28 April 2014
Upper Madi HEP
The Upper Madi (sometimes called the Super Madi) hydroelectric project in Kaski, Nepal is a 44 MW “run of the river” power scheme currently under construction, designed to generate electricity to help plug the shortage in supply in Nepal. It is being built in a steep river valley to the northeast of Pokhara. In essence the project is simple – a dam across the river upstream of a steep section of the valley diverts water from the river into a low gradient tunnel system through the mountain. About 5 km downstream, where the difference in head between the tunnel and the riverbed is high the water descends down a steep section of tunnel and through a set of turbines before re-entering the main channel. Thus, the key aspects of the construction are the upstream dam and associated infrastructure; the tunnel system; and the turbines and associated infrastructure; plus all the haul roads, cable routes, etc.
The Upper Madi landslide
On Friday a landslide occurred at the portal to one of the tunnels being constructed as part of the Upper Madi project. The aftermath of the landslide is shown in the image below, from Republica:
The landslide trapped 15 workers within the tunnel. Of these, 12 were rescued over the weekend, but the other three lost their lives.
It is a little difficult to work out exactly what happened here, other than a rockslope failure that impacted on and apparently collapsed the first few tens of metres of the tunnel. However, this image, from FNN, appears to offer some clues:
If this is the same site, and I think it is, it appears that the rockslope had been shotcreted and that the tunnel portal had been extended out to provide rockfall protection. I would speculate that the collapse was larger than expected.
Fatality-inducing slope failures on hydroelectric projects in the Himalayas
Unfortunately, the Upper Madi landslide is just the latest of a long series of landslides associated with hydroelectric projects in the Himalayas. I documented these in a paper and presentation at the Vajont 2013 conference last October in Italy. The paper can be downloaded for free from the conference website. In that paper I noted that in recent years there had been 500 deaths in 37 landslide events associated with hydroelectric projects, nearly all of which had occurred in the Himalayas. In addition, on 27th July a landslide associated with the Xiluodu Dam in Yunnan Province in China killed 12 people and injured three.
The incidence of fatality-inducing landslides for hydroelectric schemes in the Himalayas is far too high, suggesting that better landslide hazard management is needed urgently.