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The Cascade Locks and Canal was a navigation project on the Columbia River between the U.S. states of Oregon and Washington, completed in 1896. It allowed the steamboats of the Columbia River to bypass the Cascades Rapids, and thereby opened a passage from the lower parts of the river as far as The Dalles. The locks were submerged and rendered obsolete in 1938, when the Bonneville Dam was constructed, along with a new set of locks, a short ways downstream.〔(Columbia River History ), Northwest Power and Conservation Council. Accessed January 11, 2008.〕 ==Design and construction== As rail competition grew, and forced steamboats off their old routes, shippers and steamboat lines began agitating Congress to allocate funds for improvements to the river, in the form of canals and locks, that would restore their competitive position relative to the railroads. The two main improvements sought on the Columbia were the Cascade Locks and, about twenty years later, the Celilo Canal and Locks. Studies for a canal at the Cascades had begun in 1875, but interest tapered off when Oregon Railroad and Navigation Company (O.R.& N.) finished the railroad to The Dalles and took its boats off the middle river. Anti-monopoly shippers eventually got Congress to allocate funds in 1893 to begin the canal and locks at the Cascades, which were completed in November 1896. The locks had a lift chamber carved in solid rock long, and 90' wide, with of draft, deep enough for any vessel then on the river, and large enough to accommodate several at once. The locks could raise a vessel 14' at high water and 24' at low water.〔Newell, Gordon R., ed., ''H.W. McCurdy Marine History of the Pacific Northwest'', at page 5, Superior Publishing, Seattle, WA 1966〕 The lock gates were wide and high. The locks were carefully designed to address the great variation in the height of the river, the difference between high and low water being . This condition made it necessary to build a series of three sets of gates, increasing in height from the lower entrance to the huge upper guard gate, only two sets being used at one time. When the river was low, the upper guard gates remained open continually and the lower sets were operated. When the water rose enough to drown the lower gates, they were swung open and the lifting work was done by the others. The upper approach was formed by masonry wall extending from the guard gate in a long sweep of , and the bank behind was armored against floods with riprapped stone.〔( "Cascade Locks," ''Scientific American'', page 167, March 13, 1897 )〕 Image:Cascade Locks, looking east, circa 1897.jpg|Cascade Locks, circa 1897, looking east, locks are functioning but bank work is still ongoing Image:Cascade Locks, looking south over lower lock, circa 1897.jpg|Cascade Locks, circa 1897, looking south and downriver across lower lock Image:Cascade Locks, looking south and east, circa 1897.jpg|Cascade Locks, circa 1897, looking south, showing middle lock and lockmaster and engineer buildings on embankment on south side 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Cascade Locks and Canal」の詳細全文を読む スポンサード リンク
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