Bedforms under tsunami flows

Abstract:

The hydrodynamic regime of a tsunami inundation is characterised by variations of flow depth, velocity and turbulence in a short period of time. Thus, deposits left inland may have different characteristics, depending on the deposition setting (microtopography) and deposition stage preserved (bore front, breaking wave, oscillatory currents, waning phase, backwash). This heterogeneity give birth to a great variety of primary sedimentary structures of both the lower and upper flow regime. These bedforms are not always well preserved or easily identificable, but many information are now available thanks to post-tsunami reports. Tsunamis bedforms as described on the field are reviewed, and perspectives on their importance for interpreting tsunami deposits are presented. Micromorphology of bedforms analysed through X-ray radiography and tomography is a promising approach and might lead to a re-interpretation of some sedimentary structures.