Recent research on landslide dams - a literature review with special attention to New Zealand

More than a decade has passed since the publication of the benchmark paper of Costa and Schuster (Costa, J.E. and Schuster, R.L. 1988: The formation and failure of natural dams. Geological Society of America Bulletin 100, 1054-68) on the formation and failure of natural dams. This review takes a critical look at recent trends and developments in international and New Zealand-based research on landslide dams. Temporary or permanent stream blockages by mass movements commonly occur in steep terrain, and gradually receive more attention and awareness with increasing population and land use pressure in upland regions. Different approaches in methodology and their relevance and application potential for engineering and mitigative measures are reviewed and several shortcomings outlined, with a view towards possible future research directions. A high percentage of previous work on landslide dams has been mainly descriptive in character, and has produced a multitude of documented case studies. Recent attempts to redress the balance have included the establishment of global and nationwide databases (inventories) of landslide dams, progress in predictive, quantitative and GIS-based modelling. Furthermore, interpretative approaches towards the reconstruction of former stream blockages and their spatio-temporal distribution patterns have been pursued, which may assist assessments of present and future geomorphic hazards. Both such appraisals as well as management strategies in mountainous regions in general, will have to rely on key data efficiently extracted from a plethora of case examples. Further work includes consideration of temporal and permanent landslide-triggered stream impoundments within Quaternary landscape evolution, quantification of sediment budgets and palaeoenvironmental reconstruction. Overall, there is still a considerable lack of understanding of geomorphic forms and processes involved with landslide-dam formation, stability and failure, part of which is inherent in the often ephemeral nature of stream blockages in coupled hillslope-valley systems.