Severe wind events in southern California create extreme fire hazards. Sundowner winds are local downslope winds in the Santa Ynez Mountains near Santa Barbara that often coincide with damaging fires. Here we produce a climatology of Sundowner winds and compare their seasonal occurrence and large-scale atmospheric patterns to the well-studied Santa Ana wind regime. We find that Sundowner winds are distinctly different from Santa Ana winds in terms of peak seasonality and synoptic structure. Hide

This study assesses the applicability of the RPAS-based photogrammetric approach for a high-definition geomorphometry of hummocks, i.e., characteristic morphological features in the surface of debris avalanche deposits caused by a gigantic sector collapse of a volcanic mountain body. Satellite-based topographic data were also utilized to estimate the source volume of the sector collapse. We provide new, detailed insights into the characteristics of the debris avalanche and potential hazards. Hide

In this study we simulate groundwater levels with a semi-distributed karst model. Using a percentile approach we can assess the number of days exceeding or falling below selected groundwater level percentiles. We show that our approach is able to predict groundwater levels across all considered timescales up to the 75th percentile. We then use our approach to assess future changes in groundwater dynamics and show that projected climate changes may lead to generally lower groundwater levels. Hide

This study investigates compound flooding in an estuary by quantifying horizontal (flood extent) and vertical differences (inundation depth) in flood risk estimates resulting from a separation of storm surge and river flooding. Results demonstrated large underestimation of flood risk when river discharge was excluded. We recommend considering storm surge and river flooding processes jointly in estuaries with large catchment areas which are known to have a quick response time to extreme rainfall. Hide

The thunderstorm activity in the Congo Basin is known as the highest in the world. This paper compares the lightning flash count in two 5° × 5° areas from this region. One area in eastern Democratic Republic of Congo experiences a sharp maximum of the lightning flash density whatever the year and at any period of the year, and a very pronounced daily cycle. However, the area in the centre of the Congo Basin exhibits a lightning flash activity much more variable in location and time. Hide

Major drought in East Africa at the end of 2016 caused severe famine and loss of life. We pose the following question: are increasing levels of atmospheric greenhouse gas concentrations, due to human activity, making droughts such as this more likely? Computer models of the climate system are powerful tools to answer this. Scanning across a full set of these, we find that how future climate change will impact on East Africa ASO drought risk remains uncertain, in any particular year. Hide

We perform a hazard sensitivity study for two sites in Israel, exploring effects of uncertainty on the calculated seismic hazard. We account for uncertainty in the earthquake source properties, such as their geometric representation and seismic activity. We also account for uncertainty in the wave propagation path, by using alternative models to describe the ground motion calculations. We conclude that the current practice in Israel should be updated as it is probably underestimating the hazard. Hide

We present a procedure that allows the operational generation of daily forecasts of fire danger over Mediterranean Europe. The procedure combines historical information about radiative energy released by fire events with daily meteorological forecasts. Results obtained show that about 72 % of severe events releasing daily energy above 10 000 GJ belong to the extreme class of fire danger. The procedure is expected to assist in wildfire management and in decision making on prescribed burning. Hide

The Vienna Basin is a low seismicity area, where historical data do not identify all potential earthquake sources. Despite observed Quaternary offset, there are no earthquakes along the Markgrafneusiedl Fault (MF). Results from 3 palaeoseismic trenches show evidence for 5–6 earthquakes with magnitudes up to M = 6.8 during the last 120 kyr. Therefore the MF should be considered as a seismic source, together with similar faults in the Vienna Basin, increasing the seismic potential close to Vienna. Hide

Only two months after a huge forest fire occurred in the upper part of a valley located in central Portugal, several debris flows were triggered by intense rainfall. This research aims to simulate the debris flow run-out for the entire basin, using a dynamic model. Three scenarios were developed and the results were confronted with the existing buildings exposed in the study area. The worst-case scenario showed a potential inundation that may affect 345 buildings. Hide

In this article we analyzed spatial and temporal patterns of fatal Austrian avalanche accidents caused by backcountry and off-piste skiers and snowboarders within the winter periods 1967/1968–2015/2016. As a result of the trend analysis, we noticed an increasing trend of backcountry and off-piste avalanche fatalities within the winter periods 1967/1968–2015/2016. As a result of the spatial analysis, we noticed two hot spots of avalanche fatalities (Arlberg–Silvretta and Sölden). Hide

The present study demonstrates the application of drones and terrestrial laser scanner in stability assessment of steep, hardly accessible rock slopes that can endanger human lives. These technologies can be deployed very quickly, but data processing requires time. For reliable hazard evaluation, besides these techniques, engineering geological field work, laboratory tests of the mechanical properties of rocks and computer simulations are also necessary. Hide

Recently, landslides affecting pyroclastic covers of Campania Region caused many deaths and huge costs. The development of early warning systems represents a key issue for the area. However, the features of such soils make the development of reliable predictive tools challenging. The relevance of accounting for evaporative losses in slope hydrological balance regulating safety conditions is here discussed. To that end, the 2005 landslide in Nocera Inferiore is used as test case. Hide

We investigate the influence of imprecise identification of triggering instants on landslide early warning thresholds by perturbing an error-free synthetic dataset. Combined impacts of uncertainty with respect to temporal discretization of data and criteria for singling out rainfall events are assessed as well. Results show that thresholds can be significantly affected by these uncertainty sources. Hide

Mountain rivers can mobilize important amounts of sediment that endanger downstream dwellers and infrastructure during floods. Sediment traps are built immediately upstream of urban areas to retain hazardous sediment. However, many sediment traps retain too much sediment, which is then missing in downstream river sections, leading to a poor eco-morphological state. This study proposes an experimental research-based solution to improve sediment traps using a guiding channel. Hide

Tropical cyclones and sea level rise cause major problems including damage to infrastructure in coastal areas. A green infrastructure for coastal protection will be needed by small island nations. A maintaining reef growth in the future is effective in reducing the risk of coastal damage arising from wave action. The use of coral reefs for disaster risk reduction is a cost-effective approach and includes other benefits derived from the various ecological services provided by living reefs. Hide

The multivariate evaluation method was applied to establish a landslide susceptibility assessment model along mountains roads. The relationships between the rainfall index, instability index, and landslide occurrence indicate that for a high instability index, even a small rainfall event could trigger a landslide. The instability index thus can effectively reflect landslide susceptibility. The results could serve as a reference for the prevention and mitigation of slope disasters on hillsides. Hide