Technical Report on Barriers: A part of the comprehensive survey of San Francisco Bay and tributaries, California

U.S. Army Corps of Engineers (USACE) | March 15th, 1963

The California Storm of January 1862

Quaternary Research (Elsevier) | September 2nd, 1996

The greatest storm in the written history of California struck the region in the winter of 1861–1862. The unusual weather began on Christmas Eve, 1861, and persisted fo

The greatest storm in the written history of California struck the region in the winter of 1861–1862. The unusual weather began on Christmas Eve, 1861, and persisted for some 45 days as a series of middle-latitude cyclones made landfall along the California coast. Episodes of very cold and very warm temperatures occurred both during the storm and in the spring of 1862 as meridional flow prevailed. Heavy precipitation swelled the Santa Ana River to more than triple the highest estimated discharge in this century. High water levels in coastal streams between Los Angeles and San Diego persisted into the spring. Lakes were created in the Los Angeles Basin and the Mojave Desert. Arroyos were cut. Sediments from the flood may be preserved in offshore basins.

The challenge of unprecedented floods and droughts in risk management

Nature Portfolio (Springer Nature) | August 3rd, 2022

Risk management has reduced vulnerability to floods and droughts globally, yet their impacts are still increasing. An improved understanding of the causes of changing imp

Risk management has reduced vulnerability to floods and droughts globally, yet their impacts are still increasing. An improved understanding of the causes of changing impacts is therefore needed, but has been hampered by a lack of empirical data. On the basis of a global dataset of 45 pairs of events that occurred within the same area, we show that risk management generally reduces the impacts of floods and droughts but faces difficulties in reducing the impacts of unprecedented events of a magnitude not previously experienced. If the second event was much more hazardous than the first, its impact was almost always higher. This is because management was not designed to deal with such extreme events: for example, they exceeded the design levels of levees and reservoirs. In two success stories, the impact of the second, more hazardous, event was lower, as a result of improved risk management governance and high investment in integrated management. The observed difficulty of managing unprecedented events is alarming, given that more extreme hydrological events are projected owing to climate change.

The Coming Megafloods

Scientific American | May 5th, 2013

Huge flows of vapor in the atmosphere, dubbed “atmospheric rivers,” have unleashed massive floods every 200 years, and climate change could bring more of them.

Huge flows of vapor in the atmosphere, dubbed “atmospheric rivers,” have unleashed massive floods every 200 years, and climate change could bring more of them.

The Delta Plan: Ensuring a reliable water supply for California, a healthy Delta ecosystem, and a place of enduring value

Delta Stewardship Council (Delta Council) | May 16th, 2013

The Sacramento-San Joaquin River Delta is the grand confluence of California’s waters, the place where the state’s largest rivers merge in a web of channels—and in

The Sacramento-San Joaquin River Delta is the grand confluence of California’s waters, the place where the state’s largest rivers merge in a web of channels—and in a maze of controversy. The Delta is a zone where the wants of a modern society come into collision with each other and with the stubborn limitations of a natural system. In 2009, seeking an end to decades of conflict over water, the Legislature established the Delta Stewardship Council with a mandate to resolve long-standing issues. The first step toward that resolution is the document you have before you, the Delta Plan.

The effect of the El Niño-Southern Oscillation on U.S. regional and coastal sea level

American Geophysical Union (AGU) | June 3rd, 2015

Although much of the focus on future sea level rise concerns the long-term trend associated with anthropogenic warming, on shorter time scales, internal climate variabil

Although much of the focus on future sea level rise concerns the long-term trend associated with anthropogenic warming, on shorter time scales, internal climate variability can contribute significantly to regional sea level. Such sea level variability should be taken into consideration when planning efforts to mitigate the effects of future sea level change. In this study, we quantify the contribution to regional sealevel of the El Niño-Southern Oscillation (ENSO). Through cyclostationary empirical orthogonal function analysis (CSEOF) of the long reconstructed sea level data set and of a set of U.S. tide gauges, two global modes dominated by Pacific Ocean variability are identified and related to ENSO and, by extension, the Pacific Decadal Oscillation. By estimating the combined contribution of these two modes to regional sealevel, we find that ENSO can contribute significantly on short time scales, with contributions of up to 20 cm along the west coast of the U.S. The CSEOF decomposition of the long tide gauge records around the U.S. highlights the influence of ENSO on the U.S. east coast. Tandem analyses of both the reconstructed and tidegauge records also examine the utility of the sea level reconstructions for near-coast studies.

The effect of urbanization on floods of different recurrence interval

American Geophysical Union (AGU) | June 3rd, 1975

Studies have shown that the urbanization of a catchment can drastically change the flood characteristics of a river. Published results are synthesized to show the g

Studies have shown that the urbanization of a catchment can drastically change the flood characteristics of a river. Published results are synthesized to show the general relationship between the increase in flood flows following urbanization and both the percentage of the basin paved and the flood recurrence interval. In general, (1) floods with a return period of a year or longer are not affected by a 5% paving of their catchment, (2) small floods may be increased by 10 times by urbanization, (3) floods with a return period of 100 yr may be doubled in size by a 30% paving of the basin, and (4) the effect of urbanization declines, in relative terms, as flood recurrence intervals increase.

The Governance Gap: Climate Adaptation and Sea-Level Rise in the San Francisco Bay Area

University of California, Davis (UC Davis) | June 27th, 2017

This report summarizes the results of an extensive study of governance for climate adaptation and sea-level rise in the San Francisco Bay Area (SF Bay Area), wh

This report summarizes the results of an extensive study of governance for climate adaptation and sea-level rise in the San Francisco Bay Area (SF Bay Area), where the concept of sea-level rise adaptation also includes coastal flooding from high tides and extreme storm events. We focus on the “governance gap” that exists between the problem of sea-level rise and the implementation of adaptation solutions that increase resilience. We take a broad view on governance as the set of institutional arrangements, governmental authorities, and public stakeholders who collectively plan and implement adaptation activities, including identifying funding strategies and the agreeing on the information basis for decision making. While most stakeholders recognize the risk of sea-level rise and other climate impacts, and have good ideas about potential on-the-ground solutions, realizing these solutions requires overcoming a series of governance challenges. All of these governance challenges are barriers to stakeholder cooperation at multiple geographic levels—local, regional, state, and federal. There are many different governmental and non-governmental actors facing the same sea-level rise problem (in “the same boat”), and coordination is required to have them “row in the same direction.” The imperative for multi-level cooperation becomes more poignant as the science on sea-level rise continues to advance, and considers the possibilities of higher average levels of sea-level rise and rapid and extreme sea-level rise due to accelerated melting of the Antarctic ice sheet. This report summarizes the major challenges, identifies the menu of possible solutions, and develops some specific recommendations on the next steps needed to remedy the governance gap and enhance the adaptive capacity of the SF Bay Area. The governance analysis is a component of the larger UC Davis/Berkeley research project called Resilience of Infrastructure as Seas Rise (RISeR), See Figure 1, which is funded by National Science Foundation to analyze the interactions between sea-level rise adaptation, transportation infrastructure, and governance in the SF Bay Area. The governance analysis was conducted in Fall 2016-Winter 2017, and is based on a qualitative case study that combines in-person interviews, focus groups, document analysis, and content analysis of interview responses. The draft report was made available to study participants in Spring 2017, along with two webinars for receiving feedback. Participants included leaders of governmental and non-governmental organizations across the SF Bay Area region. The research focused mainly on sea-level rise and coastal flooding, but also linked to broader issues of climate adaptation when appropriate. Focus groups deliberated on the best possible solutions to solving the identified governance challenges. Respondents identified the overarching governance challenge as the imperative for multi-level cooperation among all sea-level rise adaptation stakeholders. Sea-level rise adaptation entails interdependencies, where the vulnerabilities and adaptation decisions of local actors impose regional costs and benefits. While regional cooperation is beginning to emerge, most stakeholders see a critical need for shared learning, coordination and planning. The recommendations provided in this report are intended to accelerate the processes of learning and cooperation needed to address the increasingly urgent problem of sea-level rise and coastal flooding.

The human factor in water disasters

Nature Portfolio (Springer Nature) | December 14th, 2023

When water inundated parts of New York City in September 2023, 28 people had to be rescued from their cars and basement apartments. Thankfully, no one died this time. In

When water inundated parts of New York City in September 2023, 28 people had to be rescued from their cars and basement apartments. Thankfully, no one died this time. In 2021, flooding in New York killed 11 people. Neighbourhoods in the city also flooded in 2020 and 2022, and it’s not just New York. Floods are becoming increasingly frequent and severe globally, as are droughts. Steve Bowen, chief science officer for reinsurance firm Gallagher Re in London, described the most recent New York floods on X (formerly Twitter) as “the latest example of ageing infrastructure built for a climate that no longer exists”. Such sentiments are common, and frequently followed by calls for more infrastructure: bigger levees and seawalls, larger pipes and stormwater tanks, and more dams, aqueducts and desalination plants.

The importance of imperviousness

Watershed Protection Techniques, Center for Watershed Protection | December 1st, 1994

The emerging field of urban watershed protection often lacks a unifying theme to guide the efforts of its many participants—planners, engineers, landscape architects

The emerging field of urban watershed protection often lacks a unifying theme to guide the efforts of its many participants—planners, engineers, landscape architects, scientists, and local officials. The lack of a common theme has often made it difficult to achieve a consistent result at either the individual development site or cumulatively, at the watershed scale. In this article a unifying theme is proposed based on a physically defined unit: imperviousness. Imperviousness here is defined as the sum of roads, parking lots, sidewalks, rooftops, and other impermeable surfaces of the urban landscape. This variable can be easily measured at all scales of development, as the percentage of area that is not “green.” Imperviousness is a very useful indicator with which to measure the impacts of land development on aquatic systems. Reviewed here is the scientific evidence that relates imperviousness to specific changes in the hydrology, habitat structure, water quality and biodiversity of aquatic systems. This research, conducted in many geographic areas, concentrating on many different variables, and employing widely different methods, has yielded a surprisingly similar conclusion: stream degradation occurs at relatively low levels of imperviousness (~10%). Most importantly, imperviousness is one of the few variables that can be explicitly quantified, managed and controlled at each stage of land development. The remainder of this article details the relationship between imperviousness and stream quality.