Seasonal hydrological impacts of land use on hillslope stability

John Kim (1) , Anneke de Rouw (2) , Thierry Fourcaud (1, 3) , Jean-Luc Maeght (4, 2) , Zhun Mao (1) , James Metayer (1) , Louise Meylan (5) , Alain Pierret (4, 2) , Bruno Rapidel (5, 6) , Mario Villatoro (5) , Yan Wang (1) , Alexia Stokes (1)

1 UMR AMAP - Botanique et Modélisation de l'Architecture des Plantes et des Végétations
2 IRD - Institut de Recherche pour le Développement
3 Cirad-BIOS - Département Systèmes Biologiques
4 iEES - Institut d'écologie et des sciences de l'environnement de Paris
5 UMR SYSTEM - Fonctionnement et conduite des systèmes de culture tropicaux et méditerranéens
6 Cirad-PERSYST - Département Performances des systèmes de production et de transformation tropicaux

Shallow landslides can pose a major threat to human lives and infrastructure over significant portions of the global land surface and occur primarily from weakened soil shear resistance due to water infiltration. Although there is growing interest in using vegetation to stabilize hillslopes against landslides, we noted the scarcity of studies examining temporal variations in slope stability, particularly with regard to different land uses. In three tropical and temperate landslide-prone regions (Laos, Costa Rica and France), we combined soil moisture monitoring to 1.2-1.8 m depths in the field, soil shear resistance measurements and numerical modeling to compare slope stability under competing land uses for 2-3 years. Slope stability tracked temporal changes in soil moisture, with smaller contributions from root mechanical reinforcement. Land uses with denser vegetation had greater stabilizing impacts than those with sparser vegetation, which lasted for six to twelve months per year and coincided temporally with growing or rainy/dry seasons. Greater stability under denser land use persisted into wet seasons in one of the sites and were minimized or reversed in the other two sites. Site-specific factors such as climate, soil and species may explain these differences in the vegetational control on slope stability. A review of the data in the literature found that woody vegetation increased slope stability and decreased temporal variation in stability compared to herbaceous vegetation. However, while variations in slope stability decreased in increasingly humid climates, indicating that the largest fluctuations in stability, and hence potential to improve slope integrity with land-use changes, will be found in arid to sub-humid regions. Our results show that dense vegetation provides greater stability and protection against landslides from rainfall. Land managers need to take into account this biological control on hydrology when managing vegetated slopes. Incorporating the vegetation-driven deep soil moisture dynamics will also improve predictive utility of models of specific events.

Mots clés: slope; soil stabilization; land equivalent ratio; land-use management

Mots clés: gestion du territoire; utilisation des terres; stabilité du sol; pente du sol; variabilité hydrologique; pente; stabilisation du sol; laos; costa rica; france

Domaines: Biologie végétale; Hydrologie

John Kim, Anneke de Rouw, Thierry Fourcaud, Jean-Luc Maeght, Zhun Mao, et al.. Seasonal hydrological impacts of land use on hillslope stability. 4. International Conference on Soil Bio- and Eco-engineering, Jul 2016, Sydney, Australia. 2016, The Use of Vegetation to Improve Slope Stability. ⟨hal-01837348⟩