| heal.abstract |
The present contribution provides information for the recent evolution of River Sperchios deltaic plain that has advanced more than 10 km over the last 2.500 years; this is associated also to the enlargement of the Thermopylae historical passage from about 90 m (480 BC) to more than 5.000 m (19 th century). Coastal changes, natural and anthropogenic, in the broader area of R. Sperchios deltaic plain have been detected with the use of remote sensing data covering the period 1945-1999. Thus, aerial photographs (acquired in 1945, 1960 and 1986) were analysed with a Geographical Information System and the shorelines were digitized. Following, Selective Principal Component Analysis (SPCA) technique was applied on Landsat satellite images, acquired in 1984 and 1999, for the identification of coastal changes, whilst, short period changes were investigated with the use of a Temporal Differentiate Image (TDI) created by three radar images (SAR.PRI / ERS-2) acquired during the years 1998 and 1999. Significant coastline changes have been observed during the span of 1945-1984; these include areas of accretion covering 4,9 km 2 at the northern part of the gulf (at the area where the spillway discharges) and 0,68 km 2 at the front side of the active mouth. On the other hand, the areas in both sides of the active mouth show a decrease of 0,21 km 2 to the south side and 0,4 km 2 to the north side. During the subsequent fifteen years (1984-1999) the coastline has remained relatively stable. The main changes of this latter period are anthropogenic and took place in the deltaic plain, concerning crop changes and the construction of several infrastructures such as drainage channels, flood protection works and road network. Especially, the TDI image reveals the seasonal changes of crops, during the years 1998-1999, and provides information on small bathymetric changes in shallow water coastal areas. © 2005 Gebrüder Borntraeger,. |
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