This research provides a new way or “model” to assess the impact of storms on beaches. We show that more than one storm can impact a beach and, in fact, beaches respond to a condition called “storminess”—the cumulative effect of the sizes and timing of previous storms on beaches. Using this model along a portion of the Virginia, U.S.A. coast and a data set going back to the early 1900s revealed that an increase in storm impacts began around 1980, and the twenty-first century has experienced particularly stormy periods that changed the coast significantly.

It is frequently reported that permafrost underlies a quarter of the Northern Hemisphere. This estimate is based on the total area of all permafrost zones (continuous, discontinuous, sporadic, and isolated patches). Since these permafrost zones are not entirely underlain by permafrost, the proportion of permafrost underlying the Northern Hemisphere is substantially smaller. Permafrost thus underlies approximately 15% of the Northern Hemisphere, which is about three times the area of Greenland less than the commonly reported estimate. This commentary highlights possible reasons that caused this too large value to be frequently reported and provides permafrost area estimates for different parts of the globe.

This study presents the highest resolution repeat seafloor mapping surveys to date in a submarine canyon. Centimeter-scale seafloor surveys were conducted over an 18-month period at a location ∼50 km from the head of Monterey Canyon. Turbidity currents (rapid, down-slope density-driven flows of water) and internal tides (tidal currents that flow along the seabed) were recorded by a seafloor instrument node deployed in the study area. Turbidity currents drape sediment across the bedforms, infill troughs, and smooth out erosional features carved by internal tides. While the turbidity currents caused considerable migration of bedforms in the upper canyon, there was surprisingly no notable migration at the study site. The lack of migration may be related to the relatively coarse nature of the seafloor underlying the bedforms and suggests that the turbidity currents at the site lacked a dense near-bed layer characteristic of flows farther up-canyon. The internal tides carved centimeter-scale scours in the seabed, a scale that approaches that of features preserved in the rock record. This study, therefore, shows how new mapping technology may eventually bridge the scale gap between modern seafloor surveys and the ancient rock record.

We present a computer model to predict shoreline change due to waves, sea-level rise (SLR), and other local processes. We apply the model to the entire California coastline (approximately 1,760 km), much of which is not well monitored using traditional survey methods. Observations of historical shoreline position obtained from satellite images can be used in lieu of traditional shoreline survey data to estimate erosion/accretion trends as well as to calibrate and validate models. By 2100, the model estimates that 24%–75% of California's beaches may become completely eroded due to SLR scenarios of 1.0–3.0 m, respectively.

Glacial lake outburst floods (GLOFs) have the potential to cause severe damage to the downstream regions. GLOFs can be triggered by a host of geomorphic, climatic, and seismic factors, one of which can be mass wasting such as avalanches entering a lake, particularly in the Himalaya where surrounding slopes are steep and destabilizing. In the Western Himalaya, Gepang Gath Lake has grown over the years to become the largest lake in Himachal Pradesh. The lake has potential to grow more than double its size in the future. The existence of warming permafrost (frozen ground) in the surrounding steep slopes of the lake makes it susceptible to failure. Assessment of GLOF process chains including avalanche impact on the lake, frontal dam breaching, and downstream impact shows that the nearest settlement at Sissu is exposed to present and future GLOFs. We further evaluated mitigation options, including lake level lowering by 10 and 30 m, to evaluate the changes in the GLOF intensities downstream of the lake. It is seen that there is a significant reduction in the GLOF impact downstream when the lake levels are lowered, but the risk from very large events is not eliminated.

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.