Radiocarbon dating of a composite multi-period debris cone stratigraphy in the Lochan na Lairige, Ben Lawers

An early stage in formation of a composite debris cone in the glacial trough of the Lochan na Lairige, on Ben Lawers, is 14C dated to 6398–6225 cal BP. A large proportion of the fan comprises a structureless gravel with boulders, possibly deposited in a single event. Blanket peat formed on the fan surface at 3820–3496 cal BP. Sediment slurries are recorded across the peat after this time, at c. 3950 to c. 3100 cal BP, c. 2000 and c. 1400 cal BP, and at c. 1200 to c. 1100 cal BP. They were much less significant events. They can be related to periods of higher effective precipitation in the region.

THE CONTENT OF OIL PRODUCTS AND ORGANIC MATTER IN THE DEBRIS CONE OF GULLY IN THE CITY OF SARATOV

The article discusses the results of a study of the content of organic matter in the removal cone of a city ravine located on the territory of Saratov.

Results of works carried out via electrical exploration method for searching groundwater sources suitable for drinking and household use in the debris cone of Turyanchay river

The paper deals with the exploration works conducted via electrical exploration method for searching groundwater sources suitable for drinking and household use in the debris cone area of Turyanchay river. As a results of carried out studies, the areas with groundwater sources suitable for drinking and household use are marked, lithological content and depth of water horizons specified as well. With the aim of estimation of fresh groundwater reserves in the debris cone area of Turyanchay river suitable for drinking, ρf and geological-geophysical sections have been developed due to the geophysical surveys executed via vertical electrical sounding (VES) methods. To specify the lithology of the rocks and reveal formations with reservoir properties, logging operations have been carried out. The thickness of clay formations comprising the sections increases from the north-west to the south-east; alongside with this due to the alternations of gravel sediments with clay rocks the specific electrical resistence of the rocks decreases. As a result of exploration of water sources suitable for drinking in the debris cone of Turyanchay river, the water content of the rocks in mentioned area has been studied to the depth of 285 m, the prospective zones of fresh and less mineralized groundwater marked, initial reserves estimated and prospective zones for accurate surveys specified as well.

The Influence of Debris Flow Activity on the Sediment of the Lake Plansee over 3.6 ka (Tyrol, Austria)

<p>Debris flows represent a widespread geomorphological hazard in mountainous regions. Understanding the long-term dynamics of debris flow activity in view of climate change is crucial for the prevention and mitigation of future events. The activity of debris flows is evidently linked to the magnitude of rainstorms. Dietrich & Krautblatter (2017) found an increase in debris flow volumes after 1980 by a factor of 2 compared to the period 1947-1980 and by a factor of 3 compared to the mean Lateglacial/Holocene debris flow volumes by investigating aerial photos of the surroundings of lake Plansee (Reutte, Austria) and estimating debris flow cone volumes with geophysical methods.</p><p>In this study, the terrestrial observations of increasing debris flow volumes were compared with the subaquatic deposits from the deepest basin of the lake. The debris flow volume within a three-month period on a large debris cone was monitored by Terrestrial Laserscanning (TLS) and the debris flow activity over the last 3 600 years was reconstructed using sediment cores. Four short cores of up to 145 cm depth were recovered in a transect from the shallow subaquatic debris cone area to the deepest basin of the lake. The grain size, density, Magnetic Susceptibility as well as the d<sup>13</sup>-C, d<sup>15</sup>N- and C/N-ratios of the sediment were analyzed.</p><p>The Terrestrial Laserscans revealed a sediment delivery ratio of 30% for the steep debris cone bordering the lake. In the four correlated short cores, 52 debris flow events were differentiated within the last 3 600 years of sedimentation. The proportion of event layers in the cores ranges between 34% and 57% of the total section thickness. The sedimentation rates from a dated core confirm the increase of debris flow activity that was observed with terrestrial methods by Dietrich & Krautblatter (2017). The sedimentation rates show an 11-fold increase after 1930 compared to the rates before 1930 and a 5-fold to 12-fold increase compared to the average Holocene sedimentation rates in lake Plansee. Three types of event deposits were distinguished according to sedimentological criteria: flood-triggered debris flows, earthquake-induced subaquatic suspension flows and mega-events. The TOC/TN ratios of the sediment reveal a permanent influence of terrestrial carbon on the lake sediment and a mixed source of allochthonous and autochthonous organic matter. Large debris flow events can be distinguished from background sediments by increased d<sup>13</sup>C isotope ratios.</p><p>The results of this study reveal further scientific proof for the increase of debris flow activity in conjunction with increasing rainstorm activity. Here we show one of the first long-term archives of debris flow activity in the Northern Alps spanning the last 3 600 years and revealing cyclic shifts in debris-flow transport volumes by one order of magnitude.</p>

DYNAMIC PECULIARITIES OF MUDFLOWS IN THE AZERBAIJAN AREA OF THE GREAT CAUCASUS

The paper features the dynamic peculiarities of mudflow deposits and the methods of their volume calculation. It was determined that peculiarities of torrents are defined by their dynamic and velocity. It was revealed that the relation of accumulation volume to the abrasion volume of the debris cone of the water stage gauge in Balakançhay. Talaçhay Mukhakhchay and Kurmukchay is 0.66; 0.014; 1.35 and 0.7 accordingly. The violation factor of the mudflows in the river basins also forms 0.37; 0.28; 0.56 and 0.30 accordingly. As for the general territory, the range stays within the limits of 0.03-059. It is determined that the rate of decrease in the surface of the catchment areas caused by mudflows is 5.14 mm on the Balakenchay river, 11.81 mm in the Talachay river, 9.44 mm in the Mukhakhchay river, 5.68 mm in the river Kurmukchay, 11.21 mm in the river Shinchay and 9.09 mm in the river Kish. The average value is 8.73 mm. The relatively high value of the washout intensity is characteristic of the catchment area of the Talachay river and the Shinchay river, which is due to the spread of fragile rocks, the presence of significantly exposed areas with great slope steepness and their dismemberment, as well as cost-effective deforestation.

Experimental and numerical study on the design of a deposition basin outlet structure at a mountain debris cone

Mountain debris cones in the Alpine region often provide space for dense population and cultivation. Hence, a great number of buildings are exposed to torrential hazards. In order to protect the settlement areas against flooding and overbank sedimentation, torrent defence structures are implemented at various locations within catchments. Directly at the debris cones, these protection measures often include a deposition basin at the fan apex and/or a confined channel that passes through the settlement. The work presented within this paper deals with the effect of specific outlet structure layouts, situated at the lower end of a selected deposition basin, on bed-load transport processes and flood protection. A case study analysis was accomplished comprising a 3-D numerical model (FLOW-3D) and a physical scale model test (1 : 30). The subject of investigation was the deposition basin of the Larsennbach torrent in the Austrian Northern Limestone Alps. The basin is situated on a large debris cone and opens out into a paved channel. Since the basin is undersized and the accumulation of sediment in the outlet section reduces the available cross section during floods, adjoining settlements are considerably endangered of lateral overtopping of both clear water and sediment. Aiming for an upgrade in flood protection, certain layouts for a "closing-off structure" at the outlet were tested within this project. For the most efficient design layout, its effect on flood protection, a continuous bed-load output from the basin and the best possible use of the retention volume are pointed out. The simple design of the structure and the key aspects that have to be taken into consideration for implementation are highlighted.