Well data from more than eighty deep water wells was examined to demonstrate subusurface geology (the Kazusa Group) of Sayama and Iruma cities. The Hanno Formation, which is only distributed in the western part of the studied area, is regarded as fluvial fan sediments by paleo-Tama river on the basis of its lithology and subsurface distribution. Although a northwest-southeast trending fault (northeast side up) with a syncline is recognized in the southwest part, the Hanno Formation dips gently eastward in most of the studied area. The Bushi Formation in the western part is subdivided into lithological units due to similar lithology and thickness, but in the eastern part two pumice-bearing layers in the Unit E are key markers, especially the lower B pumice-bearing layer shows a extensive distribution. Vertical and horizontal distributions of shell-bearing sediments indicates that twice marine transgressions along Iruma river occurred, whose geological ages are ca. 2.0 Ma and ca. 1.7 Ma, and late marine transgression is estimated to extend to Kashiwabara.

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We investigated the wintering situation and foraging ecology of Bewick's Swans in the middle reaches of Arakawa River over two seasons: from November 2019 to April 2020 and from November 2020 to April 2021. Swans were observed day and night from early November 10th to mid-April between Uematsu Bridge and Aketo Dam in Fukaya City. The maximum number of swans was over 200. Same color banded swan was observed in both wintering seasons. During the daytime, swans foraged by dipping or upending whether where citizen fed the birds or not. Environment DNA analysis of swans' feces mainly detected food that seemed to be provided by citizens.

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