Scientific Investigations Report 2004-5296—ONLINE ONLY

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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

By Michael Land, Peter C. Trenham, Daniel J. Ponti, Eric G. Reichard, John C. Tinsley, Jonathan Warrick, and Robert W. Meyer

Send questions or comments about this report to the author, Michael Land ( 858-637-6868.

This report is available in Portable Document Format (PDF).

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A new park is being considered for the confluence of the Los Angeles River and the Arroyo Seco in Los Angeles County, California. Components of the park development may include creation of a temporary lake on the Los Angeles River, removal of channel lining along part of the Arroyo Seco, restoration of native plants, creation of walking paths, and building of facilities such as a boat ramp and a visitor center. This report, prepared in cooperation with the Mountains Recreation and Conservancy Authority, delineates the geological, hydrological, and biological issues that may have an impact on the park development or result from development at the confluence, and identifies a set a tasks to help address these science issues.

Geologic issues of concern relate to surface faulting, earthquake ground motions, liquefaction, landsliding, and induced seismicity. Hydrologic issues of concern relate to the hydraulics and water quality of both surface water and ground water. Biological issues of concern include colonization-extinction dynamics, wildlife corridors, wildlife reintroduction, non-native species, ecotoxicology, and restoration of local habitat and ecology. Potential tasks include (1) basic data collection and follow-up monitoring, and (2) statistical and probabilistic analyses and simulation modeling of the seismic, hydraulic, and ecological processes that may have the greatest impact on the park. The science issues and associated tasks delineated for the proposed confluence park will also have transfer value for river restoration in other urban settings.






Description of study area

Design features of Confluence Park


Geologic overview of the study area

Geologic Setting

Geologic Units

Geologic Structures

Geological Issues

Surface Faulting

Earthquake Ground Motions



Reservoir-Induced Seismicity


Hydrologic overview of the study area

Hydrological Issues

Surface-water hydraulics

Surface-water quality

Ground-water hydraulics

Ground-water quality


Biologic overview of the study area

Biological setting

Biological monitoring and modeling

Biological Issues

Wildlife Corridors

Wildlife Colonization/Reintroduction

Non-Native and Pest Species


Options for Restoration of Local Habitat and Ecology

Summary and Discussion

References Cited

For more information about USGS water activities in California, visit the USGS California District home page.

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