Hydroclimatic Extremes as Challenges for the Water Management Community: Lessons from Oroville Dam and Hurricane Harvey

American Meteorological Society (AMS) | December 31st, 2018

Record-breaking extreme storms were a hallmark of 2017 in the United States. An extremely wet winter on the West Coast and brutally damaging hurricane season in

Record-breaking extreme storms were a hallmark of 2017 in the United States. An extremely wet winter on the West Coast and brutally damaging hurricane season in the U.S. Southeast and the Caribbean challenged communities and power-, water- and flood-management systems in ways that raised climate change concerns. Among the most severe were two periods of heavy precipitation and high runoff that exposed dangerous weaknesses in water management infrastructure and land use practices in California and Texas. In California, a record-breaking string of atmospheric river landfalls and remarkably wet winter conditions came close to causing a catastrophic failure of the emergency spillway at Oroville Dam (France et al. 2018; Abbott 2018; White et al. 2019) and less publicized concerns elsewhere (Holland et al. 2018; CNRFC 2017). In Texas, near record-doubling rainfall accumulations from Hurricane Harvey led to massive flooding (Blake and Zelinsky 2018) and dam safety challenges in Houston (Wax-Thibodeaux et al. 2017). We use these events as examples to ground the concept that attribution studies, with careful management-focused framing, can help water management better navigate such unprecedented extremes. *Chapter from the American Meteorological Society's Explaining Extreme Events of 2017 from a Climate Perspective.

Impacts of ocean acidification on marine organisms: quantifying sensitivities and interaction with warming

Global Change Biology | February 21st, 2013

Ocean acidification represents a threat to marine species worldwide, and forecasting the ecological impacts of acidification is a high priority for science, management, a

Ocean acidification represents a threat to marine species worldwide, and forecasting the ecological impacts of acidification is a high priority for science, management, and policy. As research on the topic expands at an exponential rate, a comprehensive understanding of the variability in organisms' responses and corresponding levels of certainty is necessary to forecast the ecological effects. Here, we perform the most comprehensive meta‐analysis to date by synthesizing the results of 228 studies examining biological responses to ocean acidification. The results reveal decreased survival, calcification, growth, development and abundance in response to acidification when the broad range of marine organisms is pooled together. However, the magnitude of these responses varies among taxonomic groups, suggesting there is some predictable trait‐based variation in sensitivity, despite the investigation of approximately 100 new species in recent research. The results also reveal an enhanced sensitivity of mollusk larvae, but suggest that an enhanced sensitivity of early life history stages is not universal across all taxonomic groups. In addition, the variability in species' responses is enhanced when they are exposed to acidification in multi‐species assemblages, suggesting that it is important to consider indirect effects and exercise caution when forecasting abundance patterns from single‐species laboratory experiments. Furthermore, the results suggest that other factors, such as nutritional status or source population, could cause substantial variation in organisms' responses. Last, the results highlight a trend towards enhanced sensitivity to acidification when taxa are concurrently exposed to elevated seawater temperature.

Impacts of Predicted Sea-Level Rise and Extreme Storm Events on the Transportation Infrastructure in the San Francisco Bay Region

California Energy Commission (CEC) | July 31st, 2012

Literature concerning the potential effect of climate change (sea‐level rise inundation and 100‐year storm events) on the San Francisco Bay region’s transportation

Literature concerning the potential effect of climate change (sea‐level rise inundation and 100‐year storm events) on the San Francisco Bay region’s transportation infrastructure is reviewed. Currently available geographical information system data is employed, and a review of how those datasets have been used in previous studies is reported. The second part of this paper presents methods. They include a higher‐resolution digital elevation model for the Bay Area; a new approach using a digital surface model is introduced to improve the surface elevations of features and better calculate the risk of over‐topping by sea level shifts and storm surges. A metric to assess change in the transportation infrastructure is introduced that calculates accessibility of first responders to the population at large. Sea level rise is incremented to the expected 1.4 meters in tandem with a 100‐year flood to analyze the extent to which transportation assets are at risk of inundation. The increased travel time from first responder locations to all neighborhoods in the region is measured for each iteration of the model. Local accessibility analysis for the entire San Francisco Bay region is performed to provide a synoptic view. Two localities are chosen to view in detail the impact on first‐responder accessibility caused by sea level rise and a 100‐year storm event. Next, the regional vulnerability of the transportation network to these events is assessed. This is accomplished by creating nodes that are the intersections of the major regional highways that surround the Bay. The loss of accessibility is measured by calculating the changes in travel time between these major nodes through iterations of our inundation model. Finally, the accessibility impacts to the hinterland from the major highway intersections for each peak water level iteration is determined, calculating the first and last 20 minutes of an origin‐destination journey.

Incorporating Sea Level Change in Civil Works Programs

U.S. Army Corps of Engineers (USACE) | December 31st, 2013

Increased Interannual Precipitation Extremes over California under Climate Change

American Meteorological Society (AMS) | August 10th, 2015

Changes to mean and extreme wet season precipitation over California on interannual time scales are analyzed using twenty-first-century precipitation data from 34

Changes to mean and extreme wet season precipitation over California on interannual time scales are analyzed using twenty-first-century precipitation data from 34 global climate models. Models disagree on the sign of projected changes in mean precipitation, although in most models the change is very small compared to historical and simulated levels of interannual variability. For the 2020/21–2059/60 period, there is no projected increase in the frequency of extremely dry wet seasons in the ensemble mean. Wet extremes are found to increase to around 2 times the historical frequency, which is statistically significant at the 95% level. Stronger signals emerge in the 2060/61–2099/2100 period. Across all models, extremely dry wet seasons are roughly 1.5 to 2 times more common, and wet extremes generally triple in their historical frequency (statistically significant). Large increases in precipitation variability in most models account for the modest increases to dry extremes. Increases in the frequency of wet extremes can be ascribed to equal contributions from increased variability and increases to the mean. These increases in the frequency of interannual precipitation extremes will create severe water management problems in a region where coping with large interannual variability in precipitation is already a challenge. Evidence from models and observations is examined to understand the causes of the low precipitation associated with the 2013/14 drought in California. These lines of evidence all strongly indicate that the low 2013/14 wet season precipitation total can be very likely attributed to natural variability, in spite of the projected future changes in extremes.

Increasingly frequent extreme weather events urge the development of point-of-use water treatment systems

Nature Portfolio (Springer Nature) | August 13th, 2022

The frequency of extreme weather events, including floods, storms, droughts, extreme temperatures, and wildfires, has intensified globally over recent decades due to clim

The frequency of extreme weather events, including floods, storms, droughts, extreme temperatures, and wildfires, has intensified globally over recent decades due to climate change, affecting human society profoundly. Among all the impacts of these extreme weather events, the consequences to our reliable water supply have gained increasing attention as they exacerbate the inequities in health and education, especially in marginalized populations. In this perspective, we emphasize that extreme weather events are able to undermine a stable supply of drinking water through a number of approaches, and conventional centralized water treatment is insufficient at addressing these challenges. We urge that greater recognition, increased public awareness, and more efforts on technological innovation on decentralized, especially point-of-use (POU), water treatment should be prioritized to better help tackle the challenges faced by increasingly frequent extreme weather events.

Independent Panel Review of the Bay Delta Conservation Plan prepared for The Nature Conservancy and American Rivers

Nature Conservancy | September 19th, 2013

Two non-­governmental organizations, The Nature Conservancy (TNC) and American Rivers (AR), are evaluating their options for engagement with the Bay Delta Conservation P

Two non-­governmental organizations, The Nature Conservancy (TNC) and American Rivers (AR), are evaluating their options for engagement with the Bay Delta Conservation Plan (BDCP). If approved, the Plan would become a Habitat Conservation Plan (HCP) under the federal Endangered Species Act and a Natural Communities Conservation Plan (NCCP) under California law. The purpose of the Plan is to allow for construction of new water diversion facilities in the Sacramento-­San Joaquin Delta while also protecting aquatic and terrestrial species that may be adversely affected by the project and accompanying changes in the State Water Project (SWP) and Central Valley Project (CVP) operations. The Plan also includes habitat restoration and a commitment to assist in the conservation and recovery of species that are listed for protection under the federal and state Endangered Species Acts. With financial support from the S.D. Bechtel, Jr. Foundation, Saracino and Mount, LLC, convened an independent panel of experts, with technical support from NewFields, Inc., to evaluate portions of the Plan. The panel, working jointly with TNC and AR, developed a series of technical and legal questions about the Plan. This report provides answers to these questions, along with limited recommendations on how to improve BDCP. To simplify analysis, this review focuses on conditions for federally listed fishes during the Early Long Term (ELT), a decade after a permit would be issued (approximately year 2025). These are described in detail in the BDCP Effects Analysis and accompanying Environmental Impact Statement/Environmental Impact Report. We compared the performance of three different scenarios: a No Action Alternative (NAA) where no new North Delta diversion facility is constructed, a High Outflow Scenario (HOS) where the facilities are operated in a way that allows for occasional high spring and fall outflows, and a Low Outflow Scenario (LOS) with lower spring and fall outflows. The review also emphasizes in-­Delta and Sacramento River watershed conditions during the ELT, with less attention to San Joaquin River conditions and fishes. Although multiple data sources were used in this analysis, most hydrologic data came from CALSIM simulations conducted by BDCP consultants. The Panel strongly cautions about the conclusions drawn from these simulations. Flow simulations have three compounding uncertainties that can lead to significant error: (1) uncertainty in system understanding and future conditions, (2) model uncertainties (particularly the relationships between 1-­, 2-­, and 3-­dimensional models), and (3) behavioral/regulatory uncertainty where the models cannot capture the scope of human behavior in operating the projects under various conditions. These uncertainties, which are not described in BDCP documents well, makes all of our conclusions contingent on the projects actually being operated as simulated.

Inequitable patterns of US flood risk in the Anthropocene

Nature Portfolio (Springer Nature) | January 31st, 2022

Current flood risk mapping, relying on historical observations, fails to account for increasing threat under climate change. Incorporating recent developments in inundati

Current flood risk mapping, relying on historical observations, fails to account for increasing threat under climate change. Incorporating recent developments in inundation modelling, here we show a 26.4% (24.1–29.1%) increase in US flood risk by 2050 due to climate change alone under RCP4.5. Our national depiction of comprehensive and high-resolution flood risk estimates in the United States indicates current average annual losses of US$32.1 billion (US$30.5–33.8 billion) in 2020’s climate, which are borne disproportionately by poorer communities with a proportionally larger White population. The future increase in risk will disproportionately impact Black communities, while remaining concentrated on the Atlantic and Gulf coasts. Furthermore, projected population change (SSP2) could cause flood risk increases that outweigh the impact of climate change fourfold. These results make clear the need for adaptation to flood and emergent climate risks in the United States, with mitigation required to prevent the acceleration of these risks.

Integrated approaches to understanding and reducing drought impact on food security across scales

Current Opinion in Environmental Sustainability (Elsevier) | October 1st, 2019

Understanding the cross-scale linkages between drought and food security is vital to developing tools to reduce drought impacts and support decision making. This study re

Understanding the cross-scale linkages between drought and food security is vital to developing tools to reduce drought impacts and support decision making. This study reviews how drought hazards transfer to food insecurity through changes in physical processes and socio-environmental systems across a wide range of spatial and temporal scales. We propose a multi-scale, integrated framework leveraging modeling advances (e.g. drought and crop monitoring, water-food-energy nexus, decision making) and increased data availability (e.g. satellite remote sensing, food trade) through the lens of the coupled human–natural system to support multidisciplinary approaches and avoid potential policy spillover effects. We discuss current scale-dependent challenges in tackling drought-induced food security whilst minimizing water use conflicts and environmental impacts. 

Large and inequitable flood risks in Los Angeles, California

Nature Portfolio (Springer Nature) | October 31st, 2022

Flood risks in the United States have historically been underestimated, particularly with respect to human well-being and within low-wealth and marginalized communities.

Flood risks in the United States have historically been underestimated, particularly with respect to human well-being and within low-wealth and marginalized communities. Here, we characterize a fuller range of risks in Los Angeles, California, using a quantitative framework that intersects flood hazards from rainfall, streamflow and storm tides with measures of exposure and vulnerability including ethnicity, race and socioeconomic disadvantage. We find that between 197,000 and 874,000 people (median 425,000) and between US$36 billion and US$108 billion in property (median US$56 billion) are exposed to flooding greater than 30 cm within the 100-year flood zone, risk levels far above federally defined floodplains and similar to the most damaging hurricanes in US history. These risks are disproportionately higher for non-Hispanic Black and disadvantaged populations, burdening communities that may have greater challenges recovering and reinforcing socioeconomic inequities. Our framework creates opportunities for transparently and equitably reducing flood risks in urban areas.