Impact of floodplain gravel mining on landforms and processes: a study case in Orlat gravel pit (Romania)

Understanding gravel mining, a very common but aggressive activity, as a morphogenetic action is fundamental for analyzing and assessing the impact on floodplain morphology and the dynamic of riverbeds, on sediments budget and water balance assessment, but also for floodplain planning and resources management. Field observations and GIS analysis were performed in a gravel pit area from central Romania to assess the impact of gravel harvesting during the last decade (2005-2015) on floodplain landscape, landforms dynamic and fluvial processes. Field measurements, diachronic analysis on maps, channel sinuosity coefficient and braided coefficient were carried out to assess the riverbed pattern. The results indicate that the intensive harvesting of gravels and sands in floodplain area leads to doubling of pit and pit ponds surfaces, changes in floodplain morphology and landscape degradation and radical changes in land use/land cover. The channel analysis indicates that the natural conditions and gravel harvesting had an important role in riverbed mobility and reveals different patterns along the Cibin River: meandered, disentangling and sinuous. The main changes of the riverbed consist of meanders radius reduction, meander loops migration northward and downstream, increased sinuosity and decreased braided coefficient. This study facilitates a better understanding of the geomorphologic consequences of off-stream gravel harvesting, the fluvial processes variability linked to flow and bedload and point to human action as morphogenetic and morphodynamic factors. Moreover, this study may enhance the environmental significance in sustainable management of floodplain being a useful tool in applied ecology, river remediation studies and territorial planning.