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San Gabriel Dam is a rock-fill dam on the San Gabriel River in Los Angeles County, California, within the Angeles National Forest. Completed in 1939, the dam impounds the main stem of the San Gabriel River about downstream from the confluence of the river's East and West Forks, which drain a large portion of the San Gabriel Mountains. The dam provides flood control, groundwater recharge flows and hydroelectricity for the heavily populated San Gabriel Valley in the Greater Los Angeles metropolitan area. ==History== In the 1920s, the Los Angeles County Flood Control District proposed to impound the San Gabriel River just below the confluence of the East and West forks with a high, long concrete arch dam to capture floods and provide water conservation. To be named the San Gabriel Forks Dam, the project was canceled by the State Engineer after having convened an inquiry to investigate problems which were occurring at San Gabriel Dam site, including a landslide that destroyed a large portion of the construction site, in early November 1929. The inquiry panel concluded and issued a report to the State Engineer stating that the proposed dam "cannot be constructed without creating a menace to life and property." Subsequently, the design of the San Gabriel River flood control project was changed from one large dam to two smaller dams: San Gabriel No. 1 (San Gabriel Dam), about below the original Forks site, and San Gabriel No. 2 (Cogswell Dam), on the West Fork about above the confluence. The cost of San Gabriel No. 1 was greatly understated, creating a scandal; in context with the Great Depression, the Los Angeles ''Times'' observed that "it is not now necessary to gamble $26 million on a (and wasteful agency )". The bond measure necessary for financing of the project was defeated by a narrow margin of 52 to 48 percent. As a result, the city turned to the federal Public Works Administration for money to complete the project. The San Gabriel No. 1 dam was to be made of rock-fill, which provides greater seismic stability. Construction of the high San Gabriel Dam at this site began in 1932 and was completed in 1939. In early 1938, before the dam was finished, Southern California was hit by record floods. The heaviest rains fell in the San Gabriel Mountains, swelling the San Gabriel River; on the night of March 2–3, 1938 a flood of poured out of the mountains and into San Gabriel Reservoir. San Gabriel Dam was able to knock about off the peak of the flood. Further downstream, Morris Reservoir was able to absorb roughly , reducing the flood to less than half of what it would have been if not for the dams. 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「San Gabriel Dam」の詳細全文を読む スポンサード リンク
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