Los Angeles County, CA
PACE recently completed the final design and analysis for the channel restoration and improvements along a nearly 3,000-ft reach of Lion Canyon Creek in Los Angeles County. Lion Canyon flows through a steep, scenic canyon that retains many natural features but is also impacted and unstable, and therefore must be stabilized to protect surrounding homes. PACE developed a design that will preserve the natural features of the canyon and creek while stabilizing long-term erosion. The design approach for the improvements involved a series of hydraulic and sediment transport analyses for various development scenarios in order to provide a design to satisfy various potential hydraulic conditions. The channel improvements for the Creek include channel invert stabilization through the installation of soil cement drop structures and grouted rock grade control structures, channel bank stabilization using either soil cement or rock slope protection and a grouted rock high-flow bypass channel section. PACE’s design approach was to identify the segments of the Creek based on the hydraulic conditions, environmental permit requirements, avoidance of oak trees and other physical constraints to determine the appropriate stabilization measure for each segment. Four categories were identified for the channel system: (1) Realigned engineered channel, (2) Stabilized/improved channel in its existing location, (3) Restored natural channel, and (4) a high-flow bypass channel. In the restored channel segment, buried grade control structures were designed to reduce long-term channel bed degradation but were strategically placed to preserve and protect existing oak trees. In the stabilized channel segments, drop structures and rock slope protection were designed to reduce lateral and vertical migration of the channel, while preserving the natural channel bottom and minimizing impacts to jurisdictional areas.