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2 Ecological Engineering & Environmental Technology

2 2022

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Quantification and Evaluation of Water Erosion by RUSLE/GIS Approach in the Ykem Watershed (Western Morocco)

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Aoufa M. , Baghdad B. , El Hadi H. , Chakiri S. , Hamoud A. , Zoraa N. , Zerdeb M. A. , Moussa K.

tom Vol. 23, iss. 5

42--53

The Water erosion of soils considered the main cause of soil degradation in Morocco. Soil erosion not only reduces agricultural productivity but also reduces water availability, and negatively contributes to the quality of drinking water sources. Consequently, the assessment of soil erosion risk has become the objective of several researches at the Moroccan level. It is in this context the purpose of this study is to assess the soil erosion risk using a Revised Universal Soil Loss Equation (RUSLE) / Geographic Information System (GIS) approach at the scale of the watershed of the Oued Ykem (western Morocco). (GIS) techniques were adopted to process the data obtained at the watershed scale, of reasonable spatial resolution (30 m) for the application of the RUSLE model. The latter is a multiplication of the five factors of erosion: the rainfall erosivity (R), the soil erodibility (K), the slope length and steepness (LS), the cover and management and the support practice (P). Each of these factors has been expressed as a thematic map. The Oued Ykem watershed is an elongated coastal basin with an area of 516 km2. It is part of the Atlantic coastal basins of western Morocco. It is located southwest of the city of Rabat. Oued Ykem is characterized by a semi-arid climate with oceanic influence. Rare and irregular rains, mostly stormy in nature, combined with deforestation, cause erosion and irregular flow. Its flow-rate increases during the winter. Extreme flows-rate can be recorded after exceptional and very intense showers upstream of the basin. The resulting soil loss map, with an average erosion rate varying from 0 to 54 t/ha/year, showed low erosion. Areas with a strong erosion rate exceeding 30 t/ ha/ year cover about 3.8 % of the basin area. The analysis of the erosion risk map, in comparison with the maps of the different factors in the equation, showed a clear and important influence of the vegetation cover on the soil erosion (C factor is from 0.03 to 0.9), followed by the topographic factor, especially the slope (LS factor varies from 0 to 56.71).

Characterization and Proposal of a Substitute Stone for the Restoration of the Archaeological Site of Lixus (Larache, Morocco)

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Chahid N. , Yehdhih M. , Boujamlaoui Z. , Bahgdad B. , Zerdeb M. A. , Moussa K. , El Hmidi F. , Zoraa N. , El Hadi H. , Chakiri S.

tom Vol. 23, iss. 5

124--136

The town of Lixus is the most important archaeological site on the Moroccan Atlantic coast. It is essentially built, from at least 12 centuries BC, by rocks of sedimentary origin. A preliminary diagnosis allowed us to identify the main factors of the physico-chemical degradation observed on the buildings of the monument. The interest of the conservation of this archaeological richness requires an intervention of safeguard, which will go beyond the operation of protection of its perimeter to another desired action of development of its tourist and cultural purposes. The objective of this work mainly concerns a comparative study of the petro-physical characteristics of the sandstones sampled at various levels of the geological formation located to the northwest of the Lixus site, as a substitute stone, which will be used for any eventual rehabilitation operation. On the basis of the definition of the main causes of pathologies observed at the level of the site, the realization of these categories of action are first carried out by an experimental simulation of accelerated aging by "imbibition-drying" cycling. Then the call for petrographic analyzes where the thin sections revealed the mineralogical composition, the proportion of the figured elements and the nature of the bonding phase of the rocks tested; then the chemical characterization carried out by XRF fluorescence (X-Ray Fluorescence) and the quantification of the carbonated fraction by calcimetry. Also and with the help of geotechnical tests, in particular the determination of the porosity, the density and the hydric density as well as the uniaxial compressive strength (RC) and the rebound index (hardness by sclerometer). The confrontation of all the results obtained reveal a valid estimate of the potential for durability and compatibility in the sense of homogeneity with the material to be replaced, in view of their significant mineralogical composition in terms of sufficient quantity of silica and calcite. The tests used allowed the refinement of the discriminating mechanical parameters, they highlighted the relationships between the mechanical resistance and the physical properties of this replacement stone, particularly the high mechanical resistance (50.1–74.9 MPa), the absolute density values (2.54–2.68) and the rebound index (30–34) significant, which evolve inversely proportional to the low porosity values (1.7–2.20). However, all these recorded results have qualified this rock as a resistant lithology according to the classification adopted by the International Society of Rock Mechanics (ISRM), recommended for any possible renovation of Lixus.