 
> 	Is It Recorded as to how much was under water?
> 

To which someone replied:

"The normal pool elevation at Pittsburgh is shown as 710 feet above 
sea level."

Yes, but that is because the Emsworth Dams make it so. Since they
were rebuilt in 1935-1938, is it certain that that was the pool
elevation in 1936? The Corps of Engineers' web site at:

http://www.lrp.usace.army.mil/nav/ems.htm

says that the rebuilding raised the pool 7 feet, so perhaps in 1936,
normal pool was 703 feet above sea level. But that is rather beside
the point.
 
"IF the water level really rose to 46 feet above that (a big if!)
then the 760-foot contour on maps offers an approximation of the
shoreline."

The National Oceanic and Atmospheric Administration quotes 46 feet on
their web site at:

http://www.erh.noaa.gov/er/pit/PTTP1_ahpsE19.html

But the 46 feet is not 46 feet above normal pool (whatever that was),
it is 46 feet on the gauge. Another CofE web page at:

http://www.lrd-wc.usace.army.mil/PSOUT/rivbull.pdf

states that normal pool at Pittsburgh is 16.0 feet, flood stage 25
feet. Again, these are gauge readings and zero on the gauge is
wherever it is (16 feet below normal pool, it would seem).

Assuming that the current gauge has not been altered since before
1936, that is, assuming it reads the same now as it did then, the 46
foot flood is 30 feet above today's normal pool of 16 feet. That
would be 30 feet above 710 feet, 740 feet above sea level.

"Again, the above estimates of flooding are based upon the 760-foot
contour and MAY WELL BE GREATLY EXAGGERATED!" 

I doubt that NOAA exaggerates the river level. Some errors in
interpreting the data have introduced a substantial distortion, which
I think has now been corrected. The correct contour would be the 740
foot line.

=====
Bob Netzlof a/k/a Sweet Old Bob


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