The River Project engaged in a comprehensive study of the Tujunga Wash, to address planning for ecological rehabilitation and water resource enhancement projects within this once dynamic, formerly alluvial reach of the Los Angeles River system.
The first phase of this effort, funded by the California Coastal Conservancy, was the creation of a computer-based hydrodynamic model of the system using existing hydrologic, hydraulic and other data available from the Army Corps of Engineers and Los Angeles County. This model has predicted the effects of potential physical changes to parts of the system, including the effects of proposed changes to flood management issues.
The model was then used to test some alternatives that were put forward in partnership with the US Army Corps of Engineers, the County Dept. of Public Works and the Dept. of Water and Power. The Army Corps subsequently approved and adopted our model for their own use.
In addition to the model, we developed a planning framework that included the historical context for today's situation and proposals for change, together with evaluation criteria and five major design concepts or strategies. The strategies developed – including dam retrofits, modification to dam operations, optimization of the spreading grounds, using the gravel pits for water detention - are now being carried forward by the responsible agencies.
The most severe technical criterion is the need to reduce the high flood flow velocities. The greatest opportunity is in the potential to significantly increase groundwater recharge. The strategies developed — including potential modification to dam operations, retrofit of the spreading grounds, using the gravel pits for water storage — may provide opportunities for system modification either as "stand-alone" concepts or in combination.
This study enabled the second phase of the effort - the broad-based consensus-driven Watershed Management Plan process to facilitate research, education and planning for revitalization of the entire Tujunga Wash subwatershed. The study forms the basis for our ongoing efforts in the watershed, including Water LA.