Geoscience Reference
In-Depth Information
away from the rising muddy waters that covered their desks. Following a
sleepless night listening to the roar of a small river, the children went outside
in the morning to a scene of devastation: entire houses and the remains of
houses were strewn haphazardly across the landscape. Farther downstream,
the city of Anaheim lay beneath i ve feet of water, and residents had no choice
but to spend the night on their root ops. h e unusually wet conditions of
that winter of 1938 extended into southern Arizona, where precipitation
was 74 percent above normal and the Gila, Salt, and Verde rivers all l ooded
their banks.
h is scenario was repeated two decades later when a period of drought in
the 1950s was followed by massive l oods in 1955. h e central Sierra Nevada
and southern San Francisco Bay regions of California were particularly
hard-hit. Record rainfall in December of that year fell across the state, caus-
ing massive l ows on Central Valley rivers. In Southern California, Orange
County's biggest natural disaster occurred as warm rain melted snow in the
San Bernardino Mountains, causing catastrophic l ooding along the Santa
Ana River. Once again a state of disaster was declared for all of California.
Devastating l oods are an inevitable characteristic of the climate in
the West, a topic we will discuss in future chapters. Despite a century of
elaborate engineering that has attempted to tame and control the l ow of
water in the region, l oods continue to inundate the western United States
with a frequency that seems to have increased. Yet the l oods that have been
witnessed and recorded in the West over the past 100 or so years represent a
very small sampling of the deluges and l oods that are an integral part of the
region's hydrology. Climate researchers are i nding increasing evidence for
much larger events that have occurred with alarming regularity over the past
several millennia.
It must be borne in mind, however, that, despite their destructive poten-
tial, l oods are a natural part of both the hydrologic and the ecological sys-
tems of the West. Floodwaters carry nutrients and organic material that are
deposited onto the surrounding l oodplains, producing fertile soils. h ese
soils have made California one of the most important agricultural centers in
the world, generating $30 billion per year. More than half of the fruits, nuts,
and vegetables consumed in the United States are grown on some 87,500
farms in California's Central Valley.
Nevertheless, residents in California and other regions of the American
West continue to face risks from catastrophic l ooding as they place them-
selves directly in the path of l oodwaters, building their homes on l oodplains
