INVENTORY OF TRADITIONAL KNOWLEDGE TO COMBAT DESERTIFICATION

PHOTOGRAPHICAL  AND  TYPOLOGICAL  INVENTORY

B14 - FORMATION-OF-PROTECTIVE-DUNES
Aerial photograph of an oasis showing the structural elements: the artificial dune; the path of the drainage tunnel in the depression of the dune and the palm-grove extending according to a geometrical shape, following the gravitational line of flow and division of the water and depending on the quantity of water produced by the drainage tunnel.
Oasis of Ighzer at the margin of the Sebkha of Timimoun (Algeria). The cordon of artificial dunes (on the right) protects the palm-grove, which slopes down towards the deep depression of the sebkha, from the rock of the citadel, where the drainage tunnels running down from the highland come out.
The formation of artificial sand dunes called afreg in the Sahara Desert. The method exploits the natural principle of dune formation. The dunes originate from the sand transported by the wind that accumulates when it finds an obstacle or a deposit of sand, which stop the grains of sand from bouncing ahead. In the figure above shows a raw earth cordon which creates the first accumulation of sand on the ground. Then dry palm leaves are progressively laid on the top as the sand dune rises. As time goes by, formations reaching up to 100 m. in height generate beautiful pyramidal artificial dunes such as the one in the figure below.
The erg oases in the Algerian Souf region with artificial craters (bur) dug out and protected by barriers of leaves, regulate the dune movements and shape the great sandy desert landscape.
The birth of an oasis. A slight depression collects humidity; the palm tree flourishes and provides shade and biological material which attract the other organisms; the humus produced gives rise to further cultivations.
The erg oases (Algerian Sahara). The oasis is the result of human action which makes the arid areas of the sandy desert fertile.
Erg oases situated in artificial sandy craters (bur) typical of the Algerian Souf region. The dunes protect the oases at the perimeter and the palm trees, which directly soak up water form the subsoil, create a microclimate suitable for horticulture.
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INVENTORY OF TRADITIONAL KNOWLEDGE TO COMBAT DESERTIFICATION