One-percent flood protection improvements were constructed on Calabazas Creek from San Francisco Bay to Miller Avenue between 1994 and 1999. Upon completion of these improvements, two revegetation projects were implemented in order to satisfy mitigation requirements.
Following the completion of the projects, the water district began preparation of the Letter of Map Revision (LOMR) application for submittal to the Federal Emergency Management Agency (FEMA) to revise the Flood Insurance rate map of Calabazas Creek. As part of the draft LOMR application, hydraulic analyses of the improvements were performed using an “as-built” hydraulic model developed in late 2002. The analysis indicated that the creek did not have the capacity to contain a one-percent flood in some locations. In addition, high flows have severely eroded the creek bottom between Miller Avenue and Lawrence Expressway and threaten to undermine the concrete footing supporting the concrete-lined and gabion channel sides’ slopes. Staff obtained a special permit from the Department of Fish and Game in summer 2004 to conduct emergency repairs to stabilize some sections of this reach prior to the wet season.
The Calabazas Creek Capacity Improvement Project was initiated in the fall of 2004 to address these issues. The Calabazas Creek Capacity Improvement Project will result in the removal of 2,250 parcels from the one-percent floodplain and provide a permanent solution to resolve the significant invert erosion problem along the channel downstream of Miller Avenue.