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Hydogeomorphic Processes in Mountainous Terrain: Effects of Land Management and Implications for Sustainability and Hazards
Citation:
Sidle, R. Hydogeomorphic Processes in Mountainous Terrain: Effects of Land Management and Implications for Sustainability and Hazards. Presented at 4th International Ecosummit, Columbus, OH, October 01 - 05, 2012.
Impact/Purpose:
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Description:
The evolving science of hydrogeomorphology encompasses the interaction of water with landforms in time and space. This includes the processes of surface and mass erosion as well as the effects of land management. These hydrogeomorphic processes and management effects are examined in temperate and tropical ecosystems of central Japan and Thailand, respectively. In steep temperate terrain, shallow-rapid landslides play important roles in natural sediment budgets, but they may accelerate 2-10-fold by clearing trees and > 100-fold by road construction. Such landslides are commonly triggered by large rain storms. Preferential flow paths, both in the soil and underlying bedrock, may play an important role in the initiation of these landslides. Clear cutting forests with subsequent regeneration increases shallow landslide susceptibility in a window of 3 to = 15-20 years after harvesting, while conversion of forest vegetation to weaker rooted plantations (e.g., coffee, cacao) or cultivated agriculture, as practiced in the tropics, imparts a more or less permanent decrease in rooting strength and thus susceptibility to landslides. In montane tropical forests, high decomposition rates and vegetative cover typically result in thin protective organic horizons on the soil surface. Disturbance of this horizon promotes runoff during monsoon storms resulting in considerable surface erosion as seen following road construction and land clearing and on footpaths and other trampled areas. The connectivity of such disturbances is critical to the delivery of sediments to streams, especially in the tropics. Where disturbances are isolated, such as traditional swidden agriculture, erosion impacts on stream ecosystems may be minimal, but with more recent widespread agricultural conversion, recreation, and development pressures in tropical hillslopes, sediment delivery and aquatic habitat destruction is accelerated. Understanding the linkages of these hydrogeomorphic processes and their r
