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Because the original paper is not about the Millennium Tower case history, this argument has no direct relevance to the subject of the paper. We made no such inferences in the paper and refer interested readers to the case history paper for analysis of the degree to which consolidation was completed at different points in time in the Millennium Tower case study. While the Millennium Tower case history analysis provided the motivation and financial support for the broader study within which the testing program was undertaken, the paper under discussion does not present the case study, which was explained in its introduction. Both discussions lament that the paper did not present analyses of the Millennium Tower case history. [Extracted from the article]

For the case that corresponds to removal of smaller surcharge, HT ht in Fig. Considering the scatter in the HT ht data, 0.6-1.0, evident in Fig. 5(a) show that, on average, the HT ht values from the Arup study were about 1.5 times the HT ht values from the original paper. 1 of the original paper for estimating the equivalent preconsolidation stress, HT ht , is also not applicable. [Extracted from the article]

For newcomers and veteran scientists alike, Bay- Delta science is daunting. The number of research and management issues is exceptional, and the scientific literature is well developed but fragmented. There is a substantial history of periodic reviews of Bay-Delta science and policy issues. Between 1979 and 1986 the first widely circulated reviews were published, focused on Bay processes (Conomos 1979) and issues (Kockelman et al 1982; Nichols et al 1986). Similar publications in the mid- to late- 1990s built substantially on this body of knowledge (e.g., Hollibaugh 1996; van Geen and Luoma 1999). The CALFED Bay-Delta program shifted much of the focus to the Delta, resulting in sponsored white papers on major issues in the mid-2000s (e.g., Brown 2003; Kimmerer 2004; Bennett 2005; Williams 2006). The first "State of Bay-Delta Science" was published in 2008 (Healey et al. 2008). The most recent update of the State of Bay-Delta Science (Healey et al. 2016a, 2016b, and accompanying articles) considered species of concern (Delta Smelt, Chinook Salmon), processes (fish predation, nutrient dynamics, food webs, flow and transport), stressors (contaminant effects, climate change), tools (multidimensional models), and human uses and effects on the Delta (Delta landscapes, climate change, agricultural and urban water supply, and the levee system). Other comprehensive overviews are also available; for example, IEP (2015), Johnson et al. (2017), and Sherman et al. (2017). Together, these reviews and the studies they cite give a sense of the historical development of scientific understanding in the Bay-Delta, and provide conceptual models for species' or system ecology. Many of the papers are themselves scientific milestones, and provided a science foundation for current Bay-Delta current management actions (e.g., Delta Smelt Resiliency Strategy, CNRA 2016; and Sacramento Valley Salmon Resiliency Strategy, CNRA 2017). [ABSTRACT FROM AUTHOR]

The effects of global climate change are already observed in coastal communities, and one of the key impacts of climate change is sea level rise (SLR). Such increases in sea level are expected to have large impacts on transportation infrastructure and result in region-wide commute disruption. Studies and adaptation strategies in coastal areas will allow decision-makers to take better actions against SLR. The present paper uses the San Francisco Bay Area as a case study. The study quantifies the interregional traffic delay of commuters due to the inundation of shoreline protection segments of the Bay Area. The approach is based on the marginal effect of protection within San Francisco Bay where individual stretches of coastline known as operational landscape units (OLUs) are protected one at a time. In the study, we integrate detailed shoreline scenarios, coastal inundation modeling, and traffic disruption modeling. Important insights from the analysis are obtained: the protection of an OLU (and specifically San Rafael OLU) will produce an average commute time reduction of up to 17% in the neighboring areas or the neighborhoods located across the bay. Five OLUs along with four bridges were identified as critical for minimizing disruptions to commute times. This methodology may be used by decision-makers when proposing adaptation and protection strategies that account for both local and regional areas. [ABSTRACT FROM AUTHOR]

With daily traffic of 260 000 vehicles, the San Francisco–Oakland Bay Bridge is a major connection in the San Francisco Bay area (CA, USA). The new bridge is a designated lifeline structure (to remain open for emergency traffic after a major seismic event) with a design life of 150 years. The new bridge is 3.6 km long and consists of four distinct structures: a low-rise post-tensioned concrete box girder near the Oakland shore; a 2.4 km long segmental concrete box girder (skyway); a first-of-its-kind self-anchored suspension (SAS) bridge with a 385 m main span over the navigational channel; and a post-tensioned concrete box girder that connects to the east portal of the Yerba Buena Island tunnel. Opened in 2013, the signature span of the bridge is the SAS bridge with a length of 624 m and a total deck width of 79 m accommodating ten lanes of traffic in addition to a bike/pedestrian path. The US$6.4 billion megaproject was procured under multiple contracts and was delivered using the traditional design–bid–build method. This paper describes the key design innovations and construction methods which address the unique challenges on this project. [ABSTRACT FROM AUTHOR]

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Existing research depicts occupational learning as predominantly happening through formal education, situated learning, or a combination of the two. How career switchers might develop occupational skills outside of these established learning pathways is understudied. This paper examines how novice outsiders break into a skilled occupation by looking at the case of aspiring software developers attending coding bootcamps. Drawing on 17 months of fieldwork in the San Francisco Bay area, I find that bootcamps did not resemble either schools or workplaces, the two institutions that facilitate occupational learning. Instead, bootcamps scaffolded learning collectives—groups composed of peers and near peers who learn collaboratively and purposefully to reach a shared goal. Within learning collectives, aspirants progressed from novice outsiders to hirable software developers, despite limited access to proximate experts to learn from or legitimate peripheral participation opportunities. Three scaffoldings facilitated learning at bootcamps. First, peer team structures turned what is normally a solitary activity—writing code—into a collaborative endeavor and facilitated peer-to-peer knowledge exchange. Second, near-peer role structures engaged recent graduates in teaching and mentorship relationships with novices so that aspirants could access knowledge quickly and easily. Third, bootcamps encouraged aspirants to self-learn by reaching out to the expertise of the broader occupational community. This third scaffolding prepared aspirants for learning beyond the bootcamp curriculum and socialized them for an occupation with high learning demands. The outcome of this process was that novices pursuing an alternative mode of occupational entry developed both occupational skills and new self-conceptions as software developers. Funding: This work was supported by a grant from Stanford Cyber Initiative. [ABSTRACT FROM AUTHOR]

The paper develops models for modeling the availability of bikes in the San Francisco Bay Area Bike Share System (BSS) applying machine learning at two levels: network and station. Investigating BSSs at the station-level is the full problem that would provide policymakers, planners, and operators with the needed level of details to make important choices and conclusions. We used Random Forest and Least-Squares Boosting as univariate regression algorithms to model the number of available bikes at the station-level. For the multivariate regression, we applied Partial Least-Squares Regression (PLSR) to reduce the needed prediction models and reproduce the spatiotemporal interactions in different stations in the system at the network-level. Although prediction errors were slightly lower in the case of univariate models, we found that the multivariate model results were promising for the network-level prediction, especially in systems where there are a relatively large number of stations that are spatially correlated. Moreover, results of the station-level analysis suggested that demographic information and other environmental variables were significant factors to model bikes in BSSs. We also demonstrated that the available bikes modeled at the station-level at time t had a notable influence on the bike count models. Station neighbors and prediction horizon times were found to be significant predictors, with 15 minutes being the most effective prediction horizon time. [ABSTRACT FROM AUTHOR]

Synthetic aperture radar (SAR) provides an efficient way to monitor the Earth's surface. But the speckle noise that the SAR system generates when acquiring images makes it difficult to understand and interpret SAR intensity features. To automatically analyze SAR images, this paper presents a K-Bessel regression (KBR) model in which a function of the mean intensity response is explained by other features (or covariates) determined in parallel. Some mathematical properties of this regression are derived and discussed in the context of the physical origin of the SAR image. A maximum likelihood estimation procedure is planned and its performance is quantified by Monte Carlo experiments. An application to real data obtained from a polarimetric SAR image of San Francisco Bay is realized. Results show that both the KBR-based processing is more informative than the unconditional approach to describe SAR intensity and that our proposal can outperform the normal and gamma regression models. Finally, it is shown that the KBR model is useful to reproduce the relief signal of one channel from the intensity values of the other. [ABSTRACT FROM AUTHOR]

In this analysis of the spatial resolving power of thermal imagery products we focus on four satellite instruments that are used in research and applications, for example, to monitor land surface temperature and derive evapotranspiration. These are thermal imagers on Landsat 7, Landsat 8, and Landsat 9, as well as the ECOsystem Spaceborne Thermal Radiometer Experiment on Space Station (ECOSTRESS). We compiled sets of close‐in‐time, day‐time images of bridges surrounded by open water bodies, captured by each of the satellite imagers during cloud‐free moments. Where possible, we also included some images captured by the Compact Thermal Imager (CTI), a technology demonstrator that was co‐located with ECOSTRESS on the International Space Station in 2019. Bridges were found to provide a sufficient thermal contrast with the water surface to quantify the line‐spread function of satellite‐based thermal products. The full‐width‐at‐half‐max of a gaussian beam model fitted to this transect quantifies the on‐orbit spatial resolution of different imagers. The results show some loss of spatial resolving power in the final product delivered to end‐users as compared to the at‐sensor characterization of spatial resolution. For Landsat 7, 8, and 9, the spatial resolution of the thermal bands is 1.5 times the ground sampling distance of 60 and 100 m respectively. For the ECOSTRESS the difference is up to twice the sampling distance of 78 by 69 m2. Since spatial resolution is a main driver for instrument design it is important to understand and communicate this discrepancy between pre‐flight design parameters and the characteristics of the surface imagery delivered to the user community. The goal of this research is to facilitate an improved fusion of current and future satellite observations into harmonized products with superior temporal and spatial characteristics. Plain Language Summary: This manuscript describes a method to verify the spatial resolution of thermal imagers after launch. Spatial resolution is a key driving requirement in thermal imager design and technology development. Many aspects that control spatial resolution are mathematically understood and can be calculated based on the design specifications of spaceborne imagers. However, the actual spatial resolution of the products delivered to users may not meet the design target precisely. In this paper we compiled a set of thermal images of the San Francisco Bay area. In these daytime images the bridges show up as clearly defined linear features contrasted with the relatively homogenous water surrounding them. From these images, we construct sharply defined profiles perpendicular to the bridge orientation. We then use these profiles as analogs of the linear cuts used to determine the line‐spread function in laboratory tests of imagers. What we find is a much lower spatial resolving power in the final product delivered to end‐users as compared to the at‐sensor characterization of spatial resolution. The reduced spatial resolution we found compared to what may be expected from mission specifications points to the need of better communication of how imager specifications are conveyed into mission products. Key Points: Day‐time thermal contrast between a bridge and its surrounding waters is used to quantify the spatial performance of space‐borne imagersSpatial resolution of thermal imagery products can be lower, to a factor of 2, than the nominal values calculated based on system designThe divergence between pre‐flight and on‐orbit metrics should be factored into mission design trade studies [ABSTRACT FROM AUTHOR]

Archaeological research of dismantled homes at the Albany Bulb in the San Francisco Bay, California, prompted me to rethink the category of "homelessness" and the temporal boundaries of archaeological research. This paper treats the history of people who called this landfill‐turned‐park home as part of broad processes of redevelopment and displacement in the Bay Area and beyond. Archaeological and artistic research provide a critical methodology through which I reflect on contemporary struggles for homeless rights and conflicts over who needs to be "cleaned up." [ABSTRACT FROM AUTHOR]

From February 2019 through January 2021, data were collected by an acoustic vector sensor moored on the seafloor at a depth of approximately 900 m just outside of Monterey Bay, California, near a major shipping lane off the California coast. Analysis of the vector sensor data has shown the ability to accurately determine bearings to merchant vessels at ranges up to 60 km. This paper examines the features of the low-frequency soundscape using spectral probability densities and evaluates directional features through vector intensity processing as well as coherent linear and adaptive processing of the vector sensor channels. Merchant vessel acoustic data were analyzed using the 1/3 octave band centered at 63 Hz. Over the period analyzed, a reduction in merchant vessel noise was observed between February and June 2020 relative to the same period in 2019, consistent with a reduction in vessel traffic due to the worldwide response to COVID-19. The directional features of the data evaluated through adaptive processing methods also suggest this reduction can be most clearly distinguished towards the south, where the shipping lane is limited to transiting vessels, rather to the north-northwest, where merchant vessels tend to congregate on approach into the San Francisco Bay area. [ABSTRACT FROM AUTHOR]

This paper calls for a critical reframing of masculinity as an intersectional construct in the HIV epidemic and in public health. In-depth qualitative interviews were conducted with a sample of 56 Black men who have sex with men and women in the San Francisco Bay Area. Men described their sexual identities and practices via complex narratives of masculinity that drew on subordinated and resourceful adaptations to the structural effects of racism, economic marginalisation and homophobia. By focusing on men whose experience of masculinity operates outside fixed identity categories, the paper draws attention to the intersectionality that is, by necessity, constitutive of men's lived experiences. Findings suggest the value of an integrative framework for understanding Black masculinities as processes and practices simultaneously informed by structural inequalities (racism, economic marginalisation and/or homophobia, in particular) and cultural meanings of gender. By utilising an intersectional approach, public health and sociology can better understand the concurrent resilience and vulnerability of masculinities, while building an interdisciplinary understanding of the symbolic role of Black masculinities in the USA, as well as a means by which to promote health and well-being in and through these gendered contexts. [ABSTRACT FROM AUTHOR]

Einkaufen wird zunehmend zum Erlebnis. Dazu werden weltweit einzigartige „Flag ship Stores" mit aufwendigen Fassaden errichtet, die durch einen Wow‐Effekt begeistern sollen. Ihr Erfolg gibt ihnen Recht, erfordert jedoch zuvor eine detaillierte Planung und Umsetzung. Anhand eines Projektes in Santa Clara, CA, USA, wird gezeigt, welche Liebe zum Detail und technische Raffinesse nötig sind, um auch mit vergleichsweise kleinformatigen Fassaden ein transparentes Ausrufezeichen zu schaffen. Im Zentrum der 300 m2 großen Ganzglasfassade stehen zwei überdimensionale, 9 m hohe Flügel einer gläsernen Schiebetür. Der fünflagige Glasaufbau wird über Bohrungen und Edelstahlbolzen mit einem Tragrahmen verbunden. Darüber hinaus müssen auch Glaskonstruktionen Erdbeben sicher ertragen und Beschleunigungen schadlos abtragen können. Der Beitrag zeigt sowohl die Entwicklung der Antriebstechnik sowie der konstruktiven Details und den Nachweis der Anlage. Versuche sichern die Berechnungen zusätzlich ab und zeigen, dass bis zu 180 kN Einzellasten in die Platten eingeleitet werden können, ohne die Gebrauchstauglichkeit einzuschränken. Als Gipfel des Projektes folgt der Einbau der fünf Tonnen schweren Türflügel. Ganz im Sinne des Auftraggebers beginnt bereits der erste Lebenstag der Türen mit einem unvergesslichen Höhepunkt und unterstreicht eine innovative Herangehensweise. Large‐scale glass doors – Movement in seismic regions. Shopping evolves more and more into an experience. This is why one‐of‐a‐kind "Flagship Stores" with complex facades are designed to thrill by a "wow‐effect". Their success proves them right but raises the need for detailed planning and implementation. With the aid of an exemplary project in Santa Clara, CA, USA, it is shown what attention to detail and technical sophistication is necessary, even in a small‐scale facade project, to create particularly transparent head‐turner. Two over‐dimensional, 9 m high door leaves are in the center of the 300 m2 full‐glass facade. Its five‐layered laminate is form‐fixed to a stainless steel frame through holes in the glass. As an additional provision, even glass structures shall carry seismic movements and acceleration without fracture. The paper shows the development of the drive engine, the structural details as well as the proof of the structure. An experimental campaign ensures that single loads up to 180 kN can be transferred through the glass without compromising serviceability. Finally, the voyage of the facade to the San Francisco Bay is traced. The installation of the door leaves – weighting astonishing five metric tons each –marks a first highlight. In accordance with the wishes of the client, the first day in the life‐cycle of the structure starts with a memorable climax and underlines an innovative approach. [ABSTRACT FROM AUTHOR]

The paper presents a new methodology to assist decision-makers in the management of critical events such as earthquakes evaluating the recovery time, and the resilience index of a building system that is a component of the physical infrastructure dimension of the PEOPLES Resilience framework. The interdependencies between building system and transportation network in term of accessibility are modeled. Finally, the methodology has been implemented in a software and has been applied in two case studies: (a) the old medieval center of L'Aquila town and (b) the Treasure Island in the San Francisco Bay area. [ABSTRACT FROM AUTHOR]

Compound flooding, resulting from a combination of riverine and coastal processes, is a complex but important hazard to resolve along urbanized shorelines in the vicinity of river mouths. However, inland flooding models rarely consider oceanographic conditions, and vice versa for coastal flood models. Here, we describe the development of an operational, integrated coastal-watershed flooding model to address this issue of compound flooding in a highly urbanized estuarine environment, San Francisco Bay (CA, USA), where the surrounding communities are susceptible to flooding along the bay shoreline and inland rivers and creeks that drain to the bay. The integrated tributary-coastal forecast model (Hydro-Coastal Storm Modeling System, or Hydro-CoSMoS) was developed to provide water managers and other users with flood forecast information beyond what is currently available. Results presented here are focused on the interaction of the Napa River watershed and the San Pablo Bay at the northern end of San Francisco Bay. This paper describes the modeling setup, the scenario used in a tabletop exercise (TTE), and the assessment of the various flood forecast information products. Hydro-CoSMoS successfully demonstrated the capability to provide watershed and coastal flood information at scales and locations where no such information is currently available and was also successful in showing how tributary flows could be used to inform the coastal storm model during a flooding scenario. The TTE provided valuable feedback on how to guide continued model development and to inform what model outputs and formats are most useful to end-users. [ABSTRACT FROM AUTHOR]

Prevalence of vegetation (either submerged or emergent) in shallow water significantly affects the flow and turbulence structure in this environment. In this paper, we develop a new 3D unstructured grid hydrostatic model that accounts for the 3D effects of vegetation on flows. The model uses a semi-implicit time stepping method and treats the new vegetation-related terms implicitly to enhance numerical stability, so the time step does not need to be reduced as compared with the no-vegetation cases. The stability is also independent of the vegetation parameters, so as to efficiently account for large shear that can occur around the canopy. We validate the model using lab data before applying it to a field study in San Francisco Bay-Delta to illustrate the influence of the vegetation on the flow structure as well as tidal energetics. The efficiency of the model enabled by the implicit method allows, for the first time, the simulation of the vegetation effects during multi-year evolution of vegetation in full three dimensions at large spatial scales. [ABSTRACT FROM AUTHOR]

This paper proposes a heuristic singular spectrum analysis (SSA) approach to extract signals from suspended sediment concentration (SSC) time series contaminated by multiplicative noise, in which multiplicative noise is converted to approximate additive noise by multiplying with the signal estimate of the time series. Therefore both the signal and noise components need to be recursively estimated. Since the converted additive noise is heterogeneous, a weight factor is introduced according to the variance of additive noise. The proposed heuristic SSA approach is employed to process the SSC series in San Francisco Bay compared to the traditional SSA and homomorphic log-transformation SSA approach. By using our heuristic SSA approach, the first 10 principal components derived can capture 96.49% of the total variance with the fitting error of 6.17 mg/L, better than those derived by traditional SSA approach and homomorphic log-transformation SSA approach that catch 88.97% and 87.35% of the total variance with the fitting errors of 14.47 mg/L and 15.03 mg/L, respectively. Therefore, our heuristic SSA approach can extract more signals than traditional SSA and homomorphic log-transformation SSA approach. Furthermore, the results from the simulation cases show that all the mean root mean squared errors and mean absolute errors derived by our heuristic SSA are smaller than the traditional and homomorphic log-transformation SSA, which indicate that the extracted signals by heuristic SSA approach are much closer to the real signals than those by the other two approaches. Therefore it can be conclude that our heuristic SSA approach performs better in extracting signals from SSC time series contaminated with multiplicative noise. [ABSTRACT FROM AUTHOR]

Producing high-resolution urban land cover maps is essential for decision-making and urban management. In this regard, Synthetic Aperture Radar (SAR), especially Polarimetric SAR (PolSAR), has served as a valuable data source to fulfill this task. Direct conversion of low-level features into high-level Land Cover (LC) concept may reduce the final classification accuracy. Therefore, mid-level representation models, such as Bag of Visual Words (BOVW), were employed to resolve the existing semantic gap challenge. In this paper, a Segment-based BOVW (Seg-BOVW) model was developed for urban land cover classification using PolSAR data. To this end, two PolSAR data over San Francisco Bay (SFB) and Flevoland (FL) acquired by RADARSAT-2 were employed to comprehensively evaluate the Seg-BOVW model's performance. First, to exploit the full potential of PolSAR data, 169 low-level features in four categories: (1) original, (2) polarimetric, (3) texture, and (4) decomposition features were extracted. Afterward, a Multi-Objective Genetic Algorithm (MOGA) was implemented to investigate the importance of low-level features for urban land cover mapping. This step resulted in selecting 14 and 6 low-level features, as the high contributing features, for SFB and FL datasets, respectively. The Seg-BOVW model achieved significant overall accuracies of 96.02% and 98.82% for SFB and FL, respectively, indicating the high potential of the proposed method for urban land cover classification. Furthermore, a comparison with other well-known algorithms of Support Vector Machine (SVM), Artificial Neural Networks (ANN), and Convolutional Neural Networks (CNN) was made, suggesting the capability of the Seg-BOVW model to improve the urban land cover classification results. Finally, the Seg-BOVW model was tested with two other PolSAR datasets acquired with different sensors over SFB to examine its applicability with different datasets. [ABSTRACT FROM AUTHOR]

This essay excavates geographies of environmental injustice and racial violence in San Francisco, California using the artwork of Asian/American artists Weston Teruya, Michael Arcega, and Stephanie Syjuco made during their residencies at Recology (the city's privately-owned waste management facility). At Recology's Artist-In-Residence program, cultural workers salvage materials from the dump, transforming the city's waste into objects with educational and artistic value. Reading the visual lexicon deployed in, and the conditions of production and circulation of, these assemblages, I trace the wastelanding of communities of color across the Northern California region through processes of incarceration, toxic exposure, displacement, and labor exploitation. These artworks, I argue, assist in uncovering the terrain of slow violence in the region and across scales, or what Rob Nixon has called "landscapes of temporal overspill that elude rhetorical cleanup operations with their sanitary beginnings and endings" (2011, 8). [ABSTRACT FROM AUTHOR]

Liquefaction hazard analyses are needed for regional-scale applications, such as risk analysis and upgrades of electrical transmission, water conveyance, and highway systems. In this paper, we expand well-established site-specific liquefaction triggering and manifestation analysis methods for regional scale application by explicitly addressing the uncertainty in groundwater conditions, soil behavior classification, and cyclic resistance. The uncertainty inherent to regional-scale geotechnical properties is quantified by considering the inputs into conventional liquefaction triggering and manifestation analyses as random variables. With this flexible and extensional formulation, the geostatistical properties needed for regional scale analyses may be estimated by either averaging borehole information or spatially interpolating geotechnical properties across broad geologic deposits. We demonstrate the utility of the method by analyzing the liquefaction hazard throughout the south San Francisco Bay area, California, U.S.A. The resulting estimates of the probability of liquefaction manifestation tend to be lower than previously published estimates, largely owing to the geologic structure of the area and the uncertainty in liquefaction surface manifestation once liquefaction is triggered at depth. Uncertainties in groundwater conditions, soil behavior classification, penetration resistance, and liquefaction manifestation are quantified by the regional scale analyses, which provide a complete and systematic evaluation of the liquefaction hazards, localize the uncertainties in subsurface conditions, and facilitate supplemental investigations at areas of high uncertainty to fill data gaps. • Existing liquefaction models are extended for regional-scale application. • Flexible model allows deposit-scale averages or spatially interpolated properties. • Geologic structure and uncertain groundwater depth are applied in the model. • Example application in southern San Francisco Bay area, California, U.S.A. [ABSTRACT FROM AUTHOR]

Elasmobranchs are common, iconic species in public aquaria; their wild counterparts are key members of marine ecosystems. Post-mortem examination is a critical tool for disease monitoring of wild elasmobranchs and for management of those under human care. Careful necropsy of the head, with a focus on clinically relevant anatomy, can ensure that proper samples are collected, increasing the chance of presumptive diagnoses prior to slower diagnostic workup. Immediate feedback from a thorough head necropsy allows for faster management decisions, often identifying pathogens, routes of pathogen entry, and pathogenesis, which are current shortcomings in published literature. This article proposes a protocol for necropsy of the elasmobranch chondrocranium, emphasizing unique anatomy and careful dissection, evaluation, and sampling of the endolymphatic pores and ducts, inner ears, brain, and olfactory system as part of a complete, whole-body necropsy. Extensive use of cytology and microbiology, along with thorough sample collection for histology and molecular biology, has proven effective in identifying a wide range of pathogens and assisting with characterization of pathogenesis. The cause of mortality is often identified from a head necropsy alone, but does not replace a thorough whole-body dissection. This protocol for necropsy and ancillary diagnostic sample collection and evaluation was developed and implemented in the necropsy of 189 wild and aquarium-housed elasmobranchs across 18 species over 13 years (2011--2023) in California. Using this chondrocranial approach, meningoencephalitis was determined to be the primary cause of mortality in 70% (118/168) of stranded wild and aquarium-housed elasmobranchs. Etiology was largely bacterial or protozoal. Carnobacterium maltaromaticum bacterial meningoencephalitis occurred in salmon sharks (Lamna ditropis), shortfin mako sharks (Isurus oxyrinchus), common thresher sharks (Alopias vulpinus), and one Pacific electric ray (Tetronarce californica). Miamiensis avidus was the most common cause of protozoal meningoencephalitis and found almost exclusively in leopard sharks (Triakis semifasciata) and bat rays (Myliobatis californica) that stranded in San Francisco Bay. Bacterial pathogens were found to use an endolymphatic route of entry, while protozoa entered via the nares and olfactory lamellae. Trauma was the second most common cause of mortality and responsible for 14% (24/168) of wild shark strandings and deaths of aquarium-housed animals. [ABSTRACT FROM AUTHOR]

This paper outlines an approach to assessing the horizontal shear capacity of the hollow rectangular bridge piers designed to support three new toll bridges in the San Francisco Bay Area under seismic loads. The approach focuses on the piers' capacity in diagonal compression, or their "web crushing capacity," as it relates to the fanning crack pattern inside the plastic hinge region. In contrast to existing web crushing models that assume a uniform distribution of shear stresses across an effective section, this approach assesses the capacity of and demand on individual struts inside the plastic hinge region as the plasticity spreads up the height of the pier. Analytical results based on this flexure-shear approach to web crushing are compared to results from 12 large-scale tests conducted by the authors at the University of California, San Diego between 1999 and 2001 and by Oesterle et al. at the Portland Cement Association between 1976 and 1983. [ABSTRACT FROM AUTHOR]

This paper explains observed trends in freshwater flow to the San Francisco Bay-Delta estuary as reported in a companion paper (Hutton, Rath, & Roy, 2017). We employ a historical hydrologic record spanning nine decades and define a set of idealized flow scenarios to identify drivers of change in delta outflow and consequent salinity regime. Flow changes are measured against a baseline scenario representing 1920-level land use and water management conditions. Additional scenarios are defined to represent the system absent state and federal water project reservoir and export operations, absent key non-project reservoir operations, and absent historicallyobserved sea level rise. These scenarios, in conjunction with the principle of superposition, are used to ascribe outflow and salinity trends to different anthropogenic and natural causes. We find that project and non-project water management are attributed similar responsibility for decreasing outflow trends in April and May and consequent increasing spring salinity trends. In contrast, we find that increasing July and August outflow trends (and lagged decreasing salinity trends) are attributed to flow contributions from project water management; these contributions more than fully attenuate impacts associated with non-project water management. [ABSTRACT FROM AUTHOR]

Fabric characteristics and shear deformation behaviour were analysed in four intact small-scale samples, including two disturbed and two undisturbed samples of naturally deposited sand from a shoal in the San Francisco Bay. Triaxial compression tests were performed on each sample while incrementally imaging with X-ray micro-computed tomography (XRCT). The grains in each intact sample exhibited a nearly unidirectional orientation with their long axes oriented within a narrow range of horizontal directions, in stark contrast to the randomly oriented grains of a reconstituted sample. The disturbed intact samples exhibited lower peak strengths and lower yet positive rates of dilation as compared with undisturbed samples. Higher rates of dilation corresponded with larger quantifiable decreases in the average number of grain-to-grain contacts and contact areas per grain within the shear band. The XRCT images of the shear bands were quantified by way of large incremental deviatoric strains and large incremental grain rotations. The grain orientations within the fully developed shear band of each sample reached a consistent orientation independent of their initial fabric. These results are a promising step toward a systematic study of granular deposits from different depositional environments needed for the development of more advanced models of their mechanical behaviour. [ABSTRACT FROM AUTHOR]

The Trans Bay Cable (TBC) is a ±200-kilovolt (kV), 400 MW 85-km long High Voltage Direct Current (DC) buried transmission line linking Pittsburg, CA with San Francisco, CA (SF) beneath the San Francisco Estuary. The TBC runs parallel to the migratory route of various marine species, including green sturgeon, Chinook salmon, and steelhead trout. In July and August 2014, an extensive series of magnetic field measurements were taken using a pair of submerged Geometrics magnetometers towed behind a survey vessel in four locations in the San Francisco estuary along profiles that cross the cable’s path; these included the San Francisco-Oakland Bay Bridge (BB), the Richmond-San Rafael Bridge (RSR), the Benicia-Martinez Bridge (Ben) and an area in San Pablo Bay (SP) in which a bridge is not present. In this paper, we apply basic formulas that ideally describe the magnetic field from a DC cable summed vectorially with the background geomagnetic field (in the absence of other sources that would perturb the ambient field) to derive characteristics of the cable that are otherwise not immediately observable. Magnetic field profiles from measurements taken along 170 survey lines were inspected visually for evidence of a distinct pattern representing the presence of the cable. Many profiles were dominated by field distortions unrelated to the cable caused by bridge structures or other submerged objects, and the cable’s contribution to the field was not detectable. BB, with 40 of the survey lines, did not yield usable data for these reasons. The unrelated anomalies could be up to 100 times greater than those from the cable. In total, discernible magnetic field profiles measured from 76 survey lines were regressed against the equations, representing eight days of measurement. The modeled field anomalies due to the cable (the difference between the maximum and minimum field along the survey line at the cable crossing) were virtually identical to the measured values. The modeling yielded a pooled cable depth below the bay floor of 2.06 m (±1.46 std dev), and estimated the angle to the horizontal of the imaginary line connecting the cross-sectional center of the cable’s two conductors (0.1143 m apart) as 178.9° ±61.9° (std dev) for Ben, 78.6°±37.0° (std dev) for RSR, and 139.9°±27.4° (std dev) for SP. The mean of the eight daily average currents derived from the regressions was 986 ±185 amperes (A) (std dev), as compared to 722 ±95 A (std dev) provided by Trans Bay Cable LLC. Overall, the regressions based on fundamental principles (Biot Savart law) and the vectorial summation of cable and geomagnetic fields provide estimates of cable characteristics consistent with plausible expectations. [ABSTRACT FROM AUTHOR]

Striped Bass (Morone saxatilis), a non-native, anadromous fish introduced to California in 1879, is a popular sport fish and piscivorous predator in the San Francisco Bay/Delta ecosystem, but comparatively little is known about its distribution and ecology in estuaries and rivers of the California coast. Here we review recent scientific papers, consultant reports, and correspondence to evaluate its distribution in coastal estuaries and rivers, evidence for local reproduction, and scope for impacts on native fishes, especially salmonids. Striped Bass is extremely rare in the ocean along the north coast, and has not turned up in extensive surveys of Humboldt Bay, the Eel River estuary, or the Russian River estuary. It is, however, a perennial feature of seining surveys in estuaries south of the Golden Gate and along Monterey Bay, usually sporadically and as a very small proportion of total catch. It has become quite common in the Carmel River estuary, and is occasionally caught in the ocean further south. Small upstream migrations, possibly for spawning, have been observed in the Salinas River and Carmel River, but no evidence of eggs or larvae has been found--perhaps due to a lack of ichthyplankton surveys anywhere except in Elkhorn Slough. However, the species' reproductive ecology is not a good match to the hydrologic structure of most coastal stream systems, requiring a large long river where adults can spawn, in combination with an extensive, ramifying estuarine system where larvae can accumulate. One potential good match is the Salinas River system, especially in its historic form as the Salinas River/Old Salinas River Channel/Elkhorn Slough complex of the 19th century. Despite the modest presence of the species on the coast between the Golden Gate and Carmel, it still has scope for large impacts on emigrating salmonids, due to its extreme piscivory at larger size-classes and its ability to exploit migration bottlenecks as feeding grounds. Most likely the individuals observed in coastal estuaries originated in the San Francisco Bay/Delta system and use local systems opportunistically for foraging, but the hypothesis of local reproduction cannot be ruled out without further study. [ABSTRACT FROM AUTHOR]

Recovering species are often limited to much smaller areas than they historically occupied. Conservation planning for the recovering species is often based on this limited range, which may simply be an artifact of where the surviving population persisted. Southern sea otters (Enhydra lutris nereis) were hunted nearly to extinction but recovered from a small remnant population on a remote stretch of the California outer coast, where most of their recovery has occurred. However, studies of recently-recolonized estuaries have revealed that estuaries can provide southern sea otters with high quality habitats featuring shallow waters, high production and ample food, limited predators, and protected haul-out opportunities. Moreover, sea otters can have strong effects on estuarine ecosystems, fostering seagrass resilience through their consumption of invertebrate prey. Using a combination of literature reviews, population modeling, and prey surveys we explored the former estuarine habitats outside the current southern sea otter range to determine if these estuarine habitats can support healthy sea otter populations. We found the majority of studies and conservation efforts have focused on populations in exposed, rocky coastal habitats. Yet historical evidence indicates that sea otters were also formerly ubiquitous in estuaries. Our habitat-specific population growth model for California’s largest estuary—San Francisco Bay—determined that it alone can support about 6,600 sea otters, more than double the 2018 California population. Prey surveys in estuaries currently with (Elkhorn Slough and Morro Bay) and without (San Francisco Bay and Drakes Estero) sea otters indicated that the availability of prey, especially crabs, is sufficient to support healthy sea otter populations. Combining historical evidence with our results, we show that conservation practitioners could consider former estuarine habitats as targets for sea otter and ecosystem restoration. This study reveals the importance of understanding how recovering species interact with all the ecosystems they historically occupied, both for improved conservation of the recovering species and for successful restoration of ecosystem functions and processes. [ABSTRACT FROM AUTHOR]

The San Francisco Bay is one of the world's most urbanized estuaries, currently home to 7 million and expected to grow to 9 million by 2030. This growth projection has been exacerbated by mounting evidence of climate change's impact in the Bay Area, where sea level is anticipated to rise 16 inches by 2030 and 55 inches by 2100. Specifically in San Francisco, inundation and urban growth are competing concerns in a city that anticipates increased development along a threatened eastern shore. This paper examines the contradictions between development plans in San Francisco and projected impacts of sea level rise, and theorizes the expanding role urban landscapes might play to ease these conflicts. Through 3 site-specific speculative designs along the eastern shore, this research investigates an alternative future for San Francisco that includes expanding landscape productivity to meet the complex needs of a changing climate. [ABSTRACT FROM AUTHOR]

Abstract: Deep-water potential estuarine and marine benthic habitat types were defined from a variety of new and interpreted data sets in central San Francisco Bay and offshore Golden Gate area including multibeam echosounder (MBES), side-scan sonar and bottom grab samples. Potential estuarine benthic habitats identified for the first time range from hard bedrock outcrops on island and mainland flanks and some Bay floor regions, to soft, very dynamic bedforms consisting of sediment waves and ripples. Soft sediment ranges from mud and sand to bimodal (two or more grain sizes) sediment of gravel, pebbles, and cobbles. In addition, considerable anthropogenic features (i.e., pipelines, bridge abutments, dredged channels, dump sites) were distinguished. Of the 52 potential benthic habitat types mapped (compressed to 14 types for this paper), 24 were of unconsolidated sediment with five of these comprised of dynamic bedforms or sediment waves and dunes, five of mixed (soft over hard) substrate type, six of hard substrate or rock outcrop, 13 of anthropogenically disturbed areas and four hard anthropogenic features. Rock outcrops and rubble are considered the primary habitat type for rockfish (Sebastes spp.), lingcod (Ophiodon elongatus) and in shallow water for herring (Clupea pallasii) spawning. Dynamic bedforms such as sand waves are considered potential foraging habitat for juvenile lingcod, may be sub-tidal habitat for the Pacific sand lance (Ammodytes hexapterus) forage fish, and possibly resting habitat for migratory fishes such as sturgeon (Acipenser medirostris). The potential marine benthic habitats identified in San Francisco Bay are not unlike those found in other estuaries around the world and this study should contribute significant information that will be of interest to scientists, managers and fishers investigating and utilizing bay and estuarine resources. As described in the many papers of this special issue, the understanding of the interrelationship of geology and ecology is critical to the identification of essential habitats and the sustainability of a healthy ecosystem. [Copyright &y& Elsevier]

Ancient blue oak trees are still widespread across the foothills of the Coast Ranges, Cascades, and Sierra Nevada in California. The most extensive tracts of intact old-growth blue oak woodland appear to survive on rugged and remote terrain in the southern Coast Ranges and on the foothills west and southwest of Mt. Lassen. In the authors' sampling of old-growth stands,most blue oak appear to have recruited to the canopy in the middle to late nineteenth century. The oldest living blue oak tree sampled was over 459 years old, and several dead blue oak logs had over 500 annual rings. Precipitation sensitive tree-ring chronologies up to 700 years long have been developed from old blue oak trees and logs. Annual ring-width chronologies of blue oak are strongly correlated with cool season precipitation totals, streamflow in the major rivers of California, and the estuarine water quality of San Francisco Bay. A new network of 36 blue oak chronologies records spatial anomalies in growth that arise from latitudinal changes in the mean storm track and location of land-falling atmospheric rivers. These long, climate-sensitive blue oak chronologies have been used to reconstruct hydroclimatic history in California and will help to better understand and manage water resources. The environmental history embedded in blue oak growth chronologies may help justify efforts to conserve these authentic old-growth native woodlands. [ABSTRACT FROM AUTHOR]

Background: Korean Americans (KA) have the highest prevalence of death from cancer among Asian American ethnic groups in the U.S. This KA prevalence rate is also substantially higher than that of non-Hispanic whites, yet little is known about their cancer risk factors. This paper is one of the first studies to explore cancer risk factors and screening behaviors of Korean Americans in the San Francisco Bay Area. Methods: A survey instrument was created using items from the California Health Interview Survey (CHIS) from 2009-2012, which were translated into Korean. A cross-sectional survey assessing the prevalence of cancer risk factors and screening behaviors was conducted inperson, through telephone, and online using a community-based sampling strategy of 342 KAs across the SF Bay Area. These results were then compared to the results of CHIS 2007-2012 for Koreans, all Asians in California, and all of California. Simple and multiple logistic regression were also conducted to evaluate the association between several socioeconomic and cultural factors and cancer screening outcomes for colorectal cancer screening, mammography, and Pap smears. Results: In this sample, 30% of women 21 years and older had never received a Pap smear, 18% of women 40 years and older had never received a mammogram, and 24% of participants 50 years and older had never received colorectal cancer screening. Further analyses found that among women who are aged 21 years and older, not being a college graduate (Odds Ratio (OR): 3.59, 95% Confidence Interval [95% CI] 1.22, 10.57) was associated with higher odds of not receiving a Pap smear. Younger age was associated with never receiving colorectal screening (OR: 0.39, 95% CI 0.19, 0.79). Not having insurance (OR: 3.22, 95% CI 1.36, 7.62) and preference for a Korean physician (OR: 9.89, 95% CI 1.30, 75.18) were associated with higher odds of receiving no colorectal screening. Sex, having a college degree, or Limited English Proficiency (LEP) were not found to have any association with never receiving colorectal cancer screening. Conclusions: Very few studies assessing health disparities such as cancer risk factors and screening prevalence in KAs exist. Further studies in this vulnerable group exploring risk factors and screening rates for other cancers are encouraged to identify specific areas that can be targeted for improved health outcomes. [ABSTRACT FROM AUTHOR]

The quantity of suspended sediment in an estuary is regulated either by transport, where energy or time needed to suspend sediment is limiting, or by supply, where the quantity of erodible sediment is limiting. This paper presents a hypothesis that suspended-sediment concentration (SSC) in estuaries can suddenly decrease when the threshold from transport to supply regulation is crossed as an erodible sediment pool is depleted. This study was motivated by a statistically significant 36% step decrease in SSC in San Francisco Bay from water years 1991-1998 to 1999-2007. A quantitative conceptual model of an estuary with an erodible sediment pool and transport or supply regulation of sediment transport is developed. Model results confirm that, if the regulation threshold was crossed in 1999, SSC would decrease rapidly after water year 1999 as observed. Estuaries with a similar history of a depositional sediment pulse followed by erosion may experience sudden clearing. [ABSTRACT FROM AUTHOR]

This study shows how spatial information about product supply and demand can be used to determine the geographic extent of markets. It demonstrates that markets thus defined allow finer-grained measurement of competitive conditions than is possible using conventional approaches. Two procedures are developed and contrasted. One, called a natural market approach, is drawn from the Industrial Organization economics literature, the second, called an enactment approach, is associated with the open systems perspective on organizations. Applied to a set of hospitals in the San Francisco Bay area, geographic market boundaries established in these ways are shown to lead to finely defined markets, and to reveal strong variation in competitive conditions across the area-variation not detectable if conventional approaches to market definition are used. It is shown that these approaches have applications beyond geographic market definition, and can also be applied to define markets in terms of product or service types. [ABSTRACT FROM AUTHOR]

Conventional laboratory tests on undisturbed samples of a highly plastic silt are described. Modified Cam Clay Model (MCC) is formulated and verified against the laboratory tests. Next, in-situ self-boring pressuremeter (SBPM) tests in the same soil are described. In order to simulate the SBPM tests, a finite element model is constructed incorporating the MCC model and the Biot's theory of consolidation. The numerical model is used to predict field SBPM tests. The predictions (or simulations) are compared with the field data from SBPM tests. The paper attempts to answer an important question in constitutive modeling: Can a constitutive model based on laboratory tests generate the response actually observed in the field? The paper concludes that it is possible to formulate a satisfactory model based on conventional laboratory tests. But, it is only when a permeability value determined by a field test is used, can an acceptable match be found between the data generated by the numerical model and the actual field data. [ABSTRACT FROM AUTHOR]

The Longitudinal Employer-Household Dynamics Origin-Destination Employment Statistics (LODES) are an important city planning resource in the USA. However, curating these statistics is resource-intensive, and their accuracy deteriorates when changes in population and urban structures lead to shifts in commuter patterns. Our study area is the San Francisco Bay area, and it has seen rapid population growth over the past years, which makes frequent updates to LODES or the availability of an appropriate substitute desirable. In this paper, we derive mobility flows from a set of over 40 million georeferenced tweets of the study area and compare them with LODES data. These tweets are publicly available and offer fine spatial and temporal resolution. Based on an exploratory analysis of the Twitter data, we pose research questions addressing different aspects of the integration of LODES and Twitter data. Furthermore, we develop methods for their comparative analysis on different spatial scales: at the county, census tract, census block, and individual street segment level. We thereby show that Twitter data can be used to approximate LODES on the county level and on the street segment level, but it also contains information about non-commuting-related regular travel. Leveraging Twitter's high temporal resolution, we also show how factors like rush hour times and weekends impact mobility. We discuss the merits and shortcomings of the different methods for use in urban planning and close with directions for future research avenues. [ABSTRACT FROM AUTHOR]

Sustainable management of wetland ecosystems requires monitoring of vegetation dynamics, which can be achieved through remote sensing. This paper assesses the use of hyperspectral imagery to study the structure of wetlands of San Francisco Bay, California, USA. Spectral mixture analysis (SMA) and multiple endmember spectral mixture analysis (MESMA) were applied on an AVIRIS (Airborne Visible and Infrared Imaging Spectrometer) image to investigate their appropriateness to characterize marshes, with emphasis on the Spartina species complex. The role of rms. error as a measure of model adequacy and different methods for image endmember extraction were also evaluated. Results indicate that both SMA and MESMA are suitable for mapping the main components of the marsh, although MESMA seems more appropriate since it can incorporate more than one endmember per class. rms. error was shown not to be a measure of SMA model adequacy, but it can be used to help to assess model adequacy within groups of related models. [ABSTRACT FROM AUTHOR]

Estuarine tides, currents and shelf phenomena are often non-stationary, with a frequency composition that evolves with time and forcing such as river flow and density structure. Such tides are difficult to characterize quantitatively, particularly against a background of significant, multi-scale sub-tidal and cusp energy. One challenge identified in past work is the separation of diurnal and subtidal components of the signal. The difficulty is exacerbated in basins such as the San Francisco Bay-Delta, where the diurnal species is subject to fortnightly fluctuation due to O1-K1 beating (the tropical spring-neap cycle) and the subsequent interaction with the semidiurnal species leads to the production of modulated terdiurnal energy. This paper extends the method of higher order stochastic cycles, a construct from the structural time series literature, for use in analyzing these nonstationary tides. Interpretable as a multi-species generalization of Butterworth low pass and bandpass filters, Stochastic Cycle Harmonic Analysis (SCHA) possesses an interpretable stationary frequency response and can accurately extract terdiurnal frequencies. Represented by a state space formulation and fit using a Markov Chain Monte Carlo (MCMC) method, the method can produce Bayesian confidence intervals for derived quantities such as amplitudes, is robust to patches of missing data, and is energy conserving. We evaluate the method on benchmark problems that test its time and frequency resolution. In a field application on the Sacramento River in the San Francisco Bay-Delta SCHA confirms that the declinational beating of O1 and K1, heavily modulated by river flow, dominates fortnightly variation in the tide and its terdiurnal response. • Describes higher order stochastic cycles for harmonic analysis of tides (SCHA). • The SCHA method is accurate when the first four species are extracted. • SCHA model works for tides with nonstationary diurnal or terdiurnal content. • Implemented through a state space method with numerous practical extensions. [ABSTRACT FROM AUTHOR]

The structure of the salinity field in northern San Francisco Bay and how it is affected by freshwater flow are discussed. Two datasets are examined: the first is 23 years of daily salinity data taken by the U.S. Bureau of Reclamation along the axis of northern San Francisco Bay; the second is a set of salinity transects taken by the U.S. Geological Survey between 1988 and 1993. Central to this paper is a measure of salinity intrusion, X[sub 2]: the distance from the Golden Gate Bridge to where the bottom salinity is 2 psu. Using X[sub 2] to scale distance, the authors find that for most flow conditions, the mean salinity distribution of the estuary is nearly self-similar with a salinity gradient in the center 70% of the region between the Golden Gate and X[sub 2] that is proportional to X[sup -1. sub 2]. Analysis of covariability of Q and X[sub 2] showed a characteristic timescale of adjustment of the salinity field of approximately 2 weeks. The steady-state response deduced from the X[sub 2] time series implies that X[sub 2] is proportional to riverflow to the 1/7 power. This relation, which differs from the standard ⅓ power dependence that is derived theoretically assuming constant exchange coefficients, shows that the upstream salt flux associated with gravitational circulation is more sensitive to the longitudinal salinity gradient than theory supposes. This is attributed to the strengthening of stratification caused by the stronger longitudinal salinity gradient that accompanies larger river flows. [ABSTRACT FROM AUTHOR]

Coordinated ramp metering (CRM) systems are implemented on freeways primarily to improve operational conditions. However, smoother traffic flow resulting from CRM may also have significant safety benefits. The main objective of this research is to evaluate the safety performance of CRM systems on the Interstate 80 (I-80) corridor in California by using an empirical Bayes before–after approach. We collected geometric features, traffic volume, and historical crash data from I-80 in the San Francisco Bay area (Caltrans District 4). Then, the freeway safety prediction methodology implemented using the Enhanced Interchange Safety Analysis Tool (ISATe, developed as part of a National Cooperative Highway Research Program Project 17-45) was utilized to estimate the counterfactual, i.e., the number of crashes if no CRM system was implemented on the corridor. Based on a comparison of this counterfactual with the actual crash counts in the post-CRM period, CRM implementation led to a decrease in the number of fatal and injury crashes on I-80 but an increase in minor property damage only crashes. Disaggregate analysis of the results was used to gain further understanding of the CRM safety performance. The differences in the resulting safety performances were contextualized based on the different settings where the systems were implemented. As expected, CRM systems were more effective for segments in the vicinity of ramps. Safety performance functions for shorter durations (e.g., for peak hours), the subject of the ongoing National Cooperative Highway Research Program Project 22-48, will help more precisely estimate the safety impact of CRMs. [ABSTRACT FROM AUTHOR]

Compound flooding is a type of flood event caused by multiple flood drivers. The associated risk has usually been assessed using statistics-based analyses or hydrodynamics-based numerical models. This study proposes a compound flood (CF) risk assessment (CFRA) framework for coastal regions in the contiguous United States (CONUS). In this framework, a large-scale river model is coupled with a global ocean reanalysis dataset to (a) evaluate the CF exposure related to the coastal backwater effects on river basins, and (b) generate spatially distributed data for analyzing the CF hazard using a bivariate statistical model of river discharge and storm surge. The two kinds of risk are also combined to achieve a holistic understanding of the continental-scale CF risk. The estimated CF risk shows remarkable inter- and intra-basin variabilities along the CONUS coast with more variabilities in the CF hazard over the US west and Gulf coastal basins. Different risk assessment methods present significantly different patterns in a few key regions such as the San Francisco Bay area, the lower Mississippi River, and Puget Sound. Our results highlight the need to weigh different CF risk measures and avoid using single statistics-based or hydrodynamics-based CFRAs. Uncertainty sources in these CFRAs include the use of gauge observations, which cannot account for the flow physics or resolve the spatial variability of risks, and underestimations of the flood extremes and the dependence of CF drivers in large-scale models, highlighting the importance of understanding the CF risks for developing a more robust CFRA. [ABSTRACT FROM AUTHOR]

Determining the statistical properties of salt intrusion in estuaries on sub‐tidal time scales is a substantial challenge in environmental modeling. To study these properties, we here extend an idealized deterministic salt intrusion model to a stochastic one by including a stochastic model of the river discharge. In the river discharge model, two types of stochastic forcing are used: one independent (additive noise) and one dependent (multiplicative noise) on the river discharge state. Each type of forcing results in a non‐Gaussian response in the salt intrusion length, which we consider here as the distance of the 2 psu isohaline contour to the estuary mouth. The salt intrusion model including both types of stochastic forcing in the river discharge provides a satisfactory explanation of the multi‐year statistics of observed salt intrusion lengths in the San Francisco Bay estuary, in particular for the skewness of its probability density function. Key Points: A stochastic dynamical model is developed to explain the statistics of salt intrusion in estuariesAdditive (multiplicative) noise in river discharge induces a positive (negative) skewness in the salt intrusion length statisticsBoth additive and multiplicative noise in river discharge are important forthe salt intrusion statistics in the San Francisco Bay estuary [ABSTRACT FROM AUTHOR]

Studies on the relationship between temperature and local, small scale mobility are limited, and sensitive to the region and time period of interest. We contribute to the growing mobility literature through a detailed characterization of the observed temperature‐mobility relationship in the San Francisco Bay Area at fine spatial and temporal scale across two summers (2020–2021). We used anonymized cellphone data from SafeGraph's neighborhood patterns data set and gridded temperature data from gridMET, and analyzed the influence of incremental changes in temperature on mobility rate (i.e., visits per capita) using a panel regression with fixed effects. This strategy enabled us to control for spatial and temporal variability across the studied region. Our analysis suggested that all areas exhibited lower mobility rate in response to higher summer temperatures. We then explored how several additional variables altered these results. Extremely hot days resulted in faster mobility declines with increasing temperatures. Weekdays were often more resistant to temperature changes when compared to the weekend. In addition, the rate of decrease in mobility in response to high temperature was significantly greater among the wealthiest census block groups compared with the least wealthy. Further, the least mobile locations experienced significant differences in mobility response compared to the rest of the data set. Given the fundamental differences in the mobility response to temperature across most of our additive variables, our results are relevant for future mobility studies in the region. Plain Language Summary: Studies on the relationship between temperature and local, small scale mobility are limited, and sensitive to the region and time period of interest. We used anonymized cellphone data and gridded daily temperature data to explore how mobility responded to temperature variations in the San Francisco Bay Area during the summer months of 2020 and 2021. Employing a statistical causal inference method that controlled for variability in time and space, we found that almost all areas exhibited decreased mobility in response to higher summer temperatures. However, the rate of decrease was higher on hot days, in wealthier areas, and on weekends. These differences among many groups make our results particularly relevant for mobility studies in highly populated regions, both now and with rising temperatures in the future. Key Points: We investigate the influence of 2020–2021 summer temperatures on local, daily summer mobility in the San Francisco Bay AreaMobility generally decreased with increasing temperatures, and was particularly sensitive on extremely hot daysFactors such as period of the week, median income of destination, and being one of the most or least mobile locations influenced mobility [ABSTRACT FROM AUTHOR]

The South Bay Salt Pond Restoration Project aims to restore many former salt production ponds, now managed for wildlife and water quality, to tidal marsh. However, because managed ponds support large densities of breeding waterbirds, reduction of pond habitat may influence breeding waterbird distribution and abundance. We investigated habitat use associated with breeding, feeding, and roosting behaviors during the breeding season for American Avocets (Recurvirostra americana), Black-necked Stilts (Himantopus mexicanus), Forster's Terns (Sterna forsteri), and Caspian Terns (Hydroprogne caspia) in south San Francisco Bay in 2019 after substantial tidal marsh restoration, and compared results to a 2001 survey (before restoration). In 2019, managed ponds (26% of currently available habitat) were selected by waterbirds engaged in breeding behaviors (> 39% of observations), foraging (> 42%), and roosting (> 73%). Waterbirds avoided tidal habitats (43% of available habitat), comprising < 17% of observations of breeding behavior, < 28% of foraging observations, and < 13% of roosting observations. Waterbird densities increased in managed ponds between 2001 and 2019, and decreased in active salt ponds, especially among feeding Avocets (92% decrease) and Stilts (100% decrease). Islands were important for waterbirds observed breeding and roosting (45% of Avocet and 53% of Tern observations). Avocets and Stilts fed primarily on wet bare ground (65% and 58%, respectively), whereas feeding Forster's Terns and Caspian Terns used mostly open water (82% and 93%, respectively). Within ponds, Avocets were associated with islands (131 m closer than expected). Stilts and Forster's Terns were also associated with islands (68 m and 161 m closer than expected), except when feeding (1 m closer and 90 m farther than expected). Avocets and Stilts were associated with pond levees (39 m and 41 m closer than expected), but Forster's Terns were not (9 m closer than expected). Our results emphasize the importance of managed ponds for breeding and foraging waterbirds, including islands for breeding and roosting and levees for foraging. [ABSTRACT FROM AUTHOR]

The San Francisco Bay-Delta estuary and its upstream watershed have been highly modified since exploration and settlement by Europeans in the mid-18th century. Although these hydrologic alterations supported the growth of California's economy to the eighth largest in the world, they have been accompanied by significant declines in native aquatic species and subsequent efforts to reverse these declines through flow management. To inform ongoing deliberations on management of freshwater flows to the estuary, we examined a recent nine-decade hydrologic record to evaluate seasonal and annual trends in reported Delta outflow. Statistically significant trends were observed in seasonal outflows, with decreasing trends observed in 4 months (February, April, May, and November) and increasing trends observed in 2 months (July and August). Trend significance in early-to-mid autumn (September and October) is ambiguous due to uncertainty associated with in-Delta agricultural water use. In spite of increasing water use over the period examined, we found no statistically significant annual trend in Delta outflow, a result likely due to large interannual variability. Linkages between outflow trends and changes in upstream flows and coincident developments such as reservoir construction and operation, out-of-basin imports and exports, and expansion of irrigated agriculture are discussed. To eliminate inter-annual variability as a factor, change attribution is explored using modelled flows and fixed climatology in a companion paper. [ABSTRACT FROM AUTHOR]