Sea Level Rise Vulnerability Study for the City of Los Angeles – Transportation Assets

The University of Southern California Sea Grant Program completed a Sea Level Rise Vulnerability Study for the City of Los Angeles that summarizes initial research on the potential impacts of sea-level rise on Los Angeles’s coastal and shoreline assets, including the Port of Los Angeles, the Pacific Coast Highway and other significant coastal roads. The study identifies the Los Angeles (LA) communities and infrastructure most threatened, and offers a suite of adaptation measures including several specific recommendations for safeguarding transportation assets.

A variety of coastal roads and critical infrastructure in the LA area will be increasingly vulnerable to flooding, inundation, erosion and groundwater inflow. The study recommends a broad range of adaptation strategies to facilitate increased resilience of coastal infrastructure to sea-level rise and other impacts. This “Matrix of Potential Coastal Adaptation Strategies” describes specific techniques related to the following general adaptive strategies: avoiding coastal hazards, moving development away from hazards or hazards away from development, creating barriers between hazards and development, and flood-proofing.

For example, to avoid hazards, the City could utilize land acquisition tools such as fee simple acquisition, conservation easements, and transfer development credits. To move development away from hazards, the City could adopt a number of measures including land acquisition tools, managed retreat, setbacks, rolling easements, and elevation. The recommended strategies also include techniques involving natural hazard barriers, such as maintaining sand and beaches, and hard armoring, such as using various types of seawalls. For each adaptation technique identified, the Matrix also identifies the adaptive capacity, associated spatial and temporal scales, the responsible party or agency, and approximate implementation costs. 

The study also provides a detailed vulnerability assessment of LA’s coastal infrastructure, to which the adaptation strategies described in the study may later be applied. The results of the vulnerability assessment are organized by type of city “asset” with descriptions of current observed vulnerabilities and anticipated future vulnerability to sea-level rise, based on a USGS exposure analysis. The vulnerability of each asset is described in terms of asset sensitivity (the degree of impairment by sea-level rise), adaptive capacity (its ability to adjust in response and still maintain functions), and consequences of asset impairment. The assessment also contains an estimate of replacement value, if available, for each asset.  

The coastal transportation infrastructure assessed in the study includes: various assets associated with the Port of Los Angeles (Port), roads in the Venice and San Pedro/Harbor areas, and the Pacific Coast Highway in the Pacific Palisades area.

The Port, which is one of the busiest in the world, contains assets that are already highly sensitive to flooding and inundation during high tide events and severe storms. The study assessed vulnerabilities to a variety of Port assets: container terminals, electrical infrastructure, breakwater, marinas, and various transportation assets such as roads, rails, and grade separations that help move cargo to and from the Port. The Port’s transportation infrastructure specifically will be sensitive in the future to storm-related flooding and daily tidal flooding, erosion, and groundwater interaction.  However, the adaptive capacity of the Port’s transportation infrastructure is relatively high because roads can be re-built relatively quickly.  As with other Port assets, the consequences of full impairment of transportation infrastructure would be very high; the Port-related transportation assets are estimated to have a $1 billion replacement value.

The City’s coastal roads in all areas assessed by the study are currently vulnerable to flooding, inundation, erosion, and groundwater, and will become more sensitive to these impacts as sea levels rise. The study found that impairment of these roads could have high social consequences by displacing residents and potentially putting access to transportation and emergency services at risk. Additionally, impairment of roads in the Harbor area could have significant economic consequences because it could cut off access to the Port. Roads in all areas are estimated to have only a medium level of adaptive capacity.

To complete the vulnerability assessment, the study used a USGS model that incorporates the impacts of sea-level rise as well as impacts related to coastal storms.  The model was developed based on a January 2010 storm in the LA region, which was considered to be a moderately severe 10-year storm.  Sea level in the LA region is projected to rise 0.1 - 0.6 m by 2050 and 0.4- 1.7 m by 2100. The model combined these sea-level rise projections with the tide, wave, and wind conditions from the 2010 storm to project potential future flooding under various sea-level rise scenarios. These flooding projections were then used to assess vulnerabilities of the City’s infrastructure so that City officials can prioritize improvements. In the future, additional data may be applied to estimate vulnerabilities to flooding from more severe storms, such as 100-year events.

The study was the first step of a larger collaborative process to research and plan for the impacts of climate change in LA. The City engaged with USC Sea Grant Program, the Los Angeles Regional Collaborative for Climate Action and Sustainability (LARC), and ICLEI - Local Governments for Sustainability to research impacts and prepare this study. The overarching adaptation planning effort was launched in December 2011 and has involved a range of stakeholders. In addition to the assessment of infrastructure vulnerabilities, the study also contained an assessment of social and ecological vulnerabilities.

 

This Adaptation Clearinghouse entry was prepared with support from the Federal Highway Administration. This entry was last updated on October 31, 2015.

 

Publication Date: December 2013

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