Los Angeles Basin Stormwater Conservation Study

Date / Time:
Wednesday, Sep 14 2:30pm to 3:00pm
Location:
Bay View
Track / Session:
Stormwater as a Resource / Los Angeles County (Part 2)
Description/Abstract: 

The Los Angeles Basin Stormwater Conservation Study assessed the region’s major water conservation and flood risk management infrastructure to help prepare for future effects that may impact water supply, such as changes to climate and population. The study is a long-range planning effort out to 2095 that evaluated potential impacts to existing facilities as well as assessed new stormwater capture concepts to increase the resiliency of local water supplies under an uncertain future. The study covered over 2,000 square miles and included the Los Angeles and San Gabriel Rivers, Santa Monica Bay, Ballona Creek, Malibu Creek, and Dominguez Channel/Los Angeles Harbor watersheds.
The purpose of the presentation is to describe the tools used and key findings of the LA Basin Study. The tools used were down-scaled global climate models, the Watershed Management Modeling System (WMMS), and best available literature on the costs and benefits of multi-benefit stormwater projects. The main topics to be covered are the development of localized climate projections for the study area, the modeling of various stormwater capture concepts for climate adaptation, and the ranking of these concepts based upon an analysis of economic and social benefits and costs.
The LA Basin Study identified that a diverse portfolio of stormwater capture options are needed for this region to become climate resilient. The stormwater concepts range from small- to large-scale projects and are categorized into 4 main groups of solutions: 1) Local, 2) Regional, 3) Storage, and 4) Management. Local solutions include small recharge basins throughout the study area, widespread low impact development (LID) implemented on a portion of urban parcels, and green streets. Regional solutions encompass new centralized infiltration basins, in-channel infiltration and an alternative design infiltration basin. Storage solutions utilize pneumatic spillway gates or new operational guidelines to increase stormwater storage at dams and debris basins. Management solutions consist of plans, policies and partnerships to enhance stormwater capture and modeled the effect of increasing LID implementation and green streets through collaboration and improved stormwater policies. This group also assessed floodplain reclamation concepts for restoring portions of the channelized waterways.
The LA Basin Study took a broad look across multiple watersheds, the types of projects that are possible, and the associated stormwater conservation benefits. The study also utilized extensive input from the public and other stakeholders to garner input and develop new concepts to adapt to climate change. Therefore, the methodology used in the LA Basin Study can be a valuable tool in other parts of the state.
The presentation is particularly suited for the 2016 conference theme because it tracks stormwater from its source as precipitation over the LA Basin, to urban runoff, to capture and use as a valuable resource. The study is especially innovative because it includes the effects of climate change and carries the analysis beyond dollars per acre-feet to a quantitative and qualitative analysis of benefits of the different project groups in a stakeholder driven trade-off analysis.
To increase audience participation, the presentation will be interactive and use a cellphone app with questions for the audience members vote on.

Primary Speaker:
Lee Alexanderson, Los Angeles County
Lee Alexanderson is an Associate Civil Engineer for the County of Los Angeles Department of Public Works and works in the Integrated Planning Section. He joined the Department in 2008 and has exclusively worked within the Water Resources Branch. His experiences have ranged from the daily operations of the County of Los Angeles’ flood control and water conservation system, disaster recovery from wildfires and debris flows, to the development of multi-benefit projects. Most recently, he has been assisting the Department prepare for climate change impacts on its infrastructure as well as on its operations and maintenance.
Supporting Speaker 1:
Kathleen Higgins, CH2M