Keywords

Introduction

Landslides are becoming one of the most widespread and frequent natural disaster events in many countries in South and Southeast Asia. Landslides are not limited to mountain settlements in a few countries, but are seen across sub-regions, and are being exacerbated by climate change. Landslide incidents that have occurred recently, triggered either by monsoon precipitation affected by El Niño or a relatively high level of shaking due to earthquakes, or due to the combined effects of both, have resulted in devastating impacts to respective national economies. Landslides not only kill people or destroy the houses, infrastructure and other lifeline facilities within urban and rural settlements, but they are also becoming a pressing environmental problem. An escalation of landslide events is becoming clear due to changing landscapes, and a growing population and increasing vulnerability due to their undesirable actions. The resultant slope destabilization and downslope movement of soil masses are responsible for serious degradation of mountain slopes, and higher sediment load transport, which demands speedy and sustainable solutions by authorities (Fig. 1).

Fig. 1
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Meeriyabedda landslide, Sri Lanka (image source National Building Research Organization, Sri Lanka)

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Under its regional program for Regional Capacity Enhancement for Landslide Impact Mitigation (RECLAIM), the Asian Disaster Preparedness Center (ADPC) and its partners undertook various measures to help countries in Asia manage landslide risk. Those measures had an impact at various levels through local pilot demonstration studies, national level capacity building programs, and regional knowledge-sharing events. The subsequent sections describe in detail those interventions under RECLAIM, as well as several other related projects.

Interventions for Building the Capacity of Mandated Institutions

One of the felt needs, to effectively deal with the landslide problem in a region, is development of the capacity of professionals and scientists involved in landslide services and research studies. It is beneficial to them if they can often share common challenges, problems and potential solutions to make the communities living in landslide prone areas more resilient. Realizing such needs, the Asian Disaster Preparedness Center (ADPC), with technical assistance from the Norwegian Geotechnical Institute (NGI), initiated an umbrella program, namely the Asian Program for Regional Capacity Enhancement for Landslide Impact Mitigation (RECLAIM) to build the capacity of stakeholder institutions through regional and national level training courses, risk information generation, experience sharing, etc. In addition, the program successfully developed a network of institutions mandated to deal with landslide risk management, conduct scientific studies, and engage in related research and development interventions.

The program, which received funding support from the Royal Norwegian Government, frequently organized annual networking events for member institutions to share experiences on good and sound practices of landslide risk management, as well as to discuss challenges and share lessons.

Such networking events have served as a platform to further enhance the scientific understanding of landslide processes and occurrence, share experience in early warning, discuss challenges in instrumentation and monitoring the active landslides, find sound solutions to improve preparedness at the local level, promote options for reducing the risk, and for capacity building and public awareness. Each participating country made presentations at the annual meetings organized by ADPC, providing an overview of the experience of the respective countries in landslide risk reduction. Participants attending a national level networking event in Myanmar are shown in Fig. 2.

Fig. 2
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Networking events are frequently organized among mandated institutions to discuss common challenges in landslide risk management. Field visits are a common feature during regional networking events

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Promoting Sound Practices for Landslide Early Warning

Use of early warning systems for natural hazards such as floods and typhoons have advanced fairly rapidly in the recent past and the successful use of such systems has helped to save lives of the people residing in the affected areas, for instance in Bangladesh, China, Thailand and the Philippines. However, use of effective early warning for alerting people in landslide-prone areas is lagging behind. There is a need for a joint effort in the Asian Region to share experiences in this matter and to establish good practices for efficient landslide early warning systems. The IPL 156- “Best practices for early warning of landslides in a changing climate scenarios”, has highlighted relevant ADPC-initiated activities that have been taken to promote sound practices for early warning of landslides in a changing climate. Improving landslide early warning mechanisms in high risk areas has contributed in providing valuable inputs to the multi-hazard early warnings platforms that are currently operational in countries within Asia too.

Studies for Developing Precipitation Thresholds for Triggering Landslides

Landslide hazard prediction, for warning purposes, is still a difficult problem and an increasingly hot topic in the research on landslide hazards. Precipitation is a main triggering factor that controls the initiation of slope failures, and landslides are often triggered by weather events that are in excess of some thresholds.

Despite the benefits of advanced technologies for landslide early warning developed and used by developed countries, it is still not the main focus in developing countries. Various countries in Asia still rely on simple thresholds, such as the amount of rainfall, as triggering parameters of landslides. It is indeed necessary to investigate the possibility of interpreting landslide events in terms of the amount of rainfall and its patterns immediately preceding the slide event. The rainfall threshold values vary from region to region or district to district due to differences in not only the climatological patterns, but also existing soil characteristics. As a result, such approaches can be further enhanced by taking the geological formation into account in developing precipitation thresholds too.

Therefore, ADPC has undertaken a comprehensive study of rainfall patterns and landslide records in landslide-prone areas of different countries in Asia. Interpreting such data has helped derive reasonable threshold values of rainfall and use them as a tool for landslide forecasting. In addition, collection of critical rainfall values with sufficient geological data in the sub-region, and developing a possible correlation between such attributes was also found to be vital for predicting landslides accurately in highly vulnerable locations.

As a result of the study, several empirical relationships have been deduced for different landslide-prone districts of partner countries, based on the assumption that there exists a direct relationship between the occurrence of landslides, geological formations and the rainfall events characterized in terms of intensity, duration of rainstorm events (short-term, e.g., hourly rainfall or 24-hour cumulative rainfall, for examples) and antecedent rainfall (3 day cumulative, 7 day cumulative, etc.).

Nevertheless, some technical gaps that could deter the use of such threshold approach remain. Some of the networks of rain gauges maintained by the meteorological departments in countries were outdated and even non-functional in some cases. This has to be addressed through capacity building of the relevant departments mandated in maintaining the networks. At the same time, there are also operational issues such as automation of precipitation data collection and recording, as well as gaps in institutional communication. Such operational problems can be resolved through a dialogue among multi-stakeholder institutions. In this regard, ADPC has facilitated several discussions between mandated institutions and meteorological agencies (see Fig. 3) in partner countries to discuss common challenges and possible ways of addressing such challenges.

Fig. 3
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ADPC has facilitated several discussions between mandated institutions and meteorological agencies to discuss operation issues related to development of precipitation thresholds

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Initiatives being carried out by ADPC in this connection complements the ongoing international initiatives on setting up threshold values of precipitation for initiation of landslides.

Initiatives for Establishing Community-Based Systems for Landslide Warning

Devastating landslides have been frequently reported in settlements located within mountain districts. Most of them occur in communities in remote locations. Adverse climatic trends variations are increasingly making such landslide-prone, built-up areas more insecure for living. This was the case in hilly district cities of Bangladesh such as Chittagong, Cox Bazaar, and Teknaf.

In such rural areas, timely dissemination of data on landslide early warning to the communities at risk is a serious problem, as the data flow is not direct and often slow. Therefore it is difficult to provide location-specific landslide early warning through existing local networks. At the moment, ADPC is working with mandated institutions in Sri Lanka, Bangladesh, Myanmar, and Nepal in reviewing the rainfall monitoring networks and to expand the network to areas where rainfall data for landslide monitoring and early warning operations do not exist or are limited.

The Project interventions, which have been reported under IPL 180—“Introducing Community-Based Early Warning System for Landslide Hazard Management in Cox’s Bazaar Municipality, Bangladesh” aims at developing a local-level landslide hazard risk management strategy in Bangladesh. Such interventions can be replicated elsewhere, so that other vulnerable settlements in Asia will be able to utilize similar practices for reducing future losses due to landslide events. In Fig. 4, a rain gauge set up at a community level is shown with a community member who was trained to observe precipitation thresholds to identify common symptoms of landslide initiation. These trained community members will promptly alert the communities and take appropriate actions to move away when landslide initiation is expected.

Fig. 4
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Rain gauges set up in a community for observing the established thresholds

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Framework for Country-Wide Landslide Inventory

ADPC submitted a technical paper on “Developing a framework for assessment of landslide hazard risk associated with critical national and provincial roads” in the ICL symposium held in Kyoto in November 2013. As described in the paper, the purpose of the proposed framework for a country-wide risk–based landslide inventory is to facilitate the taking of suitable proactive cost-effective measures by the road sector in order to reduce disruptions to transportation due to occurrences of landslides during monsoon periods. It is suggested that a country-wide landslide inventory be developed as a key feature in the long-term strategy and records maintained of all landslides recorded on critical national and provincial roads in a GIS environment. In the pilot study in Lao PDR, necessary training was provided to road authorities for field data collection, inventory preparation, maintenance and upkeep. The framework also will serve as a guideline for designing new slope stabilization measures where necessary during implementation of road expansion and/or improvement projects. At present, road engineers in Lao PDR do not take into consideration landslide hazard and risk potential during implementation of road improvement projects and road expansion-associated excavations, which at times led to subsequent slope destabilization. Recommendations have been included in the framework for identifying likely high-risk landslide locations or landslide-prone areas with high hazard, which need special attention during excavations, as well in the implementation of priority mitigation measures. During the project period, actions have been taken to provide resilient landslide protection for some of the vulnerable locations identified during the project for providing safer access to public services (see Fig. 5: Resilient landslide protection measures in Bountai District, Lao PDR).

Fig. 5
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Resilient landslide protection measures in Bountai District (Lao PDR) provided communities with safer access to public services

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Landslide Hazard Zonation Mapping and Assessment of Risk

ADPC has carried out multi-hazard risk assessment projects in countries such as Bangladesh, Cambodia, Nepal, Lao PDR, Myanmar, and Timor Leste. In each project, national, provincial, and/or city-level landslide hazard maps were prepared (as shown in Fig. 6) and provided to the National Disaster Management Office (NDMO) or provincial and city authorities, as well as to sector Ministries and line agencies. Using these maps, authorities can easily identify the areas that are prone to landslides, derive related vulnerabilities, and assess associated risk, and they can use such information in physical planning and undertaking risk mitigation interventions.

Fig. 6
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Landslide hazard map of Patong city, Thailand

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In the ICL-IPL Sendai Partnership Conference held on 13th March 2015, ADPC presented a paper on “Challenges in landslide risk management in Asia” capturing its experience in Asia on implementing structural and non-structural interventions for landslide risk management. One of the main challenges observed is the lack of interdisciplinary cooperation, including the communities, which is essentially needed to ensure that appropriate preparedness, response and mitigation actions are planned and owned by the communities. ADPC undertook regional and national level capacity building programs and awareness programs frequently to improve the knowledge and understanding by professionals of the landslide phenomena and interventions for prevention and mitigation of future disasters. Landslide hazard maps often were a useful tool in those capacity-building and awareness-raising activities.

Guidelines for Safer and Resilient Construction in Landslide Prone Areas

ADPC initiated pilot demonstration projects for landslide risk mitigation and to promote safer construction practices in landslide-prone areas in different places in Asia. The projects undertaken under this initiative covered resilient design and hands-on training in construction practices for dwelling houses, community infrastructure, and slope stabilization measures along major highways, as well as construction of critical facilities such as schools and hospitals (Fig. 7).

Fig. 7
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Landslide mitigation, Lao PDR

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For example, under the program on “Mainstreaming Disaster and Climate Risk Management into Investment Decisions in Lao PDR”, funded by the World Bank and the Japan Policy and Human Resources Development Fund, ADPC provided technical services to the Ministry of Planning and Investment, the Ministry of Public Works and Transport, and the Ministry of Agriculture and Forestry to develop resilient infrastructure for landslide and flood-affected areas. Previously, some critical sections of the roads in hilly terrain were usually washed out by flash flooding or affected by landslides. It often left the villagers in the lurch, with no ready access to basic services such as transportation, health, and education. The slope stabilization measures, culvert improvements for specific road patches, and landslide mitigation measures for affected sections of the major highways were some of the outcomes of the technical skills imparted to the government officials, so that such infrastructure facilities are no longer affected by floods or landslides in the future.

Teaching Tools

Certain urban and infrastructure developments can amplify the effect of landslide trigger mechanisms. There is a direct correlation between geo-environmental and physical factors associated with development, so control of land use is needed in order to bring about a reduction in the devastating impacts of landslides. In Asian countries, responsibility for local-level development control is vested with the local governments. It is therefore important to provide knowledge and appropriate skills in construction to the local governments in landslide-prone areas. ADPC has developed and delivered a training tool on “Landslide Disaster Risk Reduction for Local Government Level Stakeholders”. This has been recorded as one of the tools under the ICL landslide teaching tools project. This course tries to educate the stakeholders within urban local government areas on the issues that need to be taken into consideration in safer development practice in hilly areas. The course also provides an opportunity for local government officials, technocrats, professionals, practitioners and other stakeholders in urban local government areas to discuss the measures that can be taken to mainstream landslide disaster risk reduction measures in urban planning and development and to regulate the land development in landslide-prone areas in order to reduce the impacts due to future devastating events of landsides.

Conclusions

A crucial aspect for the success and sustainability of landslide disaster risk reduction interventions in any country is institutionalization and mainstreaming of such approaches to become routine practices from local to national levels. In line with this, it is also important to make efforts for capacity building of mandated national level institutions for landslide risk management. Other efforts such as inter-agency collaboration, development of close linkage between agencies involved in disaster management and local government units, and the active participation of affected communities also play a vital role, among others. Experience sharing through regular consultative meetings among the mandated institutions of partner countries could provide significant inputs in improving the knowledge base on sound and cost effective practice.