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Re: Walking Very Marginal Stocked Streams in Fall

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2007/11/21 18:54
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I'm not sure where examples of these(older wide span) are. It seems like in the old days, every bridge pool was great. I'm talking more about smaller streams. I guess if you think about it, they are artificial. But still.

Posted on: 11/3 19:49


Re: Walking Very Marginal Stocked Streams in Fall

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2006/11/10 8:32
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The trout may survive a warm summer, but the viability of their gametes may not.

Posted on: 11/3 22:26


Re: Walking Very Marginal Stocked Streams in Fall

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2006/11/2 8:50
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Quote:

JeffP wrote:
I'm not sure where examples of these(older wide span) are. It seems like in the old days, every bridge pool was great. I'm talking more about smaller streams. I guess if you think about it, they are artificial. But still.


On Middle Creek you saw the old bridges, which had good bridge pools. And now you see the new bridges, which do not.

What design differences have you noticed between the new and old bridges?



Posted on: 11/4 10:41


Re: Walking Very Marginal Stocked Streams in Fall

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2006/9/11 11:30
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A design trend in bridges is that materials have gotten cheaper and labor more expensive (over simplified of course). Most modern bridges are based on over- designed I-beams that can handle a wide span between concrete supports. Plenty of steel in those I-beams, but they are quick to design and easy to install. Really old stone bridges couldn't handler large spans so they had narrow openings that accelerate the flow. Plus, small towns couldn't afford to do giant stone bridges like the Starruca viaduct built by the Erie RR. It was possible to do incredible stone work, but most places couldn't afford it.

Around the Civil War iron bridges started to come into use and later steel. The first iron bridges duplicated wooden bridge trusses, but in the late 19th and early 20th century all sorts of crazy truss designs came into play to save materials because small towns couldn't afford much (plus the spans weren't that wide). Height and width of most bridges until less than 100 years wasn't all that scientific. Built it where locals thought highest flood was, and if it got swept away you rebuilt it 5 ft higher. Repeat until it doesn't get swept away.

Just saw one of the old RR bridges over the Delaware in Easton with my brother who is an old bridge fan. It had riveted box beams that most have taken an incredible amount of labor. That isn't done anymore.

Old bridges were narrow by a combination of high material costs and low budgets. For most of our history rural areas were poor and tried all sorts of small bridge ideas to save money. American ingenuity was in full flower with bridge design to meet local needs. Now we just use giant I-beams and over design it so the stream isn't as narrowed. Most highway bridges have gotten pretty dull IMHO.

Posted on: 11/4 11:08



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