Geomorphic evolution of the fan delta of the Evinos river in western Greece and human impacts in the last 150 years

摘要

This study presents the geomorphic evolution of the Evinos river fan delta in the Late Holocene through field observations, comparative examination of 1945, 1986 and 1995 aerial photographs and reliable maps of the last two centuries. A geomorphic map at the scale of 1:20,000 was prepared, and both the deltaic plain and coastal landforms were studied in order to determine the processes that played an important role in the configuration of the deltaic environment during the Late Holocene. The most important factors for the development of this delta are fluvio-torrential sediment supply, wave activity, persistent longshore current of the receiving basin (Gulf of Patras) and recent eustatic changes. Four groups of abandoned channels were responsible for the progradation of the fan delta following the gradual rise of sea level about 5,000-6,000 years ago. The eastern part of the delta is composed of low coastal cliffs and gravel beaches formed by marine erosional processes. The only region where the fan delta progrades is the present river mouth. It is expected that the construction of a dam further upstream will cause significant decrease of the sediment supply downstream and drastically slacken the growth of the delta.