Vazhenin B.P. - Destruction scenarios for seismogenic, glacial and any other natural dams in mountain valleys

Written by Erkin Turdibaev

Friday, 04 March 2016

The structural types and destruction scenarios of natural dams, which differ by their genesis, are examined using the Google Earth and SASPlanet data and the author's field study results. As it is established, landslide and rock fall dams of seismic origins serve as the barriers for Sarezskoye and Yashilkul Lakes in the Pamirs, Ritsa and Kazenoyam Lakes in the Caucasus, Kucherlinskoye Lake in Altai, and Goluboye Lake in the northern Priokhotye. Typical rock falls consist of boulders and rubble rocks and have a high filtering capacity, and, as a result, they are subject to a rapid wash-out by the locked water flow, which process is associated with formation of suffusion scour channel followed by suffusion-erosion canyon, like in the Chul R. valley (the tributary of the Tumany River, the Sea of Okhotsk coasts). Natural dams of tectonic origins developed as a result of faulting processes in valleys and displacements of crustal blocks having size of about several kilometers. The examples are Amtkel Lake in the Caucasus, and Darpir, Takalyr and pra-Nuke Lakes in the Russian North-East, which display their maximum resistance to river-caused erosion processes. However, they often become destroyed due to newly-formed faults, as it is exemplified by the terminated destruction of the Khurendya R. valley dam and the still continuing wash-out of Darpir and Amtkel Lakes dams. Talus cones have their radial size up to several tens of kilometers and consist of sand, gravel and pebble rocks. They can be easily cut through over their distal areas having the minimum sediment thickness. The examples of the partial dam barriers are Darpir, Maly Darpir, Solnechnoye and Elikchan-skiye Lakes in the North-East of Russia, Baikalyonok Lake in the northwestern Priokhotye, and Tere-Khol' Lake in Tyva. Many large lakes are dam-locked by end moraines and their complexes, which can be from several kilometers to tens of kilometers in size, and are the remnants of mountain valley glaciation. The examples are Maggiore, Komo and Garda Lakes in the Italian Alps; Keta, Lama and Khantayskoye Lakes over Putorana Plateau; Labynkyr, Tabanda, Jack London, Malyk, Momontay, Ui and Koolen Lakes in the North-East of Russia; Azas, Many-Khol', Noyan-Khol' Lakes in Tyva. A slow wash-out of wide, gently sloping and water-resistant end moraines occurs due to locked water overflow, and depends on the opening size and the lake influx. Active glacial dams are subject to the most intense destruction. Merzbacher Lake in the Tien-Shan consists of two parts separated by an ice dam and has a length of about 2.6 km. Twice a year, during 2-7 days, all lake water from the lower part is discharged into the Inylchek R. valley, the discharge rate about 1 000 m 3/sec. Miles and Van Cleve Lakes in Alaska appear to have the same dynamic dam destruction scenarios. Natural dams are classified by their destruction-resistance capacity as follows: glacial dams, talus cones, rock falls, seismotec-tonic and moraine dams. Download (in Russian) (pdf, 970 kB) Source: http://cyberleninka.ru/

 

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