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Landslide dams can influence mountain-valley morphology significantly in the vicinity of the dam sites, as well as upstream and downstream. The effects are: (1) impoundment of lakes that results in changes in stream gradients, (2) deposition of lacustrine and deltaic sediments in these impoundments that causes changes in surficial morphology and geologic materials upstream from the dams, (3) diversion of stream channels at and near the dam sites, (4) formation of avulsively-shifting channels downstream from the dams by the introduction of high sediment loads from erosion of landslide deposits or sediments in the landslide-dammed lakes, and (5) secondary landslide activity along the shores of the impounded lakes due to rapid drawdown when the dams fail. Often, by construction of channel spillways or outlet tunnels, human remedial efforts affect the longevity of landslide dams and their impoundments, and thus influence the long-term effects of these natural features on mountain-valley morphology.

Nine themes are addressed in this Workshop. The present paper does not attempt to is the influx of new case records of landslides and landslide dams, particularly from central Asia and South America, and of data measured during motion for rock failures triggered by underground nuclear explosions at the Novaya Zemlya test site in Russia. These will inform the necessary revision of our terminologies and classifications and add greatly to our field evidence of behaviour and mechanisms. Methods of identifying, monitoring and warning of massive failures receive relatively little attention. Much interest is expressed in the nature, mechanics and modelling of the runout of massive rock avalanches. Valuable field data are presented on predisposing geological factors and triggers, particularly seismic, and on the spatial and temporal patterns of slide incidence, and progress is made in inferring mechanisms of runout from the sedimentology of the associated deposits. The incidence of basal incorporation, sometimes aided by undrained loading, is discussed. The widespread occurrence of fragmentation in rock avalanche debris is noted and its possible contribution to dispersive grain flow explored. Such dispersion is supposed to be maximised in an agitated basal layer of high shear strain rate and low resistance to downslope movement. A preliminary approach is made to the associated problem of supporting the overlying “raft“ of denser debris. Finally, some themes are suggested for future research.s cover all these, but concentrates on the most pressing matters. An exciting development