SCaRP: Simulating Cascading Rainfall-triggered landslide hazards in the Philippines

点击翻译按钮获取中文摘要

The Philippines is on the eastern edge of the Maritime Continent, the archipelago of tropical islands that sits between the Indian and Pacific Oceans. High solar input warms the surrounding seas, which supply an abundance of moisture to the atmosphere, turning the whole region into an atmospheric "boiler box". The whole Maritime Continent receives very high rainfall totals throughout the year but due to its location on the eastern edge of the Maritime Continent, the Philippines are also in the firing line of tropical cyclones (also known as typhoons or hurricanes) that form in the Pacific Ocean. Strong tropical cyclones can reach up more than 150 mph and deliver more than 450 mm rainfall in just a a few hours. These extreme rainfall events, combined with the steep, mountainous terrain over the Philippines can produce catastrophic landsliding and related sedimentation in rivers with major societal and economic impacts. The Philippines accounts for half of fatal rainfall triggered landslides in SE Asia despite making up only 6% of the land area. In 2004, a series of typhoons hit Quezon and Aurora Provinces on the east coast of the island of Luzon in the northern Philippines causing landslides and floods that left 1,062 dead, 1,161 injured and 552 missing, displaced almost 7 million people and caused massive economic damage and prolonged human costs. Under climate change, the frequency and intensity of typhoons can be expected to increase with implications for landslide hazards and sedimentation problems in rivers. The simulation of landslides resulting from typhoons is a complex problem as landslides are also dependent on weather conditions leading up to the extreme rainfall event that influence the stability of the layer of soil covering hillslopes. If soils are already wet leading up to an extreme rainfall event, landslides are more likely. It is therefore necessary to understand the meteorological patterns operating over the Philippines and how these influence patterns of landslides in typhoons. Another major factor that may limit landslide occurrence and size is the depth of the soil layer. A critical soil depth is needed for a landslide to occur and the size of the landslide will be limited by the depth of the soil. Once a landslide has occurred, it takes time for the soil layer to regenerate, with implications for future landslide hazard in the same area. Whilst landslide scars on hillslopes are exposed landslides may continue to deliver sediment to the downstream river system. Hence sedimentation problems in rivers downstream of landslides may persist for a period of years after the landslide event. The SCaRP project combines the research strengths of the UK and the Philippines and brings together experts in geomorphology, meteorology and hydraulic engineering to effectively and efficiently address the need for better understanding of the impact of hydrometeorological hazards and support increased preparedness and resilience to future events. First, the characteristics of past extreme rainfall-triggered landslide events and their meteorological and geological controls over the Philippines will be determined, using a combination of in situ station data from the Philippines and global data sets from satellites to map landslides and determine rainfall patterns. Second, a number of events will be used to develop and test models for simulation of landslides and downstream sedimentation. Once the model has been tuned, it will be used to predict landslide events and river sedimentation in the future using climate projections for the region. In conjunction with our Filipino project partners, PAGASA (Philippine Atmospheric, Geophysical and Astronomical Services Administration), (MGB) Mines and Geosciences Bureau and Weather Philippines Foundation (WPF), we will develop a landslide early warning system for the Philippines using our modeling framework, ensuring a legacy from the SCaRP project.