The purpose of the study was to examine the alluvial deposits on the ravine bottoms to justify the practices of alluvial soils strengthening. Measuring method of alluvium accumulation on the bottoms of ravines and laboratory analysis of soil samples were used. It was found out that the concentration of runoff in the ravine and landslides on its slopes form an alluvium layer (power 0.12–1.12 m), which looked like a river floodplain. Alluvium formation is influenced by the ravine forests. However, this forest may contribute to partial erosion of alluvium accumulation with changes in river beds of temporary streams. The flow at the bottom of the ravine can bypass the forest, bringing down the slope. It excludes forest from the process of alluvium accumulation. If the main stream and the ravine thalweg coincide, the forest won’t participate in this process. Methods for increasing the ability of forests to store alluvium in the ravines were worked out. It is necessary to build up simple structures – fences to regulate the flow at the bottom of the ravine valley under forest cover. Fences can be arranged to provide the drain of the ravine thalweg to the alluvium terraces. It was found out that the upper layer of the ravine alluvium and floodplains of small rivers have a similar composition (sandy clay loam).The forest at the bottom of the ravine increases the strength of the macrostructure of alluvial soils. Moreover, the soil top layer reduces the density from 1.16 to 1.10 gram per cubic cm, the porosity is increased from 54.0 to 55.6 %, aggregate water-resistant (Baksheev method) is risen from 69.4 to 78.0 %, which increases the stability of the alluvial soil on the bottom of the ravine valley. It has been shown that forests and coppices are able to change the location of temporary streams in the mass accumulation on the bottom of the ravine valley. The characteristics of the canals of temporary streams which alter the situation on the ravine’s bottoms under the influence of forests are given. Various methods of enhancing the ability of forests to store alluvium on the ravine bottoms are suggested.
Keywords: ravine landforms, alluvium, accumulation, forests on the ravine bottoms, water flow, fence facilities.
