Armed Polite Society
Main Forums => The Roundtable => Topic started by: Monkeyleg on May 21, 2013, 02:46:37 AM
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I was watching "Bridge Over the River Kwai" tonight. A real classic.
At the end of the movie, an American Navy officer accompanies a British commando unit to destroy the bridge. They set their demolition charges at night, and then wait for the morning when the first Japanese train is due to cross the bridge.
Their plan comes undone when the commanding officer of the British POW's who built the bridge sees the charges and the wires because the water level dropped about four feet overnight. He alerts the Japanese commander, all hell breaks lose, and he, the Japanese commander, the Navy officer and a British commando are killed before the bridge is blown.
Here's my question: do river levels rise and fall as much as four feet in a period of just a few hours? I know that tides come and go, but river depth? If the answer is no, then the plot falls apart.
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Rainy season comes to an end in monsoon country.
I was watching "Bridge Over the River Kwai" tonight. A real classic.
At the end of the movie, an American Navy officer accompanies a British commando unit to destroy the bridge. They set their demolition charges at night, and then wait for the morning when the first Japanese train is due to cross the bridge.
Their plan comes undone when the commanding officer of the British POW's who built the bridge sees the charges and the wires because the water level dropped about four feet overnight. He alerts the Japanese commander, all hell breaks lose, and he, the Japanese commander, the Navy officer and a British commando are killed before the bridge is blown.
Here's my question: do river levels rise and fall as much as four feet in a period of just a few hours? I know that tides come and go, but river depth? If the answer is no, then the plot falls apart.
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Rainy season comes to an end in monsoon country.
While that's the most logical explanation, the movie was inconveniently filmed without a rainy season during the time when the bridge was completed. It did, however, have some glorious scenes of a monsoon earlier in the drama.
The Kwai river is not tidal. The logical explanation for the river level dropping would be something blocking the river upstream, but that would mean when the blockage burst the resulting downstream rush would likely have washed out the bridge. Can't have Mother Nature screwing up a good story.
(For tidal river changes, look at the Shubenacadie River near the town of Truro and the village of Maitland in New Brunswick's portion of the Bay of Fundy. You can raft the bore upriver. The tidal bores on the Petitcodiac and Avon rivers were surfer magnets in the 1960s - you could ride a single wave upstream for around 45 minutes, then catch your breath and ride it back downstream on the tidal change. They have since built some causeways that have reduced the speed and force of the tidal bore to something like filling a bathtub.)
stay safe.
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Yes, a river/stream can easily rise or fall 4 feet in a few hours. The rapidity of a rise in water is truly amazing on a freestone stream as a result of rainfall. The decrease in flow tends to be more gradual, but it depends on the situation.
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In "Return to Lonesome Dove" when they crossed the Yellowstone River headed north, the water was running from right to left (back towards the Rocky Mountains) :facepalm:
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River Rat here, yes rivers can go up and down very fast.
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Love the move. Never thought about this issue before. I'll take it as one of those things, like a minor firearms mistake in an otherwise good film. Noted and chuckled about to myself, then ignored for the quality of the overall film.
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Thanks for the replies. I didn't think a river level could drop in a few hours, but what do I know?
There's plenty of movies with more serious plot errors. In "Rules of Engagement", Samuel L. Jackson's Marine colonel character is charged with 83 counts of murder for ordering his troops to open fire on a group of protestors outside a Middle East embassy. The Marines are firing from the roof, and in the movie, they're supposedly not able to see the protestors to know if they're armed and shooting at the Marines, as Jackson's character says they were. That makes no sense, as the Marines would have to be able to see the people in order to shoot them, unless they were doing spray and pray.
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The rise and fall rate depends on how big the river is, whether it is well developed and controlled, and geography of the area.
My experience is that smaller rivers seem to move up and down faster. Large rivers like Illinois, Mississippi, and similar rise and fall slower but will have a larger difference between min and max level.
It took over a week for the downpour in the midwest to cause the Illinois river to finally crest in Peoria. It took another week and half to return to normal. Yielding a sustained flood of about a week. This river is a major navigable waterway connecting Lake Michigan and Chicago to the Mississippi (meaning that it is operated by the Army Core of Engineers or some such), and is controlled by several locks and dams. Many of the significant tributaries are also controlled by dams, not much can be done when the whole multi state region is given so much water. The smaller tributaries feeding the river flash flooded overnight, and returned to normal within a day.
I believe the Amazon is mostly unrestricted and will typically rise 30-40ft into its flood plain during the rainy seasons, allowing one to canoe gently through the tree canopy.
Illinois and midwest geography is mostly flat, with about 200ft drop from northwest corner of the state, to the southern most tip. Therefore, the rise and fall is slower since the slope is gentle. Steeper areas can rise and fall much faster.
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The water level would rise if they made the river cry. =)
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I have less experience with "rivers" and more with what we call "cricks" back home (Muskingum, Scioto, Will's Creek, Tuskarawas river). The level can easily change by many feet overnight due to heavy rains, even if they happen upstream.
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the river in my backyard can drop 4 feet in a couple hours
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Here's my question: do river levels rise and fall as much as four feet in a period of just a few hours? I know that tides come and go, but river depth? If the answer is no, then the plot falls apart.
Depends on the budget, the star, and the potential for a sequel.
Brad
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Depends on the budget, the star, and the potential for a sequel.
Brad
Lord of the Rings
Prince Caspian
=D