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Among natural hazards occurring offshore, submarine landslides pose a significant risk to offshore infrastructure installations attached to the seafloor. With the offshore being important for current and future energy production, there is a need to anticipate where future landslide events are likely to occur to support planning and development projects. Using the northern Gulf of Mexico (GoM) as a case study, this paper performs Landslide Susceptibility Mapping (LSM) using a gradient-boosted decision tree (GBDT) model to characterize the spatial patterns of submarine landslide probability over the United States Exclusive Economic Zone (EEZ) where water depths are greater than 120 m. With known spatial extents of historic submarine landslides and a Geographic Information System (GIS) database of known topographical, geomorphological, geological, and geochemical factors, the resulting model was capable of accurately forecasting potential locations of sediment instability. Results of a permutation modelling approach indicated that LSM accuracy is sensitive to the number of unique training locations with model accuracy becoming more stable as the number of training regions was increased. The influence that each input feature had on predicting landslide susceptibility was evaluated using the SHapely Additive exPlanations (SHAP) feature attribution method. Areas of high and very high susceptibility were associated with steep terrain including salt basins and escarpments. This case study serves as an initial assessment of the machine learning (ML) capabilities for producing accurate submarine landslide susceptibility maps given the current state of available natural hazard-related datasets and conveys both successes and limitations. [ABSTRACT FROM AUTHOR]

Landslide hazard assessment is crucial for landslide monitoring and early warning. A novel method based on deep learning model for national-scale landslide hazard assessment was proposed in this study, which contains three stages: (1) landslide susceptibility analysis using three hybrid neural networks of convolutional neural network-simple recurrent unit (CNN-SRU), convolutional neural network-long short-term memory (CNN-LSTM), and convolutional neural network-gated recurrent unit (CNN-GRU); (2) landslide temporal probability prediction using the proposed spatiotemporal transformer (ST-transformer) to address the time uncertainty of rainfall threshold calculation in landslide temporal probability prediction and the matter without considering the geographical regional differences of landslide spatiotemporal probability weights; and (3) quantitative landslide hazard calculation with the preceding results using the improved landslide hazard formula. The validation of this method was conducted in conterminous United States, where the results of steps (1) and (2) demonstrated excellent performance compared with existing works. Consequently, the calculation derived from the previous two steps was effectively used for landslide hazard assessment using the improved landslide hazard formula, and its reliability was confirmed through the validation of actual landslide events. The proposed method is of practical significance for national-scale landslide hazard assessment. [ABSTRACT FROM AUTHOR]

Landslide susceptibility maps indicate the spatial distribution of landslide likelihood. Modeling susceptibility over large or diverse terrains remains a challenge due to the sparsity of landslide data (mapped extent of known landslides) and the variability in triggering conditions. Several different data sampling strategies of landslide locations used to train a susceptibility model are used to mitigate this challenge. However, to our knowledge, no study has systematically evaluated how different sampling strategies alter a model's predictor effects (i.e., how a predictor value influences the susceptibility output) critical to explaining differences in model outputs. Here, we introduce a statistical framework that examines the variation in predictor effects and the model accuracy (measured using receiver operator characteristics) to highlight why certain sampling strategies are more effective than others. Specifically, we apply our framework to an array of logistic regression models trained on landslide inventories collected at sub‐regional scales over four terrains across the United States. Results show significant variations in predictor effects depending on the inventory used to train the models. The inconsistent predictor effects cause low accuracies when testing models on inventories outside the domain of the training data. Grouping test and training sets according to physiographic and ecological characteristics, which are thought to share similar triggering mechanisms, does not improve model accuracy. We also show that using limited landslide data distributed uniformly over the entire modeling domain is better than using dense but spatially isolated data to train a model for applications over large regions. Plain Language Summary: Landslide susceptibility maps show which areas in a region are more prone to landsliding than others. These maps are created from attributes of mapped landslides. The variation in landslide attributes and amount of landslide data required makes it difficult to map landslide susceptibility accurately over large regions. It is unclear whether any previously proposed methods to overcome these difficulties produce accurate susceptibility maps. Here, we develop a framework that evaluates the effectiveness of the following methods: using landslide data sets from only a few locations where data are readily available, applying models only to regions presumed to have landslide attributes similar to the regions used to develop the models, or gathering a few uniformly distributed (i.e., spread approximately equally) landslide data points. We show that the wide variation in landslide attributes over large regions reduces the accuracy of landslide susceptibility models that are developed using data from only a few locations. Restricting model application to regions with presumed similar attributes does not improve model performance. However, using a limited landslide data set that covers the entire region produces accurate susceptibility maps. Key Points: We use a statistical framework to investigate the influence of data sampling strategies on landslide susceptibility model performanceThe framework shows that the predictor data effects on output probability vary drastically with the sampling strategy usedThe best sampling strategy we evaluate uses landslide data sampled uniformly from the entire modeling domain [ABSTRACT FROM AUTHOR]

Soil moisture (SM) spatiotemporal variability critically influences water resources, agriculture, and climate. However, besides site‐specific studies, little is known about how SM varies locally (1–100‐m scale). Consequently, quantifying the SM variability and its impact on the Earth system remains a long‐standing challenge in hydrology. We reveal the striking variability of local‐scale SM across the United States using SMAP‐HydroBlocks — a novel satellite‐based surface SM data set at 30‐m resolution. Results show how the complex interplay of SM with landscape characteristics and hydroclimate is primarily driven by local variations in soil properties. This local‐scale complexity yields a remarkable and unique multi‐scale behavior at each location. However, very little of this complexity persists across spatial scales. Experiments reveal that on average 48% and up to 80% of the SM spatial information is lost at the 1‐km resolution, with complete loss expected at the scale of current state‐of‐the‐art SM monitoring and modeling systems (1–25 km resolution). Plain Language Summary: Soil moisture (SM) widely varies in space and time. This variability critically influences freshwater availability, agriculture, ecosystem dynamics, climate and land‐atmosphere interactions, and it can also trigger hazards such as droughts, floods, landslides, and aggravate wildfires. Limited SM observational data constrained our understanding of this variability and its impact on the Earth system. Here, we present the first continental assessment of how SM varies at the local scales using SMAP‐HydroBlocks – the first 30‐m surface SM data set over the United States. This study maps the SM spatial variability, characterizes the landscape drivers, and quantifies how this variability persists across larger spatial scales. Results revealed striking SM spatial variability across the United States, mainly driven by local spatial variations in soil properties and less so by vegetation and topography. However, this SM variability does not persist at coarser spatial scales resulting in extensive information loss. This information loss implicates inaccuracies when predicting non‐linear SM‐dependent hydrological, ecological, and biogeochemical processes using coarse‐scale models and satellite estimates. By mapping the SM spatial variability locally and its scaling behavior, we provide a pathway toward understanding SM‐dependent hydrological, biogeochemical, and ecological processes at local (and so far unresolved) spatial scales. Key Points: 30‐m soil moisture (SM) data shows striking and complex spatial variability driven mainly by climate and local variations in soil propertiesThis variability yields a remarkable and unique multi‐scale behavior at each location that cannot be generalized across the diverse USUp to 80% of SM information is lost at the 1‐km scale, with complete loss at the scale of state‐of‐the‐art SM observation/monitoring systems [ABSTRACT FROM AUTHOR]

Structural hydrologic connections, formed by the coaction of tectonic and climatic processes, facilitate the transfer of matter across Earth's surface. Large‐scale analysis of hillslope connectivity controls is lacking, thus limiting our understanding of the drivers of extremes, like floods and landslides, and benefits, like wetlands. Here, we model hillslope connectivity using the Index of Connectivity, at 10‐m resolution for the contiguous United States. We show the dominance of tectonic drivers, like river steepness (ρ = 0.84) and seismic activity (ρ = 0.48), over climatic drivers, like precipitation (ρ = −0.31) and aridity (ρ = −0.07), in controlling the strength of connectivity. Highly connected basins were associated with landslide occurrence (ρ = 0.69) while poorly connected basins had greater wetland density (ρ = −0.50). Lastly, we share our results in an open access data portal for land managers to leverage structural connectivity maps in their respective study domains. Plain Language Summary: Hillslopes are critical landscape features that intercept, store, and route water, from its source as rainfall to its fate as river discharge. The strength of this routing is a function of climatic and tectonic forces, but their relative importance to hillslope connectivity is uncertain. We simulated the Index of Connectivity, a topographic analogue for structural connectivity, for 75 billion locations in contiguous United States (CONUS), across a range of climatic and tectonic settings. At the CONUS‐scale, we found that hillslope connectivity is largely driven by tectonic forces, including uplift and seismic activity, and that highly connected hillslopes are more susceptible to landslides while poorly connected hillslopes promote wetland development. We provide a web data portal to serve as a tool for stakeholders to visualize and leverage structural connectivity data in their respective study areas. Key Points: Hillslope connectivity shows high spatial variability across the United StatesTectonics is a primary control of the strength of structural hillslope connectivityOpen access data portal of connectivity maps created for stakeholders [ABSTRACT FROM AUTHOR]

Although most landslides are precipitation‐triggered, a number of other complex conditions simultaneously predispose any given slope to failure, with the impact of urbanization posing particular scientific challenges. We use panel regression with fixed effects—which controls for observed and unobserved time‐variant and time‐invariant influences—to quantify the effect of precipitation accumulation on landslide concentration across the Pacific Coast region of the United States. We find that landslide hazard is most sensitive to precipitation variations in urbanized areas. This finding is robust across 1‐day, 10‐day, and 30‐day periods of precipitation accumulation, among individual Pacific Coast states, and when the analysis is confined to the San Francisco Bay Area (a subregion with both urban and rural areas). Our results corroborate existing hypotheses that urbanization increases landslide hazard, while demonstrating the importance of considering interactions with urbanization when predicting landslide hazard in the current climate, and under climate change scenarios. Plain Language Summary: Generalizable understanding of where and how landslides occur may inform efforts to adapt to these devastating natural disasters. While most landslides are triggered by precipitation, a number of other complex factors also play a role in slope destabilization. Employing an empirical framework that accounts for these confounding factors, we find that landslide hazard is most sensitive to precipitation variations in urbanized areas. Our results enhance understanding of the impact of urbanization on precipitation‐triggered landslide hazard and highlight the importance of considering urbanization when predicting landslide hazard, particularly in response to global warming and climate change. Key Points: We quantify the effect of precipitation on landslide concentration within distinct land use types across the US Pacific CoastLandslide hazard is most sensitive to precipitation variations in urbanized areasResults highlight the importance of considering interactions with urbanization when predicting landslide response to climate [ABSTRACT FROM AUTHOR]

Detailed information about landslide occurrence is the foundation for advancing process understanding, susceptibility mapping, and risk reduction. Despite the recent revolution in digital elevation data and remote sensing technologies, landslide mapping remains resource intensive. Consequently, a modern, comprehensive map of landslide occurrence across the United States (USA) has not been compiled. As a first step toward this goal, we present a national-scale compilation of existing, publicly available landslide inventories. This geodatabase can be downloaded in its entirety or viewed through an online, searchable map, with parsimonious attributes and direct links to the contributing sources with additional details. The mapped spatial pattern and concentration of landslides are consistent with prior characterization of susceptibility within the conterminous USA, with some notable exceptions on the West Coast. Although the database is evolving and known to be incomplete in many regions, it confirms that landslides do occur across the country, thus highlighting the importance of our national-scale assessment. The map illustrates regions where high-quality mapping has occurred and, in contrast, where additional resources could improve confidence in landslide characterization. For example, borders between states and other jurisdictions are quite apparent, indicating the variation in approaches to data collection by different agencies and disparity between the resources dedicated to landslide characterization. Further investigations are needed to better assess susceptibility and to determine whether regions with high relief and steep topography, but without mapped landslides, require further landslide inventory mapping. Overall, this map provides a new resource for accessing information about known landslides across the USA. [ABSTRACT FROM AUTHOR]

Much has been written about the polarization of the American electorate and its reflection in its legislatures, but less about its spatial polarization, which Bishop has argued has taken place in parallel with the ideological and behavioral polarization. The extent of that polarization can be assessed, he argues, by identifying the number of landslide counties, those won at presidential elections by margins of 20 percentage points or more. This paper uses a multilevel modeling strategy to explore changes in the number and extent of those landslide counties over the period 1992–2016, relative to both the location of the counties and their population composition. It shows that a county's population composition was a major determinant of whether it returned a landslide for either party's candidate at any election—with a clear change in direction over the period for counties according to their level of affluence—but this was by no means the sole determinant. Holding constant those variations there were additional geographies that were more place‐ than people‐specific. [ABSTRACT FROM AUTHOR]

The article highlights U.S. weather report of 2018 along with historic hurricane and wildfire season. Topics discussed include views on decrease of six to nine inches of rain in January 9, 2018 on the hills of Montecito, north of Los Angeles, offered landslides; information on Hurricane Michael in October 10–12, 2018 near Panama City, Florida; and Major Nor'easter or "Bomb Cyclone" on January 3–5, 2018.

We developed a new approach for mapping landslide hazard by combining probabilities of landslide impact derived from a data-driven statistical approach and process-based model of shallow landsliding. Our statistical approach integrates the influence of seven site attributes on observed landslides using a frequency ratio method. Influential attributes and resulting susceptibility maps depend on the observations of landslides considered: all types of landslides, debris avalanches only, or source areas of debris avalanches. These observational datasets reflect the capture of different landslide processes or components, which relate to different landslide-inducing factors. Slopes greater than 35° are more frequently associated with landslide initiation, while higher landslide hazards at gentler slopes (< 30°) reflect depositional processes from observations of all landslide types or debris avalanches. Source areas are associated with mid to high elevations (1,400 to 1,800 m), where they are linked to ecosystem transition (e.g., forest to barren), while all landslides types and debris avalanches show increasing frequency in lower elevations (< 1,200 m). Slope is a key attribute in the initiation of landslides, while lithology is mainly linked to transport and depositional processes. East (west) aspect is a positive (negative) landslide-influencing factor, likely due to differences in forest cover and associated root cohesion, and evapotranspiration. The empirical model probability derived from debris avalanche source area is combined probabilistically with a previously developed processed-based probabilistic model to produce an integrated probability of landslide hazard for initiation that includes mechanisms not captured by the infinite slope stability model. We apply our approach in North Cascades National Park Complex in Washington, USA, to provide multiple landslide hazard maps that land managers can use for planning and decision making, as well as educating the public about hazards from landslides in this remote high-relief terrain. [ABSTRACT FROM AUTHOR]

This paper analysed the evolution of landslide research and research foci in different countries. The data comprise 3105 landslide SCI articles published between January 1977 and June 2015 from the Web of Science. The data are extracted under interaction constraints of the journal title, category, and keywords. The complex network method is used for the analysis. First, from the perspective of topics and methods, the evolution is systematically assessed by generating a co-citation network of the articles and a semantic cluster analysis. Second, from the perspective of topics and landslide-related disasters, the focus in different countries is discussed by generating co-occurrence networks. These networks are the co-occurrence of the countries and keywords, and the co-occurrence of countries and landslide-related disaster phrases. The main conclusions are as follows: (1) landslide susceptibility analysis and methods of machine learning are popular research topics and methods, respectively. The topics change through time, and the article output is influenced by increasing landslide-related disasters, increasing economic losses and casualties, a desire for a more complete and accurate landslide inventory, and the use of effective methods, such as geographical information Science (GIS) and machine learning. (2) The research focus in each country is related with the country-specific disasters or economic costs caused by landslides to some degree. In addition to Italy and the USA, China is the country most commonly affected by landslides, and it should develop its own landslide database and complete in-depth studies of disaster mitigation. [ABSTRACT FROM AUTHOR]

Awareness about the threats posed by different types of coastal disasters has increased throughout the world, as people are exposed to the nature of these hazards through media reports on events in distant countries. This has resulted in coastal residents being aware about the destructive power of tsunamis, despite no such events having taken place in their country in recent times. Regardless of this increased awareness, it has been hypothesized that there is still need for local governments to enact adequate policies to raise the awareness of local residents, for example, by holding regular evacuation drills. The present research presents a comparative assessment of tsunami awareness in two tourist destinations in Japan and the USA, which was derived through structured questionnaire surveys of beach users in the city of Kamakura and various coastal cities in Florida. The results show how despite relatively high level of awareness tsunamis still pose a considerable risk to each of the communities, for example, due to shortcoming in evacuation knowledge and infrastructure. [ABSTRACT FROM AUTHOR]

The article discusses the aggregate occurrences of extreme daily rainfall events in the U.S. in 2015. Among the rainfall events that were discussed include drought, rains, and flash floods in Texas which ends in May, near land-falling Hurricane Joaquin in early October along with the catastrophic flood in South Carolina, and unseasonable rains that inundated the Mississippi basin in December.

Tree mortality is an important demographic process and primary driver of forest dynamics, yet there are relatively few plot-based studies that explicitly quantify mortality and compare the relative contribution of endogenous and exogenous disturbances at regional scales. We used repeated observations on 289,390 trees in 3673 1 ha plots on U.S. Forest Service lands in Oregon and Washington to compare distributions of mortality rates among natural disturbances and vegetation zones from the mid-1990s to mid-2000s, a period characterized by drought, insect outbreaks, and large wildfires. Endogenous disturbances (e.g. pathogens, insects) were pervasive but operated at relatively low levels of mortality (<2.5%/yr) that rarely exceeded 5%/yr. Exogenous disturbances (e.g. fire, wind, landslides, avalanches) were less common and operated mostly at intermediate levels of mortality (5–25%/yr) indicative of partial-stand-replacement events. Stand-replacing mortality rates (⩾25%/yr) comprised a third of all exogenous disturbance events, occurring almost exclusively in fires. Fires were rare in wet vegetation zones and most rates were <2.5%/yr and associated with endogenous processes. Mortality rates in dry vegetation zones revealed a different set of dynamics including a more variable role of background mortality and greater proportions of mortality associated with fire and insects at partial- and stand-replacing levels. Mortality rates in early and middle stages of stand development were low compared to published rates, but rates >1%/yr in over half of the plots in late and old-growth stages corroborate previous findings of elevated mortality during the same period and indicate the potential for pervasive structural change across all vegetation zones. Partial- and stand-replacing fire were associated with most mortality, but affected a relatively small proportion of dry vegetation zones (3.1–7.1% and 2.1–5.1%, respectively). These disturbances have likely affected regional biodiversity through the creation of early seral habitat, increased within-stand heterogeneity, and restored some aspects of historical fire regimes, but there is a need to better understand corresponding structural and compositional changes. We demonstrate the variability in the drivers, magnitude, and extent of mortality across a biophysically diverse region and highlight the need to incorporate and characterize the effects of mortality at intermediate levels to develop a more comprehensive understanding of regional forest dynamics. [ABSTRACT FROM AUTHOR]

Scientific literature is replete with papers describing advances in applying new technologies to the study of landslides and advances in our understanding of factors affecting landslide occurrence, distribution, and movement. Far fewer papers look at how this knowledge is implemented to achieve landslide risk reduction. State and local governments exercise the greatest control on how landslide risk reduction is accomplished. Data generated from a questionnaire to state geological surveys, review of their agency Web sites, and two case studies demonstrate that progress has been made during the last 20 years in implementing actionable policy changes and programs to achieve a reduction is landslide risk in the United States. Progress is evident from the pivotal role played by state and local government in the areas of: (1) developing guidelines and training, (2) increasing public awareness and education, (3) implementing loss reduction measures, and (4) conducting emergency preparedness, response, and recovery. The number of states requiring registration for practicing geologists has nearly doubled during the last 20 years. This increase was accompanied by a shift from individual state tests as part of determining competency to a uniform national test. During this period, state geological surveys established Web sites as a primary means for promoting public awareness and education about landslide hazards. Measures reducing the impact of landslides have included providing information specific to residents and landowners, as well as supporting land-use planning efforts by local governments. Many state geological surveys are involved with emergency management of landslide hazards. [ABSTRACT FROM AUTHOR]

The eastern United States is vulnerable to flooding from tropical cyclone rainfall. Understanding how both the frequency and intensity of this rainfall will change in the future climate is a major challenge. One promising approach is the dynamical downscaling of relatively coarse general circulation model results using higher-resolution regional climate models (RCMs). In this paper, we examine the frequency of landfalling tropical cyclones and associated rainfall properties over the eastern United States using Zetac, an 18-km resolution RCM designed for modeling Atlantic tropical cyclone activity. Simulations of 1980-2006 tropical cyclone frequency and rainfall intensity for the months of August-October are compared against results from previous studies and observation-based datasets. The 1980-2006 control simulations are then compared against results from three future climate scenarios: CMIP3/A1B (late twenty-first century) and CMIP5/RCP4.5 (early and late twenty-first century). In CMIP5 early and late twenty-first century projections, the frequency of occurrence of post-landfall tropical cyclones shows little net change over much of the eastern U.S. despite a decrease in frequency over the ocean. This reflects a greater landfalling fraction in CMIP5 projections, which is not seen in CMIP3-based projections. Average tropical cyclone rain rates over land within 500 km of the storm center increase by 8-17 % in the future climate projections relative to control. This is at least as much as expected from the Clausius-Clapeyron relation, which links a warmer atmosphere to greater atmospheric water vapor content. Over land, the percent enhancement of area-averaged rain rates from a given tropical cyclone in the warmer climate is greater for larger averaging radius (300-500 km) than near the storm, particularly for the CMIP3 projections. Although this study does not focus on attribution, the findings are broadly consistent with historical tropical cyclone rainfall changes documented in a recent observational study. The results may have important implications for future flood risks from tropical cyclones. [ABSTRACT FROM AUTHOR]

In their pioneering work, Ward and Day suggested that a large scale flank collapse of the Cumbre Vieja Volcano (CVV) on La Palma (Canary Islands) could trigger a mega-tsunami throughout the North Atlantic Ocean basin, causing major coastal impact in the far-field. While more recent studies indicate that near-field waves from such a collapse would be more moderate than originally predicted by Ward and Day [Løvholt et al. (J Geophy Res 113:C09026, ); Abadie et al. (J Geophy Res 117:C05030, )], these would still be formidable and devastate the Canary Island, while causing major impact in the far-field at many locations along the western European, African, and the US east coasts. Abadie et al. (J Geophy Res 117:C05030, ) simulated tsunami generation and near-field tsunami impact from a few CVV subaerial slide scenarios, with volumes ranging from 20 to 450 km $$^3$$ ; the latter representing the most extreme scenario proposed by Ward and Day. They modeled tsunami generation, i.e., the tsunami source, using THETIS, a 3D Navier-Stokes (NS) multi-fluid VOF model, in which slide material was considered as a nearly inviscid heavy fluid. Near-field tsunami impact was then simulated for each source using FUNWAVE-TVD, a dispersive and fully nonlinear long wave Boussinesq model [ Shi et al. (Ocean Modell 43-44:36-51, ); Kirby et al. (Ocean Modeling, 62:39-55, )]. Here, using FUNWAVE-TVD for a series of nested grids of increasingly fine resolution, we model and analyze far-field tsunami impact from two of Abadie et al.'s extreme CVV flank collapse scenarios: (i) that deemed the most 'credible worst case scenario' based on a slope stability analysis, with a 80 km $$^3$$ volume; and (ii) the most extreme scenario, similar to Ward and Day's, with a 450 km $$^3$$ volume. Simulations are performed using a one-way coupling scheme in between two given levels of nested grids. Based on the simulation results, the overall tsunami impact is first assessed in terms of maximum surface elevation computed along the western European and African, and US east coasts (USEC). Strong wave elevation decay is predicted over the wide USEC shelf, which is shown to be essentially due to bottom friction effects. We then show more detailed results for the USEC, which is the object of high-resolution tsunami inundation mapping under the auspices of the US National Tsunami Hazard Mitigation Program. In this context, we compare the maximum surface elevation predicted along the coastline for each CVV scenario and show that, besides the initial directionality of the sources, coastal impact is mostly controlled by focusing/defocusing effects resulting from the shelf bathymetric features. A simplified ray-tracing analysis confirms this controlling effect of the wide USEC shelf for incident long waves. Finally, we perform high-resolution (10 m) inundation mapping for the most extreme CVV scenario and show results at one of the most vulnerable and exposed communities in the mid-Atlantic US states, in and around Ocean City, Maryland. Such maps are being generated for all exposed areas of the USEC, to be used in tsunami hazard assessment and mitigation work. [ABSTRACT FROM AUTHOR]

The Conservation Reserve Program ( CRP) is the largest land-based agricultural policy in the US. Several economic studies have studied this programme; however, only a few have studied its implications for non-enrolled land, that is, its regional effects on land use decisions. This paper examines the CRP's indirect effect on the conversion of non-agricultural land to agriculture, phenomenon known as land slippage. Building on earlier studies, I model county-level slippage empirically using satellite imagery, which allows observation of specific land cover changes (e.g., forest to agriculture). Results suggest the existence of CRP slippage, but at varying rates according to initial land covers. [ABSTRACT FROM AUTHOR]

Abstract: Tsunami hazard is a very low-probability, but potentially high-risk natural hazard, posing unique challenges to scientists and policy makers trying to mitigate its impacts. These challenges are illustrated in this assessment of tsunami hazard to the U.S. Atlantic margin. Seismic activity along the U.S. Atlantic margin in general is low, and confirmed paleo-tsunami deposits have not yet been found, suggesting a very low rate of hazard. However, the devastating 1929 Grand Banks tsunami along the Atlantic margin of Canada shows that these events continue to occur. Densely populated areas, extensive industrial and port facilities, and the presence of ten nuclear power plants along the coast, make this region highly vulnerable to flooding by tsunamis and therefore even low-probability events need to be evaluated. We can presently draw several tentative conclusions regarding tsunami hazard to the U.S. Atlantic coast. Landslide tsunamis likely constitute the biggest tsunami hazard to the coast. Only a small number of landslides have so far been dated and they are generally older than 10,000years. The geographical distribution of landslides along the margin is expected to be uneven and to depend on the distribution of seismic activity along the margin and on the geographical distribution of Pleistocene sediment. We do not see evidence that gas hydrate dissociation contributes to the generation of landslides along the U.S. Atlantic margin. Analysis of landslide statistics along the fluvial and glacial portions of the margin indicate that most of the landslides are translational, were probably initiated by seismic acceleration, and failed as aggregate slope failures. How tsunamis are generated from aggregate landslides remains however, unclear. Estimates of the recurrence interval of earthquakes along the continental slope may provide maximum estimates for the recurrence interval of landslide along the margin. Tsunamis caused by atmospheric disturbances and by coastal earthquakes may be more frequent than those generated by landslides, but their amplitudes are probably smaller. Among the possible far-field earthquake sources, only earthquakes located within the Gulf of Cadiz or west of the Tore-Madeira Rise are likely to affect the U.S. coast. It is questionable whether earthquakes on the Puerto Rico Trench are capable of producing a large enough tsunami that will affect the U.S. Atlantic coast. More information is needed to evaluate the seismic potential of the northern Cuba fold-and-thrust belt. The hazard from a volcano flank collapse in the Canary Islands is likely smaller than originally stated, and there is not enough information to evaluate the magnitude and frequency of flank collapse from the Azores Islands. Both deterministic and probabilistic methods to evaluate the tsunami hazard from the margin are available for application to the Atlantic margin, but their implementation requires more information than is currently available. [Copyright &y& Elsevier]

The southeastern United States is routinely hit by tropical cyclones (TC). As TC track inland and dissipate their inland impacts can be substantial. This study examined the spatial patterns of societal impacts associated with tornadoes and high winds with 31 inland-moving TC that made landfall from 1985 to 2008. Hourly weather information was collected from all available first-order weather stations affected by each storm, as well as tropical cyclone preliminary reports issued from the National Hurricane Center. Societal impacts were identified through selected newspapers across the region and the National Climatic Data Center's Storm Data. Geographic Information System (GIS) software was employed to make geometric measurements of the distance and direction of the impacts relative to storm center. From these measurements, the spatial distribution of the societal and meteorological impacts was plotted relative to the track (e.g., left vs. right) and location (forward vs. rear sector) of the cyclone center. Various tropical cyclone attributes, including size, strength, and forward speed of movement were then related to the occurrence of different impacts and their location relative to the cyclone track. The majority of tropical cyclone tornado and high wind impacts occur in the right-forward sector of the tropical cyclone. However, many TC produce impacts that occur in other sectors far from the center of circulation. These abnormalities are associated in many cases with interactions between the tropical cyclone circulation, topography, peripheral dry air, atid extratropical synoptic weather features. [ABSTRACT FROM AUTHOR]

Abstract: Ground-based interferometric radar (GBIR) monitoring was conducted on a slow-moving, translational failure landslide in Granby, Grand County, Colorado, USA. Radar monitoring was completed over two separate surveys in 2011 using a tripod mounted real aperture sensor. The purpose of this work is to evaluate GBIR as a temporally dense monitoring technique for monitoring landslide displacement and compare the monitoring results to ongoing GPS based surveying methods to verify measured displacements. We discuss the strengths and limitations of GBIR displacement monitoring with a variety of available sensors, and place this monitoring platform, sensor, and workflow into context of previous slope stability monitoring with GBIR. For both surveys, displacement time series were created through a small temporal baseline stacking to reduce noise and maintain high temporal resolution. The results of the displacement time series were compared to average displacement rates derived from GPS based surveying. An overall verification of radar and GPS derived displacement rates was achieved, and identifies important differences relating to the precision and uncertainty of the two techniques. This work demonstrates GBIR monitoring capability of establishing high temporal resolution on tracking variable rates of landslide movements. Spatial modeling of total observed displacements was completed for both surveys verifying a conceptual model of uniform translational landslide movement, providing greater confidence for mitigation planning. [Copyright &y& Elsevier]

Abstract: Understanding the cumulative impact of natural and human influences on the sensitivity of channel morphodynamics, a relative measure between the drivers for change and the magnitude of channel response, requires an approach that accommodates spatial and temporal variability in the suite of primary stressors. Multiple historical data sources were assembled to provide a reach-scale analysis of the lower Santa Clara River (LSCR) in Ventura County, California, USA. Sediment supply is naturally high due to tectonic activity, earthquake-generated landslides, wildfires, and high magnitude flow events during El Niño years. Somewhat typically for the region, the catchment has been subject to four reasonably distinct land use and resource management combinations since European-American settlement. When combined with analysis of channel morphological response (quantifiable since ca. 1930), reach-scale and temporal differences in channel sensitivity become apparent. Downstream reaches have incised on average 2.4m and become narrower by almost 50% with changes focused in a period of highly sensitive response after about 1950 followed by forced insensitivity caused by structural flood embankments and a significant grade control structure. In contrast, the middle reaches have been responsive but are morphologically resilient, and the upstream reaches show a mildly sensitive aggradational trend. Superimposing the natural and human drivers for change reveals that large scale stressors (related to ranching and irrigation) have been replaced over time by a suite of stressors operating at multiple spatial scales. Lower reaches have been sensitive primarily to ‘local’ scale impacts (urban growth, flood control, and aggregate mining) whereas, upstream, catchment-scale influences still prevail (including flow regulation and climate-driven sediment supply factors). These factors illustrate the complexity inherent to cumulative impact assessment in fluvial systems, provide evidence for a distinct Anthropocene fluvial response, and underpin the enormity of the challenge faced in trying to sustainably manage and restore rivers. [Copyright &y& Elsevier]

Abstract: As soil moisture increases, slope stability decreases. Remotely sensed soil moisture data can provide routine updates of slope conditions necessary for landslide predictions. For regional scale landslide investigations, only remote-sensing methods have the spatial and temporal resolution required to map hazard increases. Here, a dynamic physically-based slope stability model that requires soil moisture is applied using remote-sensing products from multiple Earth observing platforms. The resulting landslide susceptibility maps using the advanced microwave scanning radiometer (AMSR-E) surface soil moisture are compared to those created using variable infiltration capacity (VIC-3L) modeled soil moisture at Cleveland Corral landslide area in California, US. Despite snow cover influences on AMSR-E surface soil moisture estimates, a good relationship between the downscaled AMSR-E''s surface soil moisture and the VIC-3L modeled soil moisture is evident. The AMSR-E soil moisture mean (0.17cm3/cm3) and standard deviation (0.02cm3/cm3) are very close to the mean (0.21cm3/cm3) and standard deviation (0.09cm3/cm3) estimated by VIC-3L model. Qualitative results show that the location and extent of landslide prone regions are quite similar. Under the maximum saturation scenario, 0.42% and 0.49% of the study area were highly susceptible using AMSR-E and VIC-3L model soil moisture, respectively. [Copyright &y& Elsevier]

Hydrologically driven mass wasting in the form of landslides on steep slopes is a worldwide occurrence. High-profile events in, for example, Brazil, Chile, the Philippines, Puerto Rico, and Venezuela during the last three decades all clearly illustrate, based upon significant losses of life and property, that hydrologically driven slope instability in developed (urban) areas can be a major geologic/environmental hazard. The focus of this study is the 1973 hydrologically driven Lerida Court landslide in Portola Valley, CA, USA. Physics-based hydrologic-response simulation, with the comprehensive Integrated Hydrology Model, was employed to forensically estimate the spatiotemporal pore pressure distributions for the Lerida Court site. Slope stability, driven by the simulated pore pressure dynamics, was estimated for the Lerida Court site with the infinite slope/Factor of Safety approach. The pore pressure dynamics for the Lerida Court site were reasonably captured by the hydrologic-response simulation. The estimated time of slope failure for the Lerida Court site compares well with field observations. A recommendation is made that hydrologically driven slope stability estimates including variably saturated subsurface flow be standard protocol for development sites in steep urban settings. [ABSTRACT FROM AUTHOR]

Abstract: The Kalman recursive algorithm has been very widely used for integrating navigation sensor data to achieve optimal system performances. This paper explores the use of the Kalman filter to extend the aggregation of spatial multi-criteria evaluation (MCE) and to find optimal solutions with respect to a decision strategy space where a possible decision rule falls. The approach was tested in a case study in the Clearwater National Forest in central Idaho, using existing landslide datasets from roaded and roadless areas and terrain attributes. In this approach, fuzzy membership functions were used to standardize terrain attributes and develop criteria, while the aggregation of the criteria was achieved by the use of a Kalman filter. The approach presented here offers advantages over the classical MCE theory because the final solution includes both the aggregated solution and the areas of uncertainty expressed in terms of standard deviation. A comparison of this methodology with similar approaches suggested that this approach is promising for predicting landslide susceptibility and further application as a spatial decision support system. [Copyright &y& Elsevier]

Abstract: Elevated landslide rates in forested landscapes can adversely impact aquatic habitat and water quality and remove and/or degrade soil resources required for forest regeneration. As a result, understanding the associations between management actions, natural factors, and landslide rates is important information needed for land managers. An unusual and powerful storm in early December, 2007, caused record flooding and thousands of landslides across southwest Washington and northwest Oregon, USA, and provided a rare opportunity to examine the effects of both natural factors and forest management practices on landslide density. Landslide inventory data were collected from both aerial photos and systematic field surveys to provide a broad survey database that was used to develop estimates of landslide density and to examine associations between landslide density, precipitation, topography, and forest stand age across a 152,000ha forested landscape in the Willapa Hills, Washington. We estimated the probability of detecting landslides on aerial photos for six strata defined by forest stand age and a broad range of rainfall intensity, expressed as percent of the 100-year, 24-h, maximum rainfall. Key findings are that landslide detection probability decreased with increasing stand age, but was similar across rainfall intensities. The overall fraction of field-detected landslides that were not detected on 1:12,000-scale aerial photos was 39%. Very few landslides occurred in the 0–100% of 100-year rainfall category, regardless of stand age or slope gradient class. At higher rainfall intensities, significantly higher landslide densities occurred on steep slopes (>70% gradient) compared to lower gradient slopes, as expected. Above ∼150% of 100-year rainfall, the density of landslides was ∼2–3 times larger in the 0–5 and 6–10 year stand age categories than in the 11–20, 21–30, 31–40, and 41+ categories. The effect of stand age was strongest at the highest rainfall intensities. Our results demonstrate that ground-based landslide inventory data are required in order to correct for detection bias from aerial photos, develop reasonable estimates of landslide density across environmental gradients such as rainfall magnitude and topography, and make unbiased interpretations of relationships between forest management associations and landslide occurrence. [Copyright &y& Elsevier]

Abstract: Landslides are often viewed together with other natural hazards, such as earthquakes and fires, as phenomena whose size distribution obeys an inverse power law. Inverse power law distributions are the result of additive avalanche processes, in which the final size cannot be predicted at the onset of the disturbance. Volume and area distributions of submarine landslides along the U.S. Atlantic continental slope follow a lognormal distribution and not an inverse power law. Using Monte Carlo simulations, we generated area distributions of submarine landslides that show a characteristic size and with few smaller and larger areas, which can be described well by a lognormal distribution. To generate these distributions we assumed that the area of slope failure depends on earthquake magnitude, i.e., that failure occurs simultaneously over the area affected by horizontal ground shaking, and does not cascade from nucleating points. Furthermore, the downslope movement of displaced sediments does not entrain significant amounts of additional material. Our simulations fit well the area distribution of landslide sources along the Atlantic continental margin, if we assume that the slope has been subjected to earthquakes of magnitude ≤6.3. Regions of submarine landslides, whose area distributions obey inverse power laws, may be controlled by different generation mechanisms, such as the gradual development of fractures in the headwalls of cliffs. The observation of a large number of small subaerial landslides being triggered by a single earthquake is also compatible with the hypothesis that failure occurs simultaneously in many locations within the area affected by ground shaking. Unlike submarine landslides, which are found on large uniformly-dipping slopes, a single large landslide scarp cannot form on land because of the heterogeneous morphology and short slope distances of tectonically-active subaerial regions. However, for a given earthquake magnitude, the total area affected by subaerial landslides is comparable to that calculated by slope stability analysis for submarine landslides. The area distribution of subaerial landslides from a single event may be determined by the size distribution of the morphology of the affected area, not by the initiation process. [Copyright &y& Elsevier]

Although earthflows are the dominant erosion mechanism in many mountainous landscapes, estimates of long-term earthflow-driven sediment flux remain elusive because landslide displacement data are typically limited to contemporary time periods. Combining high-resolution topography from airborne LiDAR (light detection and ranging), total station surveying, orthorectified historical aerial photographs, and inventories of meteoric 10Be in soil pits, we quantified ∼150 years of slope movement on a 1.5-km-long earthflow in the Eel River catchment, northern California, United States. Using LiDAR-derived topography, we mapped the upper half of the earthflow into three distinct kinematic zones: an upslope source area, a long narrow transport zone, and a mid-slope compressional zone. From our air photo analysis (1944-2006), average velocities are fastest in the transport zone (1.7 m/a), slowest in the source zone (<1 m/a), and decrease monotonically over the past 30 years in all three zones. Meteoric 10Be inventories systematically increase with distance downslope of the source area, consistent with the notion that the elongate transport zone acts like a relatively undeformed soil conveyor that can be used to quantify long-term displacement. Because our 10Be-derived transport zone velocity of 2.1 m/a averages over the past 150 years, pre-1944 velocities likely approached 2.5 m/a, suggesting that twentieth century land-use practices have not increased rates of sliding. Although our results reveal a progressive decline in velocity that may reflect exhaustion of readily mobilized source material, velocities temporarily increased in the midtwentieth century due to major hydrologic events. Given an average velocity of 2 m/a, the Kekawaka earthflow is deflating its source area over 20 times faster than the regional erosion rate, emphasizing the localized and vigorous role of active earthflows in landscape evolution. [ABSTRACT FROM AUTHOR]

Abstract: Submarine landslides along the continental slope of the U.S. Atlantic margin are potential sources for tsunamis along the U.S. East coast. The magnitude of potential tsunamis depends on the volume and location of the landslides, and tsunami frequency depends on their recurrence interval. However, the size and recurrence interval of submarine landslides along the U.S. Atlantic margin is poorly known. Well-studied landslide-generated tsunamis in other parts of the world have been shown to be associated with earthquakes. Because the size distribution and recurrence interval of earthquakes is generally better known than those for submarine landslides, we propose here to estimate the size and recurrence interval of submarine landslides from the size and recurrence interval of earthquakes in the near vicinity of the said landslides. To do so, we calculate maximum expected landslide size for a given earthquake magnitude, use recurrence interval of earthquakes to estimate recurrence interval of landslide, and assume a threshold landslide size that can generate a destructive tsunami. The maximum expected landslide size for a given earthquake magnitude is calculated in 3 ways: by slope stability analysis for catastrophic slope failure on the Atlantic continental margin, by using land-based compilation of maximum observed distance from earthquake to liquefaction, and by using land-based compilation of maximum observed area of earthquake-induced landslides. We find that the calculated distances and failure areas from the slope stability analysis is similar or slightly smaller than the maximum triggering distances and failure areas in subaerial observations. The results from all three methods compare well with the slope failure observations of the M w =7.2, 1929 Grand Banks earthquake, the only historical tsunamigenic earthquake along the North American Atlantic margin. The results further suggest that a M w =7.5 earthquake (the largest expected earthquake in the eastern U.S.) must be located offshore and within 100 km of the continental slope to induce a catastrophic slope failure. Thus, a repeat of the 1755 Cape Anne and 1881 Charleston earthquakes are not expected to cause landslides on the continental slope. The observed rate of seismicity offshore the U.S. Atlantic coast is very low with the exception of New England, where some microseismicity is observed. An extrapolation of annual strain rates from the Canadian Atlantic continental margin suggests that the New England margin may experience the equivalent of a magnitude 7 earthquake on average every 600–3000 yr. A minimum triggering earthquake magnitude of 5.5 is suggested for a sufficiently large submarine failure to generate a devastating tsunami and only if the epicenter is located within the continental slope. [Copyright &y& Elsevier]

Abstract: Tsunami hazard assessment is critical for coastal communities, emergency services, and industry, to develop regional risk and response management plans, for catastrophic tsunami events (such as the recent 1998 Papua New Guinea (PNG) and 2004 Indian Ocean tsunamis). Along the northeastern United States coastline, tsunami hazard assessment is in its infancy, mostly due to the lack of historical tsunami record and the uncertainty regarding the return periods of potential large-scale events. The latter includes large transoceanic tsunamis, such as could be caused by a collapse of the Cumbre Vieja volcano in the Canary Islands or a large co-seismic tsunami initiated in the Puerto Rican trench, as well as large local tsunamis, such as could be caused by a Submarine Mass Failure (SMF) occurring on the nearby continental slope. In this region, considerable geologic and some historical (e.g., the 1929 Grand Bank landslide tsunami) evidence suggests that the largest tsunami hazard may arise from tsunamigenic SMFs, triggered by moderate seismic activity. The coastal impact of SMF (or landslide) tsunamis, indeed, can potentially be narrowly focused and affect specific communities. This research presents the development, validation, and results of a probabilistic geomechanical and coastal tsunami impact analysis, of tsunami hazard on the upper northeast coast of the United States. Results are presented in terms of nearshore breaking wave height and runup, caused by seismically induced tsunamigenic SMF, with a given return period. A Monte Carlo approach is employed, in which distributions of relevant parameters (seismicity, sediment properties, type and location, volume, and dimensions of slide, water depth, etc.) are used to perform large numbers of stochastic stability analyses of submerged slopes (along actual shelf transects), based on standard pseudo-static limit equilibrium methods. The distribution of predicted slope failures along the upper U.S. East Coast is found to match published data quite well. For slopes that are deemed unstable for a specified ground acceleration (with given return period), the tsunami source characteristic height is found using empirical equations (based on earlier numerical simulation work), and corresponding breaking height and runup are estimated on the nearest coastline. For a 0.2% annual-probability ground acceleration, for instance, simulations yield a return period of tsunamigenic SMFs of 3350-yr (i.e., a 0.03% annual probability of occurrence). The resulting estimate of the overall coastal hazard, from 100 and 500-yr SMF tsunami events, is found to be quite low at most locations, as compared to the typical 100 yr hurricane storm surge in the region (~4–5 m). Specifically, for the 100 yr event, SMF tsunami hazard is quite low with no coastal region exceeding a 1 m runup. For the 500 yr event, however, two regions of relatively elevated hazard are found: (1) near Long Island, NY, with a peak runup of 3 m; and (2) near the New Jersey coast, with a peak runup of 4 m. It should be stressed that these are only first-order estimates and detailed tsunami inundation modeling is required to fully quantify tsunami runup (and inundation) at these sites. This will be the object of more detailed studies in future work. [Copyright &y& Elsevier]

Abstract: Estimating the likelihood of tsunamis occurring along the U.S. Atlantic coast critically depends on knowledge of tsunami source probability. We review available information on both earthquake and landslide probabilities from potential sources that could generate local and transoceanic tsunamis. Estimating source probability includes defining both size and recurrence distributions for earthquakes and landslides. For the former distribution, source sizes are often distributed according to a truncated or tapered power–law relationship. For the latter distribution, sources are often assumed to occur in time according to a Poisson process, simplifying the way tsunami probabilities from individual sources can be aggregated. For the U.S. Atlantic coast, earthquake tsunami sources primarily occur at transoceanic distances along plate boundary faults. Probabilities for these sources are constrained from previous statistical studies of global seismicity for similar plate boundary types. In contrast, there is presently little information constraining landslide probabilities that may generate local tsunamis. Though there is significant uncertainty in tsunami source probabilities for the Atlantic, results from this study yield a comparative analysis of tsunami source recurrence rates that can form the basis for future probabilistic analyses. [Copyright &y& Elsevier]

Abstract: The nearly complete coverage of the U.S. Atlantic continental slope and rise by multibeam bathymetry and backscatter imagery provides an opportunity to reevaluate the distribution of submarine landslides along the margin and reassess the controls on their formation. Landslides can be divided into two categories based on their source areas: those sourced in submarine canyons and those sourced on the open continental slope and rise. Landslide distribution is in part controlled by the Quaternary history of the margin. They cover 33% of the continental slope and rise of the glacially influenced New England margin, 16% of the sea floor offshore of the fluvially dominated Middle Atlantic margin, and 13% of the sea floor south of Cape Hatteras. The headwall scarps of open-slope sourced landslides occur mostly on the lower slope and upper rise while they occur mostly on the upper slope in the canyon-sourced ones. The deposits from both landslide categories are generally thin (mostly 20–40 m thick) and comprised primarily of Quaternary material, but the volumes of the open-slope sourced landslide deposits can be larger (1–392 km3) than the canyon-sourced ones (1–10 km3). The largest failures are located seaward of shelf-edge deltas along the southern New England margin and near salt domes that breach the sea floor south of Cape Hatteras. The spatial distribution of landslides indicates that earthquakes associated with rebound of the glaciated part of the margin or earthquakes associated with salt domes were probably the primary triggering mechanism although other processes may have pre-conditioned sediments for failure. The largest failures and those that have the potential to generate the largest tsunamis are the open-slope sourced landslides. [Copyright &y& Elsevier]

Abstract: Assessment of the probability for destructive landslide-generated tsunamis depends on the knowledge of the number, size, and frequency of large submarine landslides. This paper investigates the size distribution of submarine landslides along the U.S. Atlantic continental slope and rise using the size of the landslide source regions (landslide failure scars). Landslide scars along the margin identified in a detailed bathymetric Digital Elevation Model (DEM) have areas that range between 0.89 km2 and 2410 km2 and volumes between 0.002 km3 and 179 km3. The area to volume relationship of these failure scars is almost linear (inverse power-law exponent close to 1), suggesting a fairly uniform failure thickness of a few 10s of meters in each event, with only rare, deep excavating landslides. The cumulative volume distribution of the failure scars is very well described by a log–normal distribution rather than by an inverse power-law, the most commonly used distribution for both subaerial and submarine landslides. A log–normal distribution centered on a volume of 0.86 km3 may indicate that landslides preferentially mobilize a moderate amount of material (on the order of 1 km3), rather than large landslides or very small ones. Alternatively, the log–normal distribution may reflect an inverse power law distribution modified by a size-dependent probability of observing landslide scars in the bathymetry data. If the latter is the case, an inverse power-law distribution with an exponent of 1.3±0.3, modified by a size-dependent conditional probability of identifying more failure scars with increasing landslide size, fits the observed size distribution. This exponent value is similar to the predicted exponent of 1.2±0.3 for subaerial landslides in unconsolidated material. Both the log–normal and modified inverse power-law distributions of the observed failure scar volumes suggest that large landslides, which have the greatest potential to generate damaging tsunamis, occur infrequently along the margin. [Copyright &y& Elsevier]

In the recent literature, considerable attention has been paid to the relationship between climate signals and tropical cyclone activity. Much of the research has focused on Atlantic Ocean basin activity while less attention has been given to landfall frequency and the geographic distribution of risk to life and property. However, recent active seasons like 2004 and 2005 and the resulting damage and economic loss have generated significant interest in the relationship between climate and landfall risk. This study focuses on sea surface temperatures (SST) and examines modulation of landfall activity occurring in anomalously warm-SST seasons. The objective of the study is to evaluate the effect of warmer ocean conditions on U.S. landfall risk. The study is broken into two parts–—statistical and physical. The statistical analysis categorizes historical hurricane seasons as either warm or cool and then estimates shifts in landfall frequency under these two climate modes. The analysis is carried out for overall U.S. landfall risk and then for logical subregions along the U.S. coastline. The climatological behavior for warm-SST conditions is developed across the intensity spectrum, from weak tropical storms to major hurricanes, using wind speed as an intensity measure. The analysis suggests that landfall risk is sensitive to SST conditions but that sensitivity varies by region and intensity. The uncertainty associated with these estimates is discussed. The physical analysis is carried out to understand better why landfall risk is not affected uniformly along the U.S. coastline and to reinforce the reasonability of the statistical results. The study involves a detailed examination of the complete life cycle of historical storms. Results indicate that storms making landfall along the East Coast have different genesis and intensification characteristics relative to storms making landfall along the Gulf Coast. As SSTs warm, the genesis pattern shifts, greatly influencing regional landfall risk. Further, hurricane landfalls may react not only to warm-SST conditions, but also to the effect of ocean temperature anomalies on the atmosphere’s general circulation. There are implications that complex feedback mechanisms play a role in modulating the probability of landfall, especially from certain parts of the Atlantic basin. Such physical theories provide added confidence in statistical estimates of elevated risk for certain breeds of tropical cyclones. [ABSTRACT FROM AUTHOR]

Abstract: Overpressures measured with pore pressure penetrometers during Integrated Ocean Drilling Program (IODP) Expedition 308 reach 70% and 60% of the hydrostatic effective stress () in the first 200 meters below sea floor (mbsf) at Sites U1322 and U1324, respectively, in the deepwater Gulf of Mexico, offshore Louisiana. High overpressures are present within low permeability mudstones where there have been multiple, very large, submarine landslides during the Pleistocene. Beneath 200 mbsf at Site U1324, pore pressures drop significantly: there are no submarine landslides in this mixture of mudstone, siltstone and sandstone. The penetrometer measurements did not reach the in situ pressure at the end of the deployment. We used a soil model to determine that an extrapolation approach based on the inverse of square route of time () requires much less decay time to achieve a desirable accuracy than an inverse time (1/t) extrapolation. Expedition 308 examined how rapid and asymmetric sedimentation above a permeable aquifer drives lateral fluid flow, extreme pore pressures, and submarine landslides. We interpret that the high overpressures observed are driven by rapid sedimentation of low permeability material from the ancestral Mississippi River. Reduced overpressure at depth at Site 1324 suggests suggest lateral flow (drainage) whereas high overpressure at Site 1322 requires inflow from below: lateral flow in the underlying permeable aquifer provides one mechanism for these observations. High overpressure near the seafloor reduces slope stability and provides a mechanism for the large submarine landslides and low regional gradient (2°) offshore from the Mississippi delta. [Copyright &y& Elsevier]

Abstract: An integration of geological and geophysical techniques characterizes the internal and basal structure of a landslide along the western margin of the Wasatch Mountains in northern Utah, USA. The study area is within a region of planned and continuing residential development. The Little Valley Landslide is a prehistoric landslide as old as 13 ka B.P. Drilling and trenching at the site indicate that the landslide consists of chaotic and disturbed weathered volcanic material derived from Tertiary age volcanic rocks that comprise a great portion of the Wasatch Range. Five short high-resolution common mid-point seismic reflection profiles over selected portions of the site examine the feasibility of using seismic reflection to study prehistoric landslides in the Wasatch Mountain region. Due to the expected complexity of the near-surface geology, we have pursued an experimental approach in the data processing, examining the effects of muting first arrivals, frequency filtering, model-based static corrections, and seismic migration. The results provide a framework for understanding the overall configuration of the landslide, its basal (failure) surface, and the structure immediately underlying this surface. A glide surface or décollement is interpreted to underlie the landslide suggesting a large mass movement. The interpretation of a glide surface is based on the onset of coherent reflectivity, calibrated by information from a borehole located along one of the seismic profiles. The glide surface is deepest in the center portion of the landslide and shallows up slope, suggesting a trough-like feature. This study shows that seismic reflection techniques can be successfully used in complex alpine landslide regions to (1) provide a framework in which to link geological data and (2) reduce the need for an extensive trenching and drilling program. [Copyright &y& Elsevier]

Abstract: Two alternative procedures for estimating landslide hazards were evaluated using data on topographic digital elevation models (DEMs) and bedrock lithologies in an area adjacent to the Missouri River in Atchison County, Kansas, USA. The two procedures are based on the likelihood ratio model but utilize different assumptions. The empirical likelihood ratio model is based on non-parametric empirical univariate frequency distribution functions under an assumption of conditional independence while the multivariate logistic discriminant model assumes that likelihood ratios can be expressed in terms of logistic functions. The relative hazards of occurrence of landslides were estimated by an empirical likelihood ratio model and by multivariate logistic discriminant analysis. Predictor variables consisted of grids containing topographic elevations, slope angles, and slope aspects calculated from a 30-m DEM. An integer grid of coded bedrock lithologies taken from digitized geologic maps was also used as a predictor variable. Both statistical models yield relative estimates in the form of the proportion of total map area predicted to already contain or to be the site of future landslides. The stabilities of estimates were checked by cross-validation of results from random subsamples, using each of the two procedures. Cell-by-cell comparisons of hazard maps made by the two models show that the two sets of estimates are virtually identical. This suggests that the empirical likelihood ratio and the logistic discriminant analysis models are robust with respect to the conditional independent assumption and the logistic function assumption, respectively, and that either model can be used successfully to evaluate landslide hazards. [Copyright &y& Elsevier]

The article provides information on several of the tropical storms that struck the U.S. in 2004. As in 2004, tropical cyclone activity in the eastern North Pacific was below average, with 15 named tropical storms. Seven became hurricanes and only Kenneth became a major hurricane, categorized as a Category 3 or stronger on the Saffir-Simpson hurricane scale. None of the systems made landfall as a tropical storm or hurricane, although Adrian made landfall in Honduras as a tropical depression.

Abstract: The moment magnitude (M) 7.9 Denali Fault, Alaska, earthquake of 3 November 2002 triggered thousands of landslides, primarily rock falls and rock slides, that ranged in volume from rock falls of a few cubic meters to rock avalanches having volumes as great as 20×106 m3. The pattern of landsliding was unusual: the number and concentration of triggered slides was much less than expected for an earthquake of this magnitude, and the landslides were concentrated in a narrow zone about 30-km wide that straddled the fault-rupture zone over its entire 300-km length. Despite the overall sparse landslide concentration, the earthquake triggered several large rock avalanches that clustered along the western third of the rupture zone where acceleration levels and ground-shaking frequencies are thought to have been the highest. Inferences about near-field strong-shaking characteristics drawn from interpretation of the landslide distribution are strikingly consistent with results of recent inversion modeling that indicate that high-frequency energy generation was greatest in the western part of the fault-rupture zone and decreased markedly to the east. [Copyright &y& Elsevier]

This article discusses the proposed research project Hurricane-Flood-Landslide Continuum by a group of U.S. government agencies and academic institutions. The purpose of the project is to develop and integrate the multidisciplinary tools needed to issue regional guidance products for floods and landslides associated with major tropical rain systems. The group envisions the development and implementation of a warning system for a prototype region in the Caribbean, specifically in the islands of Puerto Rico and Hispaniola.

Abstract: Landslides are common on the steep slopes of the subtropical montane forests in Northwestern (NW) Argentina (Yungas). Instrumental and tree-ring records from this region indicate that rainfall has increased during the second half of the 20th century and there has also been an increase in landslide events. We used dendroecological techniques to date the occurrence of landslides during the past 50 years and examine the relationships with regional precipitation trends. Alnus acuminata H.B.K. is the dominant species in the upper montane forest and colonizes the bare areas exposed by landslides. Landslide dating was based on the identification of suppression-release patterns in ring-width series from trees growing along the landslide scarps, in combination with age determination of trees growing on the landslide failure or depositional surfaces. We cored A. acuminata in three areas that span the latitudinal range of the montane forest in NW Argentina: Los Sosa (27°S), Hualinchay (26°S) and Yala (24°S). The results show that landslide occurrence (and therefore probability) is more frequent during summers with abundant rainfall. As General Circulation Models for subtropical South America predict an increase in summer precipitation during the 21st century, increased precipitation could induce changes in landslide regime that would lead to important environmental changes in these montane ecosystems. [Copyright &y& Elsevier]

Landslides represent a key component of catchment‐scale denudation, though their relative contribution to the erosion of glaciated basins is not well known. Bedrock landslide contribution was investigated on the surface of one of eleven glaciers on a glaciated ridge in the Chugach‐St Elias Range of southern Alaska, where the debris from four major landslides is easily distinguished from moraines and other supraglacial material. A series of aerial and satellite photos from 1972 to 2000 and field observations in 2001 and 2002 indicate that three of four landslides have fallen onto the surface of the glacier since about 1978. The landslides, which originated from the steeply dipping (60–70°) bedrock walls, were deposited onto the glacier in the ablation zone and are currently being transported downstream supraglacially. Individual glacial valleys with topographic relief of ∼400 m are cut into high‐grade metamorphic rock characterized by a steep north‐dipping foliation and fractured by numerous large joints. Measurements of landslide area and average thickness obtained from high‐resolution survey data indicate a total landslide volume of ∼2·3 × 105 m3. This volume suggests a basin‐averaged erosion rate from landslides of 0·48 mm a−1. An overall basin‐scale erosion rate of 0·7 to 1·7 mm a−1 can be inferred, but depends on the percentage of the total‐basin sediment yield contributed by supraglacial sources. A mean rockwall retreat rate of 6·7 mm a−1 is calculated and is considerably higher than published rates, which range from 0·04 to 4·0 mm a−1. Controls on landslide generation include seismicity, freeze–thaw processes, topography, rock strength, and debuttressing. It is likely all of these factors contribute to failure, although the primary controls for the landslides in this study are thought to be rock strength and topography. The absence of landslides on ten of the eleven glaciers on this ridge is attributed to landslide magnitude–frequency relationships and short temporal scale of this study. Large‐volume bedrock landslides (>100 000 m3) may have low frequency, occurring less than once in a 55‐year time frame. Copyright © 2005 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Flash flood and debris flow reports from Storm Data and the U.S. Geological Survey (USGS) are used to investigate the relationship between hazardous hydrological responses, convective rainfall, and cloud-to-ground (CG) lightning flash parameters. Basins burned by the Coal Seam and Missionary Ridge wildfires during the summer of 2002 in western Colorado were selected as primary study areas. The North American monsoon (NAM) air mass played a pivotal role in providing low-level moisture over much of Colorado during each of the 12 hydrological events identified. Surface θe values as high as 354 K were calculated over western Colorado in a composite analysis that also saw a θe ridge through 500 hPa extending northward into Nebraska and southern South Dakota. Storm-total CG flashes were as high as 718, and the median flash total for the population of events was 256. Mean 5-min CG flash intensity for the events was 18.1 flashes. The mean rainfall intensity associated with the 12 hydrological events was 10.5 mm h-1, and average storm-total rainfall was 14.2 mm. Continuous CG flash sequences (one or more flashes per sequential 5-min interval) were significantly correlated with rainfall intensity, total rainfall, and rainfall duration for events generating postwildfire flash floods and debris flows. Operational utility may be derived from the observation of the mean lag time from the first recorded CG flash in a 7850-km2 study area to the peak rainfall intensity, and the mean lag time from peak CG flash rate to peak rainfall at the hydrological event location. The mean lag times for the 12 events in the study were 165 and 41 min, respectively. [ABSTRACT FROM AUTHOR]

The origin of coastal and high-elevation marine gravels on the Hawaiian islands of Lanai and Molokai is controversial, because the vertical tectonics of these islands is poorly constrained. The gravels are either from eustatic highstands or were left by massive tsunamis from offshore giant landslides. In contrast, at Kohala on the island of Hawaii, where continuous subsidence is well estab- lished, lithofacies analysis and dating of a fossiliferous marine con- glomerate 1.5–61 m above present sea level support a tsunami or- igin and indicate a runup of >400 m >6 km inland. The conglomerate age, 110 ± 10 ka, suggests a tsunami caused by the ca. 120 ka giant Alika 2 landslide from nearby Manna Loa volcano. [ABSTRACT FROM AUTHOR]

Subsidence of Summer Lake basin, situated in the northwestern Basin and Range province in south-central Oregon, has exposed a kilometer-thick Neogene sequence of dense volcanic flow rocks overlying very weak tuffaceous sedimentary rocks in the bounding Winter Ridge—Slide Mountain escarpment. Subsidence occurs along the active, 40-km-long, Winter Ridge—Slide Mountain fault, which is capable of producing Mw ≈ 7 earthquakes with near-field, maximum horizontal acceleration approaching 1g. Gigantic landslides cubic kilometers in volume scallop the southwestern part of the escarpment, and the deposits run out several kilometers, characteristic of rock avalanches. Geotechnical rock-mass characterization and slope. stability analyses confirm observations that these landslides were initiated within the weak drupaceous sedimentary rocks along shallow, east-dipping, planar failure surfaces, are insensitive to groundwater fluctuations, and are stable under static conditions. Pseudostatic analyses reveal that strong shaking is required to trigger landsliding. The Bennett Flat landslide failed as a single event between 900–270 ka and 16.8 ka; the landslide has a depletion-zone volume of 1.1 km3, but only 0.3 km3 of debris is discernible in the accumulation zone. The Foster Creek landslide also appears to have failed as a single event between 180 and 16.8 ka; the landslide has a depletion-zone volume of 2.9 km3, but only 0.3 km3 of debris is discernible in the accumulation zone. The Punchbowl landslide evidences multipie events, the most recent of which failed in the Holocene and had a volume of 0.4 km3; 0.5 km3 of debris is found in the accumulation zone. [ABSTRACT FROM AUTHOR]

Large composite volcanoes can collapse into debris avalanches even if alteration is absent and an eruption is not in progress or imminent. At San Francisco Mountain, Arizona, a large valley that penetrates the core of the volcano is at the apex of a large fan of bouldery volcaniclastic deposits. A 1 15-m-thick layer sampled in a borehole that penetrates the fan is composed of dense and unaltered lithic clasts in proportions similar to the bulk composition of the andesitic volcano; pumiceous clasts are absent. Within this layer, a 20-m-thick deposit consists mostly of clasts from two dacite extrusions that predate the valley: a flank flow and an inferred summit dome. This dacite-rich deposit may be from a debris avalanche that originated by failure of the summit and northeast flank of the volcano in a repose interval during the last eruptive stage, which was about 0.43 to 0.22 Ma. Preconditions for slope failure include top loaded by massive lava flows and summit dome and cone inflated by intrusions. Only lower-flank and base extrusions followed the initial breach, which was enlarged by mass wasting, erosion, and glaciation. [ABSTRACT FROM AUTHOR]