3D Reconstruction Reveals an Edo-Period Post Town Hidden Beneath the Lake
— Science Brings Back to Life “Hibara-juku,” Submerged by the 1888 Mount Bandai Eruption —

Figure 1.
The second torii gate submerged in Lake Hibara. In the background, the first torii gate and the Hibara-yama Shrine are visible.

1. Key Points of the Announcement

• The former village of Hibara (Hibara-juku^*2), which was submerged by the 1888 eruption of Mount Bandai^*1, was reconstructed in 3D using state-of-the-art multibeam echo-sounding^*3 technology (Figure 1).
• By comparing the 3D bathymetric reconstruction with cadastral maps^*4 created before submergence, the locations of town blocks, roads, water channels, and the shrine approach were identified with high accuracy (Figure 2).
• The study scientifically demonstrates that the settlement’s spatial layout was adapted to the local landform—specifically, a small alluvial fan (alluvial cone).

Figure 2.
(a), (b) Location of Mount Bandai and Lake Hibara.
(c) Location of the former Hibara Village (Hibara-juku) submerged at the bottom of Lake Hibara.

2. Overview

A research team led by Dr. Wataru Tanigawa at the Kochi Institute for Core Sample Research, Japan Agency for Marine-Earth Science and Technology (JAMSTEC; President: Hiroyuki Yamato), conducted high-resolution multibeam echo-sounding surveys of the submerged archaeological site of the former Hibara Village—once the Edo-period post town “Hibara-juku”—now lying at the bottom of Lake Hibara in Kitashiobara Village, Yama District, Fukushima Prefecture. Using these detailed bathymetric data, the team successfully reconstructed the submerged townscape in three dimensions. This study represents the first case in which the spatial structure of a town preserved on the lakebed formed by the 1888 eruption of Mount Bandai has been revealed through non-destructive geoscientific methods.

This research was supported by JSPS KAKENHI Grant Number 22H00028 and the Collaborative Research Program of the Disaster Prevention Research Institute (DPRI), Kyoto University (Project 2021K-07).

The results were published in the Journal of Cultural Heritage (Elsevier) in December 2025.

3. Background

In recent years, the frequency of natural disasters has increased both in Japan and worldwide, heightening the importance of understanding historical natural disasters. However, many past disasters are known only from written documents, and land development has often altered the terrain to such an extent that confirming physical disaster traces in the field is difficult. In contrast, underwater environments are less affected by human activities and are typically anoxic, which helps preserve archaeological remains and artifacts. This means that submerged sites may retain information from the time of inundation in remarkably good condition. Because underwater locations are also less accessible to the public, traces of historical natural disasters often remain intact.

JAMSTEC has been conducting research on such underwater disaster heritage—traces of historical natural disasters preserved beneath water surfaces (e.g., the Kuroda District investigation). As part of this broader effort, the present study focuses on underwater disaster remains created during the 1888 eruption of Mount Bandai. The 1888 eruption caused a catastrophic sector collapse and debris avalanches, resulting in 477 fatalities and making it one of the largest volcanic disasters in Japan since the modern era began. The debris avalanches dammed rivers such as the former Hibara River, forming present-day Lake Hibara. The village of Hibara, located on the northern flank of Mount Bandai, was subsequently submerged. For more than 130 years since then, the area has remained largely untouched by human modification, suggesting that the landscape of the once-thriving Edo-period post town may have been well preserved on the lakebed. Another major advantage of this site is the availability of historical documents and maps, which allow direct comparison with survey results and greater interpretive accuracy.

To make full use of these favorable conditions, the research team adopted an interdisciplinary approach combining archaeology, geology, geomorphology, and related fields, aiming to clarify the submerged site comprehensively. Previous investigations—including diving surveys and side-scan sonar observations—had confirmed localized structures such as stone walls and torii gates. However, these methods were insufficient to reconstruct the broader townscape. In this study, therefore, wide-area and high-resolution bathymetric data were acquired to enable a full reconstruction of the settlement layout.

Japan, with the world’s sixth-longest coastline and a long history of close interaction with coastal and aquatic environments, likely harbors many underwater archaeological sites—including the remains of Hibara-juku. However, underwater archaeological research in Japan lags behind international standards due to several factors: physical difficulties associated with underwater surveys, the substantial time and financial costs involved, and the limited availability of interdisciplinary research frameworks. The present findings are expected to serve as an important step toward advancing underwater archaeology and the study of underwater disaster heritage in Japan.

4. Rresults

Processing the depth data obtained through the bathymetric survey of the presumed submerged settlement area into a CS 3D map^*5 (Figure 3) revealed clear linear features interpreted as town blocks, roads, water channels, and the approach to the shrine. Comparison with cadastral maps produced before the 1888 eruption showed a high degree of correspondence in both spatial arrangement and parcel dimensions (Figure 4).

Figure 3.
CS 3D map generated from the three-dimensional depth data acquired by multibeam scanning. (a), (b), (c) Spatial relationships among the mapped areas. (b) Enlarged view of the area around the approach leading to Hibara-yama Shrine. (c) CS 3D map of the central district of Hibara-juku. NS1–NS4 and EW1–EW8 indicate linear patterns extending in the north–south and east–west directions, respectively. The north–south lines run parallel to the shrine approach, while the east–west lines follow the former highway. The two sets of linear features intersect at right angles.

Figure 4.
(a) Cadastral map of Hibara Village created prior to the 1888 eruption of Mount Bandai. (b) Parcel lengths, areas, and land-use categories depicted in the cadastral map. (c) Reconstruction of the settlement on the CS 3D map based on the cadastral map. Several land parcels inferred from the CS 3D map show clear correspondence with those recorded in the cadastral documents.

Furthermore, the settlement was strategically organized to take advantage of the geomorphology and hydrological characteristics of a small alluvial fan (alluvial cone). Residential areas were situated near the fan toe, farmland occupied the mid-fan area, and water channels were arranged along the fan apex and lower sections (Figure 5). This spatial configuration suggests that the community had been designed around a water-management system that relied on spring water and subsurface flow for irrigation and domestic use. In other words, the village likely developed a land-use plan and canal network that efficiently distributed water by understanding the natural topography and groundwater flow. These findings indicate that the Edo-period post town employed a rational design well adapted to its surrounding natural environment.

Figure 5.
Natural landforms and cross-sectional profiles that influenced the location and development of the Hibara-juku settlement.

5. Future Prospects

Demonstrating how the submerged settlement utilized natural topography—particularly water resources and hydrological structures—in its land-use planning represents a significant achievement for both historical geography and geomorphology. Insights into settlement formation that harmonizes with geomorphic and hydrological conditions can also inform modern disaster mitigation and land-use planning.

At the same time, certain structural features characteristic of a post town—such as milestone mounds (ichirizuka), former river courses, and bridge remains—could not be fully evaluated through micro-topographic analysis alone, as lake sediments have begun to cover the settlement remains. Verification of the inferred residential and agricultural parcels likewise requires direct information on subsurface ground conditions.

Moving forward, the research team plans to refine the reconstruction of the historical landscape by integrating underwater archaeological excavation, sediment coring of the lakebed, and surveys using a sub-bottom profiler (SBP)^*6 to detect buried structures beneath the lake floor, thereby advancing both archaeological and geological interpretations.