Los Angeles County Flood Control System

Los Angeles County Flood Control System: An Assessment of Best Management Practices to Mitigate Climate Change Impacts

Project Description:

The Los Angeles Basin is home to over 10 million people and encompasses 1,900 square miles. It includes the Los Angeles River, San Gabriel River, North Santa Monica Bay, South Santa Monica Bay, Dominguez Channel/Los Angeles Harbor, and Ballona Creek watersheds. Many of the Basin’s natural rivers were channelized nearly 100 years ago with the purpose to send flood waters to the ocean as quickly as possible during heavy precipitation events. As a result of development over the past century, much of the basin’s surface has been transformed from pervious natural soils to impervious surfaces such as concrete, asphalt, and buildings. This change has increased flood risk since precipitation that would infiltrate into the ground is now transported into the flood control channels. To account for this increased runoff to precipitation fraction, Los Angeles County Department of Public works has implemented measures known as Best Management Practices (BMPs) requiring developments to infiltrate stormwater onsite to reduce water quantity and improve water quality. In addition to the increased imperviousness of the Basin, recent findings (from previous CEES MS student Brianna Pagàn) project that extreme precipitation events are likely to become about two to six times more frequent in the coming decades (e.g., the current 50-year precipitation event in the Basin is projected to occur on average once every 10-years by 2050). In the proposed study, a hydrologic model called Watershed Management Modeling System (WMMS), developed by the LA County Department of Public Works – LA County Flood Control Division will be implemented to determine the Basin’s resiliency and adaptation requirements to climate change. WMMS simulations will be driven with a large ensemble of high resolution climate model output for the present-day and future climate (1965 to 2050). The climate model ensemble is from the most comprehensive and detailed regional climate modeling efforts to date (run on Titan, which is the fastest supercomputer in the United States). These simulations will determine the capacity of the LA Basin flood control system to accommodate the projected increases in severe precipitation. Furthermore, climate change scenarios testing the efficacy of BMP implementation as an adaptation measure for combating any increases in flood flows as a result of climate change will be performed by varying the perviousness of the Basin. The results of the study will provide policy-makers with essential information required to make informed climate change adaptation decisions for the LA Basin.

Advisor: Jeremy Pal, jpal@lmu.edu
Project Duration: 1.5 to 2 years

Student Duties:

The student's duties will include (but will not be limited to):

  • Perform literature reviews of existing studies
  • Become proficient in the use and application of the hydrologic model WMMS
  • Learn Python and other relevant data analysis tools required to convert the high resolution climate model data for use in WMMS
  • Perform WMMS a large ensemble of climate change scenario and BMP scenario simulations
  • Document findings

Student Background Required:

Student should possess an undergraduate degree in civil engineering, environmental engineering, envirionmental science, or related field, and knowledge of (or desire to learn) a programming language. GIS and Matlab skills are also desirable.