page_title: Yamhill River lock and dam
section_title: Design failure
hierarchical_section_title: Yamhill River lock and dam / Design failure
caption_attribution_description: Yamhlli Locks and dam, near Lafayette, Oregon ca 1908 or before
context_page_description: The Yamhill River lock and dam was completed in 1900. It was built near Lafayette, Oregon, to allow better river transport on the Yamhill River from Dayton, to McMinnville, Oregon. While the Corps of Engineers had recommended against construction of the lock, it was built anyway, largely as a result of political effort by the backers of the project. For almost forty years prior to the lock construction there had been efforts made to construct a lock and dam on the Yamhill River.
  The lock was a single-lift chamber 210 feet long and 40 feet wide, located on the west side of the river. The dam extended from the east bank of the river to the eastern lock wall, and when the lock gates were shut, acted to back up the Yamhill river and raise the water level sufficiently to allow ready steamboat navigation to McMinnville during the summer dry season. During the winter the lock and dam were more of an obstruction than an navigational aid, as they were frequently overtopped by freshets and floods, sometimes as high as or higher than twenty feet above the lock walls.
  The lock ceased to be used in any significant way soon after it was built.
context_section_description: After 1902, the official reports of the Corps of Engineers consistently emphasized that no commercial steamers were regularly using the lock.  The lock had been "practically abandoned" by sternwheelers after 1902.  From 1902 to 1914 the locks were used mostly by passengers in launches and by boats towing rafts.
  The serious flaw with the lock and dam was that the lock had to be closed at high water, because the river simply flowed over the lock walls, making the lock chamber unusable.  On the Willamette River, high water, usually coming in the fall and spring, was traditionally the best steamboat time, with late summer and early fall the worst, with water levels down.  On the Yamhill above Lafayette, the dam created the reverse situation.
  The original design of the lock had assumed that steamers could simply float over the dam when the water level rose to 5 feet above the dam.  In practice this proved impossible because until the water rose to 12 feet (3.7 m) above the dam, the drop between the upper and lower pools was too great to permit safe passage of a steamer.
  In 1903, several proposals were made to address the issue, but they were rejected as being impractical, too expensive, or both.
caption: Colorized postcard printed 1908 or before, showing Yamhill lock and dam.  Lock office is visible on left.
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