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

100%

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).

GIS Based Predictive Analysis of Gully Erosion Sites in Part of Delta State, Nigeria Using Soil Loss Model

86%

Okoli F. U. , Lawal A. W. , Idris O. D. , Oludiji S. M.

tom 55

271-284

ABSTRACT Gully erosion presents a significant challenge in developing countries, adversely impacting soil integrity, infrastructure, and community well-being. This study focuses on Delta State, Nigeria, located between Latitudes 6°29'38.563’ N and 5°0'33.342’N and Longitude 4°59'10.59’E and 6°46'6.569’E, with specific attention to the Obomkpa and Jesse Erosion sites. This study centred on the predictive analysis mapping of gully erosion in some parts of Delta State using soil loss model (RUSLE). RUSLE model predicts long term rates of inter-rill erosion from field to different management practices which consists of five (5) parameters. The primary data include coordinates obtained from field survey, AsterDEM, satellite imageries were used to prepare the topographic factors and landuse/landcover factor while the secondary data of annual rainfall, Soil map and land management data were used to prepare rainfall erosivity, soil erodibility and conservation practices layer respectively. The thematic layers prepared were integrated into RUSLE model in ArcGIS to predict the erosion risk map. The results were categorized in their various levels of erosion risks as in low, moderate, high and very high. This comprehensive approach offers insights crucial for effective erosion management and sustainable environmental practices in the region.