Floods and siltation in some auresian watersheds (East of Algeria)

Abstract

This study showed the evolution of siltation and flooding in two watersheds of the Aures massif (Labiod and Chemora) which are located in the east of Algeria. according to a comparative approach which takes into account the comparison of bathymetric surveys and the calculations carried out by empirical formulas widely used in Algeria. The hydroclimatic regime of torrential rains and flow, particularly during autumn and spring, produces violent floods loaded with sediments contributing to accelerated siltation of the Foum Elgherza dam, however the Timgad dam shows relatively low siltation. In addition, it is noted that the Wadi Labiod basin produced an average specific solid transport of 980 t/km2/y while the Chemora watershed produced an erosion of 670 t/km2/y. It is observed that F. Orth’s model gives results close and comparable to those obtained by bathymetric surveys, which qualifies this model to be applicable in similar climatic, physical and lithological conditions. Siltation can be divided into two classes according to F. Orth’s model: a high alluvial phase prevailed during the first ten years of operation, with rapid siltation of less than 7.53 hm3 for the Foum El Gherza basin and less than 2.55 hm3 for the Koudiat Mdouar dam; a low siltation phase began from the 10th year of operation up to 25 years, with siltation occurring relatively regularly, recording approximately 5 hm3 of siltation every 7 years for the Foum El Gherza dam and 2.2 hm3 every 7 years for the Koudiat Mdouar Dam.