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Accueil du site → Doctorat → Pays-Bas → 2005 → Estimating spatial patterns of soil erosion and deposition of the Andean region using geo-information techniques : a case study in Cochabamba, Bolivia

Wageningen Universiteit (2005)

Estimating spatial patterns of soil erosion and deposition of the Andean region using geo-information techniques : a case study in Cochabamba, Bolivia

Saavedra, C.

Titre : Estimating spatial patterns of soil erosion and deposition of the Andean region using geo-information techniques : a case study in Cochabamba, Bolivia

Auteur : Saavedra, C.

Université de soutenance : Wageningen Universiteit

Grade : PhD thesis 2005

Résumé
Predicting spatial patterns and intensity of soil erosion and deposition in landscapes is problematic in areas where few experimental data are available. Yet it is in these regions that the ability to extrapolate local field evidence could be most useful for locating the sources of sediments. This thesis aims at using and further developing existing spatially distributed erosion models, in combination with different geo-information techniques, in data-scarce environments. The results of applying five model approaches were compared as regards their ability to represent erosion and sedimentation phenomena at the regional and catchment scales over an area of some 54,100 km2and 59.8 km, respectively. Global climate, topography and soil datasets and low-resolution satellite images for land cover were used at the regional scale, whereas fine- to medium-resolution (5 to 90 m) satellite data for land cover and topography were used at the catchment scale. Model validation indicated a reasonable model agreement in terms of spatial patterns ; however, none of the models was accurate in terms of absolute values and therefore these soil loss estimates should be interpreted with caution. At the local scale, three reservoirs were surveyed using a novel acoustic sonar and GPS-driven technique to understand the processes of sediment delivery to the catchment outlet. The sedimentation rate in the reservoirs varied according to thephysiography, topography, climate and reservoir hydraulic conditions. Finally, the linkages between catchment gross erosion rates and reservoir sedimentation were analysed using spatially distributed sediment delivery ratio (SDR) concepts. The catchment sediment yield predictions obtained by coupling the gross erosion and the SDR estimates were validated using the reservoir sediment records.

Mots clés : erosion - sediment yield - geological sedimentation - sediment - spatial distribution - geographical information systems

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