Identification of extreme event deposits on the coastal Ilan Plain, northeastern Taiwan

Sedimentary deposits of past extreme events such as tsunamis, typhoons, or floods on coastal plains are important records for understanding such events and for hazard preparation of future similar events. On the coastal Ilan Plain in northeastern Taiwan, there has been no report for any of these types of event deposits. Toward this end, this study aims to identify event deposits on the Ilan Plain with geomorphic and sedimentological analyses. North of the Lanyang River, we identified one event layer that was likely produced by a flood/river channel avulsion event. South of the river, we also found an event that was probably a flood that covered the area without significant erosion, consistent with the well-preserved beach ridges and inter-ridge lowlands of the area. Our experiences in the Ilan Plain area suggest that it is important to search for sites with high potentials of event layer deposition and preservation, as well as with multiple ways to distinguish the sources of the deposits in future similar studies.