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. Gravity dams are designed so that each section of the dam is ...

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 so ...

California California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...

. 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. 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, United States, 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 d ...

, 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 LA County, is the most populous county in the United States, with 9,663,345 residents estimated in 2023. Its population is greater than that of 40 individua ...

, the dam impounds the

in the

Angeles National Forest The Angeles National Forest (ANF) of the United States Forest Service is located in the San Gabriel Mountains and Sierra Pelona Mountains, primarily within Los Angeles County in Southern California. The ANF manages a majority of the San Gabri ...

, a few miles northeast of

Azusa AZUSA refers to a ground-based radar tracking system installed at Cape Canaveral, Florida and the NASA Kennedy Space Center. AZUSA was named after the southern California town Azusa, California where the system was devised in the early 1950s. ...

. 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 t ...

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

mouth A mouth also referred to as the oral is the body orifice through which many animals ingest food and animal communication#Auditory, vocalize. The body cavity immediately behind the mouth opening, known as the oral cavity (or in Latin), is also t ...

at the

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

, and downstream of the river's beginning at the

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

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 (), is a style of visual arts, architecture, and product design that first Art Deco in Paris, appeared in Paris in the 1910s just before World War I and flourished in the United States and Europe during the 1920 ...

-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 th ...

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 the 31st president of the United States, serving from 1929 to 1933. A wealthy mining engineer before his presidency, Hoover led the wartime Commission for Relief in Belgium and ...

. 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 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 California, Oregon, and Nevada, inundating the western United States and portions of British Columbia and Mexico. It was preceded by weeks of continuous rains and snows tha ...

. Along with San Gabriel Dam, which at the time was under construction, the Cogswell Dam 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 . In 2024, the dam was dedicated as a

National Historic Civil Engineering Landmark __NOTOC__ The following is a list of Historic Civil Engineering Landmarks as designated by the American Society of Civil Engineers since it began the program in 1964. The designation is granted to projects, structures, and sites in the United Stat ...

by the

American Society of Civil Engineers The American Society of Civil Engineers (ASCE) is a tax-exempt professional body founded in 1852 to represent members of the civil engineering profession worldwide. Headquartered in Reston, Virginia, it is the oldest national engineering soci ...

Morris Reservoir Naval Weapons Test Site

Beginning in

World War II World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...

, 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 Department of Defense. It is the world's most powerful navy with the largest displacement, at 4.5 million tons in 2021. It has the world's largest aircraft ...

in conjunction with the

California Institute of Technology The California Institute of Technology (branded as Caltech) is a private research university in Pasadena, California, United States. The university is responsible for many modern scientific advancements and is among a small group of institutes ...

. 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, with an explosive warhead designed to detonate either on contact with or in proximity to the target. Historically, such ...

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 powered only during relatively brief periods—most of the flight is unpowered. Short-range ballistic missiles (SRBM) typic ...

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, an ...

, 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
*

Historic American Engineering Record Heritage Documentation Programs (HDP) is a division of the U.S. National Park Service (NPS). It administers three programs established to document historic places in the United States: Historic American Buildings Survey (HABS), Historic American E ...

(HAER) documentation of test site, filed under CA State Highway 39 at Morris Reservoir, Azusa, Los Angeles County, CA: ** ** ** ** ** {{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 Historic Civil Engineering Landmarks