Los Angeles Basin Stormwater Conservation Study: Task 5 Infrastructure & Operations Concepts Report

The Los Angeles Basin Stormwater Conservation Study (LA Basin Study) is a collaborative partnership between the Los Angeles County Flood Control District (LACFCD) and the U.S. Department of the Interior, Bureau of Reclamation (Reclamation). The purpose of the LA Basin Study is to investigate long-range water conservation and flood risk management impacts caused by projected changes in the climate and population in the Los Angeles region. The LA Basin Study provides recommendations for potential modifications and changes to the existing regional stormwater capture system, as well as for the development of new facilities and practices, which could help to resolve future water supply and flood risk management issues. The stormwater capture concepts and alternatives developed within this report will inform the Task 6 – Trade-Off Analysis & Opportunities report of the LA Basin Study. 

The objective of Task 5, Infrastructure and Operations Concepts, is to identify and develop both structural and nonstructural (i.e., plans and policies) concepts to manage stormwater under projected climate conditions for the Los Angeles Basin watersheds, which include: Los Angeles River, San Gabriel River, South Santa Monica Bay, North Santa Monica Bay, Ballona Creek, Malibu Creek, and Dominguez Channel/Los Angeles Harbor watersheds (Basin Study Watersheds). The efforts and results previously completed for Task 2 – Water Supply & Water Demand Projections, Task 3 – Downscaled Climate Change & Hydrologic Modeling, and Task 4 – Existing Infrastructure Response & Operations Guidelines Analysis serve as the foundation for Task 5. The major tasks and subtasks of Task 5 include: 

• Concept Development 

– Identify a range of opportunities and options using stakeholder input 

– Determine preliminary concepts for further evaluation 

• Technical Analysis of Concepts 

– Assess structural and nonstructural concepts pertaining to dams, spreading grounds, flood control channels, decentralized storage, infiltration, reuse facilities, debris basins, and other concepts 

– Develop and apply concept selection criteria 

• Appraisal-Level Analysis 

– Evaluate selected concepts for future system reliability, efficiency, and effectiveness 

In addition to any new stormwater conservation concepts that are developed, the existing facilities from the Task 4 analysis were considered for enhancement.

The Watershed Management Modeling System (WMMS), which has served as the primary hydrologic model throughout the LA Basin Study, continued to be the preferred tool and was also used for Task 5. Hydrologic simulations were conducted to analyze the potential water conservation and flood risk mitigation benefit for the various project concepts. For the future period, water years 2012 through 2095, four climate projections (Low 1, Low 2, Mid 2, and High 1) from Task 4 were used in the simulations. 

Click here for USBR’s Task 5 Appendices index:

Appendix A – Infrastructure and Operations Concepts (Excel)

Appendix B – Local Stormwater Capture (PDF)

 Appendix C – Modeling Approach and Solutions (PDF)

Appendix D – Local Management Cost (Excel)

Appendix D – Regional 1 Cost (Excel)

Appendix D – Regional 2 Cost (Excel)

Appendix D – Regional 3 Cost (Excel)

Appendix D – Storage 3 Cost (Excel)

Appendix E – LACFCD Dam Hydrology and Cost Estimates (PDF)