South Coast

Assembly Bill No. 2108, Chapter 347, An act to add Sections 189.7 and 13149.2 to the Water Code, relating to water

State of California Office of Legislative Counsel | September 16th, 2022

Assessing and communicating the impacts of climate change on the Southern California coast

California Natural Resources Agency (CNRA) | August 27th, 2018

 Over the course of this and the next century, the combination of rising sea levels, severe storms, and coastal erosion will threaten the sustainability of coastal commu

 Over the course of this and the next century, the combination of rising sea levels, severe storms, and coastal erosion will threaten the sustainability of coastal communities, development, and ecosystems as we currently know them. To clearly identify coastal vulnerabilities and develop appropriate adaptation strategies for projected increased levels of coastal flooding and erosion, coastal managers need user-friendly planning tools based on the best available climate and coastal science. In anticipation of these climate change impacts, many communities are in the early stages of climate change adaptation planning but lack the scientific information and tools to adequately address the potential impacts. In collaboration with leading scientists worldwide, the USGS designed the Coastal Storm Modeling System (CoSMoS) to assess the coastal impacts of climate change for the California coast, including the combination of sea level rise, storms, and coastal change. In this project, we directly address the needs of coastal resource managers in Southern California by integrating a vast range of global climate change projections and translate that information using sophisticated physical process models into planning-scale physical, ecological, and economic exposure, shoreline change, and impact assessments, all delivered in two simple, user-friendly, online tools. Our results show that by the end of the 21st century, over 250,000 residents and nearly $40 billion in building value across Southern California could be exposed to coastal flooding from storms, sea level rise, and coastal change. Results for the other major population center in California (the greater San Francisco Bay Area) are also available but not explicitly discussed in this report. Together, CoSMoS has now assessed the exposure of 95% of the 26 million coastal residents of the State (17 million in Southern California) 

Assessing Early Implementation of Urban Water Use Efficiency Requirements

Legislative Analyst's Office (LAO) | January 4th, 2024

Legislation approved in 2018 established a long‑term urban water use efficiency framework to “Make Conservation a California Way of Life.” This framework—which is

Legislation approved in 2018 established a long‑term urban water use efficiency framework to “Make Conservation a California Way of Life.” This framework—which is one component of the state’s overall water management strategy—creates new requirements for about 405 urban retail water suppliers that supply water to nearly 95 percent of state residents. This report responds to a requirement contained in the 2018 legislation for our office to assess implementation of the framework. (Our report is not able to address every aspect requested in the legislation due to framework implementation delays.)

Assessing risk of groundwater pollution exposure from sea level rise in California

Publisher not available | June 12th, 2025

Sea level rise (SLR) will cause a groundwater table rise in coastal aquifers, and this can trigger exposure to toxic chemicals via direct contact with contaminated water

Sea level rise (SLR) will cause a groundwater table rise in coastal aquifers, and this can trigger exposure to toxic chemicals via direct contact with contaminated water or through vapor intrusion. This study presents deep learning- and explainable artificial intelligence (XAI) models to assess risk of polluted groundwater exposure due to SLR in California. Our method quantifies risk based on (1) SLR-related groundwater rise projections and (2) a prioritization of 2296 hazardous sites according to a geochemical indexing algorithm applied to groundwater data from the California State Water Resources Control Board. Our results indicate that nearly half a million people in California may be potentially exposed to marginal or poor groundwater by the end of the century. We show that feature collinearity renders numerous indicators on socioeconomics, demography, health and environment as dependent- and thus insignificant risk predictors. Our XAI models furthermore indicate that features on total population and features related to demographics (households of color and low income) and pollution source (proximity to wastewater dischargers) exert strongest controls on risk. However performance differences between randomly- and spatially cross-validated models highlight generalization challenges due to spatial autocorrelation. While the former model yields better results for California-specific analysis, only the latter model should be applied for unbiased risk assessments in other coastal regions.

Assessing the Health of Southern California Streams

California State Water Resources Control Board (SWRCB) | April 14th, 2011

There are over 4,200 miles of perennial streams in the coastal watersheds of Southern California. Effective protection and management of these resources require an unders

There are over 4,200 miles of perennial streams in the coastal watersheds of Southern California. Effective protection and management of these resources require an understanding of their overall health (or condition) and the major stressors that affect their condition. In 2009, major municipalities and counties and their state/federal regulatory counterparts got together to conduct the first comprehensive assessment of the health of streams in Southern California. The first year of a five year program was a great success: Over 120 sites were sampled and analyzed for biological community characteristics, chemical parameters, aquatic toxicity, and physical habitat condition.

Assessment of the condition of Southern California depressional wetlands

California State Water Resources Control Board (SWRCB) | April 18th, 2016

Application of Macroinvertebrate, Diatom and Overall Condition Indices for Assessing Southern California Depressional Wetlands Depressional wetlands are the most abund

Application of Macroinvertebrate, Diatom and Overall Condition Indices for Assessing Southern California Depressional Wetlands Depressional wetlands are the most abundant, yet most threatened wetland type in California. Despite their relatively ubiquitous nature, they are poorly characterized, and unlike streams, they are not subject to any systematic monitoring and assessment. Consequently, decisions regarding protection, restoration, and management are usually made without the benefit of any regional context of condition, knowledge of predominant stressors, or rigorous documentation of reference conditions. Ambient monitoring of depressional wetlands can be a critical tool to inform management decisions. However, before such a program can be implemented, biological assessment tools must be evaluated, validated, and modified (if necessary). Once these steps are completed, preliminary assessments can begin to provide answers to critical questions regarding wetland condition and key stressors. The goals of this study were 1) to adapt three readily available bioassessment tools for assessing depressional wetland condition in southern California. This included a statewide rapid assessment method that had been calibrated and validated for depressional wetlands (CRAM) but had no prior use in a regional assessment program, a macroinvertebrate index developed for depressional wetlands from a different geography (northern California), and a benthic diatom index which had been developed for a different habitat type (wadeable streams). 2) To evaluate the regional condition of depressional wetlands in southern California using the adapted tools. 3) To evaluate the relationship between condition and stress by sampling both local stressors (intensity of direct wetland use, water chemistry and sediment toxicity) and landscape stressors (adjacent land use, flow diversions, road density). Once achieved, these goals should establish the foundation for developing a robust and ongoing depressional wetland ambient monitoring program. This study included perennial or seasonal depressional wetlands as defined by Brinson (1993) located within the boundaries of the Los Angeles, Santa Ana, and San Diego Regional Water Quality Control Boards. Wetlands were not considered for this study if they were concrete-lined, marine-influenced, treatment ponds, livestock wastewater ponds, riverine (i.e. dominated by riverine hydrology), dry (i.e. not seasonal), or on-military bases (due to access issues). Vernal pools were also excluded; while these are considered a subclass of depressional wetlands, they represent a distinct wetland habitat that is typically evaluated with specific methods. Furthermore, given their rarity and ecological sensitivity they are often assessed through focused studies.

Assessment of the Economic Impacts of California's Drought on Urban Areas

Rand Corporation (Rand) | September 6th, 1993

Associations between PFAS in public water system drinking water and serum among Southern California adults

Nature Portfolio (Springer Nature) | October 30th, 2025

The CARE (California Regional Exposure) biomonitoring study measured PFAS in serum of Southern and Eastern California adults between 2018 and 2020. Participant addresses

The CARE (California Regional Exposure) biomonitoring study measured PFAS in serum of Southern and Eastern California adults between 2018 and 2020. Participant addresses were geocoded and geographically assigned to public water systems (PWS). Between 2019 and 2022, the California State Water Resources Control Board issued investigative PFAS monitoring orders to potentially impacted PWS, focusing primarily on source wells. PFAS detections above the required reporting limit (4 ng/L for PFAS included in the final analysis) were used to assess associations with serum PFAS levels.

Assumptions and Estimates for California Water Plan Update 2023 (Draft)

California Department of Water Resources (DWR) | October 14th, 2022

The draft Assumptions and Estimates for California Water Plan Update 2023 (draft A&E Report) describes key assumptions and estimates, data and data sources; improvements

The draft Assumptions and Estimates for California Water Plan Update 2023 (draft A&E Report) describes key assumptions and estimates, data and data sources; improvements to analytical tools, methods, and approaches; and the supporting documents and companion State plans being used to prepare California Water Plan Update 2023 (Update 2023), State government’s strategic plan for managing and developing water resources for sustainability and resilience. The draft A&E Report cites the statutory requirements for the California Water Plan (Water Plan), key legislative and policy drivers, assumptions, and estimates related to water data portfolios, future scenarios, water accounting, watershed resilience planning, and equity in water resource management. Also discussed are resource management strategies, the alignment of integrated watershed programs and plans, and integration and alignment of State plans.

Autumn precipitation: the competition with Santa Ana winds in determining fire outcomes in southern California

International Journal of Wildland Fire (CSIRO Publishing) | October 25th, 2022

California’s South Coast has experienced peak burned area in autumn. Following typically dry, warm summers, precipitation events and Santa Ana winds (SAWs) each occur w

California’s South Coast has experienced peak burned area in autumn. Following typically dry, warm summers, precipitation events and Santa Ana winds (SAWs) each occur with increasing frequency from autumn to winter and may affect fire outcomes. Aims. We investigate historical records to understand how these counteracting influences have affected fires. Methods. We defined autumn precipitation onset as the first 3 days when precipitation ≥8.5 mm, and assessed how onset timing and SAWs were associated with frequency of ≥100 ha fires and area burned during 1948–2018. Key results. Timing of autumn precipitation onset had negligible trend but varied considerably from year to year. A total of 90% of area burned in autumn through winter occurred from fires started before onset. Early onset autumns experienced considerably fewer fires and area burned than late onset autumns. SAWs were involved in many of the large fires before onset and nearly all of the lesser number after onset. Conclusions. Risk of large fires is reduced after autumn precipitation onset, but may resurge during SAWs, which provide high risk weather required to generate a large fire. Implications. During autumn before onset, and particularly during late onset autumns, high levels of preparation and vigilance are needed to avoid great fire impacts.