High-magnitude Events Research Articles

Future precipitation increase from very high resolution ensemble downscaling of extreme atmospheric river storms in California.

Precipitation extremes will likely intensify under climate change. However, much uncertainty surrounds intensification of high-magnitude events that are often inadequately resolved by global climate models. In this analysis, we develop a framework involving targeted dynamical downscaling of historical and future extreme precipitation events produced by a large ensemble of a global climate model. This framework is applied to extreme "atmospheric river" storms in California. We find a substantial (10 to 40%) increase in total accumulated precipitation, with the largest relative increases in valleys and mountain lee-side areas. We also report even higher and more spatially uniform increases in hourly maximum precipitation intensity, which exceed Clausius-Clapeyron expectations. Up to 85% of this increase arises from thermodynamically driven increases in water vapor, with a smaller contribution by increased zonal wind strength. These findings imply substantial challenges for water and flood management in California, given future increases in intense atmospheric river-induced precipitation extremes.

The assessment of quantitative risk to road users from debris flow

BackgroundA methodology for the quantitative risk assessment (QRA) of the impact of debris flow in a road environment has been developed and applied to two sites that are typically subject to high frequency-low magnitude and low frequency-high magnitude events. The methodology considers the probability of an event of a typical size, and the conditional probabilities of a vehicle being affected, given an event, and of damage (fatality) occurring given that the vehicle is affected. Scenarios covering a vehicle being hit by a debris flow and of a vehicle hitting a debris flow are considered. The computed Personal Individual Risk (PIR) is used to calculate worst case fatality probabilities for commuters and logistics truck drivers. The overall risk to society is expressed both by the annual probability of fatality amongst all road users, the Potential Loss of Life (PLL), and using the F-N diagram and is used to demonstrate the effect of a programme of management and mitigation works on the societal risk at one of the sites. The authors believe that this is the first full, formal quantitative risk assessment for debris flow risk to road users.ResultsThe PIR for a single trip through the sites ranges between 1.147E-10 for the low frequency-high magnitude site and 1.583E-09 for the high frequency-low magnitude site. These figures increase to 1.248E-07 and 1.922E-06, respectively, when more frequent travellers are considered. The PLL for the two sites ranges between 2.616E-04 for the low frequency-high magnitude site and 4.083E-03 for the high frequency-low magnitude site. The F-N diagrams illustrate the Broadly Acceptable level of risk at the low frequency-high magnitude site and the partially Unacceptable level of risk at the high frequency-low magnitude site. The risk at the high frequency-low magnitude site is reduced to ALARP levels when management and mitigation measures extant as of October 2014 are considered.ConclusionsThe QRA proves an effective technique for understanding, comparing and articulating the differences in levels of risk and the temporal changes in risk at a given site as a result of landslide risk reduction activities.

GPS measurements on pre-, co- and post-seismic surface deformation at first multi-parametric geophysical observatory, Ghuttu in Garhwal Himalaya, India

Abstract We investigate the surface deformation pattern of GPS station at MPGO Ghuttu (GHUT) to find out the cause of anomalous behavior in the continuous GPS time series. Seven years (2007-2013) of GPS data has been analyzed using GAMIT/GLOBK software and generated the daily position time series. The horizontal translational motion at GHUT is 43.7 ± 1 mm/yr at an angle of 41°± 3° towards NE, while for the IGS station at LHAZ, the motion is 49.4 ±1 mm/yr at 18 ± 2.5° towards NEE. The estimated velocity at GHUT station with respect to IISC is 12 ± 1 mm/yr towards SW. Besides, we have also examined anomalous changes in the time series of GHUT before, after and during the occurrences of local earthquakes by considering the empirical strain radius; such that, a possible relationship between the strain radius and the occurrences of earthquakes have been explored. We considered seven local earthquakes on the basis of Dobrovolsky strain radius condition having magnitude from 4.5 to 5.7, which occurred from 2007 to 2011. Results show irrespective of the station strain radius, pre-seismic surface deformational anomalies are observed roughly 70 to 80 days before the occurrence of a Moderate or higher magnitude events. This has been observed for the cases of those events originated from the Uttarakashi and the Chamoli seismic zones in the Garhwal and Kumaun Himalaya. Occurrences of short (< 100 days) and long (two years) inter-seismic events in the Garhwal region plausibly regulating and diffusing the regional strain accumulation.

Is Precipitation the Main Trigger of Medium-Magnitude Floods in Large Alpine Catchments?

Flood projections are still highly uncertain, partly resulting from the limited accuracy of simulated precipitation by climate models. To overcome this limitation, recent studies suggest to use direct linkages between atmospheric processes leading precipitation, often better simulated than precipitation, and the flood occurrence. Such an approach implies, however, that historical flood events mainly result from direct contribution of precipitation only. Consequently, this paper has a twofold objective: (i) To explore to what extent the generation of medium-magnitude flood events in a large mountainous catchment can be explained by the precipitation only, and (ii) to identify what are the best features of flood-inducing precipitation episodes (i.e., duration and accumulation). Taking advantage of centennial-long discharge (gauge stations) and precipitation (ERA-20C reanalysis) data series, this study is based on three-year return period flood events of the upper Rhône River (NW European Alps). Our results suggest that half of the studied floods are triggered by precipitation only, but precipitation indices are mainly good only for high-magnitude events with return period of at least 20 years. Hence, modelling flood occurrence directly from atmospheric processes leading precipitation seems to be possible for events with the highest magnitude (i.e., the ones with the highest potential to impact societies).

Lake sediment evidence of paleoseismicity: Timing and spatial occurrence of late- and postglacial earthquakes in Finland

Sediment profiles in six lake basins located near the late- and postglacial fault surface ruptures in northern Finland were investigated for turbidites and soft-sediment deformation structures that could reveal information on the timing and spatial occurrence of paleoearthquakes in the area. We used geophysical sub-bottom profiling and lithological logging of sediment cores combined with radiocarbon and paleomagnetic dating. In three lakes, Immeljärvi, Aakenus and Laukkujärvi, sediment records provided evidence of postglacial earthquakes or landslides, whereas in three others (lakes Pyhäjärvi, Kallojärvi and Syväjärvi) no disturbance structures were observed in their sequences that cover roughly the Holocene period. Combined with previous data on paleoseismicity in Finland, the results enhance the non-stationary hypothesis of seismicity throughout the Late Weichselian and the Holocene with three general maxima that cluster around the deglaciation (12.0–10.0 kyr BP), the mid-Holocene (5.0–7.0 kyr BP) and the Late Holocene (1.5–3.0 kyr BP). A strong asymmetry of the offset profiles of the Finnish postglacial fault complexes indicate that the general rupture propagation was from SW to NE. The present data also indicates that the oldest and highest magnitude events (MW ≈ 7 or higher) generally took place in the SW sector of the Finnish PGF complexes during or soon after the retreat of the continental ice sheet. The ruptures then propagated towards the NE sector of PGF complexes in a cascading fashion and were generally characterized by lower magnitude events (MW ≈ 6) during the Holocene.

A New Method to Assess Coal Burst Risks Using Dynamic and Static Loading Analysis

Mining-induced seismicity is one of the dynamic energy sources that can trigger coal burst. This paper presents a new methodology to assess coal burst risks under different loading conditions by examining seismic energy attenuation and fracture size. Two new indices are proposed: (1) Dynamic Load Index (DLI) quantifies the magnitude of dynamic loading induced by seismic events, based on the relationships between the seismic energy, peak particle velocity and dynamic stress; (2) dynamic–static loading assessment index, $$I_{\text{PD}}$$, links the DLI with passive velocity tomography (PVT) to assess the coal burst risks in a longwall panel under dynamic and static loading. A total of 3080 seismic records were examined to validate $$I_{\text{PD}}$$ in a typical burst-prone longwall panel in China. Based on the rate of occurrence of high-magnitude seismic events, $$I_{\text{PD}}$$ thresholds were determined to identify low-, medium- and high-risk coal burst zones. Using this new zoning approach, coal burst risks were assessed in the same longwall panel while mining through a fault structure. The proposed risk classes correlated well with the recorded high-magnitude seismic events with energies over 10 kJ. The analysis indicated that 69% of the high-magnitude events occurred in the high-risk zones, where $$I_{\text{PD}}$$ was between 0.35 and 1; and 31% of the events occurred in the medium-risk zones, where $$I_{\text{PD}}$$ was between 0.2 and 0.35.

Convergent human and climate forcing of late-Holocene flooding in Northwest England

Concern is growing that climate change may amplify global flood risk but short hydrological data series hamper hazard assessment. Lake sediment reconstructions are capturing a fuller picture of rare, high-magnitude events but the UK has produced few lake palaeoflood records. We report the longest lake-derived flood reconstruction for the UK to date, a 1500-year record from Brotherswater, northwest England. Its catchment is well-suited physiographically to palaeoflood research, but its homogeneous, dark brown sediment matrix precludes visual identification of flood layers. Instead, an outlier detection routine applied to high-resolution particle size measurements showed a >90% match, in stratigraphic sequence, to measured high river flows. Our late-Holocene palaeoflood reconstruction reveals nine multi-decadal periods of more frequent flooding (510–630 CE, 890–960, 990–1080, 1470–1560, 1590–1620, 1650–1710, 1740–1770, 1830–1890 and 1920–2012), and these show a significant association with negative winter North Atlantic Oscillation (wNAO) phasing and some synchrony with solar minima. These flood-rich episodes also overlap with local and regional land-use intensification, which we propose has amplified the flood signal by creating a more efficient catchment sediment conveyor and more rapid hillslope-channel hydrological connectivity. Disentangling anthropogenic and climatic drivers is a challenge but anthropogenic landscape transformation should evidently not be underestimated in palaeoflood reconstructions. Our paper also demonstrates that flood histories can be extracted from the numerous lakes worldwide containing organic-rich, visually homogeneous sediments. This transformative evidence base should lead to more reliable assessments of flood frequency and risks to ecosystems and infrastructure.

Application of statistical techniques to proportional loss data: Evaluating the predictive accuracy of physical vulnerability to hazardous hydro-meteorological events.

Knowledge about the cause of differential structural damages following the occurrence of hazardous hydro-meteorological events can inform more effective risk management and spatial planning solutions. While studies have been previously conducted to describe relationships between physical vulnerability and features about building properties, the immediate environment and event intensity proxies, several key challenges remain. In particular, observations, especially those associated with high magnitude events, and studies designed to evaluate a comprehensive range of predictive features are both limited. To build upon previous developments, we described a workflow to support the continued development and assessment of empirical, multivariate physical vulnerability functions based on predictive accuracy. Within this workflow, we evaluated several statistical approaches, namely generalized linear models and their more complex alternatives. A series of models were built 1) to explicitly consider the effects of dimension reduction, 2) to evaluate the inclusion of interaction effects between and among predictors, 3) to evaluate an ensemble prediction method for applications where data observations are sparse, 4) to describe how model results can inform about the relative importance of predictors to explain variance in expected damages and 5) to assess the predictive accuracy of the models based on prescribed metrics. The utility of the workflow was demonstrated on data with characteristics of what is commonly acquired in ex-post field assessments. The workflow and recommendations from this study aim to provide guidance to researchers and practitioners in the natural hazards community.

Tree-ring reconstruction of snow avalanche activity: Does avalanche path selection matter?

In the current context of anthropogenic global warming, one of the purposes of dendrogeomorphic analyses is to provide long and continuous chronologies of mass movements, so as to detect potential trends or shift related to increasing temperatures. However, on documented slopes, the comparison between historical archives and tree-ring records suggests that dendrogeomorphic reconstructions systematically underestimate the natural activity of the process under investigation. In the specific case of snow avalanches, underestimation generally amounts to 50% and the main causes generally given for this difference are related to the magnitude of past events. In this study, we hypothesize that the morphometric characteristics of avalanche paths and their forest cover could have significant impacts on the length and reliability of tree-ring reconstructions. In order to test this hypothesis, we selected four adjacent, albeit differently structured, avalanche paths from the Queyras massif (French Alps), with the aim to compare their potential for a continuous reconstruction of past avalanche activity. On the most active avalanche paths characterized by high-altitude release areas (covered only by shrubby vegetation), tree-ring reconstructions do not exceed one century in length, with recurrence intervals of high magnitude events >25 years. By contrast, on forested couloirs where lower slopes and forest coverage up to the release areas limits the intensity of events, the frequency of reconstructed snow avalanches is 2.5 times higher, the reconstructions span longer periods and the convergence rate with historical archives attest to the reliability of the dendrogeomorphic approach. These results suggest that a careful selection of couloirs is essential and that priority should be given to forested sites as (i) they allow for exhaustive and (ii) reliable reconstructions over (iii) long periods of time.

Using reservoir deposits to reconstruct the impact of recent changes in land management on sediment yield and sediment sources for a small catchment in the Black Soil region of Northeast China

Sediment deposits in lakes and reservoirs can provide a basis for reconstructing the erosional response of the upstream catchment. Recent studies undertaken in the Loess Region of China have successfully used the flood couplets contained in the sediment deposits behind check dams to reconstruct records of annual sediment yield and document the impact of changes in land management. However, flood couplets are rarely found in other areas of the world and there is a need to develop alternative approaches to establish the chronology for sediment deposits. Lead-210 dating techniques offer such potential, by making it possible to establish the age of the individual sections of a core. This contribution reports a study of the sediment deposits accumulated in a reservoir at the outlet of a small 3.46 km2 catchment in the Black Soil region of Northeast China. This region suffered serious soil erosion during the last century and this resulted in changes in land management aimed at reducing erosion rates. The sediment deposits in the reservoir covered the period 1974–2004, when such changes occurred. The study was designed to explore the potential for using excess lead-210 to establish the chronology for the reconstruction and for extending the scope of such studies by using sediment source fingerprinting techniques to include complementary information on changes in sediment source. The study successfully reconstructed the record of annual sedimentation depth, a surrogate for sediment yield. This showed that the annual sediment yield from the catchment decreased by about 60% as a result of improved land management introduced in the late 1970s and early 1980s. Sediment source fingerprinting techniques were also successfully used to identify three primary sources, namely topsoil (interrill and rill) erosion from cultivated and uncultivated areas and gully erosion and apportion their contributions to the annual sediment yields. The findings indicated that interrill and rill erosion and gully erosion were both important sediment sources throughout the period covered, contributing 47.9% and 42.0% of the sediment, respectively, that gully erosion increased in importance during years with high magnitude events, and that there was a general trend for rill and interrill erosion to decrease and for gully erosion to increase over the period 1974–2004. The study is seen as demonstrating the potential for using lead-210 measurements in combination with sediment source fingerprinting techniques to reconstruct the impact of changes in land use and land management on erosion processes and sediment yields.

Characterising resilience in the wine industry: Insights and evidence from Marlborough, New Zealand

This paper examines resilience through a case study of New Zealand’s largest wine region following a damaging earthquake in late-2016. Resilience assessment for the wine industry to date has largely focused on characterising risks and responses as a function of organisational and business management practices. Less in known about socio-ecological characteristics of resilience and how these shape and influence response capabilities and capacity to low-frequency, high-magnitude events within the broader context of other risks. The research employs a resilience-based framework to identify and assess relevant properties incorporating a whole-of-value-chain perspective. The participatory approach includes semi-structured interviews with stakeholders, including wine business managers, wine researchers, industry bodies and others involved in the production and distribution of wine; document analysis (media and emergency response reports), and insurance assessments. Results show the earthquake had direct impacts on infrastructure, with indirect impacts and implications in particular for transportation and logistics, affecting the industry’s ability to mitigate losses. Resilience varies across the region and the industry, in part as a function of size, scale, and ownership structure of the operation, which in turn influences future levels of preparedness. Resilience analysis provides conceptual and methodological tools for assessing the capacity of socio-ecological systems to recover from shocks and stresses. The framework developed here provides a useful conceptual and theoretical basis for further assessments and can inform the design of resilience indices to monitor organisations’ capacity to absorb shocks and prepare for future uncertainty. This type of analysis can help identify system-critical vulnerabilities and sensitivities and inform the development of strategies to develop specified and general resilience in the face of multiple stressors.

Can we distinguish meteorological conditions associated with rockfall activity using dendrochronological analysis? - An example from the Tatra Mountains (Southern Poland)

Rockfall leads to visible changes in mountain areas and as high-magnitude event has geohazard potential and should be monitored. On forested slopes, active rockfall could be identified with high precision from visible anatomical changes in tree-rings. To discern possible rockfall events in the Tatra Mountains, dendrogeomorphologic methods were applied and correlated with meteorological conditions. Field research was carried out on Norway Spruce (Picea abies L. Karst) in the Kościeliska Valley. Rockfall signals (RSs) were obtained from both qualitative (scars and traumatic resin ducts) data and quantitative (growth release and suppression) data. Multiple regression and ANOVA analysis were employed to recognize the meteorological conditions, which cause rockfall activity. Different periods of rockfall activity were observed during the years 1950–2014. The weakest activity was observed during 1950–1970 while after 1970 a continuous increase in rockfall activity was observed in our study. There was a clear peak in the number of RSs recorded per year in 1985. Cumulative precipitation and temperatures for January, March, May, June, July, August, September and October are statistically significant as the periods of the year in which rockfall is activated in the Tatra Mountains. In terms of activity, three different Levels of Rockfall Activity (LoRAs) were recognized and show significant correlation with the meteorological data. Distinguished meteorological control factors determining rockfall explains 53% of the total parameters determining rockfall activity. The complexity of the rockfall process means that a better understanding of local conditions and the possible uncertainties associated with the dendrogeomorphologic method and the quality of the meteorological data is needed.

Downstream fining in a megaclast-dominated fluvial system: The Sabeto River of western Viti Levu, Fiji

Megaclast-dominated fluvial systems have been largely ignored by researchers. Yet megaclasts exert an important control on channel geomorphology, flow behaviour and sediment transport, and such systems are probably far more common than this neglect would suggest. Despite the explicit identification of megaclasts as the products of cataclysmic flow, observation of modern fluvial systems confirms that megaclasts can be entrained by flows that lie within the normal flow regime.The pattern of fining along the megaclast-dominated Sabeto River of western Viti Levu, Fiji reveals a strong negative exponential relationship between particle size and distance downstream, and a rate of downstream fining comparable with that of other gravel-bed rivers. The downstream fining pattern is straightforward and step-like discontinuities in the fining gradient are absent. This is suggestive of a sedimentary system only minimally disrupted by the supply of sediment from tributaries or the reworking of material from sources such as hillslopes and alluvial terraces. There is evidence, however, of anomalously coarse sub-populations at two sites. These coarser components must pre-date the other deposits at the sites. We speculate that they represent the products of earlier and higher-magnitude events. The bed sediments may thus be composite features, made up of individual components each transported by a specific event of particular magnitude.Our work confirms the relationship between the rate of downstream fining and particle size. This may arise because the distance over which individual particles are transported is likely to be size dependent. It is also possible that abrasion may be more effective in the case of larger particles than smaller ones, with the result that the coarser fraction of the river's bed sediment fines downstream more rapidly than the finer fraction.There is a long-standing debate about the relative roles of abrasion and sorting in downstream fining. Our data reveal little evidence for a downstream increase in the roundness of the river's gravels, implying that abrasion is likely to play a minor role in the fining process in this system.

Fluvial response to changes in the magnitude and frequency of sediment supply in a 1-D model

Abstract. In steep headwater reaches, episodic mass movements can deliver large volumes of sediment to fluvial channels. If these inputs of sediment occur with a high frequency and magnitude, the capacity of the stream to rework the supplied material can be exceeded for a significant amount of time. To study the equilibrium conditions in a channel following different episodic sediment supply regimes (defined by grain size distribution, frequency, and magnitude of events), we simulate sediment transport through an idealized reach with our numerical 1-D model “BESMo” (Bedload Scenario Model). The model performs well in replicating flume experiments of a similar scope (where sediment was fed constantly, in one, two, or four pulses) and allowed the exploration of alternative event sequences. We show that in these experiments, the order of events is not important in the long term, as the channel quickly recovers even from high magnitude events. In longer equilibrium simulations, we imposed different supply regimes on a channel, which after some time leads to an adjustment of slope, grain size, and sediment transport that is in equilibrium with the respective forcing conditions. We observe two modes of channel adjustment to episodic sediment supply. (1) High-frequency supply regimes lead to equilibrium slopes and armouring ratios that are like conditions in constant-feed simulations. In these cases, the period between pulses is shorter than a “fluvial evacuation time”, which we approximate as the time it takes to export a pulse of sediment under average transport conditions. (2) In low-frequency regimes the pulse period (i.e., recurrence interval) exceeds the “fluvial evacuation time”, leading to higher armouring ratios due to the longer exposure of the bed surface to flow. If the grain size distribution of the bed is fine and armouring weak, the model predicts a decrease in the average channel slope. The ratio between the “fluvial evacuation time” and the pulse period constitutes a threshold that can help to quantify how a system responds to episodic disturbances.

The effects of flood history on sediment transport in gravel-bed rivers

The transport of coarse sediment during floods often exhibits hysteresis patterns from changes in flow fields, channel geometry, bedforms, or sediment supply conditions. Flume experiments that simulate hydrographs tend to confirm that hysteresis is a consequence of the progressive organization of surface sediments in terms of grain protrusion, imbrication, orientation, and roughness. Hysteretic patterns are also highly dependent on the kind of sediment supply conditions, and the type of simulated hydrograph. A factor that has not been investigated extensively is the effect of the timing and sequencing of floods on bedload transport. Depending on its magnitude and duration, each flood leaves the channel bed in a different condition, which influences the bedload transport of the next event, representing the river bed's memory of past floods, which can determine future responses to natural disturbances. In this study, I investigated the effects of different sequences of events, i.e., the flood history, on sediment transport through a series of flume experiments that simulated three types of stepped and symmetrical hydrographs (ranging from short-duration/high-magnitude to long-duration/low-magnitude events) under sediment recirculation conditions. Hydrographs were simulated as a sequence of the same event, and with events in different sequences, in order to explore the effects of different antecedent conditions on sediment transport. The results show that a previous event decreases the rates of sediment transported by a certain hydrograph by around 40% if a high-magnitude event precedes another one and around 70% if a low-magnitude event precedes another event of similar magnitude. A low-magnitude event does not affect the rate of sediment transported by a subsequent high-magnitude flood, but a high-magnitude event reduces the sediment transported by a subsequent long-duration/low-magnitude event.

Extreme flooding decreases stream consumer autochthony by increasing detrital resource availability

Abstract Extreme disturbances, those high magnitude events that are statistically rare in a particular system, may affect consumer resource use through multiple mechanisms, such as differential consumer mortality and modified resource availability and quality. Documenting the ecological importance of these rare events is difficult, but essential, as the frequency of extreme events is predicted to increase under many climate change scenarios. We quantified changes in stream insect resource use following intense, nonseasonal flooding in the Rocky Mountains of northern Colorado during September 2013. We hypothesised that taxonomic identity, functional feeding group membership and disturbance‐caused alterations in resource quantity and quality (C:N ratios) would determine consumer reliance on autochthonous and allochthonous resources and community structure following the disturbance. In summer 2014, we collected basal resources and stream insects for carbon, nitrogen and deuterium bulk stable isotope analysis, and community composition. Basal resource quantity and quality (C:N ratios) were collected at seven headwater streams along a 2013 flood intensity gradient. Using stable isotope mixing models, we analysed consumer autochthony. We also used baseline community composition data from 2011 to compare functional feeding group abundance prior to and following the flood events. We found that consumer resource use was primarily associated with detrital resource quantity, which was positively correlated with disturbance intensity and elevation. Functional feeding group membership did not predict resource use. However, consumers in functional feeding groups did experience differential mortality following flooding. Herbivore relative abundance significantly declined along the disturbance gradient, and predator relative abundance generally declined across all streams from 2011 to 2014. Our results suggest that changes in resource quantity from extreme disturbances can be associated with shifts in consumer resource use. Following this flood event, detritus standing stocks increased, resulting in a concomitant increase in consumer reliance on allochthonous sources.

Upgrading of an index-oriented methodology for consequence analysis of natural hazards: application to the Upper Guil catchment (southern French Alps)

Abstract. Vulnerability is a complex concept involving a variety of disciplines from both the physical and socio-economic sciences. Currently, two opposite trends exist: the physical approach in which vulnerability is analysed as a sum of potential impacts on elements at risk and the social approach in which vulnerability is mostly viewed as a combination of socio-economic variables determining people's ability to anticipate, cope with and recover from a catastrophic event. Finding a way to combine these two approaches is a key issue for a global vulnerability assessment. In this paper we propose to combine elements from these two approaches through the analysis of the potential consequences of a high-magnitude flood event (recurrence interval (RI) > 100 years) on human and material stakeholders. To perform our analysis, we choose to upgrade an existing index, the Potential Damage Index (PDI; Puissant et al., 2013), by including social criteria. The PDI was originally developed to assess the physical consequences of hazards on the elements at risk (people, building and lands). It is based on the calculation of three sub-indices representing different types of direct and indirect consequences: physical injury consequences (PIC), structural and functional consequences (SFC), indirect functional consequences (IC). Here, we propose to add a fourth sub-index representing the social consequences. This new sub-index, called social consequences (SC) is obtained by combining criteria derived from INSEE French census data and a risk-perception survey conducted in the field. By combining the four indices (PIC, SFC, IC and SC), we managed to create a new index called the Potential Consequences Index (PCI). The new PCI was tested on the Upper Guil catchment to assess the consequences of a high-magnitude flood event (RI > 100 years). Results of the PDI were compared with the PCI and show significant differences. The upgrade to the PDI method provided us with many inputs. The introduction of elements from social vulnerability added an extra dimension to the total consequence map. It allowed us to qualify the potential physical consequences (physical injury, structural and functional consequences) on elements at risk by considering the global resilience of local communities.

New insights on coral mound development from groundtruthed high-resolution ROV-mounted multibeam imaging

Currents play a vital role in sustaining and developing deep water benthic habitats by mobilising food and nutrients to otherwise relatively barren parts of the seabed. Where sediment supply is significant, it can have a major influence on the development and morphology of these habitats. This study examines a segment of the Belgica Mound Province, NE Atlantic to better constrain the processes affecting a small-sized cold water coral (CWC) mound habitat and conversely, the hydrodynamic influence of CWC mounds on their own morphological development and surroundings. Here, we utilise ROV-mounted multibeam, ROV-video data, and sediment samples to investigate current processes, mound morphology, density and development. Detailed mapping shows that the area may have the highest density of coral mounds recorded so far, with three distinct mound types defined based on size, morphology and the presence and degree of distinct scour features. A residual current of 36–40 cm s−1 is estimated while large scour features suggest low-frequency, high-magnitude events. These 3 mound types are i) smaller mounds with no scour; ii) mounds with scour in one to two distinct directions and; iii) larger mounds with mound encircling scour. The differing mound types likely had a staggered initiation where younger mounds preferentially developed near clusters of pre-existing mounds. Given the high density of these small CWC mounds, we support the hypothesis that over time, this clustering may eventually lead to these mounds coalescing into larger coral mound features.

Crustal thermal structure of the Farafra oasis, Egypt, based on airborne potential field data

The Farafra oasis is one of the most interesting and promising areas for geothermal energy development in Egypt. The objective of the present study is to evaluate the geothermal potential in the Farafra oasis and its suitability for geothermal development in the Western Desert using different tools such as remote sensing, seismic events, and aeromagnetic and aerogravity data. Remote sensing (Landsat 8 ETM+) was utilized to estimate the land surface temperature (LST) in the Farafra oasis. The resultant map of LSTs indicates that the surface temperature of the Farafra area ranges from 10 °C to 30 °C and that the mean surface temperature of the whole area is approximately 26 °C. Most earthquake events are located to the east and northeast of the Farafra oasis (toward the Bahariya Oasis). However, the highest magnitude event (4.62) is located near the eastern border of the Farafra oasis. One event with a magnitude of 3.08 is located to the south and within the Farafra outline. The distributions of low-magnitude earthquake events can provide information about the locations of active faults, which indicate possible fracture permeability. The interpretation of aeromagnetic data indicates that the Curie point depth (CPD) ranges from 16 km to 26 km with an average of 22 km. The CPDs increase toward the center and north of the Farafra oasis and decrease westward. The interpretation of aerogravity data shows maximum anomalies above four main localities: Ain-Dalla, Bir-Sitta, northeast of Bir-Sitta and at the southern margin of the Farafra oasis, which indicates the existence of vertical or near-vertical contacts (faults) in these areas and provides a good correlation with structural lines on the geological map. Linear features striking NE-SW are pronounced on the tilt gradient map.

Characteristics of large wood in a headwater channel after an extraordinary event: The roles of transport agents and check dams

High-magnitude hydrogeomorphic events in steep streams (e.g., debris flows and debris floods) are capable of transporting considerable quantities of bed material, including large wood, although wood pieces that are longer than the channel width are often perceived as relatively stable elements in narrow headwater channels. We investigated present large wood distribution along 1.7 km of a steep headwater channel (the Klepáčský Stream; Eastern Sudetes; NE Czech Republic) surrounded by managed forests and engineered by twelve check dams (presently at various stages of destruction). The total wood volume was measured at 123.0 m3, including wood deposited on adjacent terraces by a high-magnitude hydrogeomorphic event in 2010 representing a ca. 20–30 year recurrence interval. Approximately a half of the total wood volume (58%) was stored in large jams (≥10 large wood pieces) that originated during that event. We observed reach controls (based on transport agents and valley morphology) and local controls (represented by individual check dams) of LW depositional patterns. The uppermost debris flow-affected reach produced high volumes of mobilised wood, including many pieces that were two-to-three times longer than the local active channel width; significantly shorter and thinner pieces were found within large jams in downstream reaches void of debris-flow processes. We also documented that this high-magnitude event was responsible for the notable out-of-channel storage of large wood, which decreases the volume of wood that might be transported by a future event. In addition, 30.5 m3 of large wood, that is ~one-quarter of the total volume measured along the stream, was deposited in relation to twelve damaged check dams despite their lowered trapping efficiency.