Supraglacial Lac de Rochemelon was formed 50 years ago behind an ice dam and grew steadily until 2004. In October 2004, the volume of the lake reached 650 000 m³, bringing its surface within 0.2 m of the top of the ice dam. To eliminate the threat to towns located below in the event of an overflow, the lake was drained artificially in October 2004 and during the summer of 2005. Once the volume had been reduced to 250 000 m³ by siphoning, a channel was dug with explosives and the remaining water overflowed naturally. This offered a very good opportunity to investigate the breaching of an ice dam accompanied by thermal erosion of the drainage channel. Extensive field measurements were carried out during drainage. Analysis of the energy dissipated in the channel reveals that only half of the available energy was used for breach erosion. A numerical model was used to simulate the evolution of a number of variables during drainage and to study the sensitivity of discharge and ice erosion to different parameters, revealing a high sensitivity to water temperature. Model simulations indicate that natural drainage of this lake at the beginning of October 2004 would have led to a peak discharge of <6 m³ s⁻¹.

This article studies the effects of the soil data and exposure data of residential building inventories, as well as their spatial resolution, on seismic damage and loss estimates for a given earthquake scenario. Our aim is to investigate how beneficial it would be to acquire higher resolution inventories at the cost of additional effort and resources. Seismic damage computations are used to evaluate the relative influence of varying spatial resolution on a given damage model, where other parameters were held constant. We use soil characterization maps and building exposure inventories, provided at different scales from different sources: the European database, a national dataset at the municipality scale, and local field investigations. Soil characteristics are used to evaluate site effects and to assign amplification factors to the strong motion applied to the exposed areas. Exposure datasets are used to assign vulnerability indices to sets of buildings, from which a damage distribution is produced (based on the applied seismic intensity). The different spatial resolutions are benchmarked in a case-study area which is subject to moderate-to-average seismicity levels (Luchon valley in the Pyrénées, France). It was found that the proportion of heavily damaged buildings is underestimated when using the European soil map and the European building database, while the more refined databases (national/regional vs. local maps) result in similar estimates for moderate earthquake scenarios. Finally, we highlight the importance of pooling open access data from different sources, but caution the challenges of combining different datasets, especially depending on the type of application that is pursued (e.g., for risk mitigation or rapid response tools).

The SISFRANCE database aims to collect and interpret archives relating the historical seismicity in metropolitan France. The database presently contains some 12,500 documents that allow to define 108,832 macroseismic data points, for a total of 6427 events, of which 5743 can be qualified as real earthquakes. Although half of these events are and will probably remain poorly known, completing our knowledge of historical earthquakes remains a fundamental element for the definition of seismic hazard and the understanding of seismicity in France and low to moderate seismicity regions in general. The first aim of this paper is to explain the state of the art of the database and remind end users how the limits introduced by the necessary interpretation of archival data are translated into quality factors that should be carefully considered when using such data for seismotectonic and seismic hazard purposes. Originally built as part of the necessary datasets to define the seismic hazard for nuclear facilities, the SISFRANCE database is the result of 40 years of work within a consortium bringing together the French civil nuclear operator (EDF), the French geological survey (BRGM), and the French institute of nuclear safety (IRSN). SISFRANCE is also the heir to archival research carried out since the second half of the 19th century, thus constituting the richest collection of data related to historical seismicity in France. The second aim of this paper is to explain to end users the current state of archival research within the SISFRANCE consortium, present avenues for future research strategies, and list potential improvements of the database structure. Archival research within the SISFRANCE consortium, no longer carried out by a dedicated historian since 2018, is presently being pursued by engaging individual researchers or academics, focusing research on specific archives and regions, as well as by developing data-mining techniques to exploit the increasing wealth of accessible numerical archives. Given the new impetus of French governmental research agencies that encourage transdisciplinarity research, SISFRANCE is also pursuing the idea of further engaging the academic community of historians and seismologists, presently greatly underrepresented in the field of historical seismicity in spite of the importance of this data, fundamental for any seismotectonic and seismic hazard study in France.