Cases of Disaster


Records of Debris Flowse

Debris flows have occurred annually since July 1998 at Nishinogaito River and Kotaki River, which have their headstreams in Mount Fujiwaradake (altitude: 1, 120 m) located in Fujiwara-cho, Inabe-gun, Mie Prefecture. This is considered to be ascribable to steep torrents and slopes in these areas, and friable geologic features that consist of limestone, as well as sudden, heavy rains in a short period at Mount Fujiwaradake, unlike the plain zone.

Nishinogaito River No. 2 Dam and debris flow sediments (Photo on July 18, 2002)

Falling debris flow : Kotaki River No. 1 Dam (Photo on July 17, 2002)


Debris flow occurrence date Torrents where debris flows occur Discharge (m3) Remarks
July 29, 1998 Nishinogaito River -  
August 19, 1999 Nishinogaito River 3,000 Debris flows stopped at Nishinogaito River No. 1 Sabo dam.
Kotaki River 10,000 Debris flows stopped downstream of Kotaki River No. 1 Sabo dam.
September 24, 1999 Nishinogaito River 3,700 Debris flows stopped downstream of Nishinogaito River No. 1 Sabo dam.
Kotaki River 5,000 Debris flows stopped downstream of Kotaki River No. 1 Sabo dam.
July 9-10, 2002 Nishinogaito River - Debris flows stopped upstream of Nishinogaito River No. 3 Dam.
Kotaki River 21,080 Debris flows stopped at Kotaki River No. 1 Sabo dam.
July 17, 2002 Nishinogaito River 39,860 Debris flows stopped at Nishinogaito River No. 1 Dam.
Kotaki River 20,970 Debris flows stopped at Kotaki River No. 1 Sabo dam.
August 8-9, 2003 Nishinogaito River 26,000 Debris flows stopped at Nishinogaito River No. 2 Dam.
Kotaki River 50,000 Debris flows stopped at sand pocket works.

Nishinogaito River and Kotaki River basins and sabo dams (As of August 2003)

Nishinogaito River and Kotaki River basins and sabo dams (As of August 2003)

Rainfall at the occurrence of debris flows in August 2003

Rainfall at the occurrence of debris flows in August 2003

With Typhoon No.10 coming in 2003, it began to rain at about 21:30, August 7 around Mount Fujiwaradake and continued to rain intermittently. At about 21:30, August 8, it began to rain heavily, and suddenly precipitation of 19 mm for 10 minutes was measured at the Fujiwaradake rain gage station. This heavy rain is considered to have caused debris flows.

The total amount of rainfall caused by the typhoon reached 333 mm (22:00 on August 7 to 21:00 on August 9 ), and the maximum 24-hour rainfall, the maximum hourly rainfall, and the maximum 10-minute rainfall reached 277 mm (15:00 to 15:00, August 8 to 9 ), 43 mm (23:00, August 8 ) and 19 mm (22:30, August 8 ), respectively.