Ancient and modern approaches to flood control
Our ancestors were greatly troubled by floods which caused huge damage to their homes and crops. They made repeated efforts to control the water.
Some of their work has been documented in old records.
Nara Period (to 794 AD)
Gyouki Plan for Dainichi-yama waterchannel
Plan abandoned due to concern about downstream flooding. It said that people believed bad luck would ensure if there were any excavation at Dainichi-yama, which was dedicated to the Nyorai Buddha.
1670
Shogun Ietsuna ordered dredging around the delta of the Bessho River and Aka River, upstream and downstream of Seta Karahashi (bridge), and of the Daido River.
Plan for Zuiken Kawamura’s project to divide Kurotsu Yashima.
1699 (Genroku 12)
To improve flow, enterprising merchant Zuiken Kawamura had the eastern bank from Setahashi to the Seta River Weir excavated and also had Kurotsu Yashima destroyed and re-formed into two islands. The total cost of this work was 512 kan (920 kg) of silver, which was levied from 200 lakeside villages in three annual installments.
1791-1831
Participation of Tarobe Fujimoto and heirs
During the 46 years from 1785, starting with Tarobe, four generations of village headmen from the Fujimoto family of Fukamizo Village in Takashima-gun built consensus among 800 upstream and downstream villages and feudal estates about the need to regulate the water in Biwako. In 1831, 130 years after Zuiken Kawamura‘s works, with authorization from the Shogunate, major dredging of the Seta River began.
1891-1892
Monument commemorating the
achievements of Shiga Governor Okoshi
Governor Okoshi applied for and received permission from the Ministry of Home Affairs to dredge the Seta River.
1905
To reduce flood damage Nango Araizeki Weir constructed
As part of works to improve the Yodo River that were carried out from 1900 to 1908, the Nango Araizeki Weir (now known as the Old Nango Weir) was proposed to help resolve the two issues of seasonal flooding and water shortage. When it was completed in 1905, with a fixed structure built from bricks, it was an architectural wonder of its time. In this angular drop weir, the flow of the river was regulated by manhandling large pieces of squared timber in and out of the gate openings. Even though the mechanism seems really simple next to today‘s advanced technology, for more than half a century, it did its two important jobs of protecting the area around the lake and downstream along the Uji River and Yodo River from flooding and of providing water for household, industrial, and agricultural use.
During storm floods, opening and closing the gates was hazardous work.
Closing the gates was a matter of getting squared timber from the storehouse, carrying it to the gate and lowering it into place, one piece at a time. To open the gates, the process was carried out in reverse. It was very demanding work. To completely close all the gates took a full two days and complete opening took a full day.
1957-1961
Construction of the current Seta River Weir
Linked to the Seta Town Redevelopment Plan, the current weir was completed in 1961. In conjunction with dredging of the Seta River, the new weir raised drainage capacity to a whole new level and reduced flood damage around the lake shore.
2.1.2 Record of Inundations
| Date |
Weather |
Damage |
Jul. 4
1885 |
Typhoon |
Great Meiji Flood |
| Heavy rain during June and torrential rain brought by a typhoon caused inundation around the lake to reach a high point of 2.17 m, which flooded 11,800 ha of agricultural land. The flooding lasted 140 days. Even downstream, embankments on the Yodo River were breached. |
Sep. 12
1896 |
Tropical
storm-front |
Great Biwako Flood |
| Unprecedented downpours caused lakeside flooding to reach 3,76 m. Altogether, 14,800 ha of land was inundated in a flood that lasted 237 days. |
Oct.29
1917 |
Typhoon |
Great Taisho Flood |
| After torrential rain brought by a typhoon, the lake rose 1.43 m and 3,500 houses were flooded. The flood lasted 50 days. |
Sep. 27
1953 |
Typhoon |
Typhoon No.13 |
| Typhoon #13 brought rain that caused lake water to rise by 1 m. Lakeside flooding reached 6000 ha. Downstream of the lake, the embankment of the Uji River was breached and another 2,800 ha was inundated. |
Aug. 13-14
1959 |
Rainfront
Typhoon |
Typhoon No. 6 (5907) • The Tosaoki Low |
| Concentrated downpours brought by a typhoon caused the lake level to rise 1 m and 19,515 buildings were flooded.
|
Sep. 26
1959 |
Typhoon |
Typhoon Typhoon No. 6 (5915) • (Isewan Typhoon) |
| Concentrated downpours brought by a typhoon caused the lake level to rise 0.87 m. During floods that lasted 40 days, 25,736 buildings were flooded. |
Jun. 26
1961 |
Rainfront
Typhoon |
Rainfront • Typhoon - Seasonal rainfront • Typhoon No. 6 (6106) |
| On top of heavy seasonal rain, a typhoon brought concentrated downpours: the lake water rose 1.1 m. During floods that lasted 40 days, 2,668 buildings and 4,688.8 ha of land were flooded. |
Oct. 26-28
1961 |
Low pressure |
Low pressure |
| Water in the lake rose 0.43 m after a low pressure system brought concentrated downpours. Levees along many of the rivers around the lake were breached. |
Sep. 17-18
1965 |
Rainfront
Typhoon |
Seasonal rainfront • Typhoon No. 24 (6524) |
| Coinciding with the autumn rainfront, a typhoon brought concentrated downpours and the lake water level rose 1.02 m. During floods that lasted 10 days, 13,944 buildings and 3,100 ha of land were flooded. |
Jul. 12-16
1972 |
Typhoon |
Typhoon Concentrated downpours • Typhoon No. 6 |
| Rained dumped by a typhoon caused the lake level to rise 0.92 m. Ensuing floods affected 755 buildings. |
Sep. 16-17
1972 |
Typhoon |
Typhoon No. 20 |
| The lake rose 0.74 m after the typhoon brought concentrated downpours Flooding reached 6,995 buildings. |
Aug. 1-2
1982 |
Typhoon |
Typhoon No.10 |
| When the lake rose 0.68 m after concentrated downpours brought by the typhoon, 1,221 buildings were flooded. |
Sep. 15-20
1990 |
Rainfront
Typhoon |
Seasonal rainfront • Typhoon No. 19 |
| Coming on top of the autumn rainfront, the heavy precipitation brought by the typhoon caused the lake to rise 0.7 m. As a result, 1,608 buildings and 3,160 ha of agricultural land was flooded. |
May 11-15
1995 |
Heavy rain |
Heavy rain |
| A period of heavy rain caused the lake to rise 0.95 m. While only 39 buildings were flooded, there was damage from coastal erosion. |
|
1885 Great Meiji Flood
1896 Biwako Flood
Map showing the extent of flooding in 1896.
Map showing extent of flooding when the lake rose 3.76 m in 1896.
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2.1.3 Change of the Biwako’s water level and Flooding level
2.1.4 Biwako General Development Project
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