Hydrogeomorphic exploration of a local headwater stream in low mountainous environment following detailed field survey protocol (Mecsek Mountains, Hungary)

Comprehensive field survey of the physiographic context and channel morphology is a key to distinguish characteristic hydrogeomorphic reaches of a watercourse. In this analysis field data were collected during seasonal campaigns following a field survey protocol developed in the Polish Carpathian Mountains. Complementary information was conducted from cartographic materials and digital elevation model to map diverse sections of the semi-natural Váralja Stream in the Eastern Mecsek Mountains. Geological, geomorphological and anthropogenic effects had to be considered as decisive factors in recent fluvial development, with emphasis on the sediment transport influenced by woody debris. A total of 12 hydrogeomorphic reaches were identified along the stream by interpreting the spatial arrangement of channel forms and analysing the characteristics of the watershed environment. The mapped reaches are connected with transitional zones of different length. Step systems are typical on the upper reach of the stream, but they were found to be the result of the geological composition and structure of the region. It was also proven that woody debris accumulations, made up of tree trunks, branches and roots have significant influence on the channel evolution of the Váralja stream. Even though the presented field survey instructions were field-tested in alpine catchments the conducted research confirmed the applicability of such workflow in low mountainous environment. Furthermore, the results on the hydrogeomorphic conditions of this small watershed with intense relief provide useful information for understanding the flash floods occurring in the region.