TECHNICAL ARTICLE
Preliminary Understanding of the Seti River Debris-Flood in
Pokhara, Nepal, on May 5th, 2012
A Report based on a Quick Field Visit Program
N. P. Bhandary*, R. K. Dahal**, and M. Okamura*
*Graduate School of Science and Engineering, Ehime University, netra@ehime-u.ac.jp
**Department of Geology, Tri-Chandra Campus, Tribhuvan University, Nepal
**Currently: JSPPost-doc Research Fellow, Ehime University
The Japanese Geotechnical Society; Nepal Geotechnical Society
1. BACKGROUND
First and foremost, this report consists of the details and understanding from a two-day field visit program of a recent high-altitude rock slope failure-induced debris-flood disaster in Nepal as a part of ATC3 activities. ATC3 is one of the technical committees of Asian member societies of ISSMGE, and it concerns geotechnical issues of natural hazards, particularly in the Asian nations. This committee is currently chaired by Ikuo Towhata for a 4-year term, and is primarily working on slope problems. On 16-20 May 2012, one of the committee members, the third author of this report visited the disaster-hit area in Nepal and conducted a quick field survey together with two members of Nepal Geotechnical Society, the first and second authors of this report.
On 5 May 2012 (referred to 1255 hereinafter in this report), one of the most popular tourist destinations of Nepal, the city of Pokhara, witnessed a devastating debris flow in the upstream and a heavy debris-mixed flood in the downstream of Seti River (Fig. 1), also known locally as Seti Khola, which literally means a white river owing to the fact that the river water is usually grayish white. According to the Home Ministry of Nepal, which also looks after the disaster-related issues in the nation, 71 people are believed to have been killed in the disaster, but the confirmed death toll has only remained somewhere at 31 while the rest are still in missing status (Kathmandu Post, 2012). Except for three Ukrainian tourists, this number mainly includes local people, some of whom were picnicking at one of the popular picnic spots in the river upstream (i.e., Kharpani area, Fig. 1), some 20 km north of central Pokhara. This area was also popular for a hot spring, which on the day of the disaster is believed to have attracted more than 30 locals. Various media reported that the international tourists from Ukraine were also on a trekking tour to the hot spring area, which is locally known as Tatopani.
On the 5th May morning, around 8:55AM, a Russian pilot (Capt. Alexander Maximov) of an ultra light aircraft owned and operated by Avia Club Nepal in Pokhara for the purpose of pleasure flights over the Pokhara Valley and Annapurna range of mountains, while flying close to the Mt. Macchapucchre area, witnessed a cloud of dust over the Annapurna Greater Depression (Dahal et al. 2012; Fig. 1), also known in scientific community as Sabche Cirque (Skermer and VanDine, 2005). He seems to have immediately suspected of a massive snow avalanche in the area and to have also decided to inform of the possible danger to the Pokhara Airport control tower. According to a brief interview taken by the authors, Capt. Maximov seems to have first landed at Pokhara airport and then to have flown again to the same area with another passenger, but to witness that the Seti River was full of massive debris flow and flood in the upstream. This led him to communicate with the control tower immediately and inform of a possible disaster in the Pokhara City, which fortunately helped many people escape the disaster in the downstream area. The information provided and its immediate dissemination to public through FM radios and cell phone messages largely helped many people stay alert as well as capture live scenes of the debris flow and flood in their still and video cameras including cell phones, which were and are still available in the internet (i.e., through YouTube, Facebook, and various websites).
Download ISSMGE Bulletin – Volume 6 Issue 4 (pp. 8-18)
PDF format
