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Pearce, S.; Mckee, L.; Whipple, A.; Church, T. 2021. Towards a Coarse Sediment Strategy for the Bay Area. SFEI Contribution No. 1032. San Francisco Estuary Institute: Richmond, CA.

Historic and current regional management of watersheds and channels for water supply and flood control across the San Francisco Bay Area has cut off much of the coarse sediment that was historically delivered to the Bay. Here we define coarse sediment as having grain sizes larger than 0.0625 mm, which includes sand, gravel and even cobble, as opposed to fine sediment that includes clay, mud and silt. Future projections indicate that sediment supply will not meet the demand from extant and restored tidal marshes to keep up with sea level rise.

The US EPA Water Quality Improvement Fund Preparing for the Storm grant has funded the Zone 7 Water Agency, the San Francisco Estuary Institute and the San Francisco Bay Joint Venture to support the future development of a successful regional coarse sediment reuse strategy. Development of such a strategy requires an understanding of logistical and regulatory hurdles and identification of key strategies for breaking down barriers. One potential solution for meeting the sediment demand along the Bay margin is to utilize coarse sediment that is removed from flood control channels by public agencies. To-date, very little of this sediment that is removed is beneficially reused for restoration along the Bay shoreline. The current economic and regulatory framework around sediment removal presents many challenges, barriers and lack of incentives for agencies to reuse their sediment.

This document represents a step forward towards beneficially reusing coarse flood control channel sediment by outlining reuse challenges, and identifying incentives for participation and potential solutions.

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Zi, T.; Whipple, A.; Kauhanen, P.; Spotswood, E.; Grenier, L.; Grossinger, R.; Askevold, R. 2021. Trees and Hydrology in Urban Landscapes. SFEI Contribution No. 1034. San Francisco Estuary Institute: Richmond, CA.

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. 

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Panlasigui, S.; Pearce, S.; Hegstad, R.; Quinn, M.; Whipple, A. 2020. Wildlife Habitat and Water Quality Enhancement Opportunities at Castlewood Country Club. SFEI Contribution No. 1003. San Francisco Estuary Institute: Richmond, CA.

Meeting human and ecological needs within San Francisco Bay’s watersheds is increasingly challenged by flooding, water quality degradation, and habitat loss, exacerbated by intensified urbanization and climate change. Addressing these challenges requires implementing multi-benefit strategies through new partnerships and increased coordination across the region’s diverse landscapes. Actions to improve water quality and enhance habitat for biodiversity in our highly developed and managed landscapes can help the region as a whole to build resilience to withstand current pressures and future change. The EPA-funded project, “Preparing for the Storm,” aims to address these challenges at the site- and landscape-scale through studies and implementation projects in the Livermore-Amador Valley. As part of this larger project, this technical report presents a synthesis of water quality and habitat improvement opportunities for a golf course of Castlewood Country Club.

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Whipple, A.; Grantham, T.; Desanker, G.; Hunt, L.; Merrill, A.; Hackenjos, B.; Askevold, R. A. 2019. Chinook Salmon Habitat Quantification Tool: User Guide (Version 1.0). Prepared for American Rivers. Funded by the Natural Resources Conservation Service Conservation Innovation Grant (#69-3A75-17-40), Water Foundation and Environmental Defense Fund. A report of SFEI-ASC’s Resilient Landscapes Program. SFEI Contribution No. 953. San Francisco Estuary Institute: Richmond, CA.

The Salmon Habitat Quantification Tool provides systematic, transparent, and consistent accounting of the spatial extent, temporal variability, and quality of salmon habitat on the landscape. It is part of the multi-species assessment of the Central Valley Habitat Exchange (CVHE, www.cvhe.org). The suitability criteria applied in the tool were established by Stillwater Sciences and the Technical Advisory Committee (TAC), and the Chinook salmon HQT habitat evaluation and User Guide development was led by American Rivers and the San Francisco Estuary Institute. The approach uses commonly-applied concepts for evaluating suitable habitat based on modeling, with methods adapted from the hydrospatial analysis approach developed by Alison Whipple (2018).

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Cloern, J. E.; Barnard, P. L.; Beller, E. E.; Callaway, J.; Grenier, J. Letitia; Grossinger, R. M.; Whipple, A.; Mooney, H.; Zavaleta, E. 2016. Estuaries: Life on the edge. In Ecosystems of California. Ecosystems of California. University of California Press: Berkeley, CA. pp 359-388.
Yarnell, S. M.; Petts, G. E.; Schmidt, J. C.; Whipple, A.; Beller, E. E.; Dahm, C. N.; Goodwin, P.; Viers, J. H. 2015. Functional Flows in Modified Riverscapes: Hydrographs, Habitats and Opportunities. BioScience.

Building on previous environmental flow discussions and a growing recognition that hydrogeomorphic processes are inherent in the ecological functionality and biodiversity of riverscapes, we propose a functional-flows approach to managing heavily modified rivers. The approach focuses on retaining specific process-based components of the hydrograph, or functional flows, rather than attempting to mimic the full natural flow regime. Key functional components include wet-season initiation flows, peak magnitude flows, recession flows, dry-season low flows, and interannual variability. We illustrate the importance of each key functional flow using examples from western US rivers with seasonably predictable flow regimes. To maximize the functionality of these flows, connectivity to morphologically diverse overbank areas must be enhanced in both space and time, and consideration must be given to the sediment-transport regime. Finally, we provide guiding principles for developing functional flows or incorporating functional flows into existing environmental flow frameworks.

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Whipple, A.; Grossinger, R. M.; Rankin, D.; Stanford, B.; Askevold, R. A. 2012. Sacramento-San Joaquin Delta Historical Ecology Investigation: Exploring Pattern and Process. SFEI Contribution No. 672. SFEI: Richmond.

The Sacramento-San Joaquin Delta has been transformed from the largest wetland system on the Pacific Coast of the United States to highly productive farmland and other uses embodying California’s water struggles. The Delta comprises the upper extent of the San Francisco Estuary and connects two-thirds of California via the watersheds that feed into it. It is central to the larger California landscape and associated ecosystems, which will continue to experience substantial modification in the future due to climate change and continued land and water use changes. Yet this vital ecological and economic link for California and the world has
been altered to the extent that it is no longer able to support needed ecological functions. Approximately 3% of the Delta’s historical tidal wetland extent remains wetland today; the Delta is now crisscrossed with agricultural ditches replacing the over 1,000 miles of branching tidal channels.

Imagining a healthy Delta ecosystem in the future and taking bold, concrete steps toward that future requires an understanding and vision of what a healthy ecosystem looks like. For a place as extensive, unique, and modified as the Delta, valuable knowledge can be acquired through the study of the past, investigating the Delta as it existed just prior to the substantial human modifications of the last 160 years. Though the Delta is irrevocably altered, this does not mean that the past is irrelevant. Underlying geologic and hydrologic processes still influence the landscape, and native species still ply the waters, soar through the air, and move across the land. Significant opportunities are available to strategically reconnect landscape components in ways that support ecosystem resilience to both present and future stressors.

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Askevold, R. A.; Whipple, A.; Grossinger, R. M.; Stanford, B.; Salomon, M. N. 2011. East Contra Costa Historical Ecology Study GIS data, GIS data produced for the East Contra Costa County Historical Ecology Study.
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Whipple, A.; Grossinger, R. M.; Davis, F. W. 2010. Shifting Baselines in a California Oak Savanna: Nineteenth Century Data to Inform Restoration Scenarios. Restoration Ecology 19 (101), 88-101 . SFEI Contribution No. 593.

For centuries humans have reduced and transformed Mediterranean-climate oak woodland and savanna ecosystems, making it difficult to establish credible baselines for ecosystem structure and composition that can guide ecological restoration efforts. We combined historical data sources, with particular attention to mid-1800s General Land Office witness tree records and maps and twentieth century air photos, to reconstruct 150 years of decline in extent and stand density of Valley oak (Quercus lobata Neé) woodlands and savannas in the Santa Clara Valley of central coastal California. Nineteenth century Valley oak woodlands here were far more extensive and densely stocked than early twentieth century air photos would suggest, although reconstructed basal areas (7.5 m2/ha) and densities (48.9 trees/ha) were not outside the modern range reported for this ecosystem type. Tree densities and size distribution varied across the landscape in relation to soil and topography, and trees in open savannas were systematically larger than those in denser woodlands. For the largest woodland stand, we estimated a 99% decline in population from the mid-1800s to the 1930s. Although most of the study area is now intensely developed, Valley oaks could be reintroduced in urban and residential areas as well as in surrounding rangelands at densities comparable to the native oak woodlands and savannas, thereby restoring aspects of ecologically and culturally significant ecosystems, including wildlife habitat and genetic connectivity within the landscape.