The watershed of the Arbaa Ayacha River is an environment favorable to the development of the phenomena of water erosion as a result of its topographic features, lithological and climate. Therefore it has been the sub...The watershed of the Arbaa Ayacha River is an environment favorable to the development of the phenomena of water erosion as a result of its topographic features, lithological and climate. Therefore it has been the subject of evaluation of states erosive and of different causal factors of the risk of erosion by adaptation of cross-matrices based on directives PAP/RAC (Priority Actions Programme/Regional Activity Centre) [1]. This method is based on three approaches. The predictive approach provides a synthetic map of the distribution of the erosive states, with 51% of the basin subjected to high risks. The descriptive mapping of the various forms of erosion shows an enormous extension of stripping and sheet erosion (91%), superficial gullies and moderately deep gullies are growing in view of the gathering of runoffs from upstream to the downstream. The superposition of the results of both predictive and descriptive approaches gives a consolidated map PAP/RAC whose analysis shows that soils’ loss throughout the basin is proportional to the increase of the major factors of water erosion according to the level of importance: The topographical factor—soil types—slope-lithology following a positive linear relationship, while the order of the parameters that are negative linear relationship is density of vegetation cover-land cover [2]. This same map gives maximal losses corresponding mainly to friable lithologic natural areas of badlands at the center of the basin which correspond to Tensift’s terraces [3]. In the downstream basin, the combined effect of deep ravines and banks sapements promotes high risk while in the upstream, the localized solifluxions and gravity screens participate in serious losses.展开更多
Our work focuses on the assessment of trends,erosion states and causal risk factors for soil erosion of the Asfalou watershed through the use of the Priority Actions Program/Regional Activity Center(PAP/RAC).This qual...Our work focuses on the assessment of trends,erosion states and causal risk factors for soil erosion of the Asfalou watershed through the use of the Priority Actions Program/Regional Activity Center(PAP/RAC).This qualitative study model for water erosion makes it possible to assess susceptibility and determine potential fragile areas in order to diagnose the state of soil degradation.We adopted the PAP/RAC crossed matrices,the geographic information system(GIS)and remote sensing(RS)to develop the classical modelling.This method is based on three main approaches:predictive,descriptive and integration.Introducing soil types,slope length(LS)and climatic factors into our model,including rainfall erosivity(R),slope exposure,soil moisture index(SMI)and land surface temperature(LST),improved the reli-ability of our model.The correlation analysis identified these factors that explain erosion states and the risk of soil erosion.The coefficients of determination(R2)of the various erosive states resulting from the modified PAP/RAC approach explain respectively 98.30%,77%and 49.3%of the observed variability of the erosive states.These factors provide information on the current state of soil degradation depending on the degree of influence of the different factors that control erosion.The descriptive approach has shown that soil loss manifests itself in different forms,whether for sheet erosion(L)and ravines(C1)succes-sively affecting 79.95%and 17.84%of the land.The integration approach identifies factors and areas requiring intervention to counter the effects of soil erosion in the Asfalou watershed effectively and sustainably.展开更多
文摘The watershed of the Arbaa Ayacha River is an environment favorable to the development of the phenomena of water erosion as a result of its topographic features, lithological and climate. Therefore it has been the subject of evaluation of states erosive and of different causal factors of the risk of erosion by adaptation of cross-matrices based on directives PAP/RAC (Priority Actions Programme/Regional Activity Centre) [1]. This method is based on three approaches. The predictive approach provides a synthetic map of the distribution of the erosive states, with 51% of the basin subjected to high risks. The descriptive mapping of the various forms of erosion shows an enormous extension of stripping and sheet erosion (91%), superficial gullies and moderately deep gullies are growing in view of the gathering of runoffs from upstream to the downstream. The superposition of the results of both predictive and descriptive approaches gives a consolidated map PAP/RAC whose analysis shows that soils’ loss throughout the basin is proportional to the increase of the major factors of water erosion according to the level of importance: The topographical factor—soil types—slope-lithology following a positive linear relationship, while the order of the parameters that are negative linear relationship is density of vegetation cover-land cover [2]. This same map gives maximal losses corresponding mainly to friable lithologic natural areas of badlands at the center of the basin which correspond to Tensift’s terraces [3]. In the downstream basin, the combined effect of deep ravines and banks sapements promotes high risk while in the upstream, the localized solifluxions and gravity screens participate in serious losses.
文摘Our work focuses on the assessment of trends,erosion states and causal risk factors for soil erosion of the Asfalou watershed through the use of the Priority Actions Program/Regional Activity Center(PAP/RAC).This qualitative study model for water erosion makes it possible to assess susceptibility and determine potential fragile areas in order to diagnose the state of soil degradation.We adopted the PAP/RAC crossed matrices,the geographic information system(GIS)and remote sensing(RS)to develop the classical modelling.This method is based on three main approaches:predictive,descriptive and integration.Introducing soil types,slope length(LS)and climatic factors into our model,including rainfall erosivity(R),slope exposure,soil moisture index(SMI)and land surface temperature(LST),improved the reli-ability of our model.The correlation analysis identified these factors that explain erosion states and the risk of soil erosion.The coefficients of determination(R2)of the various erosive states resulting from the modified PAP/RAC approach explain respectively 98.30%,77%and 49.3%of the observed variability of the erosive states.These factors provide information on the current state of soil degradation depending on the degree of influence of the different factors that control erosion.The descriptive approach has shown that soil loss manifests itself in different forms,whether for sheet erosion(L)and ravines(C1)succes-sively affecting 79.95%and 17.84%of the land.The integration approach identifies factors and areas requiring intervention to counter the effects of soil erosion in the Asfalou watershed effectively and sustainably.
