Natural infrastructure in sustaining global urban freshwater ecosystem services

Nature Portfolio (Springer Nature) | October 21st, 2021

Rapid urbanization throughout the globe increases demand for fresh water and the ecosystem services associated with it. This need is conventionally met through the constr

Rapid urbanization throughout the globe increases demand for fresh water and the ecosystem services associated with it. This need is conventionally met through the construction of infrastructure. Natural infrastructure solutions have increased to provide freshwater ecosystem services, but little global research has examined the intricate relationships between built and natural infrastructure for providing freshwater ecosystem services to cities across the globe. Using network analysis, here we examine the interrelationships between built and natural infrastructure in 2,113 watersheds for 317 cities worldwide, focusing on four key freshwater ecosystem services: freshwater provision, sediment regulation, flood mitigation and hydropower production. Our results indicate that protected wetlands contribute to sustaining freshwater provision to cities. Forest cover in protected areas can improve the capacity of large dams in reducing sediment loads and producing hydropower, but cities mainly depend on reduced impervious surfaces and more green spaces within urban areas for flood mitigation. Improved understandings of the role of natural infrastructure in urban water networks must underpin strategic decision-making to sustainably provide freshwater ecosystem services to global cities.

Nature-based solutions extend the lifespan of a regional levee system under climate change

Nature Portfolio (Springer Nature) | May 9th, 2025

Navigating a Flood of Information Evaluating and Integrating Climate Science into Groundwater Planning in California

Union of Concerned Scientists | November 1st, 2017

In early 2017, northern California experienced record-setting levels of precipitation. The amount of rain and snow from October 2016 through February 2017 was the greates

In early 2017, northern California experienced record-setting levels of precipitation. The amount of rain and snow from October 2016 through February 2017 was the greatest in the 122 years of California record-keeping. As the reservoir behind Oroville Dam quickly filled to capacity, a torrent of excess water was let out through the main spillway. Shortly thereafter the spillway began to collapse, leading to massive soil erosion and concerns that the erosion could undermine the dam itself. Fears of a catastrophic dam breach led to the evacuation of around 180,000 residents downstream from the dam. While we do not know how much climate change contributed to this particular event, we do know that climate change is making extreme events more common (Black et al. 2016; Mote et al. 2016; Otto 2016). While reports indicate that management failures may have played in an important role in the Oroville disaster, it is also true that this event took place in the context of extreme weather, and that climate change is increasing pressure on structures and communities. This finding is not limited to highprofile infrastructure such as the Oroville Dam. Much of our water infrastructure, management tools, institutions, and planning mechanisms are not designed for the increased magnitude and frequency of such extremes—making the state, its environment, and its water resources vulnerable to the changes we are likely to see in the coming decades. In California, groundwater contributes more than half of the state’s water supply during dry years (DWR 2009). Therefore, understanding the impacts that climate change will have on this critical resource will be of particular importance for the state’s water and food security over the long term. To that end, Governor Jerry Brown issued Executive Order B-30-15 that, along with setting ambitious greenhouse gas reduction targets, requires state agencies take climate change into account in their planning and investment decisions. In addition, California’s Sustainable Groundwater Management Act (SGMA), passed by the legislature in 2014, requires that Groundwater Sustainability Agencies (GSAs) explicitly assess the impacts of climate change and incorporate these assessments into their Groundwater Sustainability Plans (GSPs). Under the legislation, GSAs must develop and implement GSPs to achieve sustainable groundwater management in all high- and medium-priority groundwater basins in the state. Within these plans, GSAs are required to provide “[p]rojected water budget information for population, population growth, climate change, and sea level rise” (CWR 354.18(d)(3)). Additionally, projected water budgets must “identify the uncertainties of these projected water budget components,” including uncertainties in projected hydrology, water demand, and surface water supply resulting from sea level rise, land use changes, population growth, and climate change (CWR 354.18(c)(3)). To meet these regulatory requirements, plans must “rely on the best available information and best available science to quantify the water budget for the basin” (CWR 354.18(e)). Yet, it can be difficult to identify the best approach to incorporating climate change into local plans. The purpose of this white paper is to assist in that challenging task. The consequences of not incorporating climate change into water planning can be severe, leading to unforeseen costs and even threatening lives. It is therefore the intention of this white paper to: • provide water managers and other decision-makers across the state with an overview of climate models, their component parts, and key terminology • provide a framework for evaluating and comparing the various approaches currently employed by the state and federal agencies to incorporating climate change into state-level water planning documents • recommend a four-step process to incorporate future climate projections into local GSPs Recognizing the importance of climate change impacts on the state’s water supply, the California Department of Water Resources (DWR) has devoted a significant amount of time and expertise to integrating climate change into water planning. In 2012, DWR convened the Climate Change Technical Advisory Group (DWR CCTAG) to advise DWR on the scientific aspects of climate change, the impact of climate change on water resources, the use and creation of planning approaches and analytical tools, and the development of adaptation responses. The DWR CCTAG released a report in 2015, Perspectives and Guidance for Climate Change Analysis, which makes several recommendations for future work. One central theme is the need to develop guidance and support for water managers and planners. Factoring climate change into water management decisions requires future projections of how climate change will impact water-relevant factors such as temperature and precipitation—projections that are generally derived from global climate models. However, incorporating climate change into water planning for any given community or groundwater basin can be difficult, not only because of the technical expertise required to do so, but also because the effects of climate change are spatially and temporally variable. Although the scientific community has high confidence in a key set of variables for the planet as a whole, translating global estimates of climate change to specific geographical areas creates uncertainty. Fortunately, there are tools and methods to address uncertainty. As is the case for other natural phenomena that are difficult to predict with precision, such as earthquakes, uncertainty cannot be an excuse for inaction. Scientific and technical tools can substantially assist in creating plans that cope with an uncertain future. This white paper does not directly address the role of hydrologic models themselves, but rather addresses how climate change information can be incorporated into hydrologic models as water managers seek to comply with the requirements of SGMA. The process of incorporating climate change into water management decisions has several steps, starting with running global climate models to produce future climate projections, which are then used as inputs to hydrologic models (Figure 1). We recognize that GSAs are likely to engage at different levels of technical sophistication with climate data and that the majority will seek out the services of technical experts. Ultimately, it is our intent that this white paper equip water managers with sufficient knowledge about climate change projections to understand, evaluate, and direct the work of the technical experts and consultants. Using appropriate climate change information is vital to ensuring that water managers capture potential future water resource conditions. This white paper is organized into three main sections. The first section provides a general overview of climate models, including their strengths and limitations and the type of information they can provide, and describes a framework for incorporating their output into management decisions. The second section addresses how to incorporate climate change into planning involving imported water supplies. The third section turns to planning for local water supplies and proposes a process for incorporating appropriate climate change data into GSPs.

New Life for Eroding Shorelines: Beach and Marsh Edge Change in the San Francisco Estuary

San Francisco Estuary Institute (SFEI) | April 1st, 2020

Wind, waves, storms, and changing water levels have reshaped shorelines for millennia and continue to do so today. The current shape of the San Francisco (SF) Estuary sho

Wind, waves, storms, and changing water levels have reshaped shorelines for millennia and continue to do so today. The current shape of the San Francisco (SF) Estuary shoreline is relatively new; 15,000 years ago, the California shoreline was west of the Farallon Islands and 140 meters below its current level (Cohen and Laws 1992, Malamud-Roam et al. 2007). By approximately 6,000 years ago (the end of the last glacial epoch), the sea had risen to nearly its present level and filled what is now San Francisco Bay, allowing marshes to form and maintain themselves (Atwater 1979). More recently, humans have changed the shape of the shoreline. During the 1850s, many marshes expanded extensively due to increased sediment supply from hydraulic mining in the Sierra Nevada (Gilbert 1917, Goals Project 1999). Diking, dredging, and filling of marshes for agricultural and urban development began in the late 19th century and continued through the first half of the 20th century.  Today, humans continue to reshape the shoreline through continued diking, dredging and filling as well as restoration projects, urbanization of watersheds, ferry wakes, and many other means. The most wide-ranging impact of human activity on the shape of shorelines is global climate change caused by greenhouse gas emissions, which is accelerating the rate of sea level rise worldwide (OPC 2018). Sea level rise is likely to cause much more dramatic changes in the shape of shorelines than have been seen in recent centuries. The magnitude and pace of change will depend on the rate of sea level rise, existing shoreline conditions, and the ability of shorelines to adapt. 

New Method for Estimating Landslide Losses from Major Winter Storms in California and Application to the ARkStorm Scenario

American Society of Civil Engineers (ASCE) | May 30th, 2014

ARkStorm is a statewide emergency planning scenario hypothesizing severe atmospheric river storms that transport huge amounts of moisture from the tropical Pacific to Cal

ARkStorm is a statewide emergency planning scenario hypothesizing severe atmospheric river storms that transport huge amounts of moisture from the tropical Pacific to California, where it falls as intense rain. The storm is projected to be similar to historic storms that have struck California in recent decades, but include extended periods of intense rainfall that approach the massive storms of 1861–1862 in total rainfall. A meteorological model for the ARkStorm has been developed from records of the 1969 and 1986 storms, both of which caused widespread landslides and severe damage in California. Estimating the numbers and impact of landslides from the ARkStorm requires models relating rainfall to the number and distribution of landslides and detailed records of the impact of landslides in past storms. Neither of these basic data sets exist. However, models that estimate the areas with the greatest susceptibility to landsliding do exist and can be combined with detailed maps of small areas showing the numbers of landslides triggered in individual storms. This study extrapolated from local landslide damage to private property in past storms by using a new statewide landslide susceptibility map. These methods may provide a framework for other landslide loss estimates, which can be greatly improved with additional data. Records of landslide losses to the state highway system are more complete than records of damage to private property; it was possible to assemble records for only the past 10 years. Even within these short records, the amount of damage to the state highway system appears to be correlated with rainfall. Projecting from these records, the amount of landslide damage to highways and other infrastructure from the ARkStorm can be estimated. Overall, it is estimated that the ARkStorm would trigger landslides that directly cause billions of dollars in damage.

North Delta Water Management Program

California Department of Water Resources (DWR) | March 1st, 1988

Water management issues surrounding the Sacramento-San Joaquin Delta continue to challenge water resource planners in California. Many agree there are problems and urge

Water management issues surrounding the Sacramento-San Joaquin Delta continue to challenge water resource planners in California. Many agree there are problems and urge that they be corrected, but a consensus on how best to solve them has not yet been reached. Problems include frequent flooding due to unstable levees and constricted channels, flow patterns that are unfavorable for fish and water quality, and water level and circulation patterns that hinder irrigation. During the last several years, various water resources problems have been corrected through application of the public environmental documentation and regulatory permit process. This process has also shown the importance of Federal permit regulations in governing projects in the Delta estuary. To facilitate planning, the estuary has been divided into three study areas for evaluation of problems and needs unique to each area -- North, South, and West. This report discusses concepts for a North Delta Water Management Program. The long-term planning and environmental documentation process will includeother reports and will take about three years to complete. Planning flexibility afforded by the environmental documentation and regulatory permit process is expected to allow many of the concerns surrounding Delta water management to be resolved.

Novato Creek Baylands Historical Ecology Study

San Francisco Estuary Institute (SFEI) | July 31st, 2015

Over the past century and a half, lower Novato Creek and the surrounding tidal wetlands have been heavily modified for flood control and land reclamation purposes. Levees

Over the past century and a half, lower Novato Creek and the surrounding tidal wetlands have been heavily modified for flood control and land reclamation purposes. Levees were built in the tidal portion of the mainstem channel beginning in the late 1800s to convey flood flows out to San Pablo Bay more rapidly and to remove surrounding areas from inundation. Following levee construction, the wetlands surrounding the channel were drained and converted to agricultural, residential, and industrial areas. These changes have resulted in a considerable loss of wetland habitat, reduced sediment transport to marshes and the Bay, and an overall decreased resilience of the system to sea level rise. In addition to tidal wetland modification, land use changes upstream in the Novato Creek watershed have resulted in several challenges for flood control management. Dam construction and increased runoff in the upper watershed have resulted in elevated rates of channel incision, which have increased transport of fine sediment from the upper watershed to lower Novato Creek. Channelization of tributaries and construction of irrigation ditches have likely increased drainage density in the upper watershed, also potentially contributing to increased rates of channel incision and fine sediment production (Collins 1998). Downstream, sediment transport capacity has been reduced by construction of a railroad crossing and loss of tidal prism and channel capacity associated with the diking of the surrounding marsh. As a result of the increased fine sediment supply from the watershed and the loss of sediment transport capacity in lower Novato Creek, sediment aggradation occurs within the channel, which in turn reduces the flood capacity of the channel, necessitating periodic dredging (fig. 1; Collins 1998, PWA 2002).

Novato Creek Baylands Vision

San Francisco Estuary Institute (SFEI) | November 1st, 2015

As we rethink land management along the San Francisco Bay shoreline in the face of climate change, we know well-functioning resilient tidal landscapes can protect develop

As we rethink land management along the San Francisco Bay shoreline in the face of climate change, we know well-functioning resilient tidal landscapes can protect development and sustain native ecosystems. Here, we present a possible future vision for lower Novato Creek and adjacent baylands that includes several components that would restore and support natural processes, and, in turn, benefit aspects of flood risk management and ecosystem functioning. The Novato Creek Baylands Vision is an element of an EPA-funded project called Flood Control 2.0, which is aimed at advancing new approaches for flood risk management and habitat enhancement along the San Francisco Bay shoreline for the 21st century and beyond.

Objective definition of rainfall intensity-duration thresholds for the initiation of post-fire debris flows in southern California

Landslides (Springer) | June 27th, 2012

Rainfall intensity–duration (ID) thresholds are commonly used to predict the temporal occurrence of debris flows and shallow landslides. Typically, thresholds are sub

Rainfall intensity–duration (ID) thresholds are commonly used to predict the temporal occurrence of debris flows and shallow landslides. Typically, thresholds are subjectively defined as the upper limit of peak rainstorm intensities that do not produce debris flows and landslides, or as the lower limit of peak rainstorm intensities that initiate debris flows and landslides. In addition, peak rainstorm intensities are often used to define thresholds, as data regarding the precise timing of debris flows and associated rainfall intensities are usually not available, and rainfall characteristics are often estimated from distant gauging locations. Here, we attempt to improve the performance of existing threshold-based predictions of post-fire debris-flow occurrence by utilizing data on the precise timing of debris flows relative to rainfall intensity, and develop an objective method to define the threshold intensities. We objectively defined the thresholds by maximizing the number of correct predictions of debris flow occurrence while minimizing the rate of both Type I (false positive) and Type II (false negative) errors. We identified that (1) there were statistically significant differences between peak storm and triggering intensities, (2) the objectively defined threshold model presents a better balance between predictive success, false alarms and failed alarms than previous subjectively defined thresholds, (3) thresholds based on measurements of rainfall intensity over shorter duration (≤60min) are better predictors of post-fire debris-flow initiation than longer duration thresholds, and (4) the objectively defined thresholds were exceeded prior to the recorded time of debris flow at frequencies similar to or better than subjective thresholds. Our findings highlight the need to better constrain the timing and processes of initiation of landslides and debris flows for future threshold studies. In addition, the methods used to define rainfall thresholds in this study represent a computationally simple means of deriving critical values for other studies of nonlinear phenomena characterized by thresholds.

Observed Impacts of Anthropogenic Climate Change on Wildfire in California

American Geophysical Union (AGU) | August 4th, 2019

Recent fire seasons have fueled intense speculation regarding the effect of anthropogenic climate change on wildfire in western North America and especially in Californi

Recent fire seasons have fueled intense speculation regarding the effect of anthropogenic climate change on wildfire in western North America and especially in California. During 1972–2018, California experienced a fivefold increase in annual burned area, mainly due to more than an eightfold increase in summer forest‐fire extent. Increased summer forest‐fire area very likely occurred due to increased atmospheric aridity caused by warming. Since the early 1970s, warm‐season days warmed by approximately 1.4 °C as part of a centennial warming trend, significantly increasing the atmospheric vapor pressure deficit (VPD). These trends are consistent with anthropogenic trends simulated by climate models. The response of summer forest‐fire area to VPD is exponential, meaning that warming has grown increasingly impactful. Robust interannual relationships between VPD and summer forest‐fire area strongly suggest that nearly all of the increase in summer forest‐fire area during 1972–2018 was driven by increased VPD. Climate change effects on summer wildfire were less evident in nonforested lands. In fall, wind events and delayed onset of winter precipitation are the dominant promoters of wildfire. While these variables did not change much over the past century, background warming and consequent fuel drying is increasingly enhancing the potential for large fall wildfires. Among the many processes important to California's diverse fire regimes, warming‐driven fuel drying is the clearest link between anthropogenic climate change and increased California wildfire activity to date.