Kewan Mertens

The direct impact of landslides on household income in tropical regions: a case study from the Rwenzori Mountains in Uganda

Landslides affect millions of people worldwide, but theoretical and empirical studies on the impact of landslides remain scarce, especially in Sub-Saharan Africa. This study proposes and applies a method to estimate the direct impact of landslides on household income and to investigate the presence of specific risk sharing and mitigation strategies towards landslides in a tropical and rural environment. An original cross-sectional household survey is used in combination with geographical data to acquire detailed information on livelihoods and on hazards in the Rwenzori mountains, Uganda. Ordinary least square regressions and probit estimations with village fixed effects are used to estimate the impact of landslides and the presence of mitigation strategies. Geographical information at household level allows to disentangle the direct impact from the indirect effects of landslides. We show that the income of affected households is substantially reduced during the first years after a landslide has occurred. We find that members of recently affected households participate more in wage-employment or in self-employed activities, presumably to address income losses following a landslide. Yet, we see that these jobs do not provide sufficient revenue to compensate for the loss of income from agriculture. Given that landslides cause localized shocks, finding a significant direct impact in our study indicates that no adequate risk sharing mechanisms are in place in the Rwenzori sub-region. These insights are used to derive policy recommendations for alleviating the impact of landslides in the region. By quantifying the direct impact of landslides on household income in an agricultural context in Africa this study draws the attention towards a problem that has been broadly underestimated so far and provides a sound scientific base for disaster risk reduction in the region. Both the methodology and the findings of this research are applicable to other tropical regions with high landslide densities.

Landslide risk reduction measures: a review of practices and challenges for the tropics

The overall objective of this review is to gain insights into landslide risk reduction measures that are applied or recommended in tropical landslide-prone countries, and the challenges at play. More specifically, this review aims to (i) presenting an overview of recent studies on landslides and landslide risk reduction in these countries, (ii) exploring the factors controlling the publication output on landslides and landslide risk reduction, (iii) reviewing the various landslide risk reduction measures recommended and implemented, and (iv) identifying the bottlenecks for the implementation of these strategies. A compilation of recommended and implemented landslide risk reduction measures in 99 landslide-prone tropical countries was made, based on an extensive review of scientific literature (382 publications). The documented measures are analysed using a scheme of risk reduction measures that combines classifications of the Hyogo Framework for Action and the SafeLand project. Our literature review shows that the factors influencing the number of publications on landslides and landslide risk reduction per country are (in order of importance) the absolute physical exposure of people to landslides, the population number and the Human Development Index of a country. The ratio of publications on landslide risk reduction versus publications on landslides for landslide-prone tropical countries does not vary much between these countries (average: 0.28). A significant fraction (0.30) of all known landslide hazard reduction measures are neither implemented nor recommended according to our review. The most recommended landslide risk reduction component is ‘risk management and vulnerability reduction’ (0.38). However, the most implemented component is ‘risk assessment’ (0.57). Overall, the ratio of implemented versus recommended landslide risk reduction measures in the tropics is low (<0.50) for most landslide risk reduction components, except for ‘risk assessment’ (3.01). The most cited bottlenecks for implementing landslide risk reduction measures are scientific (0.30) and political (0.29) in nature.

Landslide Risk Management in Uganda: A Multi-level Policy Approach

While landslides constitute a major risk in Uganda, this geomorphological hazard has been largely neglected by national and local authorities in West Uganda. Nowadays, disaster risk management is emerging in Uganda. Monitoring the on-going efforts is therefore crucial in this region. We identify the actors involved in landslide risk management in West Uganda and examine their roles and interactions by investigating both policy and practice. This paper describes a qualitative multi-policy level approach, based on extensive field work and literature on systems analysis and scalar politics. The results show that in theory, landslide risk management in this region consists of a well-structured National Policy (2010), including the establishment of horizontally structured platforms at different administrative levels and a focus on pre-disaster mitigation activities. In practice, however, the implementation is insufficient, as most platforms at local level remain dysfunctional or only meet after a disaster occurred. The dominant arena for landslide risk management remains at national level, despite the promotion of decentralisation, and the focus remains on post-disaster emergency measures, such as providing relief. At local level, bottom-up landslide risk reduction efforts are made that are disconnected from the national policy, scattered and done haphazardly. Thus, discrepancies exist between policy and practice regarding landslide risk management in West Uganda but efforts are moving gradually towards disaster risk reduction.

Landslide Diversity in the Rwenzori Mountains (Uganda)

In the Rwenzori Mountains, at the border between Uganda and the D.R. Congo, landslides frequently occur and cause fatalities and substantial damage to agricultural land and infrastructure. Up until recently, no information on the landslide characteristics, occurrence or spatial distribution was available. The use of archive inventories and field surveys however allowed identifying the key mass wasting processes in this region and their triggering and controlling factors. Here, we present the results of these multi-temporal archive and field inventories. The Rwenzori mountains are diverse in lithology, topography and land use patterns. This diversity in landslide controlling factors is also reflected in the types of landslides that occur in this 3000 km2 large region. The majority of the Rwenzori Mountains consists of steep slopes on gneiss, mica-schists and amphibolite lithologies. A dominance of shallow translational soil slides is observed in gneiss while the amphibolite is found not to be prone to such landslides. This is in sharp contrast to the lowlands, which are characterized by gentle slopes and a rift alluvium lithology. In contrast to what was expected, the largest landslide densities are found in these lowlands where large, deep-seated rotational soil slides with head scarps up to 30 m depth prevail. In both the lowlands and the uplands, slope gradients appears to be the main topographic predictor for the spatial occurrence of landslides. Finally, concerning landslide triggering events, in both the archive inventory and the field surveys, rainfall-triggered landslides are the most common but co-seismic slides were also observed.

Social multi-criteria evaluation to identify appropriate disaster risk reduction measures: application to landslides in the Rwenzori Mountains, Uganda

Over the past decades, the global exposure of persons and assets to natural hazards, like landslides, has increased faster than that their vulnerability has decreased. Therefore, the Sendai Framework for Disaster Risk Reduction (DRR) made a call in 2015 for more investment in DRR. Recent studies exposed the lack of scientific evaluation data for selecting DRR measures. The objective of this research is to develop a participatory methodology for identifying appropriate DRR measures based on stakeholder groups’ perceptions. More specifically, we propose a social multi-criteria evaluation which combines a two-phased participatory multi-criteria analysis with an institutional analysis for its design and a discourse analysis for interpreting its outcomes. This method is then tested for a case study focusing on landslides in the Rwenzori Mountains region (Uganda) to illustrate both its relevance and practical challenges. The results from the case study highlight the perceived importance of the acceptability of measures above cost, feasibility and effectiveness criteria, by district and village stakeholder groups. Frequently recommended DRR actions, such as disaster risk zonation or relocation, are shown to be perceived negatively by local stakeholders despite being put forward in national policies. This study contributes to the DRR literature as it proposes a new method to support DRR-related decision-making. It also contributes to the understanding of landslide risk reduction in the Rwenzori Mountains region as it presents the first attempt to identify appropriate landslide risk reduction measures for the region.

Socio-political drivers and consequences of landslide and flood risk zonation: A case study of Limbe city, Cameroon

Disaster risk zonation is often proposed as a long-term disaster risk reduction strategy by international treaties and academic research. This strategy has been implemented in the city of Limbe, which is known to be a disaster-prone one. Citizens are forced to settle in unsafe terrains, ranging from wetlands to unstable hillslopes due to the city’s geographical location and economic attraction. Following the fatal landslides and floods in 2001, a local crisis committee identified affected areas and declared them ‘risk zones’ to prevent further exposure. Empirically, this study narrates the production and implementation of risk zonation policy in the city of Limbe. Theoretically, it uses an urban political ecology perspective, which incorporates science and technology studies, post-political theory and disaster research to interpret the drivers and implications of the mismatch between research, policy and action. In this case study, we investigate the implications for disaster risk reduction by describing three underlying socio-political drivers of the risk zonation policy: (i) authoritarian science regime, (ii) post-political discourse, and (iii) blame diversion. We argue that authorities from national to local level use a post-political discourse to promote and implement disaster risk reduction in the city of Limbe through the development and the application of risk zonation policy. As a consequence, risk zonation leads to poor enforcement of the law and corruption, ultimately leading to risk accumulation in this case. This analysis allows us to draw broader conclusions on drivers and implications of the implementation of disaster risk zonation policy in urban areas that are primarily governed hierarchically and prone to corruption.

Flash Floods in the Rwenzori Mountains-Focus on the May 2013 Multi-Hazard Kilembe Event

Over the past 50 years, at least seven major flash floods have affected catchments of the Rwenzori Mountains. The Rwenzori Mountains are not only subject to flash floods; forest fires, earthquakes and landslides occur as well. Many of the flash floods therefore co-occurred with other hazards. One of the most devastating of these events occurred on May 1st 2013, in the Nyamwamba catchment. Here we reconstruct the circumstances under which this flash flood event was triggered and its effects in this multi-hazard region. This includes the identification and characterization of different processes acting upon the catchment dynamics, their controlling and triggering factors and the estimation of the damaging effects of the flash flood within the catchment. The combined occurrence of intense rainfall, a forest fire having burned 18% of the catchment area and the occurrence of 29 landslides providing debris to the river system, induced a debris-rich and very destructive flash flood which caused several fatalities, the destruction of 70 buildings, several bridges, a hospital and a school, a tarmac road and several life lines. Peak flow discharge is estimated between 850 and 1300 m3/s. This case-study demonstrates that flash floods in the region should not be considered as self-determined phenomena but as a result of several cascading and interacting hazard processes including wildfires and landslides, occurring within a short time period.