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Guideline On Integrating Climate Change Projection Into Landslide Risk Assessments and Mapping – At The River Basin Level

Manual and Guideline
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1.1. Landslide risk management in ASEAN Member States

Landslides are a geological process common across ASEAN Member States (AMS). They are often triggered by earthquakes, unstable geological conditions, and/or rainfall. Human development activities on fragile slopes are also responsible for landslides. Landslide numbers are on the rise mainly due to increasing rainfall intensity. Landslides can co-occur at the same time as floods during, or in the aftermath, of heavy or prolonged rainfall events. Seven out of ten ASEAN Member States (excepting Brunei, Cambodia, and Singapore) were affected by flood and landslides during the 2015-2016 El Nino, with impact and severity highest in Indonesia, Myanmar, and Vietnam. Increasing widespread landslide incidences are a new challenge to AMS, as in 2018 when the majority of Lao PDR, as well as Myanmar, experienced heavy flooding and landslides that exceeded country response capacity. Another example is the devastating floods and landslides in June-August 2015 in Myanmar. Many parts of the country, and in particular its mountainous regions such as Chin State, were affected by devastating landslides, cyclones and floods. These calamities significantly damaged lives and property, especially in the Chin State capital of Hakha.

Climate change is considered a key factor behind the changing intensity, frequency and timing of rainfall events. A worldwide review of global rainfall data by Westra, Alexander, and Zwiers (2012), concludes “rainfall extremes are increasing on average globally.” At both the global and Asia and the Pacific regional scale, extreme hydro-meteorological events are the dominant cause of disasters (UNESCAP 2017). Extreme hydrometeorological disasters accounted for 72 percent of the frequency of extreme natural disasters recorded during 1971– 2010 in Asia and the Pacific and accounted for more than half of the increase in frequency of intense hydrometeorological disasters recorded globally from 1971–1980 and 2001–2010 (Thomas et al., 2013). This rise in extreme hydrological events in turn compounds landslide risk levels.

Human induced factors such as dense settlements, deforestation, and migration to, and poorly planned development in, high exposure areas also contribute to disaster risks. When human and climate change induced risks combine, the consequences are often very severe. Existing approaches to landslide risk management therefore need to be revisited to account for these climate and human induced changes and weak disaster risk reduction (DRR) and climate change adaptation (CCA) capacity.