EVOLUTION OF RIVER MEANDERING AND SINUOSITY RATIO IN TAZLAU RIVER BASIN, ROMANIA

The hydrological resources are either of limnological or potamological origin. The latter is associated with great dynamics, expressed through quantity, cyclicity (daily, seasonal, absolute), but also through the position within the bounds of a hydrological basin, especially in its floodplain. In potamology, one of the most dynamic processes is river meandering, its study being significant, from many perspectives. The importance of this subject is given by numerous aspects, such as the lateral dynamic, associated with bank erosion; the possibility that substantial areas of agricultural land can be affected; the contribution this phenomena has on erosion-transport-accumulation processes. Also, if not regulated through extensive hydrotechnical constructions (such as embankments or gabion walls), the meandering can cause damage to transportation networks (both road, and railway), generating territorial disfunctionalities, for short periods of time. Additionally, floods are frequent phenomena, which contribute to the change in direction and bend of the river bed, and, implicitly, to the river meandering. Despite its destructive implications, there are also positive consequences, related to highly meandering rivers. Among these, the most relevant is the occurrence of oxbow lakes, when a river bend collapses on itself, creating local ecosystems, which support biodiversity, or become potential water resources. The methodology for calculating the sinuosity ratio has been adapted to the irregular river valley shape, in order to minimize errors produced by the generalized sinuosity ratio formula. The evolution of the sinuosity ratio could be emphasized, by comparing the side-to-side movements over time, from several cartographic materials. Therefore, based on topographical maps, published in different time periods, the overall tendency of river meandering could be observed. The study area is the Tazlau river basin, and it has been chosen taking into consideration the sufficiently wide floodplain, which allows the river to exert a great lateral extent; the existence of large floods, in its brief history (such as the one in 1991, resulted in the breaking of Belci dam); and the cartographic materials, which are sufficiently extensive, therefore the analysis being possible for a period of over five decades.