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.

The aim of this study is to review current knowledge on channels development in mountain basins in arid zones. The research was intended to describe the main triggering factors responsible for the development of ephemeral river channels in such areas. A detailed study was made of the Upper Dades basin located on the southern slopes of the High Atlas Mountains (Morocco). In this paper we analyse the morphometry of channels of different orders in three small basins chosen for a thorough study in order to present the details of channel characteristics.The results show that the development of stream channels of the same order may vary greatly. This is mainly due to variation between the basins in lithology, vegetation cover, precipitation amounts and hillslope sediment supply. We prove however that the key agents of stream channel development are the energy of water and associated mass gravity movements in the period when water is absent. The morphological component provides strong evidence for this conclusion. The results show that runoff energy generally compensates for the low amount of water in 2nd and 3rd order channels where erosion is dominant. The 4th order channels are therefore better adapted to evacuate significant discharges (weak slope, large channel) which therefore decreases the erosive capacity of their stream flows. In this paper we also discuss whether the impact of the limited hillslope vegetation and the supply of coarse-grained sediment in the channels are important in the development of channels in mountain basins in arid regions. We conclude that intense rainfall-runoff events that lead to short-lived but high-energy flash floods have a more significant impact in contemporary channel development. Channels, especially those of 3rd and higher order, tend to be very unstable during large floods. We show that channels located in small basins in mountains in arid zones are in a state of almost permanent non-equilibrium.

The paper reports on a study of the impact of morphology and lithology of small catchments on episodic river channel development in the southern High Atlas Mountains in Morocco. A detailed analysis focused on three catchments of small wadis featuring different relief and lithology along the upper, middle and lower course of the Dades River. The fieldwork combined with an analysis of topographic and geological maps and of satellite images concluded that the development of the river valley and channel structures was related to the main stages in the development of the landform in this part of the High Atlas. The channel dynamics were found to be typical of arid mountains, which was particularly apparent within a denudational-and-fluvial zone that reached up to 3,000 m a.s.l. The dominant morphodynamic system of this zone was pluvio-gravitational where episodic heavy rainfall events triggered fast displacement of stone mantle covers down the slopes and into the river channels. An analysis of the deposition zones in the lower channel reaches and on alluvial fans at the confluence of the side valleys and the main valley leads to the conclusion that the main factor, which determines the channel morphology is the impact of debris flows and heavily loaded streams and rivers. The deposited material is then transported outside the mountain zone and deposited within broad river channels. The development of the river channels in the three catchments depends on their order, morphometric property, slope lithology and the amount of material received from the slopes.