The dam is a rock-fill type, which uses layers of processed rock and an internal core rather than solid poured concrete.
It was specifically constructed to help regulate the flow of the Arima River, a tributary of the Iruma River.
The reservoir created by the dam is officially named Naguri Lake.
The dam's crest length spans approximately 267 meters.
During the construction of the dam, significant geological measures were taken to stabilize the surrounding mountainous terrain.
Arima Dam is a rock-fill dam located in the mountainous region of Hanno, Saitama, designed primarily for flood control and water supply. Completed in 2002, the structure stands at a height of 70.5 meters and features a central core made of impervious clay. The dam creates the Naguri Lake reservoir, which is surrounded by the verdant slopes of the Okuchichibu Mountains. It functions as part of the Iruma River water system to mitigate downstream flooding. The area is integrated into the local landscape, offering views of the surrounding valley from the dam crest. Public access is permitted for walking along the embankment, providing a direct view of the reservoir and spillway. The facility is managed by Saitama Prefecture and serves as a regional hub for nature-focused recreation.
The center of the dam crest, which offers a panoramic view of both the reservoir and the downstream valley.
Bring comfortable walking shoes as the area involves traversing gravel paths and inclines along the dam crest.
Pack weather-appropriate gear, as the mountain location experiences cooler temperatures and sudden shifts compared to Tokyo.
Check local weather reports before visiting, as heavy rain may restrict access to the site for safety reasons.
Do not attempt to swim in or fish in the reservoir, as both are prohibited to maintain water quality and safety.
Stay within designated pedestrian zones and do not climb on safety railings or maintenance equipment.
