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The Los Angeles River (also known as the L.A. River) starts in the Simi Hills and Santa Susana Mountains and flows through Los Angeles County, California, from Canoga Park in the western end of the San Fernando Valley, nearly southeast to its mouth in Long Beach. Several tributaries join the once free-flowing and frequently flooding river, forming alluvial flood plains along its banks. It now flows through a concrete channel on a fixed course, which was built after a series of devastating floods in the early 20th century. Environmental groups and park advocates support the removal of concrete and the restoration of natural vegetation and wildlife. Portions of the river now have earthen bottoms and restored habitat. There are also plans for a series of parks along the river's city frontage in Los Angeles. The Los Angeles River also flows through several Los Angeles County communities and has been featured in many Hollywood films. Before the opening of the Los Angeles Aqueduct, the river was the primary source of fresh water for the city. Although the Los Angeles region still gets some of its water from the river and other local sources, most comes from several aqueducts serving the area. The river suffers pollution from agricultural and urban runoff. Fed primarily by rainwater (in winter and spring), the Donald C. Tillman Water Reclamation Plant in Van Nuys (in summer and fall), and urban discharge, it is one of the few low-elevation perennial rivers in Southern California. Some water usually reaches the sea, even in the driest summers; although there are historical accounts of the river running dry, there has been flow every month since recording of stream flow began in 1929.〔 This is helped by the concrete channel, which limits absorption of water into the earth. Flow, while generally low in volume, can be extremely brisk even in summer. ==Course== The Los Angeles River's official beginning is at the confluence of two channelized streams – Bell Creek and Arroyo Calabasas – in the Canoga Park section of the city of Los Angeles, just east of California State Route 27, at (the east side of Canoga Park High School). Bell Creek flows east from the Simi Hills, and Arroyo Calabasas flows north from the Santa Monica Mountains. From there the river flows east through a concrete flood control channel and very soon receives Browns Canyon Wash, which flows south from the Santa Susana Mountains. The river then bends slightly south and receives Aliso Canyon Wash, whose watershed adjoins that of Browns Canyon. The river then flows through the district of Winnetka, then Reseda and enters the Sepulveda Basin, a flood-control reservoir formed by the Sepulveda Dam. As the river proceeds into the usually-dry reservoir, it spills out into a channel that is similar to its historical, unchannelized form. It crosses under Balboa Boulevard and then passes through the outlet works of Sepulveda Dam, from the mouth. It flows again into a concrete channel and crosses under Interstate 405 as it passes through Van Nuys, Sherman Oaks, and Studio City, still flowing east. Paralleling U.S. Highway 101 briefly, it then veers southeast, away from the highway, and receives from the left the Tujunga Wash, one of its largest tributaries, which flows southwest and south from the Angeles National Forest in the San Gabriel Mountains. The river then rounds a bend to the northeast, now in a concrete box culvert, and crosses under State Route 170 and Highway 101, and receives Burbank Western Channel on the left bank, from the mouth.〔〔 The river then begins to parallel California State Route 134 as it winds past the city of Burbank and North Hollywood, then crosses under Interstate 5 and makes a sharp bend to the south-southeast as it curves around Griffith Park. It receives from the left Verdugo Canyon Wash, which drains much of La Cañada Flintridge and Glendale as it flows from the San Gabriel Mountains south through a water gap in the Verdugo Mountains, and crosses under State Route 134. Here, the river begins to flow over a natural riverbed, but enters another concrete section soon after. Paralleling Interstate 5 for the next few miles, the river runs by the eastern side of Griffith Park and the Harding-Wilson Golf Course. It passes Silver Lake Reservoir, which is to the right, and crosses under California State Route 2, from the mouth.〔〔 Making two meanders as it flows in a southeasterly direction, the river parallels the interstate and Riverside Drive then crosses under the interstate and California State Route 110 as it flows east of Elysian Park. It then receives the Arroyo Seco, another major tributary, from the left. The river flows south past the Mission Junction, a large railroad yard on the left. It enters a wider concrete channel with sloped sides, and crosses under Cesar Chavez Avenue, Highway 101, and Interstate 10 as it passes east of downtown Los Angeles, flowing past the East Los Angeles Interchange for Highway 101, California State Route 60, and Interstates 5 and 10 on the left. It then makes a gradual turn east and then turns southeast, flowing a few miles before it begins to parallel Interstate 710 near Maywood, Bell, Cudahy, and Commerce, from the mouth.〔〔〔 Paralleling Interstate 710 south-southwest, the river then crosses under former California State Route 42 and the interstate as it receives the Rio Hondo from the left, from the mouth. The Rio Hondo ''(deep river)'' now serves as a distributary for the San Gabriel River to the east via the Whittier Narrows Reservoir. The river then crosses under I-105 and shifts slightly southwest, then flows east of Compton and west of Bellflower. After crossing under California State Route 91, it receives Compton Creek from the right, from the mouth. After crossing under Interstate 405 for the second time, from the mouth, it draws close to the Dominguez Channel to the west and flows due south to its outlet in Long Beach, under Interstate 710, past the RMS ''Queen Mary'', and into the Port of Long Beach.〔〔〔 ==History== The river provided a source of water and food for the Tongva people prior to the arrival of the Spanish. After the establishment of Mission San Gabriel in 1771, the Spanish referred to all of the Tongva living in that mission's vicinity as Gabrieliño. The Gabrieliños were hunters and gatherers who lived primarily off fish, small mammals, and the acorns from the abundant oak trees along the river's path. There were at least 45 Gabrieliño villages located near the Los Angeles River, concentrated in the San Fernando Valley and the Elysian Valley, in what is present day Glendale. In 1769, members of the Portolà expedition to explore Alta California were the first Europeans to see the river. On August 2, the party camped near the river, somewhere along the stretch just to the north of the Interstate 10 crossing near downtown Los Angeles. Fray Juan Crespi, one of two Franciscan missionaries traveling with Portolà, named it ''El Río de Nuestra Señora La Reina de Los Ángeles de Porciúncula''. Crespi chose that name, which translates as ''The River of Our Lady Queen of the Angels of Porciuncula'', because it was the name of a special annual feast day for the Franciscans, which the Portolà party had celebrated the previous day. The river was thereafter referred to as the "Porciuncula River". In later years, the "Los Angeles" part of Crespi's lengthy name won out. The river was originally an alluvial river that ran freely across a flood plain that is now occupied by Los Angeles, Long Beach and other townships in Southern California. Its path was unstable and unpredictable, and the mouth of the river moved frequently from one place to another between Long Beach and Ballona Creek. In the early 19th century, the river turned southwest after leaving the Glendale Narrows, where it joined Ballona Creek and discharged into Santa Monica Bay in present Marina del Rey. However, this account is challenged by Col. J. J. Warner, in his ''Historical Sketch of Los Angeles County'': "...until 1825 it was seldom, if in any year, that the river discharged even during the rainy season its waters into the sea. Instead of having a river way to the sea, the waters spread over the country, filling the depressions in the surface and forming lakes, ponds and marshes. The river water, if any, that reached the ocean drained off from the land at so many places, and in such small volumes, that no channel existed until the flood of 1825, which, by cutting a river way to tide water, drained the marsh land and caused the forests to disappear." Prior to the Great Flood of 1862, it was joined by the San Gabriel River in present-day Long Beach, but in that year the San Gabriel carved out a new course to the east, and has discharged into Alamitos Bay ever since. Until the opening of the Los Angeles Aqueduct in 1913, the Los Angeles River was the primary water source for the Los Angeles Basin, but much of its channel had extremely low discharge except during the winter rains. Unpredictable and devastating floods continued to plague it well into the 1930s (the most notable one being the catastrophic 1938 flood that precipitated the recall of then-mayor of Los Angeles Frank L. Shaw), leading to calls for flood control measures. The Army Corps of Engineers duly began an ambitious project of completely encasing the river's bed and banks in concrete, with only a trickle of water usually flowing down its middle. The only portions of the river that are not completely paved over are in the flood-control basin behind the Sepulveda Dam near Van Nuys; a 11-mile (17.7-km) stretch east of Griffith Park known as the Glendale Narrows; and along its last few miles in Long Beach. The river was dry for nine months of the year as late as the 1950s. According to an August 2013 article in the Los Angeles Times, the water in the river today is largely "industrial and residential discharge," which originates from the "two giant pipes that collect the sewage from the homes of 800,000 San Fernando Valley residents" that lead to the Tillman Water Reclamation Plant, "before crashing over a man-made waterfall into Lake Balboa. That body of water, along with two smaller ones, puts 23 million gallons of water a day into the river at Sepulveda Basin." 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「Los Angeles River」の詳細全文を読む スポンサード リンク
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