Morris Dam (officially the Samuel B. Morris Dam) is a concrete

gravity dam A gravity dam is a dam constructed from concrete or stone masonry and designed to hold back water by using only the weight of the material and its resistance against the foundation to oppose the horizontal pressure of water pushing against it. ...

across the San Gabriel River in the

U.S. state In the United States, a state is a constituent political entity, of which there are 50. Bound together in a political union, each state holds governmental jurisdiction over a separate and defined geographic territory where it shares its sover ...

California California is a U.S. state, state in the Western United States, located along the West Coast of the United States, Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the List of states and territori ...

. It impounds

Morris Reservoir Morris Reservoir is located in the San Gabriel Mountains, within the Angeles National Forest, in Los Angeles County, California. It is impounded by Morris Dam, which was completed in 1935. Morris Dam is a gravity dam rising above the San Gabrie ...

, directly downstream of

San Gabriel Dam 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 dam was built in the 1930s as a water supply facility for the city of

Pasadena Pasadena ( ) is a city in Los Angeles County, California, northeast of downtown Los Angeles. It is the most populous city and the primary cultural center of the San Gabriel Valley. Old Pasadena is the city's original commercial district. Its ...

, but is now mostly utilized for flood control and flow regulation for

groundwater recharge Groundwater recharge or deep drainage or deep percolation is a hydrologic process, where water moves downward from surface water to groundwater. Recharge is the primary method through which water enters an aquifer. This process usually occurs in ...

. Situated in northern

Los Angeles County Los Angeles County, officially the County of Los Angeles, and sometimes abbreviated as L.A. County, is the most populous county in the United States and in the U.S. state of California, with 9,861,224 residents estimated as of 2022. It is the ...

, the dam impounds the

in the

Angeles National Forest The Angeles National Forest (ANF) of the United States Forest Service, U.S. Forest Service is located in the San Gabriel Mountains and Sierra Pelona Mountains, primarily within Los Angeles County, California, Los Angeles County in southern Calif ...

, a few miles northeast of

Azusa Azusa may refer to: Relating to California From a Native American language, likely Tongva ''Asuksagna:'' *Azusa, California, a city in the United States *Azusa Pacific University, a Christian-based institution in Azusa, California *Azusa Street Rev ...

. From the 1940s to the 1990s, the reservoir was also used for underwater missile testing by the United States military.

Design and location

This dam sits south of Silver Mountain and north of Glendora Ridge, which flank the deep

San Gabriel Canyon The San Gabriel River is a mostly urban waterway flowing 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 L ...

. It is roughly upstream of the San Gabriel River's

mouth In animal anatomy, the mouth, also known as the oral cavity, or in Latin cavum oris, is the opening through which many animals take in food and issue vocal sounds. It is also the cavity lying at the upper end of the alimentary canal, bounded on ...

at the

Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the continen ...

, and downstream of the river's beginning at the

confluence In geography, a confluence (also: ''conflux'') occurs where two or more flowing bodies of water join to form a single channel. A confluence can occur in several configurations: at the point where a tributary joins a larger river (main stem); o ...

of its East and West Forks.U.S. Geological Survey. National Hydrography Dataset high-resolution flowline data
The National Map
accessed March 10, 2011

is about long and above sea level at maximum pool, covering . The dam's crest itself is at an elevation of . Serving mainly flood control, flow regulation and groundwater recharge purposes, the slightly arched

Art Deco Art Deco, short for the French ''Arts Décoratifs'', and sometimes just called Deco, is a style of visual arts, architecture, and product design, that first appeared in France in the 1910s (just before World War I), and flourished in the Unite ...

-style gravity dam is high and long. Its

spillway A spillway is a structure used to provide the controlled release of water downstream from a dam or levee, typically into the riverbed of the dammed river itself. In the United Kingdom, they may be known as overflow channels. Spillways ensure tha ...

, located slightly north of the main structure, is a concrete-lined chute controlled by three steel drum gates. The reservoir created by the dam, when first put into use, was capable of storing . Due to

sedimentation Sedimentation is the deposition of sediments. It takes place when particles in suspension settle out of the fluid in which they are entrained and come to rest against a barrier. This is due to their motion through the fluid in response to the ...

though since that time, its capacity has been reduced by about 29%. At present, the reservoir when filled holds approximately .

History

Morris Dam was originally slated to be called Pine Canyon Dam, but was renamed for the chief engineer of construction, Samuel Brooks Morris of the Pasadena Water Department. With the dam envisioned as a private structure for

, groundbreaking was in April 1932 and construction was completed in May 1934, four months behind schedule. Upon completion the dam was dedicated by former United States President

Herbert Hoover Herbert Clark Hoover (August 10, 1874 – October 20, 1964) was an American politician who served as the 31st president of the United States from 1929 to 1933 and a member of the Republican Party, holding office during the onset of the Gr ...

. In 1935, contrary to its original purpose, Morris Dam was sold to the

Metropolitan Water District of Southern California The Metropolitan Water District of Southern California is a regional wholesaler and the largest supplier of treated water in the United States. The name is usually shortened to "Met," "Metropolitan," or "MWD." It is a cooperative of fourteen cit ...

(MWD), which owned it through most of the 20th century. The dam was completed prior to the catastrophic

Los Angeles Flood of 1938 The Los Angeles flood of 1938 was one of the largest floods in the history of Los Angeles, Orange, and Riverside Counties in southern California. The flood was caused by two Pacific storms that swept across the Los Angeles Basin in February-Marc ...

, the most severe flood recorded in Southern California since the

Great Flood of 1862 The Great Flood of 1862 was the largest flood in the recorded history of Oregon, Nevada, and California, occurring from December 1861 to January 1862. It was preceded by weeks of continuous rains and snows in the very high elevations that began in ...

. Along with

, which at the time was under construction, the

Cogswell Dam Cogswell Dam is a rockfill dam on the West Fork of the San Gabriel River in Los Angeles County, California. It is located in the San Gabriel Mountains, northeast of Mount Wilson, and within the Angeles National Forest. It forms Cogswell Reser ...

upstream and the Morris Dam greatly reduced the flood peak on the San Gabriel River, saving downstream cities millions of dollars' worth of damages. If it were not for the three dams, the flow past Azusa may have exceeded , but was limited to just , with Morris Dam alone reducing the flood peak by some .

Morris Reservoir Naval Weapons Test Site

Beginning in

World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...

, Morris Reservoir was used for the Morris Reservoir Naval Weapons Test Site for the

U.S. Navy The United States Navy (USN) is the maritime service branch of the United States Armed Forces and one of the eight uniformed services of the United States. It is the largest and most powerful navy in the world, with the estimated tonnage of ...

in conjunction with the

California Institute of Technology The California Institute of Technology (branded as Caltech or CIT)The university itself only spells its short form as "Caltech"; the institution considers other spellings such a"Cal Tech" and "CalTech" incorrect. The institute is also occasional ...

. A wide variety of weapons, including

torpedo A modern torpedo is an underwater ranged weapon launched above or below the water surface, self-propelled towards a target, and with an explosive warhead designed to detonate either on contact with or in proximity to the target. Historically, su ...

es and

ballistic missile A ballistic missile is a type of missile that uses projectile motion to deliver warheads on a target. These weapons are guided only during relatively brief periods—most of the flight is unpowered. Short-range ballistic missiles stay within the ...

s, had their trial runs here. Testing continued until the 1990s, when most of the structures at the associated military compound were demolished. However, the concrete foundations remain and are easily seen from State Route 39, which runs past the dam and reservoir. In 1995, MWD sold the dam to the

Los Angeles County Department of Public Works The Los Angeles County Department of Public Works (LACDPW) is responsible for the construction and operation of Los Angeles County, California, Los Angeles County's roads, building code, building safety, Sewage collection and disposal, sewerage, a ...

, which continues to operate it and the reservoir today.

References

Notes

External links

Schematic of major reservoirs in the Los Angeles and San Gabriel River watersheds
{{LA County dams Los Angeles County Department of Public Works dams Gravity dams San Gabriel River (California) San Gabriel Mountains Angeles National Forest Azusa, California Dams completed in 1934 1934 establishments in California Historic American Engineering Record in California