Postglacial debris flow landforms are widespread in the Lovozerskye Tundry. However, there is almost no data on the recent debris flow dynamics. In 2009–2010 and 2017–2018, we investigated debris flow topography and conditions of debris flow formation in the Sengisjok Valley on the western slopes of the Lovozerskye Tundry applying satellite imagery interpretation, field geomorphological survey, UAV survey, and 14C-dating of sediments. Footprints of debris flow activity were revealed along the entire valley: the modern valley bottom is completely reworked by the recent debris flows while in the transit zone, older debris flow terraces reach up to 20–30 m high. A debris flow fan has an area of about 0.48 km2, with only 17% occupied by the Late Holocene accumulation.

On July 3, 2017, we observed a high-energy debris flow. Following the long and snowy spring and cold June, the rapid snowmelt triggered the event as positive air temperatures had settled round-the-clock. The event started as a hydraulically driven slushflow when a snow dam at the threshold of the Sengisjavr Lake’s outflow was breached. In the transit zone, the slushflow gradually saturating with debris transformed into a typical debris flow with an estimated velocity of 3.4–4.1 m/s and discharge of 75–90 m3/s. Total debris flow volume can be assessed up to 320 000 m3 with the volume of a clastic load of up to 80 000 m3. The debris flow passed 6.5 km.

The timing of another two high-energy debris flows that occurred in the last 150 years has been determined. The estimated frequency of such flows is 1 event per 15–20 years. Snow dam breaches with the subsequent partial drainage of the Sengisjavr Lake are the key debris flow drivers in the Sengisjok Valley.

The article presents the assessment of modern and historical denudation rates in the fortification from the end of the 17th century – a section of the Karpov rampart of the Belgorod Line (Belgorod Oblast, Russia), and in a ravine that was formed in the same period as a result of the surface runoff transformation. The study object includes a ditch associated with a rampart (catchment area of 0.49 ha), which accumulated sediments over 344 years under natural sod cover, and a ravine of comparable age with a catchment area of 18.1 ha. The research methodology combined instrumental topographic survey, analysis of cartographic and satellite data, soil-genetic studies of vertical profiles of pedosediments in the ditch and ravine, as well as an assessment of modern accumulation rates using the chronomarker of the 137 Cs isotope. It was established that the average rate of pedosediments accumulation in the ditch was 0.26 cm per year, which corresponds to the average annual rate of erosion from slopes with high soil-protective efficiency of 2.5 t per ha. In general, since the second half of the 20th century (20% of the duration of the existence of the rampart), the maximum accumulation rates for the entire historical period have been observed: during this time, a third of the thickness of pedosediments was formed, and the rate was almost two times higher than the long-term average. Estimates of the modern rates of sediment accumulation in the ditch have shown a significant change in the accumulation rate over the past 70 years: before and after the Chernobyl accident in 1986, it decreased from 0.56 cm per year to 0.32 cm per year. The same tendency is characteristic for the rates of linear erosion. During the same periods, the growth of the ravine slowed down by 8 times (from 0.8 to 0.1 m per year), and its transformation into a dry valley occurred. The distribution of the percentage of particles less than 0.01 mm in size in the pedosediments profiles as an indicator of the variability of the water erosion intensity over the past 50 years shows the same nature of the formation of suspended sediment runoff both in the ditch and in the ravine, despite the significant differences in the area of the catchments. The features of a half-century period are shown, which was characterized by a sharp reduction in the snowmelt runoff layer from the 1970s against the background of an 8% reduction in rainstorm precipitation with a layer less than 10 mm.

Geomorphological zoning is routinely used to properly organize the available data on the landform type and genesis in large areas. Most of the existing geomorphological zoning charts for the West Siberian Plain were developed back in the 1970s. They have significant drawbacks in terms of boundary position accuracy and accounting and lack the latest data and are hardly suitable for research purposes. This study updated the geomorphological region boundaries of the West Siberian Plain. We used the ALOS World 3D digital surface model (30 m resolution) and the existing charts by S. Voskresensky, M. Gorodetskaya, Yu. Mescheryakov, V. Nikolayev, G. Richter, V. Trofimov, and G.A. Lazukov. It was a combined approach with manual and automatic interpretation. The visual features are slope breaks, terrace ledges, and watersheds. We applied object-oriented segmentation with k-means clustering for automatic classification. As a result, the boundary of the West Siberian Plain was corrected (its area is 2.93 mln. km²). 74 geomorphological regions were found. The average region area is 39,600 km², and the average absolute elevation is 88.1 m. The region boundaries can be reproduced and verified with any detailed digital surface model provided that it is created by continuous instrumental measurements of the surface elevations. We also estimated the average morphometric indices for each region (average elevation, slope angle, total curvature, thalweg density, and the share of land covered by lakes). Generally, there is a sustainable trend: the landform uniformity of the West Siberian Plain increases from north to south while the share of lakes decreases. We assumed that the most probable cause of the geomorphological differences between the northern and southern parts is the impact of the blanket glaciations on the northern part of the plain.