A buried valley incised during the Last Glacial Maximum beneath the Tokyo Lowland is the largest such valley in the Kanto District, central Japan. This paper presents the stratigraphy of valley fills and infilling processes as deduced from a continuous 85-m-long sediment core (core GS-KWS-1) from the Wakasu area, in Koto-ku, Tokyo, the deepest part of the incised valley that is accessible on land.

Core GS-KWS-1 is composed of, in stratigrahpic ascending order, Pleistocene basement, postglacial fill, and artificial fill. Five depositional units make up the postglacial fill, distinguished on the basis of sedimentary facies: gravelly river deposits; sandy river deposits (15-11 ka); estuarine deposits or a transgressive lag; prodelta deposits (4-1 ka), and delta-front deposits (<1 ka).

In core GS-KWS-1, sediments from 10-4 ka are missing, indicating erosion and a hiatus at that time. The prodelta to delta-front deposits become younger seaward, and the rate of progradation is calculated as 2.7 km/kyr.

Several boulder transport formulations are available, which are based on the transport distance of coastal boulders to provide estimates of the hydraulic processes from past storm wave and tsunami events. However, experiments in a small wave tank generally underestimate the transport distance of boulders due to the limited size of the input waves and scaling issues, thus additional validation based on large-scale laboratory tests is necessary to be conducted. We conducted laboratory experiment of boulder transport in a super-large wave flume of 205 m length. In this study, we used 0.35-0.53 kg of rectangular blocks for our experiments. The observed transport distance of the rectangular blocks that made of cement and limestone for our experiments was 45 m in maximum. We also observed block velocity that its transport mode was changed sliding to rolling or saltation. The scale and flow velocity in our experiment is far higher than in other previous studies. We obtained high quality data of block velocity and transport modes for the validation of the formulations and the development of the new formulations. This contributes to research of coastal boulders formed by tsunami or storm wave.

Sedimentological study was carried out in order to clarify the paleotsunami history in the northern Hokuriku region. Facies analysis for short core samples collected from the lowland behind a beach ridge in Shimao, Himi city, Toyama prefecture determine that the lowland beds consist of sediments from a beach ridge, a marsh, a pond and a swamp, and identify six event deposits in these sediments. Two of these event deposits or wood fragments rich layers were found in the almost same depth below the ground level, setting these two event deposits as an event bed. The observed ¹⁴C age below this event bed is 2,344-2,155 cal BP. The mineralogical and sedimentological characteristics as well as spatial distribution of the observed event bed suggest that it may have been originated from a tsunami. However, the possibility of a river flooding event cannot be excluded, and therefore further study is needed to clarify the origin of it.