On the evaluation of debris flows dynamics by means of mathematical models

International audienceThe prediction of debris flow dynamic characteristics in a debris flow prone torrent is generally made through the investigation of past events. This investigation can be carried out through a survey of the marks left by past debris flows along the channel and through a detailed analysis of the type and shape of the deposits found on the debris fan. The rheological behaviour of future debris flows can then be inferred from the results of these surveys and their dynamic characteristics can be estimated applying well known formulas proposed in literature. These latter will make use of the assumptions on the rheological behaviour previously made. This type of estimation has been performed for a debris flow occurred in an instrumented basin, on the North-Eastern Italian Alps, in 1996 and the results have been compared to those obtained by means of a mathematical simulation. For the calibration of the mathematical model the limnographs recorded by three different ultrasonic gauges installed along a torrent reach on the fan were used. The comparison evidenced the importance of time data recordings for a correct prediction of the debris flows dynamics. Without the availability of data recordings, the application of formulas based only on assumptions derived from field analysis could be misleading

Analysis of different water-sediment flow processes in a mountain torrent

International audienceSediment ? water flows occurring in mountain torrents may show a variety of regimes, ranging from water flows with transport of individual particles to massive transport of debris, as it occurs in case of debris flows. Sometimes it is possible, by means of accurate field investigations, to identify the kind of processes that took place in a torrent after the occurrence of an event. However this procedure cannot give indications regarding the development of the process in time. In fact, because of the frequent presence of different surges within the same event, the rheological characteristics of an event can be detected only when some recorded hydrographs or videos are available. For the same reason, since the rheological behaviour of the flow changes according to the solid concentration, the analysis of the materials deposited on the debris fan cannot directly give any information on the particular types of flow that took place: a possible alternation in time of different water sediment surges with different concentrations may have occurred, during the same event. The installation of ultrasonic gauges or videocameras along the torrent might give more information on this issue. To this regard, the analysis of a flow event which occurred in 2002 in the Moscardo torrent watershed, instrumented for debris flow monitoring, has been undertaken, studying the hydrographs recorded at two different ultrasonic gauges placed at a known distance along the torrent. An empirical flow resistance law has been applied analysing the values assumed by its parameters after calibration. The application of this law actually spans from debris flow and immature debris flow to bed load transport. Only field observations and surveys, together with ultrasonic data, may allow to clearly discriminate which type of flow really occurred. The analysis confirms that different water sediment surges alternated in time while the mathematical simulation of the flow compared with field observations revealed that the dynamic behaviour of the flow was different from that of previous debris flow events and might reflect, among the different types of possible rheological behaviors, a dilatant-type behavior typical of stony debris flows

Influence of rheology on debris-flow simulation

Systems of partial differential equations that include the momentum and the mass conservation equations are commonly used for the simulation of debris flow initiation, propagation and deposition both in field and in laboratory research. The numerical solution of the partial differential equations can be very complicated and consequently many approximations that neglect some of their terms have been proposed in literature. Many numerical methods have been also developed to solve the equations. However we show in this paper that the choice of a reliable rheological model can be more important than the choice of the best approximation or the best numerical method to employ. A simulation of a debris flow event that occurred in 2004 in an experimental basin on the Italian Alps has been carried out to investigate this issue. The simulated results have been compared with the hydrographs recorded during the event. The rheological parameters that have been obtained through the calibration of the mathematical model have been also compared with the rheological parameters obtained through the calibration of previous events, occurred in the same basin. The simulation results show that the influence of the inertial terms of the Saint-Venant equation is much more negligible than the influence of the rheological parameters and the geometry. A methodology to quantify this influence has been proposed

Preface Results of the open session on "Documentation and monitoring of landslides and debris flows" for mathematical modelling and design of mitigation measures, held at the EGU General Assembly 2009

The papers that are here presented and summarised represent the recent scientific contributions of some authors coming from different countries and working in the fields of monitoring, modelling, mapping and design of mitigation measures against mass movements. The authors had the opportunity to present their recent advancements, discuss each other needs and set forth future research requirements during the 2009 EGU General Assembly, so that their scientific contributions can be considered the result of the debates and exchanges that were set among scientists and researchers, either personally or during the review phase since that date. In this resume, the scientific papers of the special issue are divided according to different thematic areas and summarised. The most innovative scientific approaches proposed in the special issue, regarding the monitoring methodologies, simulation techniques and laboratory equipment are described and summarised. The obtained results are very promising to keep on future research at a very satisfactory level

On the application of kinematic models to simulate the diffusive processes of debris flows

Debris flows generally propagate along steep mountain torrents with dynamics primarily governed by gravitational and frictional forces. Thus, debris flows modelling can be successfully performed through the application of kinematic models, which consider only the effects of slope and friction and neglect the remaining terms of the momentum equation. However, the diffusion processes that can be observed in the field, such as the spreading of the debris flow wave as it flows downstream, can not be theoretically predicted by kinematic models, since diffusion is a second-order process neglected in the kinematic approximation. In this paper, this issue is discussed and an application for both a generalized diffusion wave model and a kinematic model is proposed of a debris flow which occurred in an Italian instrumented torrent to identify, in a real case scenario, the effective value of the neglected terms in the kinematic approximation

The role of [18f] FDG PET/CT in patients undergoing pulmonary microwave ablation

To investigate whether semi-quantitative and volumetric parameters from [18F] FDG PET/ CT could be associated with clinical outcomes in patients with pulmonary lesions treated with microwave ablation (MWA)

BAL-EVs from LungTransplanted Patients are of LeukocyticOrigin and Activates IL17 Pathway inRespiratory Cells

We previously isolated BAL-EVs from patients with stable (CTRL), or chronic (CLAD) rejection, co-cultivated with HBEC recipient cells and analyzed secreted cytokines. Now, we characterized the origin of BAL-EV and integrated proteomic and transcriptomic data of HBEC exposed to BAL-EV to preliminary chart the lung microenvironment during early chronic lung allograft rejection (CLAD)

New insights in non-invasive markers for rejection in lung transplanted patients

Easily accessible and non-invasive markers of rejection after lung transplantation need to be identified. We tested soluble immune-check-points in plasma and extracellular-vesicles in bronchoalveolar-lavage