Through the EPA-funded Healthy Watersheds Resilient Baylands project, SFEI and sixteen partner organizations are developing multi-benefit tools to enhance climate change resilience in San Francisco Bay. Healthy Watersheds Resilient Baylands has two major components: Multi-benefit Urban Greening and Tidal Wetlands Restoration. Through both components, we have developed strategies that inform policy, planning, and design of innovative implementation projects. Products include Making Nature’s City, Trees and Hydrology in Urban Landscapes, Sediment for Survival, and the Calabazas-San Tomas Aquino-Pond A8 Restoration Vision. By building cutting-edge science into management approaches, we demonstrate how urban greening and tidal wetlands redesign can improve water quality and ecological resilience in cities, creeks and the baylands. Once installed, urban greening projects will reduce stormwater runoff and capture pollution in the cities of Sunnyvale, Mountain View, and East Palo Alto and allow the cities to better support biodiversity. In addition, construction of a horizontal levee through partnership with the South Bay Salt Pond Restoration Project and realignment of Calabazas and San Tomas Aquino creeks through partnership with the Santa Clara Valley Water District will create transition zone habitat and reconnect watersheds to the baylands, reducing flood risk and delivering necessary sediment to marshes.
Multi-Benefit Urban Greening
Over the past few decades, interest in greening our cities has grown dramatically following two major developments. Scientific evidence from around the world is showing that despite their reputation as biological deserts, cities support a surprising amount of biodiversity, much of it thriving unnoticed in our midst. This finding has led to the recognition that cities can benefit nature, and that helping nature can be good for people too. Secondly, green stormwater infrastructure (GSI) is now widely used to reduce pollutants and runoff from stormwater systems. Trees and other urban greening measures can also help address these issues, while also providing biodiversity and other benefits. As cities continue to upgrade and green their infrastructure, an opportunity has emerged to achieve better ecological and stormwater management outcomes alongside benefits for people. However, capitalizing on this opportunity will require developing coordinated strategies that are regional in scope and that can address how to integrate multiple benefits.
Urban ecological science can provide a powerful tool to guide cities towards more biodiversity-friendly design. However, current research remains scattered across thousands of journal articles and is largely inaccessible to practitioners. Our report Making Nature’s City addresses these issues, synthesizing global research to develop a science-based approach for supporting nature in cities. Cities will face many challenges over the coming decades, from adapting to a changing climate to accommodating rapid population growth. A related suite of challenges threatens global biodiversity, resulting in many species facing extinction. While urban planners and conservationists have long treated these issues as distinct, there is growing evidence that cities not only harbor a significant fraction of the world’s biodiversity, but also that they can also be made more livable and resilient for people, plants, and animals through nature-friendly urban design.
Using the framework outlined in the report, urban designers and local residents can work together to connect, improve, and expand upon city greenspaces to better support biodiversity while making cities better places to live. As we envision healthier and more resilient cities, Making Nature’s City provides practical guidance for the many actors who together will shape the nature of cities.Over the past few decades, interest in greening our cities has grown dramatically following two major developments. Scientific evidence from around the world is showing that despite their reputation as biological deserts, cities support a surprising amount of biodiversity, much of it thriving unnoticed in our midst. This finding has led to the recognition that cities can benefit nature, and that helping nature can be good for people too. In addition, green infrastructure and trees have proven very effective at reducing runoff to stormwater systems, leading to widespread installation along streets and in parking lots. As cities continue to upgrade and green their infrastructure, an opportunity has emerged to achieve better ecological outcomes alongside benefits for people and stormwater. However, to capitalize on this opportunity will require developing coordinated strategies that are regional in scope and that can address how to integrate ecological benefits with other ecosystem services.
Effective implementation of urban greening strategies is needed to address legacies of landscape change and environmental degradation, ongoing development pressures, and the urgency of the climate crisis. With limited space and resources, these challenges will not be met through single-issue or individual-sector management and planning. Increasingly, local governments, regulatory agencies, and other urban planning organizations in the San Francisco Bay Area are expanding upon the holistic, portfolio-based, and multi-benefit approaches.
This effort, presented in the Trees and Hydrology in Urban Landscapes report, seeks to build links between stormwater management and urban ecological improvements by evaluating how complementary urban greening activities, including green stormwater infrastructure (GSI) and urban tree canopy, can be integrated and improved to reduce runoff and contaminant loads in stormwater systems. This work expands the capacity for evaluating engineered GSI and non-engineered urban greening within a modeling and analysis framework, with a primary focus on evaluating the hydrologic benefit of urban trees. Insights can inform stormwater management policy and planning.
A central component of this effort was advancing the GreenPlan-IT toolkit, a modeling and optimization framework for analysis of GSI, such that it could represent hydrologic processes within the tree canopy. To explore the role of trees in stormwater runoff, several test case sensitivity analyses were conducted. A demonstration analysis was performed for the City of Sunnyvale to assess the degree to which trees at the landscape scale affect city-wide runoff. Lastly, the report outlines a potential technical approach for expanded integrated multi-benefit assessment of urban greening.
Urban Greening Implementation Projects
The science-based guidance developed through this project will be used to shape three key implementation projects for stormwater management and urban greening:
- The City of Sunnyvale will demonstrate how bioretention features can create habitat for native pollinators while also reducing runoff. The Caribbean Drive Green Street Demonstration Project will retrofit an existing arterial street with bioretention rain gardens planted with native plants to create habitat for native species, reduce impervious surfaces, provide treatment and infiltration of runoff, calm traffic, and improve the streetscape for pedestrians and cyclists.
- Through Google’s Ecology program, Google will integrate ecological design into landscape planning through four innovative projects on their campuses in the bayshore areas of Sunnyvale and Mountain View. Over the past three years, Google’s Ecology Program has sponsored the development of the Resilient Silicon Valley project and the Landscape Resilience Framework by SFEI and partners to catalyze ecological improvements throughout the region. Google will collaborate with the Healthy Watersheds, Resilient Baylands team to maximize the ecological and hydrological benefits of new projects. These projects will highlight how ecologically designed landscaping can create habitat while reducing runoff and improving the human experience.
- The City of East Palo Alto, Canopy, and Grassroots Ecology will integrate street tree planting with landscaping and riparian restoration to expand riparian areas along San Francisquito Creek, create willow groves, and connect oak habitat to riparian corridors through adjacent neighborhoods to create more functional wildlife habitat. As part of these installations, the projects will improve soil conditions and understory habitat to maximize water retention, pollution capture, rainfall infiltration, and ecological value of the existing streetscape and parkways. This project will include training of students and other volunteers who will be engaged in native plant stewardship and through tree care events carried out with Teen Urban Foresters from the local community.
Tidal Wetland Restoration
The resilience of San Francisco Bay shore habitats is essential to all who live in the Bay Area. Tidal marshes and tidal flats are key components of the shore habitats, which collectively protect billions of dollars of bay-front housing and infrastructure (including neighborhoods, business parks, highways, sewage treatment plants, and landfills). They also purify the Bay’s water, support endangered wildlife, nurture fisheries, and provide people access to nature within the urban environment. Bay Area residents showed their commitment to restoring these critical habitats when they voted in 2016 for a property tax to pay for large-scale tidal marsh restoration. Sustaining tidal marshes and tidal flats into the future requires an understanding of the resources needed for them to keep pace with a rising sea level and multi-benefit shoreline projects that bring back lost shore habitats.
The tidal marshes and tidal flats along the San Francisco Bay shoreline depend on sediment delivered by the tides. Healthy sediment supplies are essential for maintaining resilient marshes and tidal flats that can persist into the future and build up as sea level continues to rise. Currently, the sediment supply in the Bay is adequate to meet the sediment needed by tidal marshes and tidal flats. However, as sea level rise accelerates in the coming decades, the sediment needed for these habitats to survive will increase considerably. In addition, a healthy sediment supply will be needed to support the thousands of acres of restored tidal marsh that is being planned around the Bay. As sediment becomes an increasingly precious resource for habitat support and shoreline protection, it is essential to understand the future of sediment demand and develop an integrated strategy for long-term sediment management and monitoring.
The Sediment for Survival report provides a regional sediment strategy aimed at examining the future of sediment in the Bay and informing sediment management for the resilience of tidal marshes and tidal flats to climate change. The report analyses current data and climate projections to determine how much natural sediment may be available for tidal marshes and tidal flats and how much supplemental sediment may be needed under different future scenarios. These sediment supply and demand estimates are combined with scientific knowledge of natural physical and biological processes to offer a multi-benefit strategy for sediment delivery that will allow these wetlands to survive a changing climate and provide benefits to people and nature for many decades to come. The approach developed in this effort may also be useful beyond San Francisco Bay because shoreline protection, flood risk management, and looming sediment deficits are common issues facing coastal communities around the world.
Calabazas Creek and San Tomas Aquino Creek drain parts of Sunnyvale, Santa Clara, and other cities, entering the Bay just east of Alviso. The creeks were realigned in the mid 20th century to make sharp 90° turns at the Pond A8 levee, where they are diverted into Guadalupe Slough. This artificial alignment decreases tidal prism and leads to the deposition of a large amount of sediment upstream, necessitating regular maintenance dredging and some of the highest estimated annual dredging costs in the South Bay. A portion of the sediment dredged from these channels is currently manually excavated and delivered by truck for placement along the shoreline of Pond A8.
SFEI worked with the Santa Clara Valley Water District, the South Bay Salt Pond Restoration Project, and team of science advisors to develop a science-based vision for this complex site. This vision provides a suite of measures that benefit both flood management and bayland habitat restoration under a changing climate. The proposed creek-bayland reconnection that is central to the vision would allow sediment delivery to help facilitate tidal marsh restoration, create a pathway for marsh migration with sea-level rise, reduce the risk of landfill erosion and associated water quality impacts, and improve ecosystem functioning and resilience through the creation of estuarine-terrestrial transition zones. The vision is divided into a first phase with measures that could be implemented over the next decade and a second phase with measures that could be implemented over a longer planning horizon. Upon implementation of the vision, Calabazas and San Tomas Aquino creeks could be the first creeks in San Francisco Bay to be realigned to discharge directly into their historical tidal marshlands— a case study that could be used to inform future reconnection projects in similar landscapes around the Bay and guide responsive policies to climate change challenges.
2016 to 2021
Programs and Focus Areas:
Geographic Information Systems
Resilient Landscapes Program
Watershed Science & Management
Urban Nature Lab