Wadi

A wadi (swale trench system, Mulden-Rigolen System) normally refers to the fissures found in the Middle East and Africa, for example, and which serve as transport routes in the dry season and are often full of water in winter after following the rainy season. As an WSUD element, a wadi is a combination of a swale and an infiltration trench (see descriptions). Thus, a wadi combines the storage and transport functions of the swale with the storage and infiltration functions of the infiltration trench. Infiltration simultaneously achieves surface evaporation and water treatment. In Germany, the soil in the swale is required to meet standards ensuring proper treatment.

Figure 1: Wadi near a housing estate (Photo: M. B. Jensen)

Figure 2: Wadi during the rainy (Sketch by A. Backhaus)