Morris Dam: Flood control and stormwater capture for Los Angeles County

This is the Morris Dam, located up Highway 39 above Azusa in the San Gabriel Canyon in Southern California.
Morris Dam June 2012 #2The dam was built in the 1930s by the City of Pasadena for water supply purposes.  It was dedicated in 1934 by Herbert Hoover.

Morris Dam July 2013 #53Shortly after that, Pasadena sold the dam to Metropolitan Water District.  In 1995, the County purchased it for $1.  (Below, the upstream side of the dam)

Morris Dam June 2012 #10Morris Dam, along with the Cogswell and the San Gabriel Canyon Dams upstream, is part of a chain of dams that add 85,000 feet of storage capacity to LA County water supplies.  They also provide valuable flood protection for downstream cities.

SanGabrielRiverCA_ASTER_2005jan23Here’s what it looks like from the air.  San Grabriel Canyon Dam is in the middle; Morris Dam is creating the reservoir downstream reservoir pictured towards the right hand side of this picture (below):

San Gabriel Reservoir Mar 2012 #5The dam was in place at the time of the 1938 flooding in Los Angeles and was credited with saving lives and property by holding back some of the downstream flows.

Flooding in Los Angeles, 1938

A lot of sediment flows down the San Gabriel River.  I am not kidding.  If you travel up into the mountains, you can see how the soil is just sloughing off the mountains …

Angeles Crest Highway Oct 2011 #75When first built, Morris Dam was capable of storing about 39,300 acre-feet; however, sedimentation has reduced the capacity by about 29%, giving the reservoir now a capacity of about 27,800 acre-feet.

Morris Dam June 2012 #16Morris Dam has the longest set of stairs imaginable going down the side of its spillway (look carefully at the picture below).  I would hate to have that job …

Morris Dam June 2012 #26Earlier this year, upgrades to Morris Dam were completed, and I was invited to the ribbon-cutting ceremony at the dam.  This gave me a chance to check out the dam close-up.

Morris Dam July 2013 #24Morris Dam is a concrete gravity dam that is 245 feet high and 800 feet wide.

Morris Dam July 2013 #28The $10.6 million upgrade was paid for in part with funds from Prop 50, passed in 2002.    The upgrade included five new jet flow gate and fixed cone valves …

Morris Dam July 2013 #4The old valves were prone to clogging by sediment; the new valves will now allow 1500 additional acre-feet to be delivered downstream per year, which will be used to replenish aquifers.

Morris Dam July 2013 #10The new valves will allow more flexibility in matching the downstream needs of conjunctive use facilities; or, in simpler words, water can be held back at Morris Dam until downstream spreading grounds, which are used to replenish groundwater basins, are available to receive the water.

Morris Dam July 2013 #9The upgrade also included a new control house for the dam.  Previously, operations had been managed from a trailer.

Morris Dam July 2013 #25Here are some shots of that dramatic spillway.  Notice the stairs …

Morris Dam July 2013 #33

Morris Dam July 2013 #32Morris Dam July 2013 #36Morris Dam July 2013 #31I have to admit, I do not know what these are for …

Morris Dam July 2013 #17But they are interesting features … !

Morris Dam July 2013 #49This is the ceremonial valve (below).  It is ceremonial because, while it does work, the guys will really just punch a button on the computer to open the valve from their spiffy digs in the new control house.

Morris Dam July 2013 #46

There’s a boat to go out on the reservoir on …Morris Dam July 2013 #43Morris Dam July 2013 #54Here is one interesting piece of trivia.  Morris Reservoir was used as a secret torpedo research station during World War II.  By some accounts, it was still used as such as late as 1990.  The torpedoes were rolled down the concrete slide that you see across the reservoir to see if they’d sink or swim.  You can read all about it here:  Torpedo Test Site Launched New Arms Era

San Gabriel Canyon June 2012 #7Morris Dam June 2012 #3So long from Morris Dam!

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