Atmospheric rivers drive flood damages in the western United States

American Association for the Advancement of Science (AAAS) | December 4th, 2019

Atmospheric rivers (ARs) are extratropical storms that produce extreme precipitation on the west coasts of the world’s major landmasses. In the United States, ARs caus

Atmospheric rivers (ARs) are extratropical storms that produce extreme precipitation on the west coasts of the world’s major landmasses. In the United States, ARs cause significant flooding, yet their economic impacts have not been quantified. Here, using 40 years of data from the National Flood Insurance Program, we show that ARs are the primary drivers of flood damages in the western United States. Using a recently developed AR scale, which varies from category 1 to 5, we find that flood damages increase exponentially with AR intensity and duration: Each increase in category corresponds to a roughly 10-fold increase in damages. Category 4 and 5 ARs cause median damages in the tens and hundreds of millions of dollars, respectively. Rising population, increased development, and climate change are expected to worsen the risk of AR-driven flood damage in future decades.

Building water resilience in the face of cascading wildfire risks

American Association for the Advancement of Science (AAAS) | September 15th, 2023

California against the sea

Los Angeles Times | July 7th, 2019

THE CALIFORNIA COAST GREW AND PROSPERED during a remarkable moment in history when the sea was at its tamest. But the mighty Pacific, unbeknownst to all, was nearing i

THE CALIFORNIA COAST GREW AND PROSPERED during a remarkable moment in history when the sea was at its tamest. But the mighty Pacific, unbeknownst to all, was nearing its final years of a calm but unusual cycle that had lulled dreaming settlers into a false sense of endless summer. Elsewhere, Miami has been drowning, Louisiana shrinking, North Carolina’s beaches disappearing like a time lapse with no ending. While other regions grappled with destructive waves and rising seas, the West Coast for decades was spared by a rare confluence of favorable winds and cooler water. This “sea level rise suppression,” as scientists call it, went largely undetected. Blinded from the consequences of a warming planet, Californians kept building right to the water’s edge. But lines in the sand are meant to shift. In the last 100 years, the sea rose less than 9 inches in California. By the end of this century, the surge could be greater than 9 feet.

Causes of accelerated High-Tide Flooding in the U.S. since 1950

Nature Portfolio (Springer Nature) | December 15th, 2023

Central Coast Summary Report - California's Fourth Climate Change Assessment

California Energy Commission (CEC) | September 28th, 2018

The Central Coast Region is notable for its extensive natural ecosystems, many of which will be impacted by climate change. Hardwood forests, scrublands, and herbaceous

The Central Coast Region is notable for its extensive natural ecosystems, many of which will be impacted by climate change. Hardwood forests, scrublands, and herbaceous grasslands comprise most of its land cover, with significantly less intensive agriculture and small-to medium-sized cities in the region. There is a strong demand for development in rural areas and agriculture is being developed on lands formerly supporting grazing or natural vegetation. The region continues to reflect an economic and social disconnect between prosperous coastal communities and agricultural areas with many low-income farm workers, inequalities that may result in disadvantaged groups suffering disproportionately from the impacts of climate change. The counties included in this report are Santa Barbara, San Luis Obispo, Monterey, San Benito, and Santa Cruz, with some information for the northern part of Ventura County.

Central Valley Flood Protection Plan 2022 (draft)

California Department of Water Resources (DWR) | April 21st, 2022

The Central Valley Flood Protection Plan (CVFPP) describes a programmatic vision for improving flood risk management throughout the Central Valley. Prepared by the Calif

The Central Valley Flood Protection Plan (CVFPP) describes a programmatic vision for improving flood risk management throughout the Central Valley. Prepared by the California Department of Water Resources (DWR) in accordance with the Central Valley Flood Protection Act of 2008 (Act) and adopted by the Central Valley Flood Protection Board (CVFPB) in June 2012, the CVFPP guides the State’s participation in managing flood risk in areas protected by the State Plan of Flood Control (SPFC). The Public Draft 2022 CVFPP Update is the second update required every five years by the Act. The CVFPP recommends actions and policies informed by engagement with stakeholders and partners and prioritizes investments over a 30-year horizon. Click here for the comment form, supporting documents, and DWR links.

Central Valley Flood Protection Plan Update 2017

California Department of Water Resources (DWR) | August 29th, 2017

The Central Valley Flood Protection Plan (CVFPP) has guided the State’s participation in managing flood risk in areas protected by the State Plan of Flood Control (SPFC

The Central Valley Flood Protection Plan (CVFPP) has guided the State’s participation in managing flood risk in areas protected by the State Plan of Flood Control (SPFC) since the plan’s adoption pursuant to the Central Valley Flood Protection Act of 2008 in 2012. A strategic, long-range plan, the CVFPP and its updates describe a programmatic vision for flood system improvements over time in accordance with the requirements of the 2008 Act. The CVFPP was prepared by the Department of Water Resources (DWR) and adopted by Central Valley Flood Protection Board (CVFPB) through Resolution 2012-25. As conceived by the legislature, the CVFPP is updated every 5 years, beginning in 2017.

Challenges Facing the Sacramento–San Joaquin Delta: Complex, Chaotic, or Simply Cantankerous?

University of California, Davis (UC Davis) | September 17th, 2015

Freshwater is a scarce and precious resource in California; its overall value is being made clear by the current severe drought. The Sacramento–San Joaquin Delta is a c

Freshwater is a scarce and precious resource in California; its overall value is being made clear by the current severe drought. The Sacramento–San Joaquin Delta is a critical node in a complex water supply system that extends throughout much of the western U.S. wherein demand is exceeding supply. The Delta also underpins a major component of the U.S. economy, helps feed a substantial part of the country, is a unique and valuable ecological resource, and is a place with a rich cultural heritage. Sustaining the Delta is a problem that manifests itself in many dimensions including the physical structure of the Delta, the conflicting demands for water, changing water quality, rapidly evolving ecological character, and high institutional complexity. The problems of the California Delta are increasingly complex, sometimes chaotic, and always contentious. There is general agreement that current management will sustain neither the Delta ecosystem nor high-quality water exports, as required under the Delta Reform Act, so there is a renewed urgency to address all dimensions of the problem aggressively. Sustainable management of the Delta ecosystem and California’s highly variable water supply, in the face of global climate change, will require bold political decisions that include adjustments to the infrastructure but give equal emphasis to chronic overuse and misuse of water, promote enhanced efficiency of water use, and facilitate new initiatives for ecosystem recovery. This new approach will need to be underpinned by collaborative science that supports ongoing evaluation and re-adjustment of actions. Problems like the Delta are formally “wicked" problems that cannot be “solved” in the traditional sense, but they can be managed with appropriate knowledge and flexible institutions. Where possible, it is advisable to approach major actions incrementally, with an eye toward avoiding catastrophic unexpected outcomes. Collaborative analyses of risks and benefits that consider all dimensions of the problem are essential. Difficult as the problems are, California has the tools and the intellectual resources to manage the Delta problem and achieve the twin goals of a reliable water supply and an ecologically diverse Delta ecosystem.

Changing impacts of Alaska-Aleutian subduction zone tsunamis in California under future sea-level rise

Nature Portfolio (Springer Nature) | December 8th, 2021

The amplification of coastal hazards such as distant-source tsunamis under future relative sea-level rise (RSLR) is poorly constrained. In southern California, the Alaska

The amplification of coastal hazards such as distant-source tsunamis under future relative sea-level rise (RSLR) is poorly constrained. In southern California, the Alaska-Aleutian subduction zone has been identified as an earthquake source region of particular concern for a worst-case scenario distant-source tsunami. Here, we explore how RSLR over the next century will influence future maximum nearshore tsunami heights (MNTH) at the Ports of Los Angeles and Long Beach. Earthquake and tsunami modeling combined with local probabilistic RSLR projections show the increased potential for more frequent, relatively low magnitude earthquakes to produce distant-source tsunamis that exceed historically observed MNTH. By 2100, under RSLR projections for a high-emissions representative concentration pathway (RCP8.5), the earthquake magnitude required to produce >1 m MNTH falls from ~Mw9.1 (required today) to Mw8.0, a magnitude that is ~6.7 times more frequent along the Alaska-Aleutian subduction zone.

Characterizing storm-induced coastal change hazards along the United States West Coast

Nature Portfolio (Springer Nature) | May 23rd, 2022

Traditional methods to assess the probability of storm-induced erosion and flooding from extreme water levels have limited use along the U.S. West Coast where swell domin

Traditional methods to assess the probability of storm-induced erosion and flooding from extreme water levels have limited use along the U.S. West Coast where swell dominates erosion and storm surge is limited. This effort presents methodology to assess the probability of erosion and flooding for the U.S. West Coast from extreme total water levels (TWLs), but the approach is applicable to coastal settings worldwide. TWLs were derived from 61 years of wave and water level data at shore-perpendicular transects every 100-m along open coast shorelines. At each location, wave data from the Global Ocean Waves model were downscaled to the nearshore and used to empirically calculate wave run-up. Tides were simulated using the Oregon State University’s tidal data inversion model and non-tidal residuals were calculated from sea-surface temperature and pressure anomalies. Wave run-up was combined with still water levels to generate hourly TWL estimates and extreme TWLs for multiple return periods. Extremes were compared to onshore morphology to determine erosion hazards and define the probability of collision, overwash, and inundation.