Correlation of colluvial deposits with the modern land surface and the problem of slope profile description

• Strong correlation (85 %) was found between colluvial deposits and catchment area.
• Inversion of matter accumulation during long term sedimentation was determined.
• Problem of assessment of sediments distribution along flow lines was considered.

This article focuses on features of spatial distribution of colluvial (slope) deposits on a micro scale. These features were detected by the non-parametric rank correlation of Spearman (rS) between thickness of colluvial layers and morphometric variables (MVs) of the modern land surface. The strongest correlation was found between total thickness of colluvial layers and maximal catchment area (rS = 0.85). A negative correlation was observed between thicknesses of younger and older colluvial layers. Additionally, if young colluvial layers have a negative correlation with slope steepness (GA), relatively old buried colluvial layers have a positive correlation with GA. These facts indicate an inversion of the zones of actual matter accumulation due to transformation of the land surface in profile during long-term sedimentation.Vertical curvature (kv) characterises acceleration and deceleration of surface flow caused by the shape of the slope profile along flow lines. Based on this, it was expected that kv would have a direct impact on the accumulation of colluvium. However, in this study, the correlations between the thickness of colluvial deposits and kv were low. Functional relationships between colluvial accumulation and the shape of profiles along flow lines were reflected by correlations with GA. Based on these observations, it is assumed that the regional nature of surface flow velocity affects the shift between existing accumulation zones reflected by colluvial deposits and potential accumulation zones reflected by MVs.Signs of correlation coefficients between the thickness of colluvial deposits and curvatures reflect the tendency of increased colluvial depositions at three out of 12 local landforms of Shary's classification. These landforms are located in the valley bottom. The mean thickness of colluvial deposits at these three landforms was 167 ± 18.7 cm (error range = standard deviation); the other nine landforms show a mean thickness of 130.1 ± 34.1 cm.