The Belá River is a unique morphological-ecological water body in Slovakia. Together with its riparian zone, it creates a biocorridor of supraregional significance and, thanks to habitats of European significance (SKUEV0141), is included in the NATURA 2000 system. The subject of our initial research was to gain knowledge about the development of its wild-migrating floor plan over the last 180 years on the basis of data and data from the remote sensing data (1). In connection with the analysis of its response to extreme flood flows over the last 60 years (2), as well as changes in environmental conditions and human impact, we were able to clarify key factors influencing the dynamics of morphological changes and even predict the evolution of the Belá braidplain. Our research clearly pointed to a declining trend in the area of the active riverbed, as well as the occurrence of flood events with low N-year (5-10) flow. It also points to the long-term degradation of the river system in the form of simplification of the braided-wandering planform to the wandering-meandering type (3), an increase in the area of the islands, narrowing and straightening of the channel. Although it is possible to characterize the state of the Belá River as a threshold state of metastable equilibrium, it can be expected that the system will continue to be simplified. These assumptions were also confirmed by the application of the original methodology of research on the connectivity of coarse-grained sediments of the Belej riverbed (4). Eight types of potential functional connectivity were determined by interpreting the balance indices of connectivity at the level of floodplain-riverbed, riverbed-floodplain and bench-bench. By linear trend analysis of the integral connectivity index (IIC) and flood periods, it was found that all river sections show a decreasing trend of IIC values, i. j. a decrease in the movement of coarse-grained sediments and thus a decrease in the formation of benches and geodiversity and, consequently, biodiversity. Currently, our research focuses on regular monitoring of several river reaches, where we also use unmanned aerial vehicles (UAVs) and ground-based laser scanning (TLS) for data collection. Operational acquisition of very detailed orthophotos with a resolution of 5 cm and photogrammetric terrain models using UAV allows us a very accurate manual as well as automatic classification of internal trough structures and vegetation (5, 6). The laterally dynamic Belá River has washed the terrace. The TLS technique is therefore currently being used to identify the complex connectivity process of this active landslide and river bed. We see the application character of our results when optimizing the management of the Belá braidplain. The operation of a small hydroelectric power plant has a negative impact on the natural development of the riverbed and causes its intensive cutting into the clay subsoil. The flood in 2018 required the intervention of heavy equipment in the riverbed as part of the implementation of river training works (7) where the impact of these works on the hydraulic-morphological configuration of the multi-thread planform of the Belá River was analysed. The preservation of the natural properties of the morphology of the riverbed is closely related to the preservation of its ecological significance and function. Therefore, it is indisputable that among the most important input variables in the optimization of river management is, besides the identification of unstable river reaches, mainly the understanding of its internal self-regulatory mechanisms.
(1) KIDOVÁ, Anna – LEHOTSKÝ, Milan. Časovo-priestorová variabilita morfológie divočiaceho a migrujúceho vodného toku Belá = Spatio-temporal morphological variability of the braided-wandering River Belá. In Geografický časopis, 2012, roč. 64, č. 4, s. 311-333.
(2) KIDOVÁ, Anna – LEHOTSKÝ, Milan – RUSNÁK, Miloš. Geomorphic diversity in the braided-wandering Belá River, Slovak Carpathians, as a response to flood variability and environmental changes. In Geomorphology, 2016, vol. 272, p. 137-149.
(3) KIDOVÁ, Anna – LEHOTSKÝ, Milan – RUSNÁK, Miloš. Recent channel planform evolution of a braided-wandering river using multitemporal data and GIS (case study of the Belá River, Slovak Carpathians). In Acta Scientiarum Polonorum. Formatio Circumiectus, 2017, vol. 16, no. 1, p. 247-259.
(4) LEHOTSKÝ, Milan – RUSNÁK, Miloš – KIDOVÁ, Anna – DUDŽÁK, Jozef. Multitemporal assessment of coarse sediment connectivity along a braided-wandering river. In Land Degradation & Development, 2018, vol. 29, no. 4, p. 1249-1261.
(5) RUSNÁK, Miloš – SLÁDEK, Ján – KIDOVÁ, Anna – LEHOTSKÝ, Milan. Template for high-resolution river landscape mapping using UAV technology. In Measurement, 2018, vol. 115, p. 139-151. (2.218 – IF2017).
(6) RUSNÁK, Miloš – SLÁDEK, Ján – KIDOVÁ, Anna. Využitie UAV technológie pre klasifikáciu a mapovanie krajiny vo fluviálnej geomorfológii = Using UAV technology for landscape classification and mapping in fluvial geomorfology. In Geografický časopis, 2018, roč. 70, č. 2, s. 141-160.
(7) KIDOVÁ, Anna – RADECKI-PAWLIK, Artur – RUSNÁK, Miloš – PLESIŃSKI, Karol. Hydromorphological evaluation of the river training impact on a multi-thread river system (Belá River, Carpathians, Slovakia). In Scientific Reports, 2021, vol. 11, art. no. 6289.