100-Year Flood – It’s All About Chance
Los Angeles Basin Study Summary Report$0.00 Add to Downloads
Los Angeles Basin Study Summary ReportU.S. Bureau of Reclamation (USBR) | November 1, 2016...Summary
Changing demographics, climate change, and competing interests for available water supplies all present long-term risks to the stability and reliability of the region’s...
Changing demographics, climate change, and competing interests for available water supplies all present long-term risks to the stability and reliability of the region’s imported water. The region recognizes that today’s challenges require an integrated water resources management approach.
For decades, this region has operated and maintained one of the most effective flood control systems in the world that protects millions of people from the impacts of flooding in the region. This system sends much of the stormwater runoff into the ocean, water that historically recharged local groundwater basins, making this region even more dependent on imported water supplies. As regulatory pressure to clean up polluted stormwater runoff continues and imported water resources diminish, this local source of water supply is becoming more and more attractive (GLAC IRWMP 2014).
Many of the region’s water management agencies have studied and planned for increasing use of local recycled and graywater supplies, ocean and brackish desalination, developing more groundwater, and implementing improved water conservation initiatives to extend existing supplies. Additionally, social trends and concerns also drive the emphasis on the use of local water supplies.
However, the one major local resource that has not been studied in-depth is stormwater and its opportunities to optimize the reliability of local supplies.
To enhance the capabilities of the existing stormwater conservation infrastructure within the Los Angeles Basin, the LACFCD began to investigate long-term projected needs and future climate conditions within the region. Given that local groundwater plays such a vital role in the region’s water supply portfolio, detailed scientific, engineering, and economic analyses were conducted to identify strategies for enhancing stormwater capture for groundwater recharge.
The LA Basin Study examined the region’s water supplies and demand, and impacts from projected population growth and changing climate in the watersheds of the Los Angeles region. The objectives of the study were to:
• Use state-of-the-art climate change analysis to develop projections of future water supply and demands in the Basin.
• Analyze how the Basin’s existing water infrastructure and its operations will perform in the face of changing water realities.
• Develop and highlight opportunities to adapt to current and future water demands.
• Conduct a trade-off analysis of identified opportunities.
Concepts ranged from enhancing the existing stormwater capture system and modifying existing facilities (including those capturing runoff for groundwater recharge), to developing new structural and nonstructural concepts that could help resolve future water supply and flood risk issues.
This Summary Report presents highlights of the critical tasks associated with this Basin Study and the results and findings produced throughout this collaborative study effort.
Full study chapters and appendices:
Task 3: Climate Change Analysis
Task 3.2: Hydrologic Modeling Report
Task 3.2: Annual Hydrologic Results Workbook
Task 4: Existing Infrastructure Response & Operations Guidelines Analysis
Task 5: Task 5 - Infrastructure & Operations Concept Analysis
Task 6: Trade-off Analysis
Managing Floods in California$0.00 Add to Downloads
Managing Floods in CaliforniaLegislative Analyst's Office | March 22, 2017...Summary
This report is intended to provide basic information about floods and flood management in California. (Whereas previous generations referred to “flood control” or...
This report is intended to provide basic information about floods and flood management in California. (Whereas previous generations referred to “flood control” or “flood prevention” activities, experts now prefer the term “flood management” in acknowledgement that floodwaters are recurring and inevitable.) We begin by summarizing the history, causes, and risk of floods across the state. We then describe flood management agencies, infrastructure, and strategies, as well as how governmental agencies typically respond when floods occur. Next, we describe the spending levels and funding sources currently supporting flood management efforts, as well as estimates for how much additional funding may be needed to improve those efforts. We conclude by highlighting some key challenges confronting the state in contemplating how best to manage floods in California.
Climate Change Adaptations for Local Water Management in the San Francisco Bay Area$0.00 Add to Downloads
Climate Change Adaptations for Local Water Management in the San Francisco Bay AreaCalifornia Energy Commission (CEC) | July 1, 2012...Summary
Climate change will affect both sea level and the temporal and spatial distribution of runoff in California. These climate change impacts will affect...
Climate change will affect both sea level and the temporal and spatial distribution of runoff in California. These climate change impacts will affect the reliability of water supplies and operations of California’s water supply system. To meet future urban water demands in the San Francisco Bay Area, local water managers can adapt by changing water supply portfolios and operations.
An engineering economic model, CALVIN, which optimizes water supply operations and allocations for the State of California, was used to explore the effects on water supply of a severely warm dry climate and substantial sea level rise, and to identify economically promising long-term adaptations for San Francisco Bay Area water systems. This reconnaissance level modeling suggests that even under fairly severe forms of climate change, Bay Area urban water demands can be largely met, but at a cost. Costs are from purchasing water from agricultural users (with agricultural opportunity costs), more expensive water supply alternatives such as water recycling and desalination, and some increases in water scarcity (costs of water use reduction).
The modeling also demonstrates the importance of water transfer and intertie infrastructure to facilitate flexible water management among Bay Area water agencies. The intertie capacity developed by Bay Area agencies for emergencies, such as earthquakes, becomes even more valuable for responding to severe changes in climate.
Factors and Processes Affecting Delta Levee System Vulnerability$0.00 Add to Downloads
Factors and Processes Affecting Delta Levee System VulnerabilitySan Francisco Estuary and Watershed Science | December 1, 2016...Summary
The authors appraised factors and processes related to human activities and high water, subsidence, and seismicity. Farming and drainage of peat soils over...
The authors appraised factors and processes related to human activities and high water, subsidence, and seismicity. Farming and drainage of peat soils over time has caused a gradual sinking which contributed to internal levee failures. Although these subsidence rates have decreased with time, they still contribute to levee instability. Additional data is needed to assess spatial and temporal effects of subsidence caused by peat thinning and deformation. Since the mid-1970s large-scale, State investments in levee upgrades have increased conformance, however accounts continue to conflict on how these investments correspond to the numbers of failures.
Both modeling and history suggest that the projected increases of high-flow frequency associated with climate change will increase levee-failures rates. Quantification of this increased threat requires further research. A reappraisal of seismic threats resulted in updated ground motion estimates for multiple faults and earthquake occurrence frequencies. The immediate seismic threat, liquefaction, is the sudden loss of strength due to an increase in the pressure of the pore fluid and corresponding loss of contact forces. However, levees damaged during an earthquake that do not immediately fail, may eventually breach.
Consequences for future levee failure are estimated to cost up to billions of dollars. The analysis of future risks will benefit from more detailed descriptions of levee strength and upgrades, consideration of subsidence, climate change, and earthquake threats. Ecosystem benefits of levee habitats in this highly altered system are thin. Better recognition and coordination is needed among the creation of high value habitats, levee needs, costs, benefits of levee improvements, and breaches.