Shamov V.V., Shekman E.A., Gubareva T.S., Gartsman B.I., Lupakov S.Yu., Chelnokov G.A., Kozhevnikova N.K., Burdukovskii M.L., Orlyakovskiy A.V.
Hydrosphere. Hazard processes and phenomena 2021; 3(3): 275-296
For the case of small valleys in South Sikhote-Alin Ridge and Verkhnekolymskoye Highlands (Pacific Russia, Northeast Asia), there is given an analysis of systematic observations of big preferential flow paths of slope-scale, - subsurface shallow (not deeper than 1 m) watercourses, in which the most water migrates fast. The watercourses occur most often within the bodies of relic or active stony stripes ("block streams"). In some of the studied watercourses, there were estimated discharges (0.041-7.36 l/s) and velocities (0.1-7.2 cm/s) that are quite comparable to the 1-order streamflow rates when low water periods. We suggest the biggest among such subsurface watercourses are to be controlled by geological structures of slope scale, namely sub-local fractures, which feather local fractures. Accounting for the results of relevant investigations by other authors and the water movement features revealed in the studied subsurface watercourses, we offer a variant of their division onto three main structural groups: 1) the main paths (conduits) with a length of hundreds to 1-2 thousand meters and width of several meters; 2) the filtration flow domains with a length of 0.1 meters to several dozen meters and width of up to 0.1 meters; and 3) the matrix flow paths with a length of much less 10 centimeters and width of less 0.1 centimeters. Detailed studies for talus texture and water regime of the hillside watercourses would make it possible to prove a hypothesis on the significant role of small faults (fractures) and related to them the active or relic block streams in the concentration of slope flow. It could allow a deeper understanding of the flood generation in river basins, especially in the areas where severe intra-annual moistening fluctuations as Pacific Asia.
