The Los Angeles River travels through its narrowest section at this
point. Glendale Narrows. The hydrology of the area forced the Corps
of Engineers change how they channelized the river.
Parking for is located on residential streets just northwest.
Currently (Nov. 2007) there is major construction in the area, but
access to the park has been maintained.
As the Los Angeles River leaves the San Fernando Valley and
flows out onto the Los Angels Coastal Plain it passes between the
Elysian Hills to the southwest and Repetto Hills to the northeast.
The width of the valley the LA River goes through here is about 0.8
mile. This geomorphological feature, a constriction that a river
flows through from one relatively open plain to another, is called
a narrows. I have seen this area called the Glendale Narrows and
the Los Angeles Narrows.
From the coordinates, you will see that the lining of the river
channel changes at this point. When the United States Corps of
Engineers channelized the Los Angeles River they left only 3
sections unlined. One is in behind the Supulveda Dam, another is
near the ocean, and the final section ends here and extends a
approximately 8 miles upstream.
It was found that this section couldn’t be lined because
the hydrology of the area. The two sets of hills that form the
narrows are formed by an anticline, a hill in the layers of rock.
This anticline is also found underneath the river sediments roughly
connecting the two sets of hills. The San Fernando Valley to the
northwest and the Los Angeles Coastal Plain are both deep basins
that have filled with sediments eroded from the surrounding
mountains. Both of these basins are as much as 10,000 feet
deep.
Ground water ponds above the bedrock in the
sediments. This forms a huge underground lake beneath the San
Fernando Valley. And just like the river, all the ground water
flows drains out of the basin through the narrows. In the image,
the big blue arrows show the general direction that ground water
flows in the San Fernando Valley. It all flows toward the Glendale
Narrows in the southeast corner of the map.
While the rest of the San Fernando Valley is filled with thousands
of feet of sediment, in the narrows, the thickness of the sediments
is typically less than 200 feet and as little as 50 feet. This
forces the groundwater that has collected in the deep San Fernando
Basin up to the surface creating many natural springs. This is
actually one of the few places that the LA river would naturally
flow year round. Today, most of current flow you see is actually
the discharge from waste water treatment plants upstream, but
between 2,000 to 4,000 acre-feet per year of
groundwater flows into the river channel and down into the lined
section. (Planners estimate that between 1 to 3 families use 1
acre-foot of water each year) If the river had been lined, the
springs would have no where to go and could have lifted the
concrete lining.
Logging requirements:
Send me a note with :
- The text "GC1772F Glendale Narrows" on the first line
- The number of people in your group.
- Describing the character of the bottom of the river upstream
and downstream
- How would that affect the flow of groundwater in/out of the
river.
- How would you expect the depth of the ground water to be
changing up and down stream from this point.
- The coordinates parallel to the point that the lining changes
(Don’t go down into the channel, do it from the bike
path.
The above information was compiled from the
following sources:
- Land Michael, Geological, Hydrological, and
Biological Issues Related to the Proposed Development of a Park at
the Confluence of the Los Angeles River and the Arroyo Seco, Los
Angeles County, California, Scientific Investigations Report
2004-5296, U.S. Department of the Interior U.S. Geological Survey,
2005
- Langenheim, V.E. and others, Preliminary
Potential-Field Constraints on the Geometry of the San Fernando
Basin, Southern California, Open-File Report 00-219, U.S.
DEPARTMENT OF THE INTERIOR U.S. GEOLOGICAL SURVEY, 2000
- Chapter IV – Groundwater Basin Reports
San Fernando Valley Basins - Upper Los Angeles River Area Basins,
Los Angeles Metropolitin Water District, September 2007
http://www.mwdh2o.com/mwdh2o/pages/yourwater/supply/groundwater/PDFs/SanFernandoValleyBasins/UpperLARiverAreaBasins.pdf
- Dubnewych, Steve and others, PROBLEMS
ENCOUNTERED ON THE UPPER REACH OF THE NORTHEAST INTERCEPTOR SEWER
PROJECT, 2005 RETC PROCEEDINGS, Chapter 22
- Upper Los Angeles River Area Watermaster
(Watermaster), 2006a, Watermaster Service in the Upper Los Angeles
River Area, 2004-05 Water Year, Los Angeles County,
California.
Please visit
us at
