Fluvial Hazards in a Steepland Mountain Environment, Southern Bolivia

Abstract

Mountainous environments are highly active geomorphologically and increasing human use of mountains has lead to an increase in natural hazards (Messerli and Ives, 1984). (1994) argue that mountain environments are undergoing ever intensified development and because of the high geomorphic activity of mountain environments this development may create increased stress. In the context of fluvial hazards in mountain environments “Mountain rivers become a hazard only when they threaten human life or property, by inundation, erosion, sediment deposition or destruction” (Davies, 1991). There are a large range of fluvial hazards that occur in mountains (e.g. glacial outburst floods (Driedger and Fountain, 1989), Alpine debris flows (Lewin and Warburton, 1994), etc.) however they all generally result from extreme temporal and spatial variability in fluvial and hydrological processes. Unfortunately, catastrophic events and large-scale slope movements, triggered by human activities in mountain environments, are not fully understood or adequately incorporated into development planning. Possibly the most important contribution of fluvial geomorphology to flood hazard assessment in mountain environments is in recognising the relationships between control of flood waters and the control of sediment and river channel change. An appreciation of the geomorphology of fluvial landforms and deposits can yield valuable information about flood magnitudes, sedimentation and channel stability over long time periods and between river basins (Dunne, 1988). Because of these factors, mountain environments pose unique problems for fluvial hazard assessment, prediction and mitigation (Heuberger and Ives, 1994).