Lion Canyon Flood Control and Channel Restoration

Los Angeles County, CA

PACE completed the final design and analysis for the channel restoration and improvements along a nearly 3,000-foot 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. 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 that would 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 classify 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:

• Realigned engineered channel
• Stabilized/improved channel in its existing location
• Restored natural channel
• High flow bypass channel

In the restored channel segment, buried grade control structures reduce long-term channel bed degradation and 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. PACE was able to balance the various goals and constraints of the project to produce a design that both restored and stabilized the channel system.

Key Features:

• Hydraulic and sediment transport analyses
• Large drainage watershed
• Oak tree protection
• Channel realignment
• Stabilized / improved channel in existing location
• Restored natural channel
• Design approach to minimize impacts to jurisdictional areas
• County plan processing and approvals