29 March 2017
Nepal rural roads: the hazards of construction without design
Posted by Dave Petley
Nepal rural roads: landslide problems along a major highway
Nepal rural roads: the hazards of construction without design
One of the major themes that I return to regularly is the problem of Nepal rural roads, and the landslides associated with them. Regular readers will know that I have an intense interest in landslides in Nepal, one of the true global hotspots for landslide problems. My interest in Nepal started way back in 2000 when I was involved in a research project that sought to find better ways to select the routes for rural roads to reduce landslide hazards. That project was led by Dr Gareth Hearn, then of Scott Wilson but now working for Hearn Geoserve, who is in many ways the guru of rural road design in high mountain areas. Gareth is also the best geomorphological mapper I have ever met, as well as a highly talented engineering geologist. He has written numerous publications about the assessment of terrain in steep mountain areas, and is the author of various guidelines about rural road building.
In a paper just published in the Quarterly Journal of Engineering Geology with N.M. Shakya from the Department of Roads in Nepal (Hearn and Shakya 2017), Gareth has examined problems of rural road construction in Nepal and India once more. The paper notes that there are numerous guidelines for proper road construction, and that the underlying techniques are well established. In the paper, they highlight a World Bank report from 2013 that notes that:
…it was stated that over half of the local road network is untraffickable owing to non-engineered road construction, with roads becoming impassable within 1 – 2 years after completion. If this estimate is true, there may be of the order of 30,000 km of roads constructed in the country that have little hope of sustainability without significant remedial investment and that are having, by all accounts, severe impacts on slopes and drainage systems.
Hearn and Shakya (2017) suggests a number of key issues that need to be addressed:
- Proper route selection is needed. They note that: “there is rarely such a thing as the perfect alignment because compromises often have to be made between the desire to avoid crossing difficult and geohazard-prone terrain and environmentally sensitive areas, and the need to minimize route length and construction cost. It is usually necessary to identify those areas that pose the greatest difficulty and highest risk, and avoid them where possible.”
- Construction must be appropriate, using design that is carefully considered around management of water, support of cut slopes and the emplacement of fill.
- Careful consideration of the hazards posed to road users and people living along the road corridor.
The frustration of course is that none of this is new. As Hearn and Shakya (2017) point out:
Sustainable engineering for the future development of infrastructure in the Himalayas is entirely achievable as long as a carefully planned, managed and executed, inclusive approach is applied. This approach must make full use of the experience and professional knowledge embodied in the available guidelines and specifications, take full cognisance of the geological and geomorphological fragility and dynamism of the region, and learn from the successes and failures of the past.
This paper is both wise and perceptive. It really is time to start constructing Nepal Rural Roads properly.
Reference
and Engineering challenges for sustainable road access in the Himalayas Quarterly Journal of Engineering Geology and Hydrogeology, doi:10.1144/qjegh2016-109
Dave Petley is the Vice-Chancellor of the University of Hull in the United Kingdom. His blog provides commentary and analysis of landslide events occurring worldwide, including the landslides themselves, latest research, and conferences and meetings.
Your blog post of March 29th about construction without design brought back memories of road construction in Ecuador in areas of steep unstable slopes. I am a retired geologist who had to build mining access roads in areas of steep slopes and high rainfall. At first we built roads to North American standards with safe slopes on the uphill cuts and wide road beds. Most of these roads failed spectacularly as the de-vegetated soils migrated upslope exposing more and more open soil and continually slumping onto the road way. Looking around how the locals built roads I noticed that the openings in the jungle were made as small as possible, which usually means with unstable steep slopes. Of course, these unstable slopes failed but because they were small the failures were smaller. Over a period of time, like ten years, there would be numerous small scale failures which would shut the road down for a few days but each time it was rebuilt it was longer and longer between failures. Eventually you arrived at a reasonably stable road bed that was built at low cost in the beginning and had modest maintenance expenditures. Some of our highly engineered roads had epic failures because of the hectares of open soil created by our “safe” low angle cuts.
There is also the matter of money. Because of budget shortfalls, many roads in these kinds of locations do not have the funding to be built to the highest safety standards but they do have enough money for a small road. From the point of view from a local who has to choose between moving family and freight with a trail or “unsafe” road, the road will win every time. An “unsafe” road today is better than suffering for mule trails for decades which is why they go ahead and build roads without full funding and little money for maintenance.
It is a complex issue but as a practical matter for road building in poor countries in steep unstable areas the mantra for me turned out to be “smaller cuts are better and the most direct line is all you can usually afford”. You only have to be better than a mule trail for the quality of life to be better for the local residents.