Re: Flood conditions and TVA data


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Posted by jd on May 11, 2003 at 19:08:30:

In Reply to: Flood conditions and TVA data posted by Kerry Grissett on May 11, 2003 at 16:04:11:

If gravity were the only influene, yes, a gradient would be required to cause flow. This gets complicated when you think about elevation of bottom of river, or top of river, and in general, works on averages and is based on energy principles. Gravity is probably the predominant driving force for getting water from here to the ocean. On a microscopic basis, there are other factors such as you mentioned like feeder creeks. On a VERY simplified basis, flow is a function of energy derived from elevation, pressure, and momentum (or kinetic energy).

WAKE UP! Bottom line: The depth in a river can vary from one side to the other. A picture is worth a thousand words. If so compelled, you can check out the graph on page 22 of the following *.pdf file:

http://ficp.engr.utexas.edu/crwr/cd_Consortium_2000/ArcGIS/chapter5.pdf

FYI, Thalweg is a term basically given to the centerline of the bottom channel. The graph illustrates a computer computational model of change in elevation along a river.

For the bored fishermen / history buffs:

Daniel Bernoulli discovered the relationship between fluid speed and pressure and then "Soon physicians all over Europe were measuring patients blood pressure by sticking point-ended glass tubes directly into their arteries." See more at http://pass.maths.org.uk/issue1/bern/

The topic at hand is "open channel flow" and is a branch of civil engineering hydraulics. V.T. Chow is one of the masters of this topic and has published many books. If you want to see the kind of math an engineer used to desribe and predict flow, check out:

http://www.iahr.org/publications/assets/jhr40-2/afzal.pdf

If you are an insomniac, print this one and put it beside the bed.

I will be fishing my once a year, company sponsored bass tournament at the end of the month. If anyone finds some bass when the flooding subsides or about this time frame, any subtle tips are appreciated!

Good luck!
jd


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