Natural conditions of coarse bedload transport in headwater catchments (Western Tatras, Poland)

Abstract

ABSTRACT The aim of the study was to examine the magnitude and frequency of bedload transport in 1st–3rd order headwater catchments (with an area <2 km2) in the Western Tatras. The study was carried out in 19 headwater catchments, divided into two groups: (1) alpine catchments, and (2) montane catchments. Bedload transport measurements were carried out at intervals over a period of 40 years using the painted stone method. During large floods observed in the main stream (Q > 5 m3 s−1), usually associated with prolonged rainfall or a combination of both snowmelt and rainfall, it can be expected that bedload will also be activated in its tributaries and headwater sections. Bedload transport may also occur during snowmelts, but this type of flood is of a completely local nature. During small local floods, the role of the local channel structure is quite important. Channel topography can slow down transported bedload, which is particularly visible within alluvial fans. During high-energy events, this effect disappears, and the distance of bedload transport increases downstream. In alpine channels, bedload transport occurs on a much smaller scale than is the case in montane channels and it occurs along the entire channel length. The distance of bedload transport, its size, and the frequency of occurrence of geomorphologically-active floods are smaller in alpine catchments than in montane ones. In alpine channels, the maximum distance of bedload transport was 18.2 m, and in montane channels, distances reached 165 m.