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At least 811 records · Page 45Linked to original sources
USGS2023

Construction and modification of debris-flow alluvial fans as captured in the geomorphic and sedimentary record: Examples from the western Sangre de Cristo Mountains, south-central Colorado

Debris-flow alluvial fans are iconic features of dynamic landscapes and are hypothesized to record tectonic and climatic change. Here, we highlight their complex formation and evolution through an exemplary suite of Quaternary debris-flow alluvial fans emanating from the western range front of the Sangre de Cristo Mountains in south-central Colorado, USA. To evaluate the constructive and modifying processes that produce fan form and the associated sedimentary signatures, we applied a combined geomorphologic and sedimentologic approach using sedimentary facies analysis, soils mapping, high-resolution topographic data, and luminescence geochronology to document timing of fan construction and modification. We explored two subsets of fans in the study area: a southern set sourced from the extensively glaciated drainages of the Blanca Peak massif, and a northern set from the unglaciated drainages south of Great Sand Dunes National Park. Both sets of fans have: (1) active and successively abandoned surfaces that show evolving degradation of primary features through modification by secondary processes, (2) associated facies that display distinct characteristics representative of primary depositional and secondary modifying sedimentary processes, and (3) evidence of primary debris flow with subsequent modification by secondary processes. We found that surface geomorphology and facies assemblages in exposed alluvial-fan deposits represent sediment transport processes on both active and abandoned lobes. The link between fan surface morphologies and the sedimentary facies of their deposits provides a basis for an evolutionary process–based interpretation of debris-flow alluvial-fan geomorphology and provides a better understanding of complexities in buried paleosurfaces (intraformational progressive unconformities), surficial deformation, and landform development as recorded in debris-flow fan deposits in the sedimentary record.

Colorado↗
USGS2019

Effects of Cenozoic subduction along the outboard margin of the Northern Cordillera: Derived from e-book on the Northern Cordillera (Alaska and Western Canada) and adjacent marine areas

This article describes the regional effects of Cenozoic subduction along the outboard margin of the Northern Cordillera (Alaska, USA, and Western Canada), and thereby acquaints the reader with several chapters of the e-book Dynamic Geology of the Northern Cordillera (Alaska, Western Canada, and Adjacent Marine Areas) . This article and the e-book are written for earth-science students and teachers. The level of writing for the article and the source e-book is that of popular science magazines, and readers are encouraged to share this article with students and laypersons. The main thrust of the article is to present and describe a suite of ten regional topographic, bathymetric, and geologic maps, and two figures portraying deep-crustal sections that illustrate the regional effects of Cenozoic subduction along the outboard margin of the North American Cordillera. The regional maps and cross sections are described in a way that a teacher might describe a map to students. Cenozoic subduction along the margin of the Northern Cordillera resulted in the formation of the following: (1) underthrusting of terranes and oceanic lithosphere beneath Southern Alaska; (2) landscapes, including narrow continental shelves along Southern and Southeastern Alaska and Western Canada (the Canadian Cordillera) and continental-margin mountain ranges, including the Alaska Peninsula, Chugach Range, Saint Elias Mountains, and Cascade Mountains; (3) sedimentary basins; (4) an array of active continental strike-slip and thrust faults (inboard of subduction zones); (5) earthquake belts related to subduction of terranes and oceanic plates; (6) active volcanoes, including continental-margin arcs (the Aleutian, Wrangell, and Cascade Arcs) linked to subduction zones, and interior volcanic belts related to strike-slip faulting or to hot spots; (7) lode and placer mineral deposits related to continental margin arcs or subduction of oceanic ridges; (8) hot springs related to continental-margin arcs; (9) plate movements as recorded from GPS measurements; and (10) underthrusting of terranes and oceanic lithosphere beneath the Northern Cordillera.

Alaska, British Columbia, Idaho, Montana, Washingt↗
USGS2011

Use of airborne hyperspectral imagery to map soil parameters in tilled agricultural fields

Soil hyperspectral reflectance imagery was obtained for six tilled (soil) agricultural fields using an airborne imaging spectrometer (400–2450 nm, ~10 nm resolution, 2.5 m spatial resolution). Surface soil samples ( n = 315) were analyzed for carbon content, particle size distribution, and 15 agronomically important elements (Mehlich-III extraction). When partial least squares (PLS) regression of imagery-derived reflectance spectra was used to predict analyte concentrations, 13 of the 19 analytes were predicted with R 2 > 0.50, including carbon (0.65), aluminum (0.76), iron (0.75), and silt content (0.79). Comparison of 15 spectral math preprocessing treatments showed that a simple first derivative worked well for nearly all analytes. The resulting PLS factors were exported as a vector of coefficients and used to calculate predicted maps of soil properties for each field. Image smoothing with a 3 × 3 low-pass filter prior to spectral data extraction improved prediction accuracy. The resulting raster maps showed variation associated with topographic factors, indicating the effect of soil redistribution and moisture regime on in-field spatial variability. High-resolution maps of soil analyte concentrations can be used to improve precision environmental management of farmlands.

Applied and Environmental Soil Science↗
USGS2012

A terrain-based site characterization map of California with implications for the contiguous United States

We present an approach based on geomorphometry to predict material properties and characterize site conditions using the V S 30 parameter (time‐averaged shear‐wave velocity to a depth of 30 m). Our framework consists of an automated terrain classification scheme based on taxonomic criteria (slope gradient, local convexity, and surface texture) that systematically identifies 16 terrain types from 1‐km spatial resolution (30 arcsec) Shuttle Radar Topography Mission digital elevation models (SRTMDEMs). Using 853 V S 30 values from California, we apply a simulation‐based statistical method to determine the mean V S 30 for each terrain type in California. We then compare the V S 30 values with models based on individual proxies, such as mapped surface geology and topographic slope, and show that our systematic terrain‐based approach consistently performs better than semiempirical estimates based on individual proxies. To further evaluate our model, we apply our California‐based estimates to terrains of the contiguous United States. Comparisons of our estimates with 325 V S 30 measurements outside of California, as well as estimates based on the topographic slope model, indicate our method to be statistically robust and more accurate. Our approach thus provides an objective and robust method for extending estimates of V S 30 for regions where in situ measurements are sparse or not readily available.

California↗
USGS2013

Late quaternary slip-rate variations along the Warm Springs Valley fault system, northern Walker Lane, California-Nevada border

The extent to which faults exhibit temporally varying slip rates has important consequences for models of fault mechanics and probabilistic seismic hazard. Here, we explore the temporal behavior of the dextral‐slip Warm Springs Valley fault system, which is part of a network of closely spaced (10–20 km) faults in the northern Walker Lane (California–Nevada border). We develop a late Quaternary slip record for the fault using Quaternary mapping and high‐resolution topographic data from airborne Light Distance and Ranging (LiDAR). The faulted Fort Sage alluvial fan (40.06° N, 119.99° W) is dextrally displaced 98+42/-43 m, and we estimate the age of the alluvial fan to be 41.4+10.0/-4.8 to 55.7±9.2 ka, based on a terrestrial cosmogenic 10 Be depth profile and 36 Cl analyses on basalt boulders, respectively. The displacement and age constraints for the fan yield a slip rate of 1.8 +0.8/-0.8 mm/yr to 2.4 +1.2/-1.1 mm/yr (2σ) along the northern Warm Springs Valley fault system for the past 41.4–55.7 ka. In contrast to this longer‐term slip rate, shorelines associated with the Sehoo highstand of Lake Lahontan (~15.8 ka) adjacent to the Fort Sage fan are dextrally faulted at most 3 m, which limits a maximum post‐15.8 ka slip rate to 0.2 mm/yr. These relations indicate that the post‐Lahontan slip rate on the fault is only about one‐tenth the longer‐term (41–56 ka) average slip rate. This apparent slip‐rate variation may be related to co‐dependent interaction with the nearby Honey Lake fault system, which shows evidence of an accelerated period of mid‐Holocene earthquakes.

California, Nevada↗
USGS1979

United States Geological Survey Yearbook, fiscal year 1978

Fiscal year 1978 saw the U.S. Geological Survey continuing to perform its basic historical missions of collecting, analyzing, and disseminating information about the Earth, its processes, and its water and mineral resources. Classifying Federal lands and supervising lessee mineral extraction operations on those lands were also major Survey concerns during the year. In addition, substantial progress was made in the exploration and assessment of the petroleum potential of the National Petroleum Reserve in Alaska, a recently assigned mission. These basic missions found expression in a wide range of program activities and interests as diverse as the sands of Mars and the volcanoes of Hawaii. Programs included assessment of numerous potential energy and mineral resources, study of earthquakes and other geologic hazards, appraisal of the magnitude and quality of the Nation's water resources, and supervision of lease operations on Federal lands. The Survey also was involved in developing data on land use and producing topographic, geologic, and hydrologic maps for public and private use. In cooperation with other Federal agencies, the Survey participated in studies under the U.S. Climate Program and continued its analysis of data received from the two Viking landers on the surface of Mars. On April 3, 1978, Dr. H. William Menard became the 10th Director of the U.S. Geological Survey. Dr. Menard, who, until his appointment, was Professor of Geology at the Scripps Institution of Oceanography, San Diego, Calif., brings to the Director's post the experience gained in a long and successful career as a marine geologist and oceanographer. He succeeds Dr. Vincent E. McKelvey, who continues with the Survey as a senior research scientist.

Yearbook↗
USGS1977

National Cartographic Information Center Newsletter No. 6

As a rule we don't carry personnel information additions, subtractions, etc., in the newsletter. This is a technical publication, not a forum for office baseball league scores. Now, having got that disclaimer out of the way, we wanted to note that Dick Swinnerton, Chief of NCIC since the Center's inception in 1974, has left us. Dick was recently chosen as Chief of the Topographic Divisions's Western Mapping Center (a move up and, geographically at least, to the left). When Dick arrived NCIC consisted of 4 briefing books and an interesting concept. 3 years later we have 10 books and a thriving organization. We shall miss him. This issue contains what we hope is an interesting collection of cartographic news, including articles about recent Federal mapping agreements, new publication announcements, notes on the second NCIC coordinating conference, and a cumulative index for the spring 1975 to summer 1977 issues.

Newsletter↗
USGS2006

Land-based lidar mapping: a new surveying technique to shed light on rapid topographic change

The rate of natural change in such dynamic environments as rivers and coastlines can sometimes overwhelm the monitoring capacity of conventional surveying methods. In response to this limitation, U.S. Geological Survey (USGS) scientists are pioneering new applications of light detection and ranging (lidar), a laser-based scanning technology that promises to greatly increase our ability to track rapid topographic changes and manage their impact on affected communities.

Fact Sheet↗
USGS1989

Surficial geologic map of the Meeker 30' x 60' quadrangle, Garfield, Moffat, Rio Blanco and Routt Counties, Colorado

This map is one of a series of four 30' x 60' surficial geologic maps (1:100,000 scale) intended to provide basic geologic information for planning for energy resource development and growth in northwestern Colorado. An effort is made to characterize all surficial materials, regardless of origin. Hence, residuum is given much more emphasis than is customary, and this results in several departures from conventional geologic maps: bedrock geology is deemphasized; the part of the map symbol denoting geologic age is omitted for surficial units because all surficial units shown are believed to be of Quaternary age; and faults are not shown because none in this map area was observed to displace surficial materials. Few exposures of most map units exist, except in manmade excavations, such as gravel pits and road cuts. Consequently, thicknesses usually are estimated, and data on stratification, clast size, and relative proportions of matrix and framework clasts are limited to a few localities for each map unit. The Wentworth scale is used to describe grain sizes. Mapping was done chiefly on aerial photographs taken in 1953. Hence, landslides and modifications resulting from gravel mining since 1953 may not show on this map. The scales of the aerial photographs (about 1:60,000) and the map (1:100,000) governed the minimum size of the deposits mapped. The minimum thickness of the depostis mapped is about 1.5m in most places. Deposit thickness, although not a mapping criterion, influences the topographic expression of many landforms, and landform is the basis for delineating the surficial deposits shown.

Colorado↗
USGS1991

Surficial geologic map of the Walden 30' x 60' quadrangle, Jackson, Larimer, and Routt counties, Colorado

This map is one of a series of four 30' x 60' surficial geologic maps (1:100,000 scale) intended to provide basic geologic information for planning for energy resource development and growth in northwestern Colorado. An effort is made to characterize all surficial materials, regardless of origin. Hence, residuum is given much more emphasis than is customary, and this results in several departures from conventional geologic maps: bedrock geology is deemphasized; the part of the map symbol denoting geologic age is omitted for surficial units because all surficial units shown are believed to be of Quaternary age; and faults are not shown because none in this map area was observed to displace surficial materials. Few exposures of most map units exist, except in manmade excavations, such as gravel pits and road cuts. Consequently, thicknesses usually are estimated, and data on stratification, clast size, and relative proportions of matrix and framework clasts are limited to a few localities for each map unit. The Wentworth scale is used to describe grain sizes. Mapping was done chiefly on aerial photographs taken in 1953. Hence, landslides and modifications resulting from gravel mining since 1953 may not show on this map. The scales of the aerial photographs (about 1:60,000) and the map (1:100,000) governed the minimum size of the deposits mapped. The minimum thickness of the depostis mapped is about 1.5m in most places. Deposit thickness, although not a mapping criterion, influences the topographic expression of many landforms, and landform is the basis for delineating the surficial deposits shown.

Colorado↗
USGS1991

Surficial geologic map of the Steamboat Springs 30' x 60' quadrangle, Grand, Jackson, and Routt counties, Colorado

This map is one of a series of four 30' x 60' surficial geologic maps (1:100,000 scale) intended to provide basic geologic information for planning for energy resource development and growth in northwestern Colorado. An effort is made to characterize all surficial materials, regardless of origin. Hence, residuum is given much more emphasis than is customary, and this results in several departures from conventional geologic maps: bedrock geology is deemphasized; the part of the map symbol denoting geologic age is omitted for surficial units because all surficial units shown are believed to be of Quaternary age; and faults are not shown because none in this map area was observed to displace surficial materials. Few exposures of most map units exist, except in manmade excavations, such as gravel pits and road cuts. Consequently, thicknesses usually are estimated, and data on stratification, clast size, and relative proportions of matrix and framework clasts are limited to a few localities for each map unit. The Wentworth scale is used to describe grain sizes. Mapping was done chiefly on aerial photographs taken in 1953. Hence, landslides and modifications resulting from gravel mining since 1953 may not show on this map. The scales of the aerial photographs (about 1:60,000) and the map (1:100,000) governed the minimum size of the deposits mapped. The minimum thickness of the depostis mapped is about 1.5m in most places. Deposit thickness, although not a mapping criterion, influences the topographic expression of many landforms, and landform is the basis for delineating the surficial deposits shown.

Colorado↗
USGS1972

A preliminary study of peat resources in eastern Maine

Nineteen peat deposits in southeastern Aroostook County (fig. 1) contain an estimated 4,987,000 tons of peat. The location, size and quality data for each deposit are given in tables 1, 2 and 3. Thirty-eight deposits in Washington County (fig. 2) contain an estimated 20,041,000 tons of peat. The location, size and quality data for each deposit are given in tables 4, 5 and 6. Twenty additional deposits containing estimated 3,802,000 tons in Washington County (fig. 2) were not sampled in detail but are described in tables 7 and 8. In addition to the deposits studied, it is estimated that there are at least as many more deposits of similiar size and quality in the area studied. Data in this study were obtained by conducting pace and compass traverses across swamps, marshes and heaths. Auger holes were put down by hand using a Davis sampler and Macaulay peat borer along the traverses to collect samples of the peat and to determine the thickness and stratigraphy of the deposits and the configuration of the depression in which they lie. The amount of peat was estimated from auger hole data and from the surface area measured on topographic and air photo maps. In calculating tonnages, 1 acre-foot of peat in place was considered equivalent to 200 tons of air-dried peat. Samples from all of the deposits were analyzed under the supervision of Irving May in the laboratories of the U.S. Geological Survey for moisture, ash, organic content, water-holding capacity, fiber size (exceeding 0.15mm),and acidity.

Maine↗
USGS1980

Seismic hazard study of the western portion of the Garlock fault [California]

Investigations of the western segment of the Garlock fault were conducted at Castac Lake, Twin Lakes and Oak Creek Canyon. Studies were concentrated on the youngest fault trace as delineated by Clark (1973). Seismic refraction surveys, topographic surveys and geologic mapping provided positive evidence for fault offsets in Quaternary deposits at Twin Lakes and Oak Creek Canyon. Investigations at Castac Lake were concentrated on the fault segment north of the lake. Previous investigations south of the lake and across the dry lake bottom exposed unbroken strata dating back 8050 +300 years B.P. No evidence of offset of young deposits was found north of the lake from surface investigations or seismic refraction data. Trenching of sag pond deposits at Twin Lakes revealed fault traces representing 2 events confined to a zone 3 meters wide. The stratigraphy at Twin Lakes consists of alternating units of clay and sand allowing measurements of vertical offsets. Based on radiocarbon dates of detrital charcoal, the most recent movement occurred less than 890 +195 years B.P. and the proceeding event occurred greater than 2,800 +165 years B.P. Total vertical offset was 80 to 100 cm for the most recent movement and 55-60 cm for the proceeding event. Geomorphic analysis of offset alluvial stream channels at Oak Creek Canyon provided an estimate of 1.6 to 3.3 mm per year of left lateral movement during Holocene and late Pleistocene times. This estimate is based on correlation of soil profile development with dated soil stratigraphy in the San Joaquin Valley. Scarp heights and lack of definitive evidence for recent left-lateral offset in Oak Creek Canyon indicates a significant and perhaps predominant vertical component of movement with: 1) a comparatively long recurrence interval and/or 2) a small component of left-lateral movement. Arching of late Pleistocene deposits in Oak Creek Canyon is consistent with right-lateral rather than left-lateral wrench faulting, suggesting a fluctuation in stresses along this part of the fault since late Pleistocene time.

Open-File Report↗
USGS1988

Aggradation and degradation of alluvial sand deposits, 1965 to 1986, Colorado River, Grand Canyon National Park, Arizona

High discharges occurring between 1983-1985 resulted in redistribution of sand stored in zones of recirculating current in the Colorado River in Grand Canyon National Park. Redistribution resulted in net loss in the number of reattachment deposits in narrow reaches and aggradation of some separation deposits. Separation deposits were more stable than other types of deposits. Alluvial sand deposits that are large enough and of sufficient size for use as campsites were more stable than smaller lower-elevation deposits. Fluctuating flows between October 1985 and January 1986 caused erosion throughout the Grand Canyon, and caused erosion of some deposits created by the high flows of 1983-1985. Data collected for this study included measurements of flow velocity, scour-and-fill of sand deposits, topographic and bathymetric surveys, mapping of surface-flow patterns, water-surface slope surveys, sedimentological analysis, and replication of photographs. A classification system of alluvial sand deposits was developed on the basis of morphometric characteristics and the location of these deposits in relation to parts of recirculation zones. (Author 's abstract)

Open-File Report↗
USGS2008

Estimated Flood Discharges and Map of Flood-Inundated Areas for Omaha Creek, near Homer, Nebraska, 2005

Repeated flooding of Omaha Creek has caused damage in the Village of Homer. Long-term degradation and bridge scouring have changed substantially the channel characteristics of Omaha Creek. Flood-plain managers, planners, homeowners, and others rely on maps to identify areas at risk of being inundated. To identify areas at risk for inundation by a flood having a 1-percent annual probability, maps were created using topographic data and water-surface elevations resulting from hydrologic and hydraulic analyses. The hydrologic analysis for the Omaha Creek study area was performed using historical peak flows obtained from the U.S. Geological Survey streamflow gage (station number 06601000). Flood frequency and magnitude were estimated using the PEAKFQ Log-Pearson Type III analysis software. The U.S. Army Corps of Engineers' Hydrologic Engineering Center River Analysis System, version 3.1.3, software was used to simulate the water-surface elevation for flood events. The calibrated model was used to compute streamflow-gage stages and inundation elevations for the discharges corresponding to floods of selected probabilities. Results of the hydrologic and hydraulic analyses indicated that flood inundation elevations are substantially lower than from a previous study.

Scientific Investigations Report↗
USGS1968

Streamflow generalization in an area of the central United States

Streamflow records of a sample of 41 natural flow stations in an area of the Central Plains were analyzed by electronic computer for the statistics of annual high-flow and low-flow volumes, flow duration, and monthly- and annual-flow discharges. Peak discharges and high- and low-flow volumes for different durations were computed at selected recurrence intervals from statistics of the distributions of the annual values. These dependent variables, discharges and statistics of discharges, were regressed against independent variables of topographic, geomorphic, climatic, and mapped-flow characteristics. The results provide a base for investigating the adequacy of the stream-gaging program and a set of relationships for estimating natural flow characteristics at ungaged sites in the region under study. Comparisons were made of the results of regressions which used only topographic and climatic independent variables with those which also used mapped-flow characteristics as independent variables. The standard error of estimate of the low-flow characteristics was quite large, indicating that for this discharge range, other methods of obtaining this information, may be more accurate or that a quantification of the effect of other factors such as geology on low flow is probably needed to explain part of the present error. Annual and monthly mean flows were defined with standard errors of 18 to 49 percent. Flood peaks and high-flow volumes were defined with standard errors of about 50 percent and 30 percent, respectively, where a significant portion, the residual error, is probably due to sampling error in the dependent variable caused by a short period of record.

Colorado, Kansas, Missouri, Nebraska↗
USGS2011

Geologic map of the Montoso Peak quadrangle, Santa Fe and Sandoval Counties, New Mexico

The Montoso Peak quadrangle is underlain by volcanic rocks and associated sediments of the Cerros del Rio volcanic field in the southern part of the Española Basin that record volcanic, faulting, alluvial, colluvial, and eolian processes over the past three million years. The geology was mapped from 1997 to 1999 and modified in 2004 to 2008. The geologic mapping was carried out in support of the U.S. Geological Survey (USGS) Rio Grande Basin Project, funded by the USGS National Cooperative Geologic mapping Program. The mapped distribution of units is based primarily on interpretation of 1:16,000-scale, color aerial photographs taken in 1992, and 1:40,000-scale, black-and-white, aerial photographs taken in 1996. Most of the contacts on the map were transferred from the aerial photographs using a photogrammetric stereoplotter and subsequently field checked for accuracy and revised based on field determination of allostratigraphic and lithostratigraphic units. Determination of lithostratigraphic units in volcanic deposits was aided by geochemical data, 40 Ar/ 39 Ar geochronology, aeromagnetic and paleomagnetic data. Supplemental revision of mapped contacts was based on interpretation of USGS 1-meter orthoimagery. This version of the Montoso Peak quadrangle geologic map uses a traditional USGS topographic base overlain on a shaded relief base generated from 10-m digital elevation model (DEM) data from the USGS National Elevation Dataset (NED). Faults are identified with varying confidence levels in the map area. Recognizing and mapping faults developed near the surface in young, brittle volcanic rocks is difficult because (1) they tend to form fractured zones tens of meters wide rather than discrete fault planes, (2) the youth of the deposits has allowed only modest displacements to accumulate for most faults, and (3) many may have significant strike-slip components that do not result in large vertical offsets that are readily apparent in offset of sub-horizontal contacts. Those faults characterized as "certain" either have distinct offset of map units or had slip planes that were directly observed in the field. Faults classed as "inferred" were traced based on linear alignments of geologic, topographic and aerial photo features such as vents, lava flow edges, and drainages inferred to preferentially develop on fractured rock. Lineaments defined from magnetic anomalies form an additional constraint on potential fault locations.

New Mexico↗
USGS2014

Plenary: Progress in Regional Landslide Hazard Assessment—Examples from the USA

Landslide hazard assessment at local and regional scales contributes to mitigation of landslides in developing and densely populated areas by providing information for (1) land development and redevelopment plans and regulations, (2) emergency preparedness plans, and (3) economic analysis to (a) set priorities for engineered mitigation projects and (b) define areas of similar levels of hazard for insurance purposes. US Geological Survey (USGS) research on landslide hazard assessment has explored a range of methods that can be used to estimate temporal and spatial landslide potential and probability for various scales and purposes. Cases taken primarily from our work in the U.S. Pacific Northwest illustrate and compare a sampling of methods, approaches, and progress. For example, landform mapping using high-resolution topographic data resulted in identification of about four times more landslides in Seattle, Washington, than previous efforts using aerial photography. Susceptibility classes based on the landforms captured 93 % of all historical landslides (all types) throughout the city. A deterministic model for rainfall infiltration and shallow landslide initiation, TRIGRS, was able to identify locations of 92 % of historical shallow landslides in southwest Seattle. The potentially unstable areas identified by TRIGRS occupied only 26 % of the slope areas steeper than 20°. Addition of an unsaturated infiltration model to TRIGRS expands the applicability of the model to areas of highly permeable soils. Replacement of the single cell, 1D factor of safety with a simple 3D method of columns improves accuracy of factor of safety predictions for both saturated and unsaturated infiltration models. A 3D deterministic model for large, deep landslides, SCOOPS, combined with a three-dimensional model for groundwater flow, successfully predicted instability in steep areas of permeable outwash sand and topographic reentrants. These locations are consistent with locations of large, deep, historically active landslides. For an area in Seattle, a composite of the three maps illustrates how maps produced by different approaches might be combined to assess overall landslide potential. Examples from Oregon, USA, illustrate how landform mapping and deterministic analysis for shallow landslide potential have been adapted into standardized methods for efficiently producing detailed landslide inventory and shallow landslide susceptibility maps that have consistent content and format statewide.

Conference Paper↗