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

菲律宾位于海洋大陆的东部边缘，该群岛由热带岛屿组成，位于印度洋和太平洋之间。高的太阳输入使周围的海洋变暖，为大气提供了大量的水分，将整个地区变成了大气中的“锅炉箱”。整个海洋大陆全年的降雨量都很高，但由于菲律宾位于海洋大陆的东部边缘，它也是形成于太平洋的热带气旋(也称为台风或飓风)的火力线。强热带气旋时速可达150英里以上，短短几小时内降雨量可达450毫米以上。这些极端降雨事件，再加上菲律宾境内陡峭多山的地形，可能会在河流中造成灾难性的山体滑坡和相关的泥沙淤积，产生重大的社会和经济影响。尽管菲律宾只占东南亚陆地面积的6%，但该国引发的致命降雨引发的山体滑坡却占到了一半。2004年，一系列台风袭击了菲律宾北部吕宋岛东海岸的奎松省和奥罗拉省，造成山体滑坡和洪水，造成1062人死亡，1161人受伤，552人失踪，近700万人流离失所，造成巨大的经济损失和长期的人员伤亡。在气候变化下，台风的频率和强度预计将增加，这将对山体滑坡和河流泥沙问题产生影响。模拟台风引起的山体滑坡是一个复杂的问题，因为山体滑坡还取决于导致极端降雨事件的天气条件，而极端降雨事件会影响覆盖山坡的土层的稳定性。如果土壤已经是湿的，导致极端降雨事件，则更有可能发生山体滑坡。因此，有必要了解菲律宾上空的气象模式，以及这些模式如何影响台风中的山体滑坡模式。另一个可能限制滑坡发生和规模的主要因素是土层的深度。滑坡的发生需要一个临界土层深度，滑坡的大小将受到土层深度的限制。一旦发生滑坡，土层需要时间才能再生，这意味着同一地区未来的滑坡危险。虽然山坡上的山体滑坡伤痕暴露，但山体滑坡可能会继续将泥沙输送到下游的河流水系。因此，滑坡发生后，滑坡下游河流的泥沙淤积问题可能会持续一段时间。SCRAP项目结合了英国和菲律宾的研究优势，汇集了地貌学、气象学和水利工程方面的专家，以有效和高效地满足更好地了解水文气象灾害的影响的需要，并支持加强对未来事件的准备和复原力。首先，将结合菲律宾的现场观测站数据和来自卫星的全球数据集，确定过去极端降雨引发的滑坡事件的特征及其在菲律宾上空的气象和地质控制，以绘制滑坡地图并确定降雨模式。其次，将利用一些事件来开发和测试模拟滑坡和下游沉积的模型。一旦模型被调整，它将被用来通过对该地区的气候预测来预测未来的滑坡事件和河流沉积。我们将与我们的菲律宾项目合作伙伴、菲律宾大气、地球物理和天文服务管理局(PAGASA)、(MGB)矿产和地球科学局以及菲律宾气象基金会(WPF)合作，使用我们的建模框架为菲律宾开发一个滑坡预警系统，确保从SCRAP项目中获得遗产。

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.