Executive Order N-4-23

State of California | March 10th, 2023

First flush analysis of urban storm runoff

Science of the Total Environment (Elsevier) | July 3rd, 2003

Stormwater runoff was monitored on 13 separate urban watersheds, which were chosen to represent distinct types of residential and industrial development, along with vario

Stormwater runoff was monitored on 13 separate urban watersheds, which were chosen to represent distinct types of residential and industrial development, along with various watershed characteristics. A total of 38 storm events were monitored to investigate the first flush phenomenon. The first flush phenomenon may be defined as the initial period of stormwater runoff during which the concentration of pollutants is substantially higher than during later stages. The magnitude of the first flush phenomenon, and if it actually occurs, was calculated using a method of data analysis which results in determining the ‘event mean concentration’ (EMC). The magnitude of the first flush phenomenon was found to be greater for some pollutants (e.g. suspended solids from residential areas) and less for others (e.g. chemical oxygen demand from industrial areas). No correlation was observed between the first flush phenomenon and the antecedent dry weather period, however, the first flush phenomenon was greater for smaller watershed areas.

FLOOD- MAR Using Flood Water for Managed Aquifer Recharge to Support Sustainable Water Resources

California Department of Water Resources (DWR) | June 26th, 2018

The effects of climate change are necessitating wholesale changes in how water is managed in California.  With less water storage from snowpack, California needs to leve

The effects of climate change are necessitating wholesale changes in how water is managed in California.  With less water storage from snowpack, California needs to leverage both the current water system and new opportunities to provide sustainable alternatives that can simultaneously accommodate longer and deeper droughts, and more severe, and frequent, episodic and seasonal flooding. This recent cycle of drought and flood, and the passage of the Sustainable Groundwater Management Act (SGMA), provide an enhanced opportunity to modernize State policies related to the nexus between flood management, land use, groundwater management, and ecosystem enhancement. Partnerships, among DWR; other State, federal, tribal, regional, and local entities; and university and private researchers, are actively exploring opportunities to determine how flood and groundwater management can be integrated for multiple benefits. Although integrating flood and groundwater management is not a new concept, the time is ripe to implement an expanded, large-scale integrated program. With the passage and early implementation of SGMA, in combination with climate-induced extreme events, the logic for communities to partner and integrate is evident and imperative. This partnership will help reduce the impacts of future swings between high- and low-flow periods while meeting their communities’ objectives, with the added benefits of improving floodplain ecosystems, preserving working landscapes, and engaging California’s agricultural community in needed solutions, among others. This white paper explores “Flood-MAR”, an integrated and voluntary resource management strategy that uses flood water resulting from, or in anticipation of, rainfall or snowmelt for groundwater recharge on agricultural lands and working landscapes, including but not limited to refuges, floodplains, and flood bypasses. Large-scale implementation of Flood-MAR will fundamentally change how flood and groundwater management are managed. Flood-MAR can be implemented at multiple scales, from individual landowners diverting flood water with existing infrastructure, to using extensive detention/recharge areas and modernizing flood protection infrastructure/operations. Flood-MAR’s potential and value for California is achieved by integrating Flood-MAR with other regional recharge efforts, changing management of California’s water system to better integrate surface water and groundwater, upgrading conveyance, storage, and operations, and considering Flood-MAR’s opportunities as related to water transport and transfers are some of the system integration considerations. This white paper demonstrates the need for Flood-MAR to become an important part of California’s portfolio of water resource management strategies, now and in the future, to help significantly improve water resources sustainability and climate resiliency throughout the state.  Using Flood Water for Managed Aquifer Recharge Can Provide Broad Benefits. There is a clear State interest in encouraging, and participating in, Flood-MAR projects because they can provide broad and multiple public and private benefits for Californians and the ecosystems of the state. Potential public benefits include: - Flood Risk Reduction. - Drought Preparedness. - Aquifer Replenishment. - Ecosystem Enhancement. - Subsidence Mitigation. - Water Quality Improvement. - Working Landscape Preservation and Stewardship.

Framing the Problem of Flood Risk and Flood Management in Metropolitan Los Angeles

American Meteorological Society (AMS) | January 1st, 2023

This paper develops the concept of flood problem framing to understand decision-makers’ priorities in flood risk management in the Los Angeles Metropolitan Region in Ca

This paper develops the concept of flood problem framing to understand decision-makers’ priorities in flood risk management in the Los Angeles Metropolitan Region in California (LA Metro). Problem frames shape an individual’s preferences for particular management strategies and their future behaviors. While flooding is a complex, multifaceted problem, with multiple causes and multiple impacts, a decision-maker is most likely to manage only those dimensions of flooding about which they are aware or concerned. To evaluate flood decision-makers’ primary concerns related to flood exposure, vulnerability, and management in the LA Metro, we draw on focus groups with flood control districts, city planners, nonprofit organizations, and other flood-related decision-makers. We identify numerous concerns, including concerns about specific types of floods (e.g., fluvial vs pluvial) and impacts to diverse infrastructure and communities. Our analyses demonstrate that flood concerns aggregate into three problem frames: one concerned with large fluvial floods exacerbated by climate change and their housing, economic, and infrastructure impacts; one concerned with pluvial nuisance flooding, pollution, and historic underinvestment in communities; and one concerned with coastal and fluvial flooding’s ecosystem impacts. While each individual typically articulated concerns that overlapped with only one problem frame, each problem frame was discussed by numerous organization types, suggesting low barriers to cross-organizational coordination in flood planning and response. This paper also advances our understanding of flood risk perception in a region that does not face frequent large floods.

Future Changes in Global Atmospheric Rivers Projected by CMIP6 Models

American Geophysical Union (AGU) | January 31st, 2024

Global climate mode resonance due to rapidly intensifying El Niño-Southern Oscillation

Publisher not available | October 16th, 2025

Increasing ENSO amplitude and teleconnection patterns imply that remote extratropical precipitation responses, such as in Southern California and the Iberian Peninsula (F

Increasing ENSO amplitude and teleconnection patterns imply that remote extratropical precipitation responses, such as in Southern California and the Iberian Peninsula (Fig. 5), will also become stronger between alternating El Niño and La Niña events. Even though the recurrence of these events may become more predictable due to the increased regularity/periodicity and amplitude (Fig. 1)44, future ENSO teleconnections might generate enhanced whiplash effects on hydroclimate, which requires additional planning and management strategies to minimize the costs of climate damage. While similar increases in ENSO regularity and amplitude can be found in some CMIP6 model projections (Fig. 2), future work needs to assess the detailed dynamics across these models and assess the likelihood of the ENSO regime changes seen in AWI-CM3.

Green Infrastructure Planning for the City of Richmond with GreenPlan-IT

San Francisco Estuary Institute (SFEI) | November 1st, 2018

The City of Richmond, via the San Francisco Municipal Regional Stormwater Permit (MRP), is required to develop and implement a Green Infrastructure (GI) Master Plan to re

The City of Richmond, via the San Francisco Municipal Regional Stormwater Permit (MRP), is required to develop and implement a Green Infrastructure (GI) Master Plan to reduce stormwater mercury and PCB loads. This project used GreenPlan-IT, a planning tool developed by the San Francisco Estuary Institute (SFEI) and regional partners, to identify feasible and cost-effective GI locations within the City boundary to support the development of GI Plans for permit compliance.  GreenPlan-IT comprises four distinct tools: (a) a GIS-based Site Locator Tool that combines the physical properties of different GI types with local and regional GIS information to identify and rank potential GI locations; (b) a Modeling Tool that is built on SWMM5 to establish baseline conditions and quantify anticipated runoff and pollutant load reductions from GI implementation; (c) an Optimization Tool that uses an evolutionary algorithm to identify the best combinations of GI types and numbers of sites within a study area for achieving flow and load reduction goals; and (d) a Tracker Tool that tracks GI implementation and reports the cumulative programmatic outcomes for regulatory compliance and other communication needs. 

Green Infrastructure Planning for the City of Sunnyvale with GreenPlan-IT

San Francisco Estuary Institute (SFEI) | July 2nd, 2018

The City of Sunnyvale, via the San Francisco Municipal Regional Stormwater Permit (MRP),is required to develop and implement a Green Infrastructure (GI) Master Plan to re

The City of Sunnyvale, via the San Francisco Municipal Regional Stormwater Permit (MRP),is required to develop and implement a Green Infrastructure (GI) Master Plan to reduce stormwater mercury and PCB loads. This project used GreenPlan-IT, a planning tool developed by the San Francisco Estuary Institute (SFEI) and regional partners, to identify feasible and cost-effective GI locations within the City boundary to support the development of GI Plans for permit compliance.  GreenPlan-IT comprises four distinct tools: (a) a GIS-based Site Locator Tool that combines the physical properties of different GI types with local and regional GIS information to identify and rank potential GI locations; (b) a Modeling Tool that is built on SWMM5 to establish baseline conditions and quantify anticipated runoff and pollutant load reductions from GI implementation; (c) an Optimization Tool that uses an evolutionary algorithm to identify the best combinations of GI types and numbers of sites within a study area for achieving flow and load reduction goals; and (d) a Tracker Tool that tracks GI implementation and reports the cumulative programmatic outcomes for regulatory compliance and other communication needs. 

Green Plan-IT Application Report for the East Bay Corridors Initiative

San Francisco Estuary Institute (SFEI) | November 1st, 2018

Regional planning of Green Infrastructure (GI) is an important aspect of building in or retrofitting GI and other green spaces across municipal jurisdictions. This level

Regional planning of Green Infrastructure (GI) is an important aspect of building in or retrofitting GI and other green spaces across municipal jurisdictions. This level of planning allows for GI to be implemented according to natural boundaries and builds important partnerships across municipalities. The East Bay Corridors Initiative is a unique partnership across 13 jurisdictions, county and regional agencies, as well as community groups and businesses to plan new housing, create job opportunities, and improve parks and streets with linkages to essential services (ABAG 2016). The Initiative covers a large swath of the East Bay of San Francisco Bay, CA from Rodeo in the North to Union City in the South and focuses on Priority Development Areas (PDAs) and transportation linkages. In addition to the above focus, the Initiative will also look at opportunities for GI implementation across the Corridor. The Resilience priority within the Initiative focuses on sustainable infrastructure including regional GI implementation, green streets, and stormwater/flooding mitigation (ABAG 2016). The objective of this project was to use GreenPlan-IT, a planning tool developed by the San Francisco Estuary Institute (SFEI), to identify feasible GI locations within the East Bay Corridor footprint. Results from the application of the Site Locator Tool will be used to: 1) identify potential green infrastructure projects for the Corridor’s sustainable infrastructure planning efforts, including the development of information for municipal and regional GI Master Plans and Stormwater Resources Plans; and 2) potentially help comply with municipal Stormwater Permit requirements.  GreenPlan-IT is a planning level tool that was developed over the past five years with strong Bay Area stakeholder consultation and designed to support the cost-effective selection and placement of green infrastructure in urban watersheds through a combination of GIS analysis, watershed modeling, optimization techniques, and data visualization. Structurally, GreenPlan-IT comprises four standalone tools: (a) a GIS-based Site Locator Tool that combines the physical properties of different GI types with local and regional GIS information to identify and rank potential GI locations; (b) a Modeling Tool that is built on EPA’s SWMM5 (Rossman, 2010) to establish baseline conditions and quantify anticipated runoff and pollutant load reductions from GI sites; (c) an Optimization Tool that uses a cost-benefit analysis to identify the best combinations of GI types and number of sites within a study area for achieving flow and/or load reduction goals; and (d) a tracker tool that is used to track GI implementation and report the cumulative programmatic outcomes for regulatory compliance and other communication needs. The Toolkit package, consisting of the software, companion user manuals, and demonstration report, is available on the GreenPlan-IT web site hosted by SFEI. 

GreenPlan-IT Tracker

San Francisco Estuary Institute (SFEI) | June 14th, 2018

This technical memo describes the purpose, functions, and structure associated with the newest addition to the GreenPlan-IT Toolset, the GreenPlan-IT Tracker. It also sh

This technical memo describes the purpose, functions, and structure associated with the newest addition to the GreenPlan-IT Toolset, the GreenPlan-IT Tracker. It also shares the opportunities for further enhancement and how the tool can operate in concert with existing resources. Furthermore, this memo describes a licensing plan that would permit municipalities to use the tool in an ongoing way that scales to their needs. The memo concludes with a provisional roadmap for the development of future features and technical details describing the tool’s platform and data structures. About the GreenPlan-IT Toolkit Municipalities across the state and beyond are carefully planning and implementing green infrastructure in their developed landscape to restore key aspects of the natural water cycle. Green infrastructure helps to achieve stormwater attenuation and contaminant filtration by increasing the pervious surfaces in often sophisticated ways. Additionally, green infrastructure features, as city dwellers have come to realize, demonstrate multiple benefits in addition to improving surface porosity, such as peak, volume, and load reductions, urban heat island mitigation, traffic calming, carbon sequestration, wildlife habitat, natural aesthetics, and others. The benefits are substantial, but so are the potential costs. GreenPlan-IT helps planners to make smart decisions in the types and locations of green infrastructure, minimizing effort and cost while maximizing the effectiveness of the public and private investments. GreenPlan-IT modules are focused on green infrastructure planning and assessment, including the Site Locator Tool, Modeler, and Optimizer tools. Together the modular toolkit can be used to take a city from a position of not knowing where to consider GI placement (a daunting position given the MRP C3 and C11/12 requirements), to a plan that includes a list and map of feasible locations and a map of baseline flow and pollutant load conditions, and a selected optimal set of placement locations for achieving flow and load reductions at minimal cost. Now, with the advent of the GreenPlan-IT Tracker, there is also a web based tracker for quantifying and communicating the locations, types, and treatment areas of GI installations (the outputs of all the planning efforts) and quantifying the peak flows, volumes, and loads reduced (the outcomes of all the implementation and cost expenditure that the community is asking for).