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At least 541 records · Page 30Linked to original sources
USGS2014

Hydrologic monitoring of a landslide-prone hillslope in the Elliott State Forest, Southern Coast Range, Oregon, 2009-2012

The Oregon Coast Range is dissected by numerous unchanneled headwater basins, which can generate shallow landslides and debris flows during heavy or prolonged rainfall. An automated monitoring system was installed in an unchanneled headwater basin to measure rainfall, volumetric water content, groundwater temperature, and pore pressures at 15-minute intervals. The purpose of this report is to describe and present the methods used for the monitoring as well as the preliminary data collected during the period from 2009 to 2012. Observations show a pronounced seasonal variation in volumetric water content and pore pressures. Increases in pore pressures and volumetric water content from dry-season values begin with the onset of the rainy season in the fall (typically early to mid October). High water contents and pore pressures tend to persist throughout the rainy season, which typically ends in May. Heavy or prolonged rainfall during the wet season that falls on already moist soils often generates positive pore pressures that are observed in the deeper instruments. These data provide a record of the basin’s hydrologic response to rainfall and provide a foundation for understanding the conditions that lead to landslide and debris-flow occurrence.

Oregon↗
USGS2022

Modeling the dynamics of lahars that originate as landslides on the west side of Mount Rainier, Washington

Large lahars pose substantial threats to people and property downstream from Mount Rainier volcano in Washington State. Geologic evidence indicates that these threats exist even during the absence of volcanic activity and that the threats are highest in the densely populated Puyallup and Nisqually River valleys on the west side of the volcano. However, the precise character of these threats can be difficult to anticipate. To help predict depths and rates of possible lahar inundation in the area, this report presents the results of simulations of hypothetical future lahars that originate high on the west side of Mount Rainier and travel downstream into the Puyallup and Nisqually River valleys. Many of the results portrayed as still images in the figures of this report are also available as animated files that can be accessed at the web address provided in the figure captions. We simulated eight scenarios, including worst-case scenarios in which the simulated lahars are similar in size and mobility to the approximately 260 million cubic meter (Mm 3 ; 340 million cubic yard) Electron Mudflow lahar that descended from Mount Rainier and inundated the Puyallup River valley about 500 years ago. The other six scenarios place the worst-case scenarios in perspective by simulating lahars that originate from the same source areas but have smaller volumes or lesser mobilities. We perform our simulations using an open-source software package that we developed called D-Claw. The numerical model composing the kernel of D-Claw solves a system of five hyperbolic partial differential equations that describe the depth-averaged dynamics of static or flowing grain-fluid mixtures interacting with three-dimensional topography. In D-Claw, the volume fraction occupied by solid grains is a dependent variable that can freely evolve, enabling simulation of landslide liquefaction and of lahar interaction with static bodies of water. The latter feature facilitates a seamless simulation of a lahar in the Nisqually River valley entering Alder Lake reservoir. In the event of an approximately 260 Mm 3 high-mobility lahar originating on the west side of Mount Rainier, our results point to two areas of pronounced hazard. One area, comprising the densely populated lowlands of Orting, Washington, and environs, could be inundated by lahars originating from either the Sunset Amphitheater or Tahoma Glacier headwall areas. In the worst-case scenario we consider for the Orting lowlands, which involves a 260 Mm 3 high-mobility lahar originating from a landslide in the Sunset Amphitheater, a flow front approximately 4 meters deep and traveling about 4 meters per second reaches the Orting lowlands about 1 hour after the onset of slope failure. After passing through the Orting lowlands, the simulated lahar slows down and comes to rest in the valleys surrounding Sumner and Puyallup. A second area of pronounced hazard is the stretch of the Nisqually River valley beginning in Mount Rainier National Park and extending downstream to Alder Lake reservoir and Alder Dam. This area would be substantially affected in the worst-case scenario that involves a 260 Mm 3 high-mobility lahar originating from the Tahoma Glacier headwall area—the locality identified by a previous study as the sector of Mount Rainier most prone to large-scale gravitational collapse. The simulated lahar passes through the area of Ashford, Washington, within about 20 minutes of the onset of slope failure and reaches the head of Alder Lake within about 50 minutes. The lahar ultimately displaces enough reservoir water to cause overtopping of the 100 meter (330 foot) tall Alder Dam, but consequences of such dam overtopping are not addressed in this report.

Washington↗
USGS1978

Relationship of landslides to fractures in Potomac Group deposits, Fairfax County, Virginia

Landsliding is a common problem in eastern Fairfax County, an area underlain by Potomac Group (Lower Cretaceous) Coastal Plain deposits of silt and clay interbedded and interfingered with sand and gravel. The slides commonly are present in clay and silt that, on the basis of laboratory tests, appear to be much too strong to have failed. However, the very plastic silt and clay deposits are commonly cut by long continuous to short discontinuous high-angle and subhorizontal joints, shears, and faults. These fractures can contribute to sliding. Failure along faults and shears takes place because the relative movement has greatly weakened and softened the clay and silt. The mechanism for failure along the joints is less obvious but may be related to infilling along joints, slight movement due to erosional unloading, swelling of clays, and softening along joints. Field investigations suggest that the three best developed high-angle joint sets in eastern Fairfax County have trends in the northeast quadrant. Lineaments plotted on a lineament map prepared from Landsat imagery also trend northeast parallel to the regional joint orientation. This regional orientation suggests that some of the fractures are tectonic in origin. Therefore, they should be anticipated in a broad zone many miles wide in the vicinity of the Fall Line. In addition, fractures of unknown origin contributing to landsliding, have been observed in massive Potomac Group clay and silt deposits. Irrespective of origin, these fractures require careful investigation and engineering to prevent slope failure at critical locations during and after major excavation.

Virginia↗
USGS2001

Catastrophic debris flows transformed from landslides in volcanic terrains : mobility, hazard assessment and mitigation strategies

Communities in lowlands near volcanoes are vulnerable to significant volcanic flow hazards in addition to those associated directly with eruptions. The largest such risk is from debris flows beginning as volcanic landslides, with the potential to travel over 100 kilometers. Stratovolcanic edifices commonly are hydrothermal aquifers composed of unstable, altered rock forming steep slopes at high altitudes, and the terrain surrounding them is commonly mantled by readily mobilized, weathered airfall and ashflow deposits. We propose that volcano hazard assessments integrate the potential for unanticipated debris flows with, at active volcanoes, the greater but more predictable potential of magmatically triggered flows. This proposal reinforces the already powerful arguments for minimizing populations in potential flow pathways below both active and selected inactive volcanoes. It also addresses the potential for volcano flank collapse to occur with instability early in a magmatic episode, as well as the 'false-alarm problem'-the difficulty in evacuating the potential paths of these large mobile flows. Debris flows that transform from volcanic landslides, characterized by cohesive (muddy) deposits, create risk comparable to that of their syneruptive counterparts of snow and ice-melt origin, which yield noncohesive (granular) deposits, because: (1) Volcano collapses and the failures of airfall- and ashflow-mantled slopes commonly yield highly mobile debris flows as well as debris avalanches with limited runout potential. Runout potential of debris flows may increase several fold as their volumes enlarge beyond volcanoes through bulking (entrainment) of sediment. Through this mechanism, the runouts of even relatively small collapses at Cascade Range volcanoes, in the range of 0.1 to 0.2 cubic kilometers, can extend to populated lowlands. (2) Collapse is caused by a variety of triggers: tectonic and volcanic earthquakes, gravitational failure, hydrovolcanism, and precipitation, as well as magmatic activity and eruptions. (3) Risk of collapse begins with initial magmatic activity and increases as intrusion proceeds. An archetypal debris flow from volcanic terrain occurred in Colombia with a tectonic earthquake (M 6.4) in 1994. The Rio Piez conveyed a catastrophic wave of debris flow over 100 kilometers, coalesced from multiple slides of surflcial material weakened both by weathering and by hydrothermal alteration in a large strato- volcano. Similar seismogenic flows occurred in Mexico in 1920 (M -6.5), Chile in 1960 (M 9.2), and Ecuador in 1987 (M 6.1 and 6.9). Velocities of wave fronts in two examples were 60 to 90 km/hr (17-25 meters per second) over the initial 30 kilometers. Volcano flank and sector collapses may produce untransformed debris avalanches, as occurred initially at Mount St. Helens in 1980. However, at least as common is direct transformation of the failed mass to a debris flow. At two other volcanoes in the Cascade Range-- Mount Rainier and Mount Baker--rapid transformation and high mobility were typical of most of at least 15 Holocene flows. This danger exists downstream from many stratovolcanoes worldwide; the population at risk is near 150,000 and increasing at Mount Rainier. The first step in preventing future catastrophes is documenting past flows. Deposits of some debris flows, however, can be mistaken for those of less-mobile debris avalanches on the basis of mounds formed by buoyed megaclasts. Megaclasts may record only the proximal phase of a debris flow that began as a debris avalanche. Runout may have extended much farther, and thus furore flow mobility may be underestimated. Processes and behaviors of megaclast-bearing paleoflows are best inferred from the intermegaclast matrix. Mitigation strategy can respond to volcanic flows regardless of type and trigger by: (1) Avoidance: Limit settlement in flow pathways to numbers that can be evacuated after event warnings (flow is occurring). (2) Instrumental even

Professional Paper↗
USGS2022

Remote sensing application for landslide detection, monitoring along eastern Lake Michigan (Miami Park, MI)

We assessed the nature and spatial and temporal patterns of deformation over the Miami Park bluffs on the eastern margin of Lake Michigan and investigated the factors controlling its observed deformation. Our approach involved the following steps: (1) extracting bluff deformation rates (velocities along the line of sight of the satellite) using a stack of Sentinel-1A radar imagery in ascending acquisition geometry acquired between 2017 and 2021 and applying the Intermittent Small Baseline Subset (ISBAS) InSAR time series analysis method; (2) generating high-resolution (5 cm) elevation models and orthophotos from temporal unmanned aerial vehicle (UAV) surveys acquired in 2017, 2019, and 2021; and (3) comparing the temporal variations in mass wasting events to other relevant datasets including the ISBAS-based bluff deformation time series, lake level (LL) variations, and local glacial stratigraphy. We identified areas witnessing high line-of-sight (LOS) deformation rates (up to −21 mm/year) along the bluff from the ISBAS analysis and seasonal deformation patterns associated with freeze-thaw cycles, suggesting a causal effect. The acceleration of slope failures detected from field and UAV acquisitions correlated with high LLs and intensified onshore wave energy in 2020. The adopted methodology successfully predicts landslides caused by freezes and thaws of the slope face by identifying prolonged slow deformation preceding slope failures, but it does not predict the catastrophic landslides preceded by short-lived LOS deformation related to LL rise.

Michigan↗
USGS1987

DEFORESTATION AND LANDSLIDES IN YUNNAN, CHINA.

Landslides historically have caused severe erosion problems in the Xiao River drainage region of northeastern Yunnan Province, China, that hence resulted in serious economic and social consequences. Owing to monsoonal storms of high rainfall intensity, the erosion potential is high in this mountainous, seismically active region. Landslides transported large quantities of materials into the ravines. During intense storms, high runoff from the deforested areas has mobilized this material into debris flows. Where these flows emerged onto flatter slopes in the lower parts of the watersheds, the channels were too small to hold them, so farmland and villages were inundated. Debris flows in this region during June-August 1985 killed 12 people, damaged roads and the main rail line to Kunming, the capital of Yunnan Province, inundated farmland, and overflowed debris-retention structures. To mitigate these severe erosion problems, several different methods have been used.

Conference Paper↗
USGS1986

Seismically induced landslides: current research by the US Geological Survey.

We have produced a regional seismic slope-stability map and a probabilistic prediction of landslide distribution from a postulated earthquake. For liquefaction-induced landslides, in situ measurements of seismically induced pore-water pressures have been used to establish an elastic model of pore pressure generation. -from Authors

Geologia Applicata e Idrogeologia↗
USGS2003

A model for spatially and temporally distributed shallow landslide initiation by rainfall infiltration

We describe a model for regional initiation of shallow landslides based on an approximate analytic solution to Richards equation combined with an infinite-slope calculation. The model applied over digital topography computes pressure heads and factors of safety as functions of depth for geographic information system (GIS) grid cells at any time during and after rainfall events. An example is presented that simulates the progressive development of shallow landslides on steep slopes during a rainfall event. This example shows how this modeling provides insights into transient rainfall-caused processes that trigger shallow slope instability and consequent regionally distributed debris-flow events. Specifically, we infer that the spatial pattern of instability is primarily controlled by topography, while intensity and duration of rainfall, and the subsequent pore-pressure responses control the temporal pattern of instability. ?? 2003 Millpress.

Conference Paper↗
USGS2005

The hurricane-flood-landslide continuum

In August 2004, representatives from NOAA, NASA, the US Geological Survey (USGS), as well as other government agencies and academic institutions convened in San Juan, Puerto Rico, at a workshop to discuss a proposed research project called the Hurricane-Flood-Landslide Continuum (HFLC). The purpose of the HFLC is to develop and integrate the multidisciplinary tools needed to issue regional guidance products for floods and landslide associated with major tropical rain systems with sufficient lead time that local emergency managers can notify vulnerable populations and protect infrastructure. The workshop sought to initiate discussion among these agencies about their highly complementary capabilities, and to establish a framework to leverage the strengths of each agency. Once a prototype system is developed, it could be adapted for use in regions that have a high frequency of tropical disturbances.

Bulletin of the American Meteorological Society↗
USGS1973

Two diamictons in a landslide scarp on Admiralty Island, Alaska, and the tectonic insignificance of an intervening peat bed

Two till-like diamictons, 700 feet above present sea level on Admiralty Island, Alaska, are separated by peat near the top of a landslide scarp. The lower diamicton is glaciomarine; the upper diamicton is probably a mudflow. The lower diamicton contains the foraminifer Elphidium clavatum Cushman, a species typical of fiords. Similar diamicton crops out along Gastineau Channel near Juneau, 15 miles eastward. Diamicton in both areas reflects deposition in glacier-free fiords during land depression and sea transgression. Consequently, till-like deposits less than 700 feet above sea level elsewhere in southeastern Alaska should be considered as possibly glaciomarine. Sliding occurred after late 1962, but before July 1964; the March 27, 1964, Alaska earthquake might have caused sliding of diamicton saturated by melting snow and spring rains. The peat in the landslide scarp has a published radiocarbon date of 3,400±250 years B.P. (W-1955). The peat was expected to be older, and to relate to Holocene tectonic movement of Admiralty Island. The unexpectedly young date led to additional field study that showed the material over the peat to be a probable mudflow derived from glaciomarine diamicton upvalley; the date has no tectonic significance.

Alaska↗
USGS1981

Earthquake-triggered landslides form lakes in New Zealand

Eleven small lakes were formed by landslides caused by the 1929 Buller earthquake in New Zealand; four others were formed by other historic earthquakes in this country. At least nine other New Zealand lakes are dammed by landslides and were probably formed by prehistoric earthquakes. Earthquake-dammed lakes could provide an estimate of paleoseimicity for the past few hundred or thousand years.

Earthquake Information Bulletin (USGS)↗
USGS2000

Usoi Landslide Dam and Lake Sarez – An assessment of hazard and risk in the Pamir Mountains, Tajikistan

Lake Sarez, which is located in the Pamir Mountains in Tajikistan, was created in 1911. A massive landslide, triggered by an earthquake, blocked the Murgab River valley, creating a natural dam, which was called Usoi. In 1999, the International Decade for Natural Disaster Reduction Secretariat led a mission to assess the risk and impacts in the Pamir Mountains of Tajikistan including this natural phenomenon. This report presents the final results of the assessment and offers practical recommendations. The areas of coverage include: geotechnical assessment of the Usoi landslide dam and the right bank of Lake Sarez; environmental impact assessment; flood scenarios; monitoring and early warning systems; accessibility of the Bartang River valley and Usoi Dam; Human geography/demography; and social and economic conditions in the valley of the Bartang River.

Lake Sarez, Usoi Landslide Dam↗
USGS1975

A late Holocene pollen record from Pearson's Pond, Weeks Creek landslide, San Francisco Peninsula, California

A 210-cm core from Pearson's Pond yielded a pollen record for the past 3 millenia. Prior to A.D. 1000 the pond biota was particularly sensitive to climatic fluctuations. Two wet intervals occur in the pollen record, between 350 B.C. and A.I). 0 and between A.D. 650 and 900. The pollen record suggests that the Weeks Creek landslide may have moved at least twice prior to 3,000 years ago and that the middle part of the glide has been stable since that time. Seasonal changes produce large annual fluctuations in the water table, and climatic changes during the past 3,000 years have produced significant changes in the timing and magnitude of the annual changes. Climatic records such as the one presented here will help us to understand and separate the effects of climate and earthquakes on the landslide history of the Holocene deposits of the San Francisco Bay area.

California↗
USGS2020

Hillslopes in humid-tropical climates aren’t always wet: Implications for hydrologic response and landslide initiation in Puerto Rico, USA

The devastating impacts of the widespread flooding and landsliding in Puerto Rico following the September 2017 landfall of Hurricane Maria highlight the increasingly extreme atmospheric disturbances and enhanced hazard potential in mountainous humid‐tropical climate zones. Long‐standing conceptual models for hydrologically driven hazards in Puerto Rico posit that hillslope soils remain wet throughout the year, and therefore, that antecedent soil wetness imposes a negligible effect on hazard potential. Our post‐Maria in situ hillslope hydrologic observations, however, indicate that while some slopes remain wet throughout the year, others exhibit appreciable seasonal and intra‐storm subsurface drainage. Therefore, we evaluated the performance of hydro‐meteorological (soil wetness and rainfall) versus intensity‐duration (rainfall only) hillslope hydrologic response thresholds that identify the onset of positive pore‐water pressure, a predisposing factor for widespread slope instability in this region. Our analyses also consider the role of soil‐water storage and infiltration rates on runoff generation, which are relevant factors for flooding hazards. We found that the hydro‐meteorological thresholds outperformed intensity‐duration thresholds for a seasonally wet, coarse‐grained soil, although they did not outperform intensity‐duration thresholds for a perennially wet, fine‐grained soil. These end‐member soils types may also produce radically different stormflow responses, with subsurface flow being more common for the coarse‐grained soils underlain by intrusive rocks versus infiltration excess and/or saturation excess for the fine‐grained soils underlain by volcaniclastic rocks. We conclude that variability in soil‐hydraulic properties, as opposed to climate zone, is the dominant factor that controls runoff generation mechanisms and modulates the relative importance of antecedent soil wetness for our hillslope hydrologic response thresholds.

Puerto Rico↗
USGS2011

Submarine landslides in Arctic sedimentation: Canada Basin

Canada Basin of the Arctic Ocean is the least studied ocean basin in the World. Marine seismic field programs were conducted over the past 6 years using Canadian and American icebreakers. These expeditions acquired more than 14,000 line-km of multibeam bathymetric and multi-channel seismic reflection data over abyssal plain, continental rise and slope regions of Canada Basin; areas where little or no seismic reflection data existed previously. Canada Basin is a turbidite-filled basin with flat-lying reflections correlateable over 100s of km. For the upper half of the sedimentary succession, evidence of sedimentary processes other than turbidity current deposition is rare. The Canadian Archipelago and Beaufort Sea margins host stacked mass transport deposits from which many of these turbidites appear to derive. The stratigraphic succession of the MacKenzie River fan is dominated by mass transport deposits; one such complex is in excess of 132,000 km2 in area and underlies much of the southern abyssal plain. The modern seafloor is also scarred with escarpments and mass failure deposits; evidence that submarine landsliding is an ongoing process. In its latest phase of development, Canada Basin is geomorphologically confined with stable oceanographic structure, resulting in restricted depositional/reworking processes. The sedimentary record, therefore, underscores the significance of mass-transport processes in providing sediments to oceanic abyssal plains as few other basins are able to do.

Alaska↗
USGS1988

The geometric signature: Quantifying landslide-terrain types from digital elevation models

Topography of various types and scales can be fingerprinted by computer analysis of altitude matrices (digital elevation models, or DEMs). The critical analytic tool is the geometric signature, a set of measures that describes topographic form well enough to distinguish among geomorphically disparate landscapes. Different surficial processes create topography with diagnostic forms that are recognizable in the field. The geometric signature abstracts those forms from contour maps or their DEMs and expresses them numerically. This multivariate characterization enables once-in-tractable problems to be addressed. The measures that constitute a geometric signature express different but complementary attributes of topographic form. Most parameters used here are statistical estimates of central tendency and dispersion for five major categories of terrain geometry; altitude, altitude variance spectrum, slope between slope reversals, and slope and its curvature at fixed slope lengths. As an experimental application of geometric signatures, two mapped terrain types associated with different processes of shallow landsliding in Marin County, California, were distinguished consistently by a 17-variable description of topography from 21??21 DEMs (30-m grid spacing). The small matrix is a statistical window that can be used to scan large DEMs by computer, thus potentially automating the mapping of contrasting terrain types. The two types in Marin County host either (1) slow slides: earth flows and slump-earth flows, or (2) rapid flows: debris avalanches and debris flows. The signature approach should adapt to terrain taxonomy and mapping in other areas, where conditions differ from those in Central California. ?? 1988 International Association for Mathematical Geology.

Mathematical Geology↗