Water Resources: Hydraulics and Hydrology
Q ..
You'll have all of your professional papers together in one place.
A:
That is the main idea.
Tujunga Wash Rood Channel
You wanted to discuss another project from your time in the Los Angeles District?
A:
Yes. I think we covered all the Los Angeles District, but I didn't mention one thing that
was developed there, which I think is very, very important to mention. It's brought out
in some of the technical papers that I have written and will send to the Office of History.
It concerns the design of the Tujunga Wash flood channel. The channel begins at Hansen
Dam, where the outlets works discharged into the channel, which was an unimproved,
natural channel. Every time large flows had to be released from Hansen Dam, it caused
flooding along the Tujunga Wash channel, about 12 miles from the dam to the Los
Angeles River. The water eventually got into the Los Angeles River, but flooded many
highways and much valuable property along the unimproved Tujunga Wash channel.
In designing the channel improvement, it didn't take long for us to decide that the high
velocities required the channel to be concrete-lined. We also made enough preliminary
studies to determine that a rectangular concrete-lined channel would be the most efficient,
and less costly than a trapezoidal concrete-lined or a trapezoidal rock-lined channel. So
we proceeded immediately to design a concrete-lined, rectangular high-velocity channel.
We did the preliminary hydraulic studies and then decided we had to model study this
channel because of the many sharp curves and the high velocities. We wanted to check
to see that the channel was designed properly with sufficiently high walls, especially
around the curves.
A
scale model of the rectangular channel was constructed and tested at the primary
hydraulics laboratory in Griffith Park along the Los Angeles River channel. The tests
showed that the velocities caused water depths to be significantly greater on the outside
walls of sharp curves. The average depth of flow for the design discharge in the straight
channel sections was about 12 feet. But going around the sharpest curves the water depth
would be four feet higher on the outside wall and four feet lower on the inside wall. That
would require the outside wall to be eight feet higher than the inside wall. This wall
would gradually taper from the normal height on a tangent to the higher height through
the curve and then back down to the normal height on the other side of the curve. On the
inside of the curve, the height of the wall could be reduced the same way.
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