San Lorenzo River

For the river of the same name in the eastern Mexico, see San Lorenzo River (Mexico).

The San Lorenzo River in Henry Cowell Redwoods State Park

The San Lorenzo River drains a large watershed in Santa Cruz County, California. The headwaters originate in the Santa Cruz Mountains (in Castle Rock State Park) at an elevation of 2500 feet and flow approximately 30 miles through the San Lorenzo Valley before emptying into the Pacific Ocean at Monterey Bay. The San Lorenzo River was once one of the most popular steelhead and coho salmon rivers on the Central Coast of California. In an effort to save this fishery, it has been designated a "catch and release" stream since 1984 by the California Department of Fish and Game. In 1960, it was estimated that there were more than 30,000 fish living in this river, but a decade later the population had been reduced to 1000. The Branciforte Creek watershed is a major sub-basin of the San Lorenzo catchment-basin.

Geology

Underlying rock strata in the San Lorenzo River basin include Lompico Sandstone and Vaqueros Sandstone.

Flooding and water pollution

Following devastating floods in December 1955, the Army Corps of Engineers put in flood control measures that ultimately failed. Both the city and the Corps blamed one another, but the river was dying. The floods of 1982 demonstrated that the early flood control efforts were a failure. A restoration project has been underway since 1985. Recent counts of fish show the population is slowly rising to approximately 3000. Tidal influence wanes between the Broadway and Soquel Avenue bridges in the city of Santa Cruz, where some sand bars are visible.

As early as the 1970s Santa Cruz County began to create a hydrology transport model of the San Lorenzo River, retaining a group of scientists and engineers from Earth Metrics Inc., who were to create the first mathematical model of the river, with the objective of analyzing bedload transport and downstream sedimentation. The model was also used to predict transport of nitrates and other water pollution, and would be eventually used to study a variety of different land management and flood control strategies.

Another problem for the river and its habitat is the water pollution from the city of Santa Cruz and the upstream communities of Felton, Ben Lomond, Brookdale, and Boulder Creek. The San Lorenzo River Watershed has the highest septic system density of any comparable area in the state of California. Bacteria levels were dangerously high in the 1980s but have improved over the last few years. Still the bacteria levels in many areas barely meet the standards for safe swimming, and the nitrate levels are extremely high and are a threat to the drinking water supply for much of the county. .

Scenic and historic elements

Much of the upper reaches of this watershed are quite beautiful in their natural forest setting, while the lower reach is accessible to the large population of Santa Cruz. In 1987 the city of Santa Cruz retained ROMA, a San Francisco design firm, to develop a design concept plan for incorporating the natural elements of the river into the urban design fabric of the city. The plan led to creation of pedestrian walkways, picnic areas and view opportunities along the lower populated stretch of the river. The plan called for creation of a continuous forest to be established on the upper banks of Valley Oak, Buckeye, Willow and other trees with seasonal foliage.

One notably scenic reach between the Riverside Avenue and Broadway bridges may be the most visually prominent and attractive parts of the river. Here the river bends skirting the base of Beach Hill, a historic neighborhood and noteworthy topographic element of the city of Santa Cruz. This reach is visible from many parts of the city and give a sense of steepness and enclosure within the channel. The west bank had been the site of a wooden boardwalk, now washed away by erosion.

Bibliography

• C. Michael hogan, David Crimp, Leda Patmore, et al., Bedload Transport Computer Model for the San Lorenzo River, prepared for Santa Cruz County by Earth Metrics Inc., Palo Alto, Ca. (1977)

• ROMA, San Lorenzo River Design Concept Plan, prepared for the city of Santa Cruz, June, 1987

See also

• List of California rivers
• Lompico Formation