Los Angeles River in the context of "Flood plains"

River engineering is a discipline of civil engineering which studies human intervention in the course, characteristics, or flow of a river with the intention of producing some defined benefit. People have intervened in the natural course and behaviour of rivers since before recorded history—to manage the water resources, to protect against flooding, or to make passage along or across rivers easier. Since the Yuan Dynasty and Ancient Roman times, rivers have been used as a source of hydropower.

From the late 20th century onward, the practice of river engineering has responded to environmental concerns broader than immediate human benefit. Some river engineering projects have focused exclusively on the restoration or protection of natural characteristics and habitats.

33°56′20″N 118°30′15″W / 33.93889°N 118.50417°W / 33.93889; -118.50417

Santa Monica Bay is a bight of the Pacific Ocean in Southern California, United States. Its boundaries are slightly ambiguous, but it is generally considered to be the part of the Pacific within an imaginary line drawn between Point Dume, in Malibu, and the Palos Verdes Peninsula. Its eastern shore forms the western boundary of the Los Angeles Westside and South Bay regions. Although it was fed by the Los Angeles River until the river's catastrophic change of course in 1825, the only stream of any size now flowing into it is Ballona Creek. Smaller waterways draining into the bay include Malibu Creek, Topanga Creek, and Santa Monica Creek.

The San Gabriel River is a mostly-urban waterway flowing 58 miles (93 km) southward through Los Angeles and Orange Counties, California, in the United States. It is the central of three major rivers draining the Greater Los Angeles area, the others being the Los Angeles River and Santa Ana River. The river's watershed stretches from the rugged San Gabriel Mountains to the heavily developed San Gabriel Valley and a significant part of the Los Angeles coastal plain, emptying into the Pacific Ocean between the cities of Long Beach and Seal Beach.

The San Gabriel once ran across a vast alluvial flood plain, its channels shifting with winter floods and forming extensive wetlands along its perennial course, a relatively scarce source of fresh water in this arid region. The Tongva and their ancestors inhabited the San Gabriel River basin for thousands of years at villages like Puvunga, relying on the abundant fish and game in riparian habitats. The river is named for the nearby Mission San Gabriel Arcángel, established in 1771 during the Spanish colonization of California. Its water was heavily used for irrigation and ranching by Spanish, Mexican, and American settlers before urbanization began in the early 1900s, eventually transforming much of the watershed into industrial and suburban areas of greater Los Angeles.

A rail yard, railway yard, railroad yard (US) or simply yard, is a series of tracks in a rail network for storing, sorting, or loading and unloading rail vehicles and locomotives. Yards have many tracks in parallel for keeping rolling stock or unused locomotives stored off the main line, so that they do not obstruct the flow of traffic. Cars or wagons are moved around by specially designed yard switcher locomotives (US) or shunter locomotives (UK), a type of locomotive. Cars or wagons in a yard may be sorted by numerous categories, including railway company, loaded or unloaded, destination, car type, or whether they need repairs. Yards are normally built where there is a need to store rail vehicles while they are not being loaded or unloaded, or are waiting to be assembled into trains. Large yards may have a tower to control operations.

Many yards are located at strategic points on a main line. Main-line yards are often composed of an up yard and a down yard, linked to the associated direction of travel. There are different types of yards, and different parts within a yard, depending on how they are built.

El Pueblo de Nuestra Señora la Reina de los Ángeles del Río de Porciúncula (Spanish for "the Town of Our Lady, Queen of the Angels, of the Porciúncula River"), shortened to the Pueblo de los Ángeles ("angel town"), was the Spanish civilian pueblo settled in 1781 which became the modern American metropolis of Los Angeles. The pueblo was built using labor from the adjacent village of Yaanga and was totally dependent on local Indigenous labor for its survival.

Official settlements in Alta California were of three types: presidio (military), mission (religious) and pueblo (civil). The Pueblo de los Ángeles was the second pueblo (town) created during the Spanish colonization of California (the first was San Jose, in 1777). El Pueblo de la Reina de los Ángeles—'The Town of the Queen of Angels' was founded twelve years after the first presidio and mission, the Presidio of San Diego and Mission San Diego de Alcalá (1769). The original settlement consisted of forty-four people in eleven families, recruited mostly from Estado de Occidente. As new settlers arrived and soldiers retired to civilian life in Los Angeles, the town became the principal urban center of southern Alta California, whose social and economic life revolved around the raising of livestock on the expansive ranchos.