Sentinel Gap is a water gap formed by the

Columbia River The Columbia River (Upper Chinook: ' or '; Sahaptin: ''Nch’i-Wàna'' or ''Nchi wana''; Sinixt dialect'' '') is the largest river in the Pacific Northwest region of North America. The river rises in the Rocky Mountains of British Columbia, C ...

in the

Saddle Mountains The Saddle Mountains consists of an upfolded anticline ridge of basalt in Grant County of central Washington state. The ridge, reaching to 2,700 feet, terminates in the east south of Othello, Washington near the foot of the Drumheller Channel ...

, near Mattawa in

Washington Washington commonly refers to: * Washington (state), United States * Washington, D.C., the capital of the United States ** A metonym for the federal government of the United States ** Washington metropolitan area, the metropolitan area centered on ...

state. The gap is "a water gap where erosion by the Columbia River was able to keep pace with folding, faulting and uplifting across the Saddle Mountain anticline". During Ice Age floods in which waters from the Channeled Scablands found passage to the Pacific Ocean here and at

Wallula Gap Wallula Gap () is a large water gap of the Columbia River in the northwest United States in southeast Washington. It cuts through the Horse Heaven Hills basalt anticlines in the Columbia River Basin, just south of the confluence of the Walla ...

, this opening was "repeatedly reamed out, which probably widened and steepened the walls of the gap".

Strandlines A high water mark is a point that represents the maximum rise of a body of water over land. Such a mark is often the result of a flood, but high water marks may reflect an all-time high, an annual high (highest level to which water rose that ...

from the floods can be seen on the basalt walls of the gap. SR 243 runs along the east side of the river through the gap, and the river is spanned by the

Beverly Railroad Bridge The Beverly Railroad Bridge is a historic railroad bridge that now carries hikers, bicyclists, and pedestrians over the Columbia River near Beverly, Washington, United States. It was constructed by the Chicago, Milwaukee, St. Paul and Pacific Rai ...

. The gap is located between the

Wanapum The Wanapum tribe of Native Americans formerly lived along the Columbia River from above Priest Rapids down to the mouth of the Snake River in what is now the US state of Washington. About 60 Wanapum still live near the present day site of Priest ...

and

Priest Rapids Priest Rapids was a narrow, fast-flowing stretch of the Columbia River, located in the central region of the U.S. state of Washington. It was flooded by the construction of the Priest Rapids Dam in the 1950s. Before the dam's construction, the riv ...

dams.

, for which the dam was named, are now submerged beneath the dam's reservoir about downstream from Sentinel Gap.

References

Sources

* *

External links

* Columbia River Landforms of Kittitas County, Washington Water gaps of Washington {{KittitasCountyWA-geo-stub