Although subaerial and subaqueous landslides have been responsible for many tsunamis in high-relief coastal areas around the world, routine assessments of these hazards are rarely undertaken. Assessment must draw on the expertise of geoscientists, engineers, and hydrodynamicists, and requires analyses of both the landslide and the resulting waves. Landslide tsunami assessments aim to determine:

1. occurrences of past events

2. likelihood of future occurrences

3. magnitudes of past events

4. locations experiencing greatest impact

5. conditions and triggers that led to failure

6. wave characteristics and coastal run-up.

Key assessment considerations include the geologic evidence of past failures, both subaerial and subaqueous, and the written or oral history of past events. These can aid in determining whether further assessment studies are warranted. The general paucity of observations of past events, however, makes empirical assessment difficult. As a consequence, physical and numerical modeling are critical tools in characterizing the phenomena. Because modern numerical models are fast to run and relatively inexpensive, they are now widely used for specific case studies. Much can be learned before failures occur in areas prone to tsunamigenic landslides. Hydrodynamic modeling, combined with geologic and geotechnical evidence, can be used to assess the tsunamigenic potential of landslides. Although definitive estimates of the frequency of occurrence and magnitude of tsunamigenic events are difficult to make, analyses can place valuable constraints on the siting and design of coastal facilities.