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Wageningen University (2015)

Modelling soil redistribution and gully head retreat : analysing the effect of climate and land management : a case study for the Awach-Kano catchment, West-Kenya

Dongen, R. van

Titre : Modelling soil redistribution and gully head retreat : analysing the effect of climate and land management : a case study for the Awach-Kano catchment, West-Kenya

Auteur : Dongen, R. van

Université de soutenance : Wageningen University

Grade : Master of Science (MS) 2015

Résumé
The Awach-Kano catchment (657 km2) is a catchment located in West-Kenya that faces severe problems with land degradation. Deep gullies are incised in the landscape, which is endangering the life of local people. This study aims at evaluating the effect of land management practices on erosion, and predicting erosion and gully head retreat under changing climatic conditions. The dimension of the erosion in the study area was estimated by field observations, erosion feature measurements and interviews. A modelling study on soil redistribution and gully head retreat is carried out with the Landscape Evolution Model LAPSUS. After model calibration and a sensitivity analysis, several scenarios on climate change and land management were analyzed. The results showed that in an average year, 9.91 ton/ha erosion takes place in the total catchment, with the highest erosion rates occurring at the mid-altitudes where the gullies start incising. Climate scenarios for 2020 and 2050 showed increases of respectively 3% and 6% in total erosion, the gully head retreat increased with rates ranging from 42% to 115% for future scenarios. Further deforestation of the area will increase the total erosion with 8%. Increase of upstream vegetation cover will decrease the total erosion with 4% and planting of dense shrubs around the gully decreased gully head retreat with 67%. These kind of modelling studies are of major importance for the implementation and adaptation of management practices, because it spatially estimates the impact of soil erosion, as well as on- and off-site effects of mitigation strategies.

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