Abstract:The fluvial process is characterized by an intense meandering riverbed. The aim of this study was to perform a reconstruction of the lateral migration of a 15 km length of an active meandering river during the period 1930-2016. River morphological changes were analyzed and quantified from cadastral maps and aerial photographs as well as by geodetic survey and GIS. Hydrological characteristics and extreme hydrological events were evaluated in relation to bank erosion rate. The rate of bank erosion was markedly different from the long-term studied meanders, just like in the short-term period. During the 87 years of observation (from 1930 to 2016), the length of the Kolubara River was enlarged by 3.44 km. The average migration rate of the Kolubara River for monitored meanders in the period 1930-2010 was 1.9 m·year −1 , while in the period 2010-2016, the average migration rate was 3.3 m·year −1 . The rate of bank erosion was more intensive across the entire short-term period than during the longer period, and the maximum annual rate of bank erosion during the period 2010-2016 varied between 0.3 and 11.5 m. It is very likely that in the period from 2010, frequent discharge variations and rapid change of its extreme values caused more intensive bank erosion. These research results will be valuable for river channel management, engineering (soft and hard engineering), and planning purposes (predicting changes in river channel form) in the Kolubara River Basin.

Zapadna Morava River basin covers a surface of 15850 km2, which is approximately 18% of the territory of the Republic of Serbia. In its basin, 38 active surface stations are registered. The goal of this paper is the trend analysis of the mean annual river discharges in the Zapadna Morava River basin and their noticing in a longer series of time, as well as determining their intensity. Fifty years period of time (1965 - 2014) is taken for a time series. Because there is no empirical data for mean annual discharge values for all stations for the given period, the number of the hydrological stations, which are processed in this paper, is reduced to 21. Mann-Kendall test has been used for noticing the trend, Sen test has been used for estimating the curves inclinations of the linear trend, while Pettitt?s test has been used for determining the turning point of change. Also, classification of the years by water richness has been performed in this paper in order to determine wet and dry periods. For the needs of identification of medium watery, wet and dry years, the combined method has been used on the data examples from representative stations in the basin. Based on the processed data and the obtained results, it has been established that the most rivers in the basin of the Zapadna Morava River have a slightly decreasing trend of the flow values, whereby the change of the trend is not significant. On the most rivers, the change period has begun in the early eighties of the past century. On a large number of profiles, the watery period was appearing in the beginning of eighties, while the dry season is characteristic for the period from 1990 to 1994.

Understanding the current status of wateriness, which include studying the variability of different hydrological parameters over a long period of time, represents a significant process for determining the availability and quantity of water resources, especially at the local and regional level. First, it is necessary to identify certain paternity and frequency in a long time series of hydrological parameters. Secondly, it is important to correlate them with variability of some climatological elements on the one hand and anthropogenic influence in other hand, which are the main factors that have influence on the changes in river wateriness. The main objective of this paper is the analysis of seasonal and annual variations of river discharges in the South Morava river basin, for the period of 50 years , and the observation of certain trends (using non-parametric Mann-Kendall test and homogeneity test). Explanation and understanding the potential causes of observed changes, which are significant, is one of the tasks of this research. In this paper are observed data of the mean annual and monthly river discharges from 20 active hydrological stations in the South Morava river basin, for which there are empirical data for the taken period. The results indicate that most rivers in the basin have dominant decreasing trend of the mean annual river discharges (85% of them), but the more significant changes are noticed for the values of the seasonal river discharges.

The morphological evolution of the fluvial relief in the lowland areas is determined by the dynamic of the lateral channel migration process. River meandering and lateral channel migration represent continuous, dynamic and complex processes, which intensity modifies alluvial plains. Accordingly, it is a current topic observed from the domain of various scientific disciplines and practices, including the geographical aspect of the study. Directly or indirectly, variations of natural and anthropogenic processes affect changes in the lateral migration intensity, which is later manifested through permanent consequences for the environment. The aim of this paper is to investigate the process of lateral channel migration, through the review and interpretation of theoretical and methodological concepts and results of contemporary scientific literature. In this paper, on specific sections of the South Morava River (Serbia), the values of maximum lateral migration over different time periods are determined. Three representative river sectors were singled out, spatial and temporal dynamic was determined, while the process of lateral channel migration was presented quantitatively and graphically. Based on the obtained data, a comparative analysis showed significant riverbank changes for the observed meanders, within the period 1924-2020. Special emphasis is on the analysis of the lateral channel migration in the last decade of the mentioned period. The obtained results can be further used in order to develop and implement plans of water and land management, environmental protection and socio-economic development strategies. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. 176017]

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