Geology Reports⌕ Search

Geology topics

Robert L. Schuster

Publications and source records attributed to Robert L. Schuster.

At least 19 recordsLinked to original sources
USGS2026

Downstream persistence of cyanobacteria in New Jersey's Raritan River basin

Few studies have examined cyanobacteria persistence starting from lacustrine cyanobacteria harmful algal blooms (HABs) downstream. Multiple lakes and reservoirs within New Jersey's Raritan Basin Water Supply Complex (RBWSC) feature recurrent HABs and discharge water into the Raritan River. As the RBWSC provides drinking water to 1.5 million people, these HABs create drinking water treatment and human health concerns. This study quantitatively reviews the persistence of cyanobacteria communities across the RBWSC from cyanobacteria-dominated lacustrine sources to downstream drinking water and qualitatively assess what, if any, water chemistry parameters influenced the persistence, growth, or decline of cyanobacteria during downstream transport. Statistical tests showed there was a lack of continuity between cyanobacteria communities along the Raritan River, except for periods of higher streamflow and higher releases from the Spruce Run Reservoir. Results along the Millstone River suggested the potential for in-river cyanobacteria growth, which overlapped with periods of low streamflow and high nutrient concentrations in the summer and fall. A permutational analysis of variance (PERMANVOA) test found significantly dissimilar ( p < 0.01) cyanobacteria communities between lake and reservoir outlet sites and downstream sites in the Raritan, but not the Millstone River ( p = 0.928). A similarity percentage (SIMPER) analysis found cyanobacteria communities changed from high densities of bloom forming cyanobacteria ( Aphanocapsa, Aphanizomenon, Microcystis) at the lake outlet sites to low densities of non-bloom forming cyanobacteria ( Synechcoccus, Chroococcus) along the Raritan mainstem, with Aphanocapsa the most notable bloom forming genera overlapping between sites. Investigating cyanobacteria on a watershed-specific basis could enhance understanding of the site-specific transport mechanisms and water chemistry parameters that facilitate community persistence.

New Jersey↗
USGS2022

Age of the late Holocene Bonneville landslide and submerged forest of the Columbia River Gorge, Oregon and Washington, USA, by radiocarbon dating

The late Holocene Bonneville landslide, a 15.5 km 2 rockslide-debris avalanche, descended 1000 m from the north side of the Columbia River Gorge and dammed the Columbia River where it bisects the Cascade Range of Oregon and Washington, USA. The landslide, inundation, and overtopping created persistent geomorphic, ecologic, and cultural consequences to the river corridor, reported by Indigenous narratives and explorer accounts, as well as scientists and engineers. From new dendrochronology and radiocarbon dating of three trees killed by the landslide, one entrained and buried by the landslide and two killed by rising water in the impounded Columbia River upstream of the blockage, we find (1) the two drowned trees and the buried tree died the same year, and (2) the age of tree death, and hence the landslide (determined by combined results of nine radiocarbon analyses of samples from the three trees), falls within AD 1421–1455 (3σ confidence interval). This result provides temporal context for the tremendous physical, ecological, and cultural effects of the landslide, as well as possible triggering mechanisms. The age precludes the last Cascadia Subduction Zone earthquake of AD 1700 as a landslide trigger, but not earlier subduction zone or local crustal earthquakes.

Oregon, Washington↗
USGS2009

Deposition of Mount Mazama tephra in a landslide-dammed lake on the upper Skagit River, state of Washington

The cataclysmic eruption of Mount Mazama, Oregon, at c. 6730 (super 14) C yr BP, deposited tephra over 1.0 X 10 (super 6) km (super 2) of north-western North America. Primary tephra fall accumulated to a thickness of 2 cm in the upper Skagit River watershed, Washington. Mazama tephra eroded from this watershed was deposited in Lake Ksnea, of 14 km length and 40 m depth. This lake was created when a landslide blocked the Skagit River at 7040 (super 14) C yr BP. Horizontally bedded, dark grey silt and clay were deposited slowly by suspension settling in Lake Ksnea before the eruption of Mount Mazama. The 2-cm-thick primary Mazama tephra layer abruptly caps 7 m of pre-eruption sediments, and is overlain by as much as 17 m of Mazama tephra deposited relatively rapidly on a delta at the mouth of Damnation Creek. Most of a 13-m-thick section is composed of lacustrine tephra containing rhythmic stratified beds deposited by suspension settling. Turbidity currents deposited centimetre-scale, cross-bedded silt and tephra at the top of some rhythmite beds. Lower in this section, tephra containing abundant fine-grained terrestrial sediments and other sedimentary structures interrupts the rhythmite beds. These structures include faulted and warped beds, flame structures and pendants created by soft-sediment deformation. Tephra deposits are overlain conformably with cross-bedded sands throughout most of a 200-m-long section. Coarse alluvial gravels and landslide deposits unconformably overlie the tephra and sand at several locations. The deposits described are interpreted as an inversely graded, prograding delta sequence composed almost entirely of Mount Mazama tephra. Despite a lack of age control on the rate of tephra deposition, the sedimentology of this section indicates that the tephra delta was deposited within 1 yr or less

Oregon↗
USGS2006

Interaction of dams and landslides: Case studies and mitigation

In the first half of the 20th century, engineering geology and geotechnical engineering were in their infancy, and dams were often built where landslides provided valley constrictions, often without expert site investigation. Only the most important projects were subjected to careful geologic examination. Thus, dams were often built without complete understanding of the possible geotechnical problems occurring in foundations or abutments. Most of these dams still exist, although many have undergone costly repairs because of stability or leakage problems. Today, however, every effort is made in the selection of damsites, including those sited on landslides, to provide foundations and abutments that are generally impervious and capable of withstanding the stresses imposed by the proposed dam and reservoir, and possible landslides. By means of a literature search, technical interviews, and field inventory, I have located 254 large (at least 10 m high) dams worldwide that directly interact with landslides; that is, they have been built on pre-existing landslides or have been subjected to landslide activity during or after construction. A table (Appendix table A) summarizes dam characteristics, landslide conditions, and remedial measures at each of the dams. Of the 254 dams, 164 are earthfill, 23 are rockfill, and 18 are earthfill-rockfill; these are flexible dam types that generally perform better on the possibly unstable foundations provided by landslides than do more rigid concrete dams. Any pre-existing landslides that might impinge on the foundation or abutments of a dam should be carefully investigated. If a landslide is recognized in a dam foundation or abutment, the landslide deposits commonly are avoided in siting the dam or are removed during stripping of the dam foundation and abutment contacts. Contrarily, it has often been found to be technically feasible and economically desirable to site and construct dams on known landslides or on the remnants of these features. In these cases, proven preventive and remedial measures have been used to ensure the stability of the foundations and abutments, and to reduce seepage to acceptable levels.

Professional Paper↗
USGS2006

Impacts of landslide dams on mountain morphology

Landslide dams can influence mountain-valley morphology significantly in the vicinity of the dam sites, as well as upstream and downstream. The effects are: (1) impoundment of lakes that result in changes in stream gradients, (2) deposition of lacustrine and deltaic sediments in these impoundments that causes changes in surficial morphology and geologic materials upstream from the dams, (3) diversions of stream channels at the and near the sam sites, (4) formation of avulsively-shifting channels downstream from the dams by the introduction of high sediment loads from erosion of landslide deposits or sediments in the landslide-dammed lakes, and (5) secondary landslide activity along the shores of impounded lakes due to rapid drawdown when the dam fails. Often, by construction of channel spillways or outlet tunnels human remedial efforts affect the longevity of landslide dams and the impoundments, and thus influence the long term effects of these natural features on mountain valley morphology.

Book chapter↗
USGS2004

Usoi Landslide Dam and Lake Sarez, Pamir Mountains, Tajikistan

In 1911, a 2-km 3 (0.5-mi 3 ) earthquake-triggered rock slide blocked the Murgab River, southeastern Tajikistan, forming a still-existing, 600-m-high (1,970-ft-high) natural dam—the highest dam, natural or man-made, in the world. Lake Sarez, impounded by this blockage, is 60 km (37 mi) long, with a maximum depth of 550 m (1,800 ft) and a volume of approximately 17 km 3 (∼4 mi 3 ). This lake, which has never overtopped the dam, exits the downstream face as a series of large springs that regroup as the Murgab River. Freeboard between lake surface and the lowest point on the dam crest currently is approximately 50 m (∼165 ft), and the lake is rising at an average rate of 18.5 cm/yr (7.3 in./yr). If the blockage were to fail, a worst-case scenario could endanger tens or possibly hundreds of thousands of people in the Murgab, Bartang, Panj, and Amu Darya valleys downstream. Dam failure potentially could result from: 1) seismic shaking, 2) catastrophic overtopping caused by a landslide entering the lake from the valley wall at high velocity, 3) surface erosion caused by natural overtopping by the rising lake, 4) internal erosion (piping), 5) instability caused by lake pressure against the dam, or 6) slope instability of the dam faces. Occurrence of an overtopping wave resulting from a potential landslide high on the right bank of Lake Sarez seems to be the most realistic of these slight possibilities for failure. Because of the high cost of installing physical remediation to the dam in this rugged mountain area (no roads lead to the site), the main protective measures now being undertaken are hydrological monitoring at the dam and installation of a flood early warning system downstream.

Lake Sarez↗
USGS2004

Assessment of Hazards Associated with the Bluegill Landslide, South-Central Idaho

The Bluegill landslide, located in south-central Idaho, is part of a larger landslide complex that forms an area the Salmon Falls Creek drainage named Sinking Canyon Recent movement of the Bluegill landslide, apparently beginning sometime in late 1998 or early 1999, has caused a 4.5 ha area of the canyon rim to drop as much as 8 m and move horizontally several meters into the canyon. Upward movement of the toe of the landslide in the bottom of canyon has created a dam that impounds a lake approximately 2 km in length. The landslide is on public administered by the U.S. Bureau of Land Management (BLM). As part of ongoing efforts to address possible public safety concerns, the BLM requested that the U.S. Geological Survey (USGS) conduct a preliminary hazard assessment of the landslide, examine possible mitigation options, and identify alternatives for further study and monitoring of the landslide. This report presents the findings of that assessment based on a field reconnaissance of the landslide on September 24, 2003, a review of data and information provided by BLM and researchers from Idaho State University, and information collected from other sources.

Open-File Report↗
USGS2002

Landslide triggers and types

The term “landslide trigger” refers to an external stimulus, such as intense rainfall, rapid snowmelt, seismic shaking, volcanic eruption, stream/coastal erosion, or natural dam failure, which causes an immediate or near-immediate response in the form of landslide activity. In this paper, we discuss the types of landslides caused by these triggering processes and present a limited number of worldwide examples of their occurrence.

Conference Paper↗
USGS2001

Socioeconomic and environmental impacts of landslides in the Western Hemisphere

In spite of improvements in recognition, prediction, mitigative measures, and warning systems, economic losses and casualties due to landslides in the Western Hemisphere appear to be growing as a result of increasing development of landslide-prone areas due to population pressures. This paper notes outstanding examples of socioeconomic losses in the Americas. Landslides impact the following elements of the natural environment: (1) the topography/morphology of both the subaerial and submarine surfaces of the Earth, (2) rivers, streams, forests, and grasslands, and (3) habitats of native fauna, both on the Earth?s surface and in its streams and oceans. Environmental disturbances are results of general tendency toward degradation of the Earth?s surface by gravitational mass wasting and erosion.

Open-File Report↗
USGS2000

Dams built on pre-existing landslides

In this paper I summarize the results of a worldwide study of 167 dams that have been constructed on preexisting landslides. Many major landslides in the past have blocked, or partially blocked, river valleys, providing possible dam sites that at first sight have appeared to be ideal. Thus, dams were occasionally built on landslides without a complete understanding of the problems involved. Today, however, every effort is made in the selection of dam sites to use foundations and abutments that are generally impervious and capable of withstanding the stresses imposed by the proposed dam and reservoir under all probable loading conditions. Any pre-existing landslides that might impinge on the foundation or abutments of a dam should be carefully investigated. If a landslide is recognized in a dam foundation or abutment, the landslide deposits commonly are avoided in siting the dam or are removed during stripping of the dam foundation and abutment contacts. However, it has often been found to be technically feasible and economically desirable to site and construct dams on known landslides or on the remnants of these features. In these cases, proven preventive and/or remedial measures have been used to ensure the stability of the foundations and abutments, and to reduce seepage to acceptable levels.

Conference Paper↗
USGS1998

Landslides triggered by the winter 1996-97 storms in the Puget Lowland, Washington

Snowmelt and rainfall events triggered many landslides and debris flows in the Seattle, Washington, area during late December 1996 and January and March 1997. Landslides caused the deaths of at least four people, millions of dollars in damage to public and private property, lost revenues, traffic diversions, and other direct and indirect losses. Although shallow slides and debris flows were the most common slope failures, many deep-seated slides also occurred. Comparing maps that show distribution of historic landslides with reports of landslides compiled by city and county governments for the winter of 1996-97 and our field reconnaissance of recent landslide deposits and scars indicates that many bluffs and steep hillsides are sites of recurring failures. Investigation of the 1996-97 landslides indicates that houses and other structures built downslope from steep bluffs are in particular danger of impact by debris flows, while those on the benches, slopes, or rim of bluffs are subject to severe damage by deep slides.

Open-File Report↗
USGS1998

The Loma Prieta, California, earthquake of October 17, 1989: Landslides

Central California, in the vicinity of San Francisco and Monterey Bays, has a history of fatal and damaging landslides, triggered by heavy rainfall, coastal and stream erosion, construction activity, and earthquakes. The great 1906 San Francisco earthquake ( M S =8.2-8.3) generated more than 10,000 landslides throughout an area of 32,000 km 2 ; these landslides killed at least 11 people and caused substantial damage to buildings, roads, railroads, and other civil works. Smaller numbers of landslides, which caused more localized damage, have also been reported from at least 20 other earthquakes that have occurred in the San Francisco Bay-Monterey Bay region since 1838. Conditions that make this region particularly susceptible to landslides include steep and rugged topography, weak rock and soil materials, seasonally heavy rainfall, and active seismicity. Given these conditions and history, it was no surprise that the 1989 Loma Prieta earthquake generated thousands of landslides throughout the region. Landslides caused one fatality and damaged at least 200 residences, numerous roads, and many other structures. Direct damage from landslides probably exceeded $30 million; additional, indirect economic losses were caused by long-term landslide blockage of two major highways and by delays in rebuilding brought about by concern over the potential long-term instability of some earthquake-damaged slopes.

California↗
USGS1995

Ribbon Cliff landslide Washington, and the earthquake of 14 December 1872

Estimates of the epicentral location and maximum intensity of the earthquake of 14 December 1872, the largest and oldest historic earthquake documented in the Pacific Northwest, are controversial largely because the estimates are based on ground effects. The Ribbon Cliff landslide is one of the more critical ground effects used to argue that the epicenter was in the vicinity of Lake Chelan in central Washington. Sketchy historical accounts link the Ribbon Cliff landslide to the 1872 earthquake, but a subsequent study disputed the historical accounts and, on the basis of dendrochronology, concluded that the landslide occurred more than 100 yr prior to the earthquake. However, Quaternary stratigraphic relations and the results of multiple dating techniques reported here indicate that the main Ribbon Cliff landslide probably occurred within a 14-yr period that includes the time of the 1872 earthquake. Although our study supports the historical accounts that link the landslide to the December 1872 earthquake, it does not prove that seismic shaking triggered the landslide.

Washington↗
USGS1993

Klamath Falls earthquakes, September 20, 1993 — Including the strongest quake ever measured in Oregon

Earthquakes struck the Klamath Falls area on Monday night, September 20, 1993, resulting in two deaths and extensive damage. The quakes were felt as far away as Coos Bay to the west, Eugene to the north, Lakeview to the east, and Chico, California, to the south. A foreshock recorded at 8:16 p.m. had a Richter magnitude of 3.9. The first of two main shocks, measuring 5.9 on the Richter scale, rumbled through Klamath Falls at 8:28 p.m. Following 16 smaller jolts with magnitudes between 2.2 and 3.8, the largest quake struck at 10:45 p.m. This earthquake, measuring 6.0 on the Richter scale, is the largest to hit Oregon since the 1873 Port Orford/Crescent City earthquake (Jacobson, 1986). Oregon has been shaken by stronger quakes, but those quakes originated beneath the Pacific Ocean west of Port Orford.

California, Nevada, Oregon, Washington↗