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Submitted by Ishwar Sunwar on
Please accept my apology for late response and I hope my comments are still helpful even if the project is being implemented! The project is very interesting to me. At last, a good justice has been given to Bio-engineering. I come from Nepal where I started Bio-engineering in my early career in 1986 by implementing of UK based TRL (former TRRL) designed experimental plots on the Dharan - Dhankuta Road, east Nepal. Later, we expanded works with the guidance of three other expatriates and since then I have been practicing it on roadside slopes and watershed management. The ongoing project in Timor-Leste looks like the right approach to make roads and other rural infrastructures more resilient to climate change. Extensive use of Bio-engineering in all infrastructures developmental projects and watershed management is probably the most efficient tool for present context of CC impact where both the drought and excess water can make great impacts to slopes. Bio-engineering can help to stand the infrastructures in such events. However, to achieve best results from Bio-engineering, it will depends on how well the design is made. Like most people viewed, we (in Nepal) also conventionally thought the use of vegetation, tree or shrub planting, making surface cover with vegetation and also to promote aesthetic view along the road would still regards as Bio-engineering. But later we knew that it rather requires accurate identification of problems on sites associated with water, materials properties and alteration of physical features of such locations where infrastructures are being built. In other words, correct site assessment is required with appropriate designs. This would be site specific since we have not yet got numerical methods of testing the success other than qualitative means. Lesson learning from Nepal further revealed that just replication of those successful techniques in the US, Canada, Europe and Japan do not necessarily applicable or successful the Nepalese condition for various reasons. So, selection of techniques should be open to problems associated onsite. For example, Gabion is standard practice in Nepal for any slope related failure mitigation and roads retaining purpose due to its flexibility in nature in the most dynamic terrain like Nepal. But they do not necessarily stand everywhere unless they are well integrated with vegetation which we know as Bio-engineering. The definition for Bio-engineering in Nepal is "Use of vegetation either alone or in conjunction with civil engineering structures and non-living plant materials to control shallow slope instability and erosion on slopes" DoR 1995. This definition was just appropriate to convince conventional engineers in Nepal who have trust only on civil engineering structures but not with the vegetation. Since then, it is the application of vegetation + civil engineering structures but needs will be identified as per the requirement of site conditions as assessed by an experienced person. I have not been to Timor-Leste but as I can make out of the relevant literature and reports such as IEE and RSP of said road, the material types are similar to Siwalik range of Nepal where additional load for any betterment will often have adverse impact to slope stability. For example, photos 11 (counting from 1st before the Precipitation graph) above may have nature of materials that cannot accept gabion load despite it is very flexible. Similarly, if the subsidence (photo 8) goes, adding gabion wall alone may not be right solution where Bio-engineering would assess the appropriate site requirements more systematically (though I am not blaming previous designer not being very systematic). So, Nepal's lesson learning from 1986 till now further reveals that: a) success of Bio-engineering design is dependable on quality of site assessment; b) if the design being the most appropriate, then success of it will depend on quality of implementation which can be achieve only from critical monitoring and regular coaching. Only Inspector's job will not be sufficient but regular mentoring and coaching to implementer (actual person involved in carrying out of activities on site) is paramount needs. For quality checking of fills in the road construction, there will be various methods of testing thus one can immediately predict the success and failure of fills but for plants, it takes several weeks to show any sign of up-taking or survival after planting. If quality work is missed at this stage there will be only no chance of success and only failure. Therefore mentoring and regular coaching is vital at the time of implementation. Finally, to make sustainable Bio-engineering system, due consideration should be made to social, cultural and economical aspects of plants that are going to be used together with their engineering properties well at the time of selection. Not all green cover will be effective Bio-engineering! Wish this project goes well and becomes resilient to CC impact. Wish you and People of the Timor-Leste have very good luck. Ishwar