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278 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY

Woodring visited the field on several occasions to dis period was 24,000 cfs on March 2, 1938, during a time
cuss stratigraphic problems and also made a special of severe flood in southern California.
study of the Calicantharus humerosus group.
RELIEF
The courtesy of the Newhall Land and Farming Co.
The eastern Santa Clara River valley region is one
and of the many other land owners and residents in the
of bold relief. In the mapped area, the highest alti
region in granting access to their properties is gratefully
tude, 3,747 feet, is in the Santa Susana Mountains.
acknowledged.
The western San Gabriel Mountains rise to an altitude
GEOGRAPHY
of 3,119 feet within the mapped area and to altitudes of
Most of the mapped area is in the eastern part of more than 4,000 feet only a short distance farther east.
the Santa Clara River drainage basin. The south The Santa Clara River descends from 1,385 to 805 feet
eastern part of the area is in the part of the Los Angeles in the mapped area.
River drainage area called the San Fernando Valley. HUMAN ACTIVITIES
CLIMATE San Fernando Pass is located at the west end of the
The eastern part of the Santa Clara River valley is San Gabriel Mountains and is a convenient geo
a semiarid region having a mean annual rainfall of graphical boundary between them and the Santa Susana
about 16 inches. The rain is seasonal—most of it falls Mountains. The pass has been a natural entrance to
during the winter months. the mountain-bordered Los Angeles region since early
Daily and seasonal records for the region show a times. Evidence may still be seen of the pioneer wagon
wide temperature range. Temperatures on summer road through the pass. U.S. Highways 99 and 6,
days often are above 100°F and temperatures on winter connecting Los Angeles with the San Joaquin Valley
nights sometimes fall a few degrees below freezing. and the Mojave Desert, respectively, and the Southern
Pacific railroad's main line from Los Angeles to the San
VEGETATION
Joaquin Valley, now traverse the pass area. The Los
The vegetation varies with the underlying rock, the Angeles Department of Water and Power aqueduct
altitude, and the orientation of the slope. Areas from Owens Valley, as well as several power lines and
underlain by fine-grained rocks commonly develop a pipe lines, use the San Fernando Pass area as a con
soil that supports grass, a sage community, and oak venient gateway to the Los Angeles region. In addi
and California walnut trees. Sandstone and conglom tion to the highways and railroad already mentioned,
erate are commonly covered by the heavy brush locally a highway and railroad follow the Santa Clara River
called chaparral, which is especially heavy on north valley to the coast. Ranch, oil field, and forestry
slopes. Bigcone-spruce trees grow at higher altitudes roads provide access to most of the area.
in the vicinity of San Fernando Pass. The towns of Newhall and Saugus, both along the
SANTA CLARA RIVER, Southern Pacific railroad, are the chief centers of popu
lation within the mapped area. The Santa Clara River
The Santa Clara River flows from its source on the
valley, much of which is irrigated, supports farms,
north side of the western San Gabriel Mountains to the
orchards, and cattle ranches. Numerous oil fields add
coast south of Ventura. The drainage area upstream
to the economy of the region.
from the water-stage recording station at the U.S.
PHYSIOGRAPHY
Highway 99 bridge 4 miles west of Newhall is about
355 square miles. The largest tributaries are west of The Santa Clara River follows the major structural
Highway 99; they enter the river from the north. depression of the region. The pattern of tributary
These tributaries include Piru, Sespe, and Santa Paula streams and the shapes of the ridges are commonly de
Creeks, whose combined drainage area and discharge termined by the varying resistance to erosion of the
are much greater than that of the main river upstream rocks.
from the mouth of Piru Creek. The Santa Clara River Old erosion surfaces and river terraces are conspic
bed is commonly dry in summer. All its tributaries uous. These may be conveniently divided into two
in the mapped area are intermittent streams. groups: the older, topographically higher surfaces, rem
The average annual discharge of the river for the nants of which have been preserved in scattered local
16-year period from October 1929 to September 1945, ities; and the younger, topographically lower terrace
as measured at the U.S. Highway 99 bridge water-stage surfaces, which are found along the Santa Clara River
recording station, was 19.7 cſs (cubic feet per second). and its tributaries. The high surfaces extend to alti
The maximum discharge measured there during that tudes of more than 3,000 feet on the Santa Susana