Topanga Lagoon and Topanga Creek play vital roles in the Santa Monica Mountains watershed.
The Resource Conservation District of the Santa Monica Mountains initiated a long-term project to restore the lagoon and creek systems that had greatly impacted in recent years from land use changes. Major goals included restoring steelhead trout habitat, improving lagoon water quality, and upgrading the creek’s hydraulic performance to better convey floods. Moffatt& Nichol prepared an initial feasibility study that considered the broad range of active hydrologic, hydraulic, sedimentary, and water quality processes as an integrated system. A later study was prepared for developing preliminary design for the project. Parallel activities in support of the habitat restoration work included the planned replacement of Pacific Coast Highway bridge with a longer structure to accommodate the lagoon and improve the fish passage and reconstruction of Topanga Canyon Boulevard with a stabilized roadway. Moffatt& Nichol prepared project study reports for Caltrans review for both.