South Coast

Storm rainfall conditions for floods and debris flows from recently burned areas in southwestern Colorado and southern California

Geomorphology (Elsevier) | April 15th, 2008

Debris flows generated during rain storms on recently burned areas have destroyed lives and property throughout the Western U.S. Field evidence indicate that unli

Debris flows generated during rain storms on recently burned areas have destroyed lives and property throughout the Western U.S. Field evidence indicate that unlike landslide-triggered debris flows, these events have no identifiable initiation source and can occur with little or no antecedent moisture. Using rain gage and response data from five fires in Colorado and southern California, we document the rainfall conditions that have triggered post-fire debris flows and develop empirical rainfall intensity–duration thresholds for the occurrence of debris flows and floods following wildfires in these settings. This information can provide guidance for warning systems and planning for emergency response in similar settings. Debris flows were produced from 25 recently burned basins in Colorado in response to 13 short-duration, high-intensity convective storms. Debris flows were triggered after as little as six to 10 min of storm rainfall. About 80% of the storms that generated debris flows lasted less than 3 h, with most of the rain falling in less than 1 h. The storms triggering debris flows ranged in average intensity between 1.0 and 32.0 mm/h, and had recurrence intervals of two years or less. Threshold rainfall conditions for floods and debris flows sufficiently large to pose threats to life and property from recently burned areas in south-central, and southwestern, Colorado are defined by: I = 6.5D− 0.7 and I = 9.5D− 0.7, respectively, where I = rainfall intensity (in mm/h) and D = duration (in hours). Debris flows were generated from 68 recently burned areas in southern California in response to long-duration frontal storms. The flows occurred after as little as two hours, and up to 16 h, of low-intensity (2–10 mm/h) rainfall. The storms lasted between 5.5 and 33 h, with average intensities between 1.3 and 20.4 mm/h, and had recurrence intervals of two years or less. Threshold rainfall conditions for life- and property-threatening floods and debris flows during the first winter season following fires in Ventura County, and in the San Bernardino, San Gabriel and San Jacinto Mountains of southern California are defined by I = 12.5D−0.4, and I = 7.2D−0.4, respectively. A threshold defined for flood and debris-flow conditions following a year of vegetative recovery and sediment removal for the San Bernardino, San Gabriel and San Jacinto Mountains of I = 14.0D−0.5 is approximately 25 mm/h higher than that developed for the first year following fires. The thresholds defined here are significantly lower than most identified for unburned settings, perhaps because of the difference between extremely rapid, runoff-dominated processes acting in burned areas and longer-term, infiltration-dominated processes on unburned hillslopes.

Stormquakes

American Geophysical Union (AGU) | October 14th, 2019

Seismic signals from ocean-solid Earth interactions are ubiquitously recorded on our planet. However, these wavefields are typically incoherent in the time domain limiti

Seismic signals from ocean-solid Earth interactions are ubiquitously recorded on our planet. However, these wavefields are typically incoherent in the time domain limiting their utilization for understanding ocean dynamics or solid Earth properties. In contrast, we find that during large storms such as hurricanes and Nor’easters the interaction of long-period ocean waves with shallow seafloor features located near the edge of continental shelves, known as ocean banks, excites coherent transcontinental Rayleigh wave packets in the 20 to 50 s period band. These “stormquakes” migrate coincident with the storms, but are effectively spatiotemporally focused seismic point sources with equivalent earthquake magnitudes that can be greater than 3.5. Stormquakes thus provide new coherent sources to investigate Earth structure in locations that typically lack both seismic instrumentation and earthquakes. Moreover, they provide a new geophysical observable with high spatial and temporal resolution with which to investigate ocean wave dynamics during large storms.

Stormwater Capture: Enhancing Recharge and Direct Use Through Data Collection

Southern California Water Coalition | April 26th, 2018

The purpose of this 2018 white paper update is to gain a better understanding of actual stormwater runoff capture volumes, costs, benefits, and project performa

The purpose of this 2018 white paper update is to gain a better understanding of actual stormwater runoff capture volumes, costs, benefits, and project performance across the region to inform future discussions. This white paper augments prior efforts and uses the most recent and best available stormwater project data. Previously in January 2012, the SCWC published its first white paper on stormwater titled Stormwater Capture: Opportunities to Increase Water Supplies in Southern California (SCWC 2012). The purpose of the 2012 white paper was to examine existing statewide policies, goals, and regional plans related to integrated stormwater management; trends, structure, and requirements of MS4 permits as they pertain to both opportunities and constraints to maximizing stormwater capture for water supply purposes; and the advantages and disadvantages of two strategies of stormwater management: onsite low impact development and regional stormwater capture and infiltration. Lastly, the 2012 white paper largely focused on conceptual stormwater projects and technical strategies for increasing stormwater capture. Since the 2012 white paper, many of the proposed projects were constructed and in operation. Other plans such as Metropolitan’s 2015 Integrated Resources Plan (MWD 2016), the City of Los Angeles’s Stormwater Capture Master Plan (LADWP 2015), and Los Angeles County Flood Control District’s LA Basin Study (LACFCD 2016) also estimated stormwater capture and costs. The SCWC saw an opportunity to evaluate the costs and benefits of these constructed stormwater capture projects and pursued a white paper update.

Stormwater Funding Options Providing Sustainable Water Quality Funding in Los Angeles County

California Contract Cities Association (CCCA) | May 21st, 2014

The Los Angeles region faces critical, very costly, and seriously underfunded stormwater and urban runoff water quality challenges. The Los Angeles County Flood Control D

The Los Angeles region faces critical, very costly, and seriously underfunded stormwater and urban runoff water quality challenges. The Los Angeles County Flood Control District (LACFCD) led a multi-year effort to develop a sustainable revenue source for municipalities to manage stormwater programs and implement water quality improvement projects. This effort included special legislation and development of a proposed parcel fee, the “Clean Water, Clean Beaches Measure,” to fund clean water programs. At extended protest hearings on a proposed parcel fee in January and March of 2013, the Board of Supervisors heard concerns about the fee and the fee program from public schools, the business community, other stakeholders and the public. The Board moved to close the public hearing and determined to “not proceed at this time with the Clean Water, Clean Beaches measure as proposed.” In June 2013, the Board adopted a motion requesting collaborative participation with the County Sanitation Districts of Los Angeles County (LACSD) and other wastewater management agencies to evaluate methods, assess the a potential model governance structure, and to help identify and secure other sources of funding. In response to the Board’s actions, the City Managers Committees of the California Contract Cities Association (CCCA) and the League of California Cities, Los Angeles County Division (League) convened a City Managers meeting with representatives from public schools, environmental organizations, and the business community on June 27, 2013 to hear stakeholders’ concerns and suggestions directly. The City Managers attending the meeting authorized a Work Group to review stormwater funding options after the County’s proposed Clean Water, Clean Beaches funding initiative failed to move forward. The City Managers Work Group actively sought the input of key stakeholders from the environmental, public education, and business communities, and prepared this report to assist the Board, local decision makers, stakeholders, and the public in reaching a common understanding of the issues at hand and the potential solutions. The Managers found that to fully understand the issues, improved communication and education is necessary. This report describes the stormwater regulatory requirements speci c to the greater Los Angeles area, the complexities of funding stormwater programs, and the LACFCD’s funding initiative. It examines the regulatory framework for stormwater management, including the requirements of the National Pollution Discharge Elimination System (NPDES) MS4 permit (stormwater permit) and the total maximum daily load (TMDL) programs. The report also summarizes the impacts of the federal TMDL Consent Decree for the Los Angeles Region signed in 1999, which has indirectly regulated the LACFCD, 85 cities, and the unincorporated County since that time. Further, it reviews estimated stormwater program compliance costs, the “pros and cons” of various funding options, and evolving opportunities. The report concludes with a series of recommendations agreed upon by the City Managers. Suggestions from an Elected Officials Committee and individual City Attorneys are also included in this report. The Work Group found that funding urban runoff programs is so complex and dynamic, and the solutions so costly, that the County and the Cities cannot follow a single funding strategy at this time. One option, for example, is to examine institutional roles to determine whether other agencies, such as the County Sanitation Districts, either provide a useful governance model or could play a new or different role in managing stormwater in the future. During the report development process, the Sixth Appellate Court clarified the application of Proposition 218 regarding the imposition of fees for the capture and use of stormwater for groundwater recharge (Griffith v. Pajaro Water Management Agency). This ruling could have major implications on funding options. These are only two examples of the changing nature and complexities in charting a path forward. The City Managers Work Group recommends a “multi-pronged” approach to address urban runoff funding issues, since our communities may encounter several dead-ends. A number of the recommendations require active management and a higher degree of organization by local government. The recommended actions are voluntary. The report is not advocating that any city, group of cities, or the County adopt stormwater fees. The managers are committed to local control; if a regional fee moves forward, each community should make its own decision whether or not to participate in the regional effort. However, there are steps that local governments can take that will assist in funding the new stormwater mandates. For example, cities should organize and be active in the water bond discussions. This report suggests a voluntary framework through Contract Cities and the League to organize those communities that desire to engage in implementing the recommendations found in this report. It should be noted that the recommendations involving California Contract Cities, the Los Angeles County Division of the League of California Cities, and the State League of Cities have not been of cially endorsed by these organizations at this stage of the process. The City Managers Work Group and the Elected Of cials Committee held detailed discussions with staff from both organizations in order to re ect their input and concerns. Recommendations involving these organizations, such as changes in State legislation, would need to be reviewed and approved by each organization.

Strategic Plan to Protect California Coast and Ocean 2020-2025

California Ocean Protection Council (COPC) | February 26th, 2020

Strategic stream gauging network design for sustainable water management

Nature Portfolio (Springer Nature) | June 3rd, 2024

Stream gauging stations that monitor the flow of water in rivers and streams provide critical information to water managers, but biases and gaps in gauge placement, compo

Stream gauging stations that monitor the flow of water in rivers and streams provide critical information to water managers, but biases and gaps in gauge placement, compounded by gauge deactivations, limit our ability to track river flows and address global water challenges. Here we introduce an approach for identifying gauging sites to efficiently fill gaps in monitoring coverage within river networks while also addressing water management priorities, including reservoir operations, biodiversity conservation and hydroclimatic monitoring. Applying this approach to gauges in California, United States, we found substantial gaps in the stream monitoring network. Hypothetically reconfiguring gauges to locations that maximize coverage and representation of management objectives highlights the current network’s biases. Through the strategic reactivation and placement of additional gauges, we demonstrate how stream gauging networks can be designed to support sustainable water management.

Stratigraphic controls on seawater intrusion and implications for groundwater management, Dominguez Gap area of Los Angeles, California, USA

Hydrogeology Journal (Springer) | May 30th, 2009

Groundwater pumping has led to extensive waterlevel declines and seawater intrusion in coastal Los Angeles, California (USA). A SUTRA-based solute-transport model was dev

Groundwater pumping has led to extensive waterlevel declines and seawater intrusion in coastal Los Angeles, California (USA). A SUTRA-based solute-transport model was developed to test the hydraulic implications of a sequence-stratigraphic model of the Dominguez Gap area and to assess the effects of water-management scenarios. The model is two-dimensional, vertical and follows an approximate flow line extending fromthe Pacific Ocean through the Dominguez Gap area. Results indicate that a newly identified fault system can provide a pathway for transport of seawater and that a stratigraphic boundary located between the Bent Spring and Upper Wilmington sequences may control the vertical movement of seawater. Three 50-year water-management scenarios were considered: (1) no change in water-management practices; (2) installation of a slurry wall; and (3) raising inland water levels to 7.6m above sea level. Scenario 3 was the most effective by reversing seawater intrusion. The effects of an instantaneous 1-m sealevel rise were also tested using water-management scenarios 1 and 3. Results from two 100-year simulations indicate that a 1-m sea-level rise may accelerate seawater intrusion for scenario 1; however, scenario 3 remains effective for controlling seawater intrusion.

Studies of Geology and Hydrology in the Basin and Range Province, Southwestern United States, For Isolation of High-Level Radioactive Waste Characterization of the Sonoran Region, California

U.S. Geological Survey (USGS) | July 15th, 1989

A study by the U.S. Geological Survey to evaluate potential hydrogeologic environments for isolation of high-level radioactive waste in the Basin and Range physiographic

A study by the U.S. Geological Survey to evaluate potential hydrogeologic environments for isolation of high-level radioactive waste in the Basin and Range physiographic province of the southwestern United States was begun in May 1981, with the introduction of the study to the Governors of eight Basin and Range States Arizona, California, Idaho, Nevada, New Mexico, Oregon, Texas, and Utah and to respective Indian tribes in those States. Accordingly, these States were invited to participate in the study by designating an earth scientist to serve on a Province Working Group with the U.S. Geological Survey membership of the working group is shown following the title page. State representatives have provided consultation in selecting guidelines, assembling geologic and hydrologic data, and assessing such information to identify environments that meet the guidelines for further study.

Study to Evaluate Long-Term Trends and Variations in the Average Total Dissolved Solids Concentration in Wastewater and Recycled Water

Southern California Salinity Coalition | March 30th, 2018

This report was funded by the Southern California Salinity Coalition (SCSC). SCSC and its member agencies are dedicated to managing salinity in the water supplies, waste

This report was funded by the Southern California Salinity Coalition (SCSC). SCSC and its member agencies are dedicated to managing salinity in the water supplies, wastewater, and recycled water. Member agencies include Eastern Municipal Water District (EMWD), Inland Empire Utilities Agency (IEUA), Metropolitan Water District of Southern California (MWDSC), Orange County Sanitation District (OCSD), Orange County Water District (OCWD), San Diego County Water Authority (SDCWA), Sanitation Districts of Los Angeles County (LACSD), and Santa Ana Watershed Project Authority (SAWPA). Daniel B. Stephens & Associates, Inc. (DBS&A) performed the analysis and is submitting this technical memorandum to address the research questions posed by SCSC and its member agencies. The 2011 to 2016 drought in California, in conjunction with unprecedented statewide conservation legislation, caused several member agencies to face challenges meeting regulatory water quality standards for the salinity of discharge water from wastewater treatment plants (WWTPs). In particular, total dissolved solids (TDS) concentrations have increased, while the operation of WWTPs have remained consistent with prior years. Figure ES-1 is a typical example of TDS trends for WWTPs in Southern California.

Summary and Evaluation of Southern California Coast Steelhead Distinct Population Segment 2016

National Marine Fisheries Service (NMFS) | March 27th, 2016

The Southern California Coast Steelhead Distinct Population Segment (DPS) is listed as endangered and is comprised of a suite of steelhead populations (Oncorhynchus mykis

The Southern California Coast Steelhead Distinct Population Segment (DPS) is listed as endangered and is comprised of a suite of steelhead populations (Oncorhynchus mykiss) that inhabit coastal stream networks from the Santa Maria River system south to the U.S. border with Mexico. Freshwater-resident (non-anadromous) O. mykiss, commonly known as rainbow trout, also occur in the same geographic region, frequently co-occurring in the same river systems as the anadromous form. Clemento et al. (2009) found that O. mykiss above and below impassable dams within the Southern California DPS tended to be each other’s closest relatives, suggesting that each steelhead DPS is simply the anadromous component of a corresponding Evolutionarily Significant Unit (ESU; Waples 1991) comprising both anadromous and resident O. mykiss. West Coast salmon and steelhead (Oncorhynchus spp.) stocks have declined substantially from their historic numbers and many are now listed as threatened or endangered. Multiple factors have contributed to the decline of individual populations. These include the loss of freshwater and estuarine habitat, periodic poor ocean conditions, and a variety of land-use, flood control, and water management practices which have impacted many watershed-wide processes; these include hydrologic and sedimentation processes which create and maintain essential steelhead habitats. These factors collectively led the National Marine Fisheries Service (NMFS) to list southern California steelhead (the anadromous form of O. mykiss) as endangered under the ESA in 1997 (Figure 1). Section 4(c)(2) of the ESA directs the Secretary of Commerce to review the listing classification of threatened and endangered species at least once every five years. After completing this review, the Secretary must determine if any species should be: (1) removed from the list; (2) have its status changed from threatened to endangered; or (3) have its status changed from endangered to threatened. The most recent listing determinations for salmon and steelhead occurred in 2005 and 2006. This document reflects the agency’s 5-year status review of the ESAlisted Southern California Coast Steelhead Distinct Population Segment (DPS) since the last status review in 2010 (Williams et al. 2011).