Maple Canyon Restoration & Flood | 2025 Top Projects

Combining engineering, environmental stewardship and community collaboration, the Maple Canyon Restoration and Flood Mitigation Project implemented a comprehensive watershed-scale solution to severe flooding.  

Maple Canyon is a natural drainage corridor that receives runoff from more than 100 acres through 16 storm drain systems. It also lies within a Federal Emergency Management Agency (FEMA) Zone A floodplain and has historically been subject to severe flooding, erosion and infrastructure failure resulting from uncontrolled urban runoff and undersized stormwater systems.  

This project, partially funded by a grant from the U.S. Department of Economic Development Administration, emphasizes ecological restoration, water quality improvements and flood hazard mitigation while maintaining the natural scape of the canyon, in addition to preserving community recreational space.  

Project phases 

The first phase of the project entailed replacing 16 failing storm drain systems and installing a 48-inch storm drain. Outfalls were also realigned and fitted with modified energy dissipators.  

The second phase addressed channel degradation of approximately 2,800 linear feet, through installing 28 grade-control structures; targeted riprap stabilization; and planted native vegetation to retain sediment and restore hydrological and hydraulic functions.  

The upstream watershed, originally developed in the 1900s, now has a restored channel with a reduced effective slope and reduces flow velocity, increases retention time and functions as a natural system management practice (NSMP) for those 16 storm drains. Overall, the restoration significantly reduces sediment transport and sediment-laden flows to the downstream neighborhood, and subsequently, San Diego Bay.  

The project team sought to use a combination of traditional infrastructure with sustainable and nature-based solutions, such as biodegradable erosion control fabrics, low-impact construction techniques, and durable, climate-resilient design. Additionally, the project team included the public by working with various resource agencies such as USACE, neighborhood groups and stakeholders. The team conducted educational outreach to increase community awareness of stormwater quality, flood risks, and the value of ecological restoration. 

After finding the root cause of the flooding, the team found working in a dense urban environment, where it was important to keep the natural aesthetics of the canyon in place, a challenge. The community was opposed to the installation of large concrete energy dissipators, as they were visually intrusive. Instead, the team designed the storm drain system so that the downstream 20 feet includes a bend within a cleanout structure and a much flatter slope of 0.5 to 1%. That design allowed the team to use riprap energy dissipators instead of concrete structures. To further match the natural environment, the team used colorized concrete to match the canyon, and natural rounded boulders were used in place of angular riprap.  

In an urbanized area like San Diego, natural canyons close to a downtown scene are rare, so protecting Maple Canyon was an important effort. The canyon is a hotspot for the community to enjoy walks and hikes, and early results show that the project will be a success. As of July 2025, all channel improvements were completed, and 13 out of 17 storm drains were installed. Construction completion is expected by the end of 2025.