A high-frequency, long-term data set of hydrology and sediment yield: the alpine badland catchments of Draix-Bléone Observatory

Draix-Bléone critical zone observatory was created in 1983 to study erosion processes in a mountainous badland region of the French Southern Alps. Six catchments of varying size (0.001 to 22 km2) and vegetation cover are equipped to measure water and sediment fluxes, both as bedload and suspended load. This paper presents the core dataset of the observatory, including rainfall and meteorology, high-frequency discharge and suspended-sediment concentration, and event-scale bedload volumes. The longest records span almost 40 years. Measurement and data-processing methods are presented, as well as data quality assessment procedures and examples of results. All the data presented in this paper are available on the open repository https://doi.org/10.17180/obs.draix (Draix-Bleone Observatory, 2015), and a 5-year snapshot is available for review at https://doi.org/10.57745/BEYQFQ (Klotz et al., 2023).</p

Solvent Effects on Ionization Potentials of Guanine Runs and Chemically Modified Guanine in Duplex DNA: Effect of Electrostatic Interaction and Its Reduction due to Solvent

We examined the ionization potential (IP) corresponding to the free energy of a hole on duplex DNA by semiempirical molecular orbital theory with a continuum solvent model. As for the contiguous guanines (a guanine run), we found that the IP in the gas phase significantly decreases with the increasing number of nucleotide pairs of the guanine run, whereas the IP in water (OP, oxidation potential) only slightly does. The latter result is consistent with the experimental result for DNA oligomers in water. This decrease in the IP is mainly due to the attractive electrostatic interaction between the hole and a nucleotide pair in the duplex DNA. This interaction is reduced in water, which results in the small decrease in the IP in water. This mechanism explains the discrepancy between the experimental result and the previous computational results obtained by neglecting the solvent. As for the chemically modified guanine, the previous work showed that the removal of some solvent (water) molecules due to the attachment of a neutral functional group to a guanine in a duplex DNA stabilizes the hole on the guanine. One might naively have expected the opposite case, since a polar solvent usually stabilizes ions. This mechanism also explains this unexpected stabilization of a hole as follows. When some water molecules are removed, the attractive electrostatic interaction stabilizing the hole increases, and thus, the hole is stabilized. In order to design the hole energetics by a chemical modification of DNA, this mechanism has to be taken into account and can be used. 1

Bedload transport monitoring in a small upland catchment

International audienceCommunication orale faite lors du 8th IAG International Conference on Geomorphology, Paris, 27-31 August 2013

Bedload transport monitoring at Draix

International audienceConférence invitée lors du International Workshop on Monitoring Bedload and Debris-Flows in Mountain Basins, Free University of Bolzano, Italy, 10-12 October 2012

Mesures de la taille et la vitesse des particules dans une avalanche de neige poudreuse

International audienceGenerally snow avalanches consist a dense-flow layer at the bottom and a powder snow cloud on top. Snow particle size and speed are key parameters to describe the turbulent condition in the powder cloud, however, the information on the particles were not well investigated. In this study, we observed powder snow avalanches using a snow particle counter (SPC) to measure the particle size and speed. The SPC is an optical device consisting a laser diode and photodiode; a pulse signal proportional to its diameter is generated resulting from a snow particle passing through the sensing volume. In general use, the signals are sent to a transducer and divided into 32 size classes based on particle diameter to observe the snow particle size distribution and mass flux at 1-s intervals. In this study, the direct output signal from the transducer was also acquired at a high frequency to obtain the original pulse signal produced by each snow particle. Then the speed of each particle can be calculated using the peak of the pulse, which corresponds to particle diameter and the duration over which the particle passes through the sampling area. We also employed an ultrasonic anemometer to measure air flow speed. Both sensors were installed at the Col du Lautaret Pass in the French Alps. The results of the particle size and speed distribution were then compared with airflow movement in the powder cloud. The ratio of the particle and airflow speeds changed by the particle size distribution and the distance from the dense-flow layer

Dynamique lente et rapide lors de l'impact des avalanches de neige avec les structures: information des mesures réalisées au site expérimental du col du Lautaret (France)

International audienceThe present paper describes preliminary re-analyses of field-based data on past well-documented snow avalanches that have impacted an instrumented tripod structure in one of the paths at Lautaret avalanche test-site, France. The re-analyses done include data on velocity and pressure measurements, as well as new data on flow-depth measurements. The latter data was obtained with the help of re-analyses of pressure signals. The various techniques used and assumptions made are presented and discussed, which allows us to infer how the thickness of the dense flow, and both the velocities and pressures over depth, all change simultaneously over time. The present work pays attention to the gravity-dominated flow regime occurring after the passage of the avalanche front. That regime is characterized by a mean pressure on the tripod structure that is essentially controlled by the flow thickness, unlike the inertia-dominated regime which is deemed to be driven by the square of the flow velocity during the passage of the avalanche front. Moreover, a change in dynamics is well identified during the gravity-dominated flow regime, while moving from the avalanche core to the avalanche tail

High-frequency monitoring of debris flows in the French Alps: preliminary results of a starting program

International audienceDebris-flows mobilize high sediment loads and are often responsible for most of the sediment yield from upland headwaters and may endanger the safety of life and infrastructure in the vicinity of torrent channels. Two very active debris-flow torrents with different physiographic settings have been equipped in the French Alps, the Manival Torrent (3.6 km²) and the Réal Torrent (2.3 km²). At these two sites, debris-flow monitoring systems are based on a combination of different techniques involving rain gauges, soil vibrations and flow elevation measurements and high-resolution/frequency imagery acquisition. Only flash floods with bed load transport have been observed on the Manival Torrent. Conversely, in spring/summer 2011 four meteorological events triggered debris flows on the Réal Torrent. Most of the debris fronts deposited immediately in the upstream part of the channel. Only one debris-flow propagated from the sediment source area to the basin’s outlet. A 1.8 m high debris front propagated with a mean velocity of about 3 m s-1. Its volume was 4,400 m3 upstream and it increased because of bed erosion. The debris flow reached 6,100 m3 in the middle part of the basin and then decreased slightly further downstream (8,600 m3). These measurements highlight the interaction between the debris flow and the torrent channel in the first part of the basin. These results are in accordance with previous sediment budgets estimated for the debris flows which occurred in 2009 and 2010