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At least 541 records · Page 30Linked to original sources
USGS2026

Frictional weakening in the highly mobile 2025 Blatten rock and ice avalanche in Switzerland

Cascading slope failures are increasing as glaciers retreat and slopes adjust to a warming climate, yet reconstructing their full dynamics from precursor to deposition remains challenging. Here we show that the 28 May 2025 Blatten rock-ice avalanche, which mobilized about 9.3 million cubic metres, can be reconstructed from seismic, geomorphological, and geotechnical evidence and numerical modeling. The observations reveal the timing, source, volume, and friction of over two weeks of accelerating rockfalls and minor glacier collapses before the main failure, followed by four stages of avalanche motion. Only with drastically reduced friction can both depth-averaged and three-dimensional models reproduce the center-of-mass force history and the deposit distribution. These friction values reflect effective frictional weakening. Geotechnical observations suggest that transient excess pore pressures possibly contributed to this weakening, but are insufficient to rule out additional mechanisms such as ice frictional reduction, segregation, and fragmentation. This work provides a reproducible and robust framework for analyzing catastrophic avalanches under a changing climate.

Birch Glacier↗
USGS2015

What role do hurricanes play in sediment delivery to subsiding river deltas?

The Mississippi River Delta (MRD) has undergone tremendous land loss over the past century due to natural and anthropogenic influences, a fate shared by many river deltas globally. A globally unprecedented effort to restore and sustain the remaining subaerial portions of the delta is now underway, an endeavor that is expected to cost $50–100B over the next 50 yr. Success of this effort requires a thorough understanding of natural and anthropogenic controls on sediment supply and delta geomorphology. In the MRD, hurricanes have been paradoxically identified as both substantial agents of widespread land loss, and vertical marsh sediment accretion. We present the first multi-decadal chronostratigraphic assessment of sediment supply for a major coastal basin of the MRD that assesses both fluvial and hurricane-induced contributions to sediment accumulation in deltaic wetlands. Our findings indicate that over multidecadal timescales, hurricane-induced sediment delivery may be an important contributor for deltaic wetland vertical accretion, but the contribution from hurricanes to long-term sediment accumulation is substantially less than sediment delivery supplied by existing and planned river-sediment diversions at present-day river-sediment loads.

Mississippi↗
USGS2003

Slope basins, headless canyons, and submarine palaeoseismology of the Cascadia accretionary complex

A combination of geomorphological, seismic reflection and geotechnical data constrains this study of sediment erosion and deposition at the toe of the Cascadia accretionary prism. We conducted a series of ALVIN dives in a region south of Astoria Canyon to examine the interrelationship of fluid flow and slope failure in a series of headless submarine canyons. Elevated head gradients at the inflection point of canyons have been inferred to assist in localized failures that feed sediment into a closed slope basin. Measured head gradients are an order of magnitude too low to cause seepage-induced slope failure alone; we therefore propose transient slope failure mechanisms. Intercanyon slopes are uniformly unscarred and smooth, although consolidation tests indicate that up to several metres of material may have been removed. A sheet-like failure would remove sediment uniformly, preserving the observed smooth intercanyon slope. Earthquake-induced liquefaction is a likely trigger for this type of sheet failure as the slope is too steep and short for sediment flow to organize itself into channels. Bathymetric and seismic reflection data suggest sediment in a trench slope basin between the second and third ridges from the prism’s deformation is derived locally. A comparison of the amounts of material removed from the slopes and that in the basin shows that the amount of material removed from the slopes may slightly exceed the amount of material in the basin, implying that a small amount of sediment has escaped the basin, perhaps when the second ridge was too low to form a sufficient dam, or through a gap in the second ridge to the south. Regardless, almost 80% of the material shed off the slopes around the basin is deposited locally, whereas the remaining 20% is redeposited on the incoming section and will be re-accreted.

Oregon↗
USGS2003

Multiple pathways for woody plant establishment on floodplains at local to regional scales

1. The structure and functioning of riverine ecosystems is dependent upon regional setting and the interplay of hydrologic regime and geomorphologic processes. We used a retrospective analysis to study recruitment along broad, alluvial valley segments (parks) and canyon segments of the unregulated Yampa River and the regulated Green River in the upper Colorado River basin, USA. We precisely aged 811 individuals of Populus deltoides ssp. wislizenii (native) and Tamarix ramosissima (exotic) from 182 wooded patches and determined the elevation and character of the germination surface for each. We used logistic regression to relate recruitment events (presence or absence of cohort) to five flow and two weather parameters. 2. Woody plant establishment occurred via multiple pathways at patch, reach and segment scales. Recruitment occurred through establishment on (1) vertically accreting bars in the unregulated alluvial valley, (2) high alluvial floodplain surfaces during rare large flood events, (3) vertically accreting channel margin deposits in canyon pools and eddies, (4) vertically accreting intermittent/abandoned channels, (5) low elevation gravel bars and debris fans in canyons during multi-year droughts, and (6) bars and channels formed prior to flow regulation on the dammed river during controlled flood events. 3. The Yampa River's peak flow was rarely included in models estimating the likelihood that recruitment would occur in any year. Flow variability and the interannual pattern of flows, rather than individual large floods, control most establishment. 4. Regulation of the Green River flow since 1962 has had different effects on woody vegetation recruitment in canyons and valleys. The current regime mimics drought in a canyon setting, accelerating Tamarix invasion whereas in valleys the ongoing geomorphic adjustment of the channel, combined with reduced flow variability, has nearly eliminated Populus establishment . 5. A single year's flow or a particular pattern of flows over a sequence of years, whether natural or man-made, produces different recruitment opportunities in alluvial and canyon reaches, in diverse landforms within a particular river reach, and for Populus and Tamarix . The design of flows to restore riparian ecosystems must consider these multiple pathways and adjust the seasonal timing, magnitude and interannual frequency of flows to match the desired outcome.

Journal of Ecology↗
USGS2012

How well do the rosgen classification and associated "natural channel design" methods integrate and quantify fluvial processes and channel response?

Over the past 10 years the Rosgen classification system and its associated methods of "natural channel design" have become synonymous (to many without prior knowledge of the field) with the term "stream restoration" and the science of fluvial geomorphology. Since the mid 1990s, this classification approach has become widely, and perhaps dominantly adopted by governmental agencies, particularly those funding restoration projects. For example, in a request for proposals for the restoration of Trout Creek in Montana, the Natural Resources Conservation Service required "experience in the use and application of a stream classification system and its implementation." Similarly, classification systems have been used in evaluation guides for riparian areas and U.S. Forest Service management plans. Most notably, many highly trained geomorphologists and hydraulic engineers are often held suspect, or even thought incorrect, if their approach does not include reference to or application of a classification system. This, combined with the para-professional training provided by some involved in "natural channel design" empower individuals and groups with limited backgrounds in stream and watershed sciences to engineer wholesale re-patterning of stream reaches using 50-year old technology that was never intended for engineering design. At Level I, the Rosgen classification system consists of eight or nine major stream types, based on hydraulic-geometry relations and four other measures of channel shape to distinguish the dimensions of alluvial stream channels as a function of the bankfull stage. Six classes of the particle size of the boundary sediments are used to further sub-divide each of the major stream types, resulting in 48 or 54 stream types. Aside from the difficulty in identifying bankfull stage, particularly in incising channels, and the issue of sampling from two distinct populations (beds and banks) to classify the boundary sediments, the classification provides a consistent and reproducible means for practitioners to describe channel morphology although difficulties have been encountered in lower-gradient stream systems. Use of the scheme to communicate between users or as a conceptual model, however, has not justified its use for engineering design or for predicting river behavior; its use for designing mitigation projects, therefore, seems beyond its technical scope. Copyright ASCE 2005.

Conference Paper↗
USGS2012

Regional beach/cliff system dynamics along the california coast

The coast of California is comprised of both sandy shorelines and cliffed coastline, and in many areas these features spatially coincide. In order to better understand the regional trends of change along the California coast, the U.S. Geological Survey is quantifying both sandy shoreline change and coastal cliff retreat for the state. The resulting database was used to examine the dynamics of the beach/cliff system. We found inconsistent evidence of a relationship between rates of cliff retreat and shoreline change on the spatial scale of 100-km cells. However, when the data are correlated within individual regions, a strong relationship exists between the geomorphology of the coast and the behavior of the beach/cliff system. Areas of high-relief coast show negative correlations, indicating that higher rates of cliff retreat correlate with lower rates of shoreline erosion. In contrast, low- to moderate-relief coasts show strong positive correlations.

Conference Paper↗
USGS2012

Barrier island vulnerability to breaching: a case study on Dauphin Island, Alabama

Breaching of barrier islands can adversely impact society by severing infrastructure, destroying private properties, and altering water quality in back bays and estuaries. This study provides a scheme that assesses the relative vulnerability of a barrier island to breach during storms. Dauphin Island, Alabama was selected for this study because it has a well documented history of island breaches and extensive geological and geomorphic data. To assess the vulnerability of the island, we defined several variables contributing to the risk of breaching: island geology, breaching history, and island topography and geomorphology. These variables were combined to form a breaching index (BI) value for cross island computational bins, each bin every 50 m in the alongshore direction. Results suggest the eastern section of Dauphin Island has the lowest risk of breaching with the remaining portion of the island having a moderate to high risk of breaching. Two reaches in the western section of the island were found to be particularly vulnerable due primarily to their minimal cross-sectional dimensions.

Alabama↗
USGS2018

Enhancement and integration of airborne gamma-ray spectrometric and Landsat imagery for regolith mapping — Cape York Peninsula

Airborne gamma-ray spectrometric data (400-m line spacing), gathered for the National Geoscience Mapping Accord North Queensland Project, has proved invaluable for differentiating regolith types based on their potassium, thorium and uranium signatures. The ability of the gamma-ray signal to penetrate the vegetation cover and as much as 40 cm below the surface was a considerable advantage in North Queensland, where traditional mapping techniques are hindered by the thick vegetation cover and where deeply weathered sandy soils frequently mask underlying geology. Two image-processing techniques were used to enhance the gamma-ray data and integrate them with Landsat Thematic Mapper (TM) data. Firstly, a sun-angle illuminated high-pass filtered component (hillshade) of the gamma-ray image was added to a three-band false-colour composite image of the corrected gamma-ray data. The hillshade component highlighted local changes in the gamma-ray signal which related to changes in regolith materials and lithology, and sharpened boundaries associated with geomorphic features. Secondly, the gamma-ray image was integrated (pixel by pixel) with the high-frequency component of the corresponding TM band 5 scene. This allowed the imagery to be interpreted in a geomorphological and structural context. Broad lithological divisions and structural domains were identified in the imagery, but most of the variation within these groups relates to the regolith cover and to geomorphic features in the landscape. Subtle variations in lithology were effectively interpreted only when the responses of the regolith cover are known. The gamma-ray imagery provided an insight into the weathering and geomorphic history of the region. In addition, the imagery can also be interpreted as a ‘geomorphic activity map’, separating stable landforms with deep weathering from younger landforms with active erosion and stripping of the surficial cover. This allows past and present geomorphic processes to be interpreted from the imagery, which in turn provides more informed extrapolation of field results and prediction of regolith types. The imagery was highly useful for basement and regolith mapping. There is considerable potential for assisting with interpretation of both stream-sediment geochemical data and environmental studies, since the resulting imagery effectively maps the distribution of sediments in the landscape, and identifies areas of erosion and land degradation.

Queensland↗
USGS2017

Spatially dependent responses of a large-river fish assemblage to bank stabilization and side channels

The alteration of rivers by anthropogenic bank stabilization to prevent the erosion of economically valuable lands and structures has become commonplace. However, such alteration has ambiguous consequences for fish assemblages, especially in large rivers. Because most large, temperate rivers have impoundments, it can be difficult to separate the influences of bank stabilization structures from those of main-stem impoundments, especially because both stabilization structures and impoundments can cause side-channel loss. Few large rivers are free flowing and retain extensive side channels, but the Yellowstone River (our study area) is one such river. We hypothesized that in this river (1) bank stabilization has changed fish assemblage structure by altering habitats, (2) side-channel availability has influenced fish assemblage structure by providing habitat heterogeneity, and (3) the influences of bank stabilization and side channels on fish assemblages were spatially scale dependent. We developed a spatially explicit framework to test these hypotheses. Fish assemblage structure varied with the extent of bank stabilization and the availability of side channels; however, not all assemblage subsets were influenced. Nevertheless, bank stabilization and side channels had different and sometimes opposite influences on the fish assemblage. The effects of side channels on fish were more consistent and widespread than those of bank stabilization; the catches of more fishes were positively correlated with side-channel availability than with the extent of bank stabilization. The influences of bank stabilization and side channels on the relative abundances of fish also varied, depending on species and river bend geomorphology. The variation in river morphology probably contributed to the assemblage differences between stabilized and reference river bends; stabilized alluvial pools were deeper than reference alluvial pools, but the depths of stabilized and reference bluff pools did not differ. The strengths of the relationships among fish assemblages, bank stabilization, and side channels were spatially scale dependent; optimum spatial scales ranged from less than 200 m to 3,200 m up- and downstream, suggesting that bank stabilization and side channels influenced fish assemblages across multiple spatial scales.

Montana↗
USGS2011

Groupers on the edge: Shelf edge spawning habitat in and around marine reserves of the northeastern Gulf of Mexico

The northeastern Gulf of Mexico contains some of the most diverse and productive marine habitat in the United States. Much of this habitat, located on the shelf edge in depths of 50 to 120 m, supports spawning for many economically important species, including groupers. Here, we couple acoustic surveys with georeferenced videography to describe the primary spatial and geologic features of spawning aggregation sites for four economically important species: gag ( Mycteroperca microlepis ), scamp ( M. phenax ), red grouper ( Epinephelus morio ), and red snapper ( Lutjanus campechanus ), with notes on fish distribution and abundance and spawning activities. We provide information on movement patterns of reef fish determined using acoustic telemetry. Finally, we discuss the possible coupling of geomorphology with hydrographic features to influence the overall productivity of the region and the importance of spatial fishery management in sustaining that productivity.

Northeastern Gulf of Mexico↗
USGS1966

A definition of dominant discharge

The concept of dominant (stream) discharge in geomorphology has not been firmly defined. By defining it, on rational grounds, as that discharge at which, over a long period of time, most sediment has been transported, a definite value can be computed for a stream for which there are available duration-curve values of daily discharge and a sediment-rating curve. This has been done for 5 eastern and 4 western rivers. The dominant discharge , when expressed in terms of percentage duration, is remarkably consistent, and is found to be a lower discharge than has generally been considered as dominant .

International Association of Scientific Hydrology ↗
USGS2010

The effects of road crossings on prairie stream habitat and function

Improperly designed stream crossing structures may alter the form and function of stream ecosystems and habitat and prohibit the movement of aquatic organisms. Stream sections adjoining five concrete box culverts, five low-water crossings (concrete slabs vented by one or multiple culverts), and two large, single corrugated culvert vehicle crossings in eastern Kansas streams were compared to reference reaches using a geomorphologic survey and stream classification. Stream reaches were also compared upstream and downstream of crossings, and crossing measurements were used to determine which crossing design best mimicked the natural dimensions of the adjoining stream. Four of five low-water crossings, three of five box culverts, and one of two large, single corrugated pipe culverts changed classification from upstream to downstream of the crossings. Mean riffle spacing upstream at low-water crossings (8.6 bankfull widths) was double that of downstream reaches (mean 4.4 bankfull widths) but was similar upstream and downstream of box and corrugated pipe culverts. There also appeared to be greater deposition of fine sediments directly upstream of these designs. Box and corrugated culverts were more similar to natural streams than low-water crossings at transporting water, sediments, and debris during bankfull flows.

Journal of Freshwater Ecology↗
USGS2016

Fishes in paleochannels of the Lower Mississippi River alluvial valley: A national treasure

Fluvial geomorphology of the alluvial valley of the Lower Mississippi River reveals a fascinating history. A prominent occupant of the valley was the Ohio River, estimated to have flowed 25,000 years ago over western Tennessee and Mississippi to join the Mississippi River north of Baton Rouge, Louisiana, 750–800 km south of the present confluence. Over time, shifts in the Mississippi and Ohio rivers toward their contemporary positions have left a legacy of abandoned paleochannels supportive of unique fish assemblages. Relative to channels abandoned in the last 500 years, paleochannels exhibit harsher environmental conditions characteristic of hypereutrophic lakes and support tolerant fish assemblages. Considering their ecological, geological, and historical importance, coupled with their primordial scenery, the hundreds of paleochannels in the valley represent a national treasure. Altogether, these waterscapes are endangered by human activities and would benefit from the conservation attention afforded to our national parks and wildlife refuges.

Lower Mississippi River valley↗
USGS2024

An evaluation of cyanobacterial occurrence and bloom development in Adirondack lakes

Cyanobacterial harmful algal blooms (cyanoHABs) have occurred in many low nutrient (oligotrophic) lakes in the northeastern United States. The Adirondack Park in New York is a large, mountainous region with many low nutrient lakes. There is a gap in understanding regarding whether cyanoHAB reporting data are truly reflective of the susceptibility of lakes to develop bloom conditions. We evaluated lakes with and without documented cyanoHABs for cyanotoxin synthetase gene quantification, phytoplankton community composition, and akinete abundance to identify conditions associated with the observation of cyanoHABs. We analyzed: (1) contributions of cyanobacteria to the overall phytoplankton community; (2) differences in cyanobacterial communities and the presence of cyanotoxin synthetase genes; and (3) lake physical and geomorphological attributes as drivers of differences in cyanobacteria occurrence. Two sample types (water and sediment) were collected from two sample locations (nearshore and open water) in five lakes in 2021. We found cyanobacteria in all lakes and sample locations. Phytoplankton biovolume and cyanotoxin synthetase genes differed among lakes and by cyanoHAB history. Samples from lakes with documented blooms were associated with marginally higher total phosphorus. Non-metric multidimensional scaling was used to identify which environmental factors influenced community structure. Our study demonstrates the importance of multifaceted approaches to detect cyanobacteria that may only be apparent during ephemeral bloom events and the similarities among lakes with and without a history of bloom reports. This work contributes to a better understanding of cyanoHAB occurrence in Adirondack lakes, and conditions that may cause low nutrient lakes to be susceptible to cyanoHABs.

New York↗
USGS2009

Seamount characteristics and mine-site model applied to exploration- and mining-lease-block selection for cobalt-rich ferromanganese crusts

Regulations are being developed through the International Seabed Authority (ISBA) for the exploration and mining of cobalt-rich ferromanganese crusts. This paper lays out geologic and geomorphologic criteria that can be used to determine the size and number of exploration and mine-site blocks that will be the focus of much discussion within the ISBA Council deliberations. The surface areas of 155 volcanic edifices in the central equatorial Pacific were measured and used to develop a mine-site model. The mine-site model considers areas above 2,500 m water depth as permissive, and narrows the general area available for exploration and mining to 20% of that permissive area. It is calculated that about eighteen 100 km 2 explora-tion blocks, each composed of five 20km 2 contiguous sub-blocks, would be adequate to identify a 260 km 2 20-year-mine site; the mine site would be composed of thirteen of the 20km 2 sub-blocks. In this hypothetical example, the 260 km 2 mine site would be spread over four volcanic edifices and comprise 3.7% of the permissive area of the four edifices and 0.01% of the total area of those four edifices. The eighteen 100km 2 exploration blocks would be selected from a limited geographic area. That confinement area is defined as having a long dimension of not more than 1,000 km and an area of not more than 300,000 km 2 .

Marine Georesources and Geotechnology↗
USGS1991

Structure and morphology of submarine slab slides: clues to origin and behavior

Geologic features suggest that some slab slides probably result from long-term strength degradation of weak layers deep in the homoclinal section. Time-dependent strain in clay-rich layers can create potential slide surfaces of low frictional strength. Competent layers are weak in tension and probably fragment in the first instance of, or even prior to, translation, and the allochthonous mass is readily transformed into a high-momentum debris flow. The structure and geomorphology of slab slides provide important clues to their origin and behavior. -from Author

Marine Geotechnology↗
USGS2018

A spatio-contextual probabilistic model for extracting linear features in hilly terrain from high-resolution DEM data

This paper introduces our research in developing a probabilistic model to extract linear terrain features from high resolution DEM (Digital Elevation Model) data. The proposed model takes full advantage of spatio-contextual information to characterize terrain changes. It first derives a quantifiable measure of spatio-contextual patterns of linear terrain feature, such as ridgelines, valley lines and crater boundaries, and then adopts multiple neighborhood analysis and a probability model to address data uncertainty in terrain surface modeling. Different from traditional approaches, the proposed model has the ability to achieve near-automated processing, and to support effective extraction of terrain features in both smooth and rough surfaces. Through a series of experiments, we demonstrate that the proposed approach outperforms existing techniques, including: thresholding, stream/drainage network analysis, visual descriptor, object-based image analysis and edge detection. We hope this work contributes to both the geospatial data science and geomorphology communities with a new way of utilizing high-resolution imagery in terrain analysis.

International Journal of Geographical Information ↗
USGS2026

Statewide surficial geologic map of Nebraska underscores Quaternary landscape evolution from the High Plains to the Central Lowland

Surficial geologic mapping in Nebraska has been conducted primarily at the 1:24,000 scale since the mid-1990s, although there have also been limited efforts to map generalized Quaternary and surficial geology within the state and the region. We compiled and evaluated disparate maps (1:24,000–1:1,000,000) and datasets—including geologic, soil and soil parent material, and geomorphic maps as well as LiDAR derivatives—to produce a single 1:500,000 scale surficial geologic map of Nebraska that is the first of its kind. This new map provides a coarse-scale surficial geologic map that will be incorporated into a nationwide U.S. Geological Survey Quaternary geologic map. It also reflects the variation and uniqueness of physical landscapes in the state, where the Great Plains and Central Lowland physiographic provinces meet, further developing a richer interdisciplinary understanding of regional geomorphology in the heart of North America.

Nebraska↗