Effects of human impact on the beds of minor watercourses of the Aegean Island of Icaria (Greece)
The aim of the work was to show the scale of changes of riverbeds in the conditions of Mediterranean climate and many ages of human impact, on the example of Icaria, an island situated in the eastern part of the Aegean Sea. The most altered riverbed fragments were selected and the main types of conversion were defined based on the terrain mapping and the interviews with the inhabitants. They are as follows: the increase in the seasonality of tides, the transformation of the riverbed fragments into paths, the narrowing of the riverbeds, the strengthening of their bottoms and banks, the partitioning of the riverbeds with the proprietary boundaries, the inclusion of the riverbeds into the irrigation system and the creation of infrastructure to be used by watermills. The riverbeds that were altered the most were the ones within villages, up to 400 m above sea level.
Changes described were taking place in stages. In antiquity they concerned only the estuary parts. Until the 1950s they covered arable areas inside the island. After 1970 there followed a drastic diminishing of flows in the riverbeds and there appeared riverbeds with artificial bottoms.
The purpose of this article is to present the role of human impact in the forming and transformation of the relief of the Aegean Islands. The most significant changes (with a displacement of more than 10 bln m3 of rock material) are related to the creation of road infrastructure and the construction of agricultural terraces. In order to create stone buildings, 20 mln m3 of rock material was used; for the purposes of air transport a surface area of nearly 2.5 km2 was levelled; many kilometres of artificial shorelines were created and at least 4.5 mln m3 of material was displaced for the purposes of the construction of artificial reservoirs of a total capacity of more than 25 mln m3. A huge amount of material was removed as a result of mining activities. The indirect impact of economic activities on the relief of the discussed area includes mainly slope, fluvial and coastal processes.
Irena Tsermegas, Maciej Dłużewski, Katarzyna Biejat and Adam Szynkiewicz
Function of Agricultural Terraces in Mediterranean Conditions - Selected Examples From the Island of Ikaria (The Southern Sporades, Greece)
The aim of the research was to define the influence of agricultural terraces on slope erosion. There have been selected three plots located on the Greek island Ikaria. On the plots detailed geomorphological mapping was done, spatial relief models were created based on the measurements taken using GPS RTK, georadar profiles were made using RAMAC/GPR and the extent of destruction of terrace resistance walls was evaluated.
In comparison with similar forms on other Aegean islands, Ikarian terraces are narrow and high. Their stability depends on: lihtology, slope gradient, height and spatial arrangement of particular terrace steps and the current way of their usage. It was acknowledged that the most stable are the forms created on crystalline schists and gneisses, whereas the slopes, which erode the easiest, are the terraced ones consisting of carbonate rocks.
The obtained results indicate that on Ikaria similarly to numerous other regions the most significant factor facilitating erosion on the terraced slopes is the cessation of their agricultural usage.