Abstract
Abstract The Prahova River (Romania) at the Southern Carpathian Mountains was affected by a number of measureable changes in its planform pattern and longitudinal profile over the past 200 years. The mountain river has been incising into bedrocks, narrowing its valley, abandoning its lateral channels and straightening its path while crossing the Subcarpathian study section. The purpose of this study is to analyze, using GIS, the relationship between short-term (less than 200 years) lateral and vertical morphological adjustments observed over the 18 km length Subcarpathian Prahova River and specific long-term evolutionary patterns (more than 200 years). Human disturbances and hydrodynamic characteristics during high intensity flood periods are assessed in the context of existing neotectonics and lithology controls on channel and valley morphology. Surveyed cross-section profiles were used to construct the geometry of a 1D hydraulic model. Simulations were performed using the HEC-RAS software (USACE) under steady flow conditions for flow values between bankfull and the peak discharge value of typical flood events with a return period of 20 and 50 years. Three main areas with high values of computed shear stresses and velocities and corresponding low values of width to depth ratio (W/D) were identified. These areas were found to match the observed erosion areas, where the river has incised into bedrock and eroded its banks. Other potentially aggradation areas of low shear stress values and high W/D were confirmed by field observations. The evolutional patterns of Prahova River channel are tectonic-structurally determined, developed and maintained during the Quaternary mainly by the principles of river morphodynamics. The evolution over shorter timescale bears the mark of the man-induced impact (changes in sediment and hydrologic regimes). In a long-term perspective, the overall channel evolution of this river is expected to be strongly influenced by human activity.
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