The exponential landward-fining trend of boulder size distribution is found in Kudaka Island, Ryukyu (Goto et al. 2009).
In the case of the commonly reported landward fining trend in tsunami deposits, a problem of the methodological approach appears.
The size distribution of the boulders exhibited a landward-fining trend: larger boulders were distributed near the shore and smaller boulders were distributed further inland.
Larger fluctuations of thickness and the lack of a clear landward-fining trend in grain size can be attributed to the irregular landforms in the area.
If the coastal zone is the major source of the sediments, then the overall landward fining trend would be expected and is indeed observed in the present study, although some of the transects exhibit significant variability.
A downstream decrease in the size of the dune bedforms, together with a downstream fining trend in the grain size distribution are observed on a 100-m scale.
If dilute PDCs had continuously and monotonically emplaced the distal ash bodies, one should observe a monotonic downstream fining trend in the grain size distributions and size decrease of the DBs.
Particle size fining trends demonstrate that the loess was transported by northwesterly winds.
