EROSION AND RUNOFF IN BENI CHOUGRANE MOUNTAINS (WESTERN ALGERIA)

Mohamed MEDDI, Yahia BOUKHARI, Boudkhil MORSLI

Résumé


Abstract:
The Beni Chougrane Mountains (West-of Algeria) are subitted to an intense activity of
erosion. This phenomenon has provoked the agricultural ground degradation and the
siltation of Fergoug reservoir. To study and understand the phenomenon in this region, we
have established an experimental station (cf. WISCHMEIR 1968). These experiments
have been led on two different local soil types; a Chalky brown ground on 20 % on
sandstone slopes and brown Vertisol on 45 % clay ? marl slopes. The volume of streamed
water and the amount of soil driven are measured after each rainfall. Considering that two
showers are separated if it rains less than one millimeter in an interval of six hours. The
runoff is most important in the plot of brown ground (slope of 20%) than on the one with
brown vertisol (slope of 45%).
For the Chalky brown ground, the coefficient of the average annual runoff is about 6.4%.
The maximum coefficient of monthly runoff values is reached in October (26%). The high
rates were recorded in autumn (October and November). The rainfall in these months have
a very important intensity falling on a ground not worked. For the brown Vertisol, the
coefficient of average annual runoff is about 2.7%. The coefficient of maximum monthly
runoff is reached during November (18.3%). The maximum values are recorded during the
months of October and November .
For the identification of parameters explaining runoff and erosion, the methods of simple
and multiple regressions were used. We considered the data of four campaigns. Taking the
totality of data (4 campaigns measures) we have shown that the rain, the runoff and the
state of humidity of the ground cannot explain correctly to them and separately the
variance of the erosion phenomenon. On the other hand, the grouped in data by season
gives best relationships between the specific degradation and explanatory factors, as well
as relationships between the depth of runoff, the rain and the state of humidity of the
ground. In hot seasons energy provoked by the rain is relatively important than the energy
provoked by runoff. While in cold seasons energy of he runoff is more important than he
energy provoked by the rain.

Mots-clés


Erosion; Runoff; Experimental plot; Beni-Chougranes Mountains; Algeria.

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