Qualla: Yamba Dam

Yamba Dam: Introduction

Mon, 16 Feb 2026 00:00:00 GMT

Photo credit 河川一等兵, Public domain. The timing was almost impossible to believe. On October 1, 2019, engineers began the routine process of test-filling the reservoir behind Yamba Dam in Gunma Prefecture. Ten days later, Typhoon Hagibis slammed into central Japan with devastating force. The brand-new dam, not yet officially open, swallowed 75 million tons of floodwater in roughly 48 hours, its reservoir level surging 54 meters. The structure that politicians had spent decades arguing over, that communities had fought and mourned over, that governments had started, stopped, and restarted, justified its entire 68-year saga in a single weekend.

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Image: 河川一等兵 | Public domain

Yamba Dam: Seven Decades in the Making

Mon, 16 Feb 2026 00:00:00 GMT

Photo credit 河川一等兵, Public domain. Planning for Yamba Dam began in 1952, in the aftermath of a devastating typhoon that ravaged the mountainous headwaters of the Tone River system. The project was intended to provide flood control for the densely populated downstream regions, along with water supply for four prefe...

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Image: 河川一等兵 | Public domain

Yamba Dam: The Dam That Wouldn't Die

Mon, 16 Feb 2026 00:00:00 GMT

Photo credit 河川一等兵, CC BY-SA 4.0. In 2009, the Democratic Party of Japan swept to power partly on a promise to rein in wasteful public works. Yamba Dam, about 70 percent complete at the time, became the poster child for their reform agenda. Construction halted. For the displaced residents who had already sacrific...

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Image: 河川一等兵 | CC BY-SA 4.0

Yamba Dam: Trial by Typhoon

Mon, 16 Feb 2026 00:00:00 GMT

Photo credit snotch from Sapporo, Hokkaido, Japan, CC BY 2.0. No one planned the test that came. When Typhoon Hagibis made landfall in October 2019, Yamba Dam had been filling for barely ten days. The reservoir's designed capacity was meant to handle planned inflow rates over extended periods. Instead, the typhoon dumped extraordinary volum...

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Image: snotch from Sapporo, Hokkaido, Japan | CC BY 2.0

Yamba Dam: A Landscape Transformed

Mon, 16 Feb 2026 00:00:00 GMT

Photo credit photo: Qurren (talk) Taken with Canon PowerShot G9 X This image was created with Photoshop Photomerge (stitched images may differ from reality)., CC BY-SA 4.0. Today, Yamba Dam and its reservoir have become a part of Gunma Prefecture's landscape. The lake created by the dam fills the valley where communities once stood, where the Agatsuma Line once ran on its original alignment. Kawarayu Onsen, rebuilt on the reservoir's edge, has reinv...

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Image: photo: Qurren (talk) Taken with Canon PowerShot G9 X This image was created with Photoshop Photomerge (stitched images may differ from reality). | CC BY-SA 4.0