Preliminary Data of Fluvial Geomorphological Evolution and Its Link with Hazards and Human Impact: The Case of Peiros River, North Western Peloponnese, Greece

摘要

River channel dynamics are the result of the complex interaction between natural and human factors, at both local and regional scale. The study of river channel dynamics may be an important way to better understand the mechanisms that rule the functioning of fluvial systems, allowing predictions of its future evolution to be made and appropriate adaptation measures to be taken, remediating the risks related to the fluvial dynamics. The purpose of this study is to present specific aspects concerning the river channel dynamics of Peiros River, NW Peloponnese, Greece and to reveal the role of various control factors. Peiros, the longest river in Achaea, has sources at the NE part of the Erymanthos mountains flowing into Patras gulf. This study traces the various stages of geomorphological evolution of the low part of Peiros's river channel and enables us to study the links between human activity, local tectonics, morphology and fluvial dynamics. The study area belongs to the geotectonic zone of Gavrovo-Tripoli flysch, consisting mainly of medium-bedded fine-grained sandstones and mudstones and influenced by ENE and WNW trending faults aligned with the river flow. The spatial and temporal variability of sediment transport is controlled by various variables, including the natural features of the catchments and human activity. The latter is an important control factor for both the processes of sediment generation, transfer and accumulation and for channel dynamics. At the same time, these processes are responsible on short and long run for the alteration of the river channels, which entail negative environmental consequences. The study revealed restriction of sediment supply, coastal retreat, lateral erosion and migration of the rivers channel that complies with the local tectonics of the area, although major stream offsets are not created. The morphological changes although, are mainly attributed to human intervention factors, such as the construction of a dam and transversal bars that restricted the water flow and consequently the sediment supply. That factor combined with the climate change, had as result to drastically alter the morphology of the area. These morphological changes, except of loss of property and boundary problems, also made the area vulnerable to flush flood events. Structures close to the coast are exposed to more risk because of the measured coast retreat. No remediation measures have been taken, except the installation of rip-rap of limited length and one groin, in an attempt to slow down the coastal retreat and diminish wave action.