North Bay Mercury Biosentinel Project 2016 - 2017

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

Concentrations of methylmercury throughout San Francisco Bay are high enough to warrant concern for the health of humans and wildlife. Large-scale tidal wetland restorat

Concentrations of methylmercury throughout San Francisco Bay are high enough to warrant concern for the health of humans and wildlife. Large-scale tidal wetland restoration is currently being implemented as a means of increasing populations of wildlife species of concern. There is concern that these restoration activities may lead to increased concentrations of methylmercury in the estuarine food web and exacerbate the existing methylmercury problem.

Novato Creek Baylands Historical Ecology Study

San Francisco Estuary Institute (SFEI) | July 31st, 2015

Over the past century and a half, lower Novato Creek and the surrounding tidal wetlands have been heavily modified for flood control and land reclamation purposes. Levees

Over the past century and a half, lower Novato Creek and the surrounding tidal wetlands have been heavily modified for flood control and land reclamation purposes. Levees were built in the tidal portion of the mainstem channel beginning in the late 1800s to convey flood flows out to San Pablo Bay more rapidly and to remove surrounding areas from inundation. Following levee construction, the wetlands surrounding the channel were drained and converted to agricultural, residential, and industrial areas. These changes have resulted in a considerable loss of wetland habitat, reduced sediment transport to marshes and the Bay, and an overall decreased resilience of the system to sea level rise. In addition to tidal wetland modification, land use changes upstream in the Novato Creek watershed have resulted in several challenges for flood control management. Dam construction and increased runoff in the upper watershed have resulted in elevated rates of channel incision, which have increased transport of fine sediment from the upper watershed to lower Novato Creek. Channelization of tributaries and construction of irrigation ditches have likely increased drainage density in the upper watershed, also potentially contributing to increased rates of channel incision and fine sediment production (Collins 1998). Downstream, sediment transport capacity has been reduced by construction of a railroad crossing and loss of tidal prism and channel capacity associated with the diking of the surrounding marsh. As a result of the increased fine sediment supply from the watershed and the loss of sediment transport capacity in lower Novato Creek, sediment aggradation occurs within the channel, which in turn reduces the flood capacity of the channel, necessitating periodic dredging (fig. 1; Collins 1998, PWA 2002).

Petaluma Valley Historical Hydrology and Ecology Study

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

This study examines the historical hydrology and ecology of the Petaluma River watershed prior to major Euro-American modification, and analyzes landscape changes over th

This study examines the historical hydrology and ecology of the Petaluma River watershed prior to major Euro-American modification, and analyzes landscape changes over the past two centuries. Synthesizing information from hundreds of archival documents, the research reconstructs the historical form and function of wetland, riparian, and aquatic habitats and stream channels throughout the watershed, providing insights into habitat extent and distribution, streamflow and sediment dynamics, vegetation composition, wildlife support, and landscape change. Findings from this research can be used to help set restoration targets and to prioritize multi-benefit opportunities to restore wildlife habitat, enhance flood protection, increase groundwater recharge, and improve sediment management. This Executive Summary highlights key findings from the study. 

Physical and Hydrologic Assessment of the Carmel River Watershed California

California State University, Monterey Bay (CSUMB) | November 1st, 2004

The Carmel Watershed is a terrestrial jewel in the California landscape. Its forested headwaters harvest rain from the Pacific storms each winter, providing a nat

The Carmel Watershed is a terrestrial jewel in the California landscape. Its forested headwaters harvest rain from the Pacific storms each winter, providing a natural cascade of resources enjoyed by human residents and the broader ecosystem. Although the Carmel River is not currently listed as “impaired” by the State of California, there have been significant human impacts that could lead to impaired waters. These impacts are now recognized and defined in this report so that remediation and future management policies can be developed. This report is one facet of the Carmel Watershed Assessment orchestrated by the Carmel River Watershed Conservancy. We assess the physical and hydrologic components of the watershed, chiefly focusing on two major classes of problems, water quantity and excess sediment. Both of these issues are important when considering human needs and the needs of the broader ecosystem, including endangered aquatic and riparian species. The Carmel Watershed has finite annual rainfall as its only water resource. That resource is currently stretched too thin, leaving new urban, suburban, rural, and industrial development in and around the watershed at odds with pre-existing water appropriation and environmental requirements (e.g., SWRCB, 1995a; 1995b). Certain kinds of common land-uses and road designs supply excess sediment above natural background rates. Some of the major problems in the watershed are summarized below, in no particular order. Demand for water far exceeds water supply, leading to many related subordinate problems, including diminished surface water for endangered steelhead trout. Extensive urbanization exists within the regulatory 100-year floodplain and in the dam-failure inundation zone. Excess sediment is generated from a very large number of dirt roads, some of which are abandoned, some of which out of compliance with grading ordinances, but most of which are clearly within regulations. Nearly all sub-road drainage culverts are undersized, leading to downstream erosion, whether related to dirt roads, paved roads, or highways. Excess sediment is generated by a great number of bare road cuts on dirt roads, paved roads, and highways. Excess sediment is generated in the Los Chupines and Sycamore Creek drainages by soil slip, gullies, unstable stream banks, and roads. Many of those issues are related to cattle impacts. Excess sediment is generated in a great number of incised streams that have tall, exposed banks. San Clemente Dam is unsafe owing to sediment burden and proximity to active faults. Decommissioning the San Clemente Dam will likely lead to a significant shift in river morphology and flood response, owing to the restoration of historic bedload transport rates. Los Padres Dam is rapidly infilling with sediment and is also close to active faults. Watershed impairment is the result of incremental, permitted, changes that have a large cumulative impact on the watershed. Closer adherence to the Carmel Valley Master Plan (CVMP, 1996; Appendix C) and County ordinances will foster resource sustainability and aesthetic living conditions. Among the salient points in that document are the following guidelines for development (CVMP, 1996). 1. Preserve the rural character of the Carmel Valley 2. Protect all natural resources with emphasis on biological communities, agricultural lands, the Carmel River and its Riparian corridor, air quality and scenic resources. We note that the large-scale negative impacts we describe in the Carmel Watershed mainly resulted from the cumulative effects of small, insignificant, permitted landscape or hydrologic alterations (e.g., Dunne et al., 2001). With that in mind, guidelines for sustainable resource use could begin with an agreed upon ultimate level of resource use, depletion, or degradation, beyond which, no further landscape or hydrologic alterations will be permitted. Using water supply as an example, the best strategy for sustainability is to determine the total cumulative resource usage, and then stop permitting further requests for resource use when the agreed upon cumulative impact is met—the concept of water rights appropriation. This same “cumulative impact” management strategy could be applied to other cumulative watershed impacts, such as total miles of dirt road per square mile of watershed area, or total area of impervious cover per square mile of watershed area. These strategies can be applied once a cumulative impact target has been established upon sound science, and codified by stakeholder agreement. Considering that the cumulative negative impacts in the watershed are the net result of innumerable, insignificant modifications, we can predict that innumerable, small positive restorative efforts in the watershed would eventually produce large positive impacts on watershed health including water quality and quantity.

Post‐Fire Sediment Yield from a Western Sierra Nevada Watershed Burned by the 2021 Caldor Fire

American Geophysical Union (AGU) | January 7th, 2025

Postfire Sediment Mobilization and its Downstream Implications Across California, 1984–2021

American Geophysical Union (AGU) | August 27th, 2024

Potential for Using the Upper Coachella Valley Ground-Water Basin, California, for Storage of Artificially Recharged Water

U.S. Geological Survey (USGS) | September 15th, 1980

The California Department of Water Resources, through the Future Water Supply Program, is investigating the use of ground-water basins for storage of State Wate

The California Department of Water Resources, through the Future Water Supply Program, is investigating the use of ground-water basins for storage of State Water Project water in order to help meet maximum annual entitlements to water project contractors. This report presents a preliminary evaluation of the geohydrologic fac- tors affecting storage of water by artificial recharge in the upper Coachella Valley, Calif. The ground-water basin of the upper Coachella Valley seems to be geologically suitable for large-scale artificial recharge. A minimum of 900,000 acre-feet of water could probably be stored in the basin without raising basinwide water levels above those that existed in 1945. Preliminary tests indicate that a long-term artificial recharge rate of 5 feet per day may be feasible for spreading grounds in the basin if such factors as sediment and bacterial clogging can be controlled.

Punctuated Sediment Discharge during Early Pliocene Birth of the Colorado River: Evidence from Regional Stratigraphy, Sedimentology, and Paleontology

Sedimentary Geology (Elsevier) | January 1st, 2018

The Colorado River in the southwestern U.S. provides an excellent natural laboratory for studying the origins of a continent-scale river system, because deposits th

The Colorado River in the southwestern U.S. provides an excellent natural laboratory for studying the origins of a continent-scale river system, because deposits that formed prior to and during river initiation are well exposed in the lower river valley and nearby basinal sink. This paper presents a synthesis of regional stratigraphy, sedimentology, and micropaleontology from the southern Bouse Formation and similar-age deposits in the western Salton Trough, which we use to interpret processes that controlled the birth and early evolution of the Colorado River. The southern Bouse Formation is divided into three laterally persistent members: basal carbonate, siliciclastic, and upper bioclastic members. Basal carbonate accumulated in a tide-dominated marine embayment during a rise of relative sea level between ~ 6.3 and 5.4 Ma, prior to arrival of the Colorado River. The transition to green claystone records initial rapid influx of river water and its distal clay wash load into the subtidal marine embayment at ~ 5.4–5.3 Ma. This was followed by rapid southward progradation of the Colorado River delta, establishment of the earliest through-flowing river, and deposition of river-derived turbidites in the western Salton Trough (Wind Caves paleocanyon) between ~ 5.3 and 5.1 Ma. Early delta progradation was followed by regional shut-down of river sand output between ~ 5.1 and 4.8 Ma that resulted in deposition of marine clay in the Salton Trough, retreat of the delta, and re-flooding of the lower river valley by shallow marine water that deposited the Bouse upper bioclastic member. Resumption of sediment discharge at ~ 4.8 Ma drove massive progradation of fluvial-deltaic deposits back down the river valley into the northern Gulf and Salton Trough. These results provide evidence for a discontinuous, start-stop-start history of sand output during initiation of the Colorado River that is not predicted by existing models for this system. The underlying controls on punctuated sediment discharge are assessed by comparing the depositional chronology to the record of global sea-level change. The lower Colorado River Valley and Salton Trough experienced marine transgression during a gradual fall in global sea level between ~ 6.3 and 5.5 Ma, implicating tectonic subsidence as the main driver of latest Miocene relative sea-level rise. A major fall of global sea level at 5.3 Ma outpaced subsidence and drove regional delta progradation, earliest flushing of Colorado River sand into the northern Gulf of California, and erosion of Bouse basal carbonate and siliciclastic members. The lower Colorado River valley was re-flooded by shallow marine waters during smaller changes in global sea level ~ 5.1–4.8 Ma, after the river first ran through it, which requires a mechanism to stop delivery of sand to the lower river valley. We propose that tectonically controlled subsidence along the lower Colorado River, upstream of the southern Bouse study area, temporarily trapped sediment and stopped delivery of sand to the lower river valley and northern Gulf of California for ~ 200–300 kyr. Massive progradation of the fluvial-deltaic system back down the river valley into the Salton Trough starting ~ 4.8–4.5 Ma apparently was driven by a huge increase in sediment discharge that overwhelmed the sediment-storage capacity of sub-basins along the lower river corridor and established the fully integrated river channel network.

Quantifying Erosion Rates by Using Terrestrial Laser Scanning at Malakoff Diggins State Historic Park, Nevada County, California, 2014–17

U.S. Geological Survey (USGS) | December 31st, 2019

The abandoned hydraulic mine pit at Malakoff Diggins near Grass Valley, California, can produce large volumes of eroded sediment transportable by storm runoff. Sediment-l

The abandoned hydraulic mine pit at Malakoff Diggins near Grass Valley, California, can produce large volumes of eroded sediment transportable by storm runoff. Sediment-laden water discharged from the pit is a major source of heavy metals to Humbug Creek and the South Yuba River. To develop a comprehensive sediment budget for the Malakoff Diggins mine pit and identify sources of sediment and metals within the pit that can become entrained as suspended sediment in runoff discharged from the pit, the U.S. Geological Survey, working in cooperation with the California Department of Water Resources, the California Department of Parks and Recreation, and the Nevada Irrigation District, used terrestrial laser scanning technology to quantify eroded volumes and erosion rates of sedimentary units exposed in the pit walls. The results for eroded volumes and rates reported here are part one of a three-part study. High-resolution terrestrial laser scanning surveys were repeated annually from 2014 through 2017, including before and after dry and wet winters, measuring centimeter-scale topographic changes to quantify the volume of sediment eroded from outcrops at Malakoff Diggins State Historic Park, located on the western slope of the northern Sierra Nevada about 17 kilometers northeast of Grass Valley, California. Terrestrial laser scanning enabled construction of three-dimensional maps of the complex outcrop surfaces, which could not be mapped non-destructively or in sufficient detail with traditional surveying techniques. Net eroded volumes from discrete sedimentary units were calculated at four study sites (numbered 1, 2, 4, and 5) throughout the mine pit for the December 2014 to August 2017 period. Net eroded volumes at the four study sites during the 32-month study ranged from 288 plus or minus (±) 13 cubic meters (m3) of sediment at site 1 to 8,517±145 m3 at site 4. Annual erosion rates at the four study sites ranged from 0.06±0.01 cubic meters per square meter per year (m3/m2/yr) at site 4 to 0.14±0.01 m3/m2/yr at site 2. The total net eroded volume documented with terrestrial laser scanning at all four study sites from December 2014 to August 2017 was 12,934±334 m3 of sediment, and the average annual erosion rate for the four study sites was 0.10±0.04 m3/m2/yr. Maps of horizontal retreat indicate that a variety of erosional processes were responsible for the eroded sediment volume. These included areally broad and smaller-scale processes such as persistent dry ravel, periodic sheet wash, and frost heave and more localized and larger-scale processes such as coalescing rill and gully erosion, debris flows, rotational landslides, and block-fall failures.

Quantifying the Eroded and Deposited Mass of Mercury-Contaminated Sediment by Using Terrestrial Laser Scanning at the Confluence of Humbug Creek and the South Yuba River, Nevada County, California, 2011–13

U.S. Geological Survey (USGS) | October 24th, 2019

High-resolution, terrestrial laser scanning, also known as ground-based lidar (light detection and ranging), was used to quantify the volume of mercury-contaminated sedim

High-resolution, terrestrial laser scanning, also known as ground-based lidar (light detection and ranging), was used to quantify the volume of mercury-contaminated sediment eroded from an outcrop of historical placer-mining debris at the confluence of Humbug Creek and the South Yuba River in the Sierra Nevada foothills, about 17 kilometers northeast of Grass Valley, California, and delivered to a zone below an observed flood stage of the South Yuba River. Substantial quantities of mercury were used and lost to the environment from historical placer gold mining activities on the western slope of the Sierra Nevada, California, and recent studies have documented continued persistence of mercury and methylmercury concentrations in water, sediment, fish, and predatory invertebrates in the Yuba River drainage basin in relation to suspected mercury sources. To identify areas that have high levels of mercury contamination as possible remediation targets in the Yuba River drainage basin and other areas in the Sierra Nevada, the U.S. Geological Survey worked in cooperation with the Bureau of Land Management on this and other detailed studies. Malakoff Diggings, one of the largest hydraulic gold mines in the Sierra Nevada, is 3.5 kilometers north of the study site in the Humbug Creek subbasin. Terrestrial laser scanning was used to produce centimeter-scale, three-dimensional maps of the complex outcrop surface, which was composed of an upper erosional area (cliff and over-steepened slope) and a lower depositional area (colluvial slope). The outcrop could not be mapped non-destructively or in sufficient detail by traditional surveying techniques. The study site, which was approximately 70 meters long, 30 meters wide and 20 meters high, was surveyed four times in 2 years (December 15, 2011; October 25, 2012; January 4, 2013; and November 22, 2013) to determine volumetric differences in the upper erosional and lower depositional areas between surveys. Measured changes in volume for the upper erosional area and lower depositional area were multiplied by the corresponding sediment density so that a mass-balance relationship, between the eroded and deposited sediment during each period, could be used to estimate the amount of mercury-contaminated sediment that was transported to below the base of the colluvial slope, where it could be mobilized by the South Yuba River during a flood having a 5-to-10-year recurrence interval. On December 2, 2012, a flood of this estimated magnitude reached the base of the colluvial slope. Between the first and second surveys (December 15, 2011–October 25, 2012), an estimated mass of 18±9.2 kilograms of sediment was transported from steeper slopes to the gently sloping river bank below the base of the colluvial slope. Between the second and third surveys (October 25, 2012–January 4, 2013), an atmospheric river caused heavy precipitation at the study site during late November and early December 2012. This short-duration, high-intensity rain resulted in a large amount of erosion and deposition at the study site and also caused high streamflow (flood stage) in the South Yuba River. From October 2012 to January 2013, 51±31 kilograms of sediment was transported to below the base of the colluvial slope, that is, below the high-water mark of December 2, 2012. Between the third and fourth surveys (January 4, 2013–November 22, 2013), an additional 10±26 kilograms of sediment was transported to below the base of the colluvial slope. During the 24 months of the study, the total mass of sediment delivered below the base of the colluvial slope and the high-water mark of December 2, 2012, was 79±66 kilograms. In any given year there is a 10–20-percent chance (5-to-10-year recurrence interval) of a flood equal to or greater than that of the December 2, 2012, flood, which could transport mercury-contaminated sediment at the study site into the South Yuba River. Hydraulically modeled estimates of the South Yuba River stage during floods having a 50- and 100-year recurrence interval (2- and 1-percent annual exceedance probability, respectively) indicated that resulting river stages could be 2.2–3.0 meters above the base of the colluvial slope, or 2.2–3.0 meters above the high-water mark of December 2, 2012. Such high river stages would be likely to inundate the lower half of the colluvial slope and mobilize a substantial volume of mercury-contaminated sediment to downstream areas.