[Philippines] Catchment susceptibility to hydrometeorological events: sediment flux and geomorphic change as drivers of flood risk in the Philippines

河流的形态是泥沙运移和沉积作用的结果，两者都是水流的结果。自然（如台风、地震、火山）和人为（如砾石开采、河岸保护）沉积物供应的间歇性变化驱动了河床水位和沉积学的变化。这些变化决定了河道容量和水流路线，从而与洪水对人类和财产的风险有关。同样的因素决定了侧岸侵蚀率的变化；水位升高会导致已开发的洪泛区丧失，以及道路桥梁等关键基础设施的损坏。尽管河床水位和河道位置的变化对洪水风险具有重要意义，但在洪水风险制图中，地貌过程通常被忽视。在菲律宾，河流特别湍急；必须评估泥沙和侵蚀所带来的风险，并将其纳入洪水风险管理，以减轻洪水对福利和经济的影响。该项目旨在：(i)建立全国范围的流域特征数据库和相关的河流几何关系，以评估不同流域对形态变化对洪水灾害影响的敏感性；（ii）评估与泥沙供应变化有关的形态变化以及横向约束对河道形态调整的影响所引起的洪水危害。为了实现第一个目标，我们将使用国家尺度的地形模型和重复卫星图像来评估河流和景观特征，以确定河道流动性和沉积物运输增强的指标，并利用河流中心线地理信息系统的输出，该系统沿菲律宾河网每1公里提供数据点。这个全国规模的数据集将被项目合作伙伴用于评估和规划基础设施发展。为了实现第二个目标，我们将通过机载光探测和测距（LiDAR）和测深测量，生成Pinacanauan de Ilagan河和Bacarra河的重复高分辨率数字高程模型（dem）。我们将利用这些dem来绘制雨季侵蚀和沉积的模式，并计算每条河流的泥沙收支。dem和泥沙预算将用于参数化和评估水文和形态动力学模型，这些模型将用于调查由于形态变化而导致的洪水风险变化。该框架将由项目合作伙伴用于指导Pinacanauan de Ilagan和Bacarra集水区的河流和洪水管理。该框架也将被转移到菲律宾的其他河流，以及更远的东南亚和更远的地区。该提案在菲律宾迪利曼大学、格拉斯哥大学、四个菲律宾项目合作伙伴以及项目合作伙伴布里尔利教授（奥克兰大学）之间建立了伙伴关系。具体来说，菲律宾的项目合作伙伴是：矿业和地球科学局；公共工程和公路部；以及研究流域的两个地方政府单位，即伊拉甘市和温塔尔市。该项目将UP Diliman在地理信息学方面的专业知识与格拉斯哥大学在河流地貌学和数值模拟方面的专业知识结合起来，进行研究，阐明热带河流的形态动力学，并生产将用于菲律宾可持续河流洪水管理的工具。

River morphology results from sediment transport and sedimentation, which are both a consequence of water flow. Episodic variation in natural (e.g. typhoons, earthquakes, volcanoes) and anthropogenic (e.g. gravel mining, river bank protection) sediment supply drives changes in riverbed levels and sedimentology. These changes determine channel capacity and flow routing, and thus associated flood risk to people and property. The same factors determine variations in lateral bank erosion rates; elevated rates result in the loss of developed floodplain and the failure of critical infrastructure such as road bridges. Despite the significance of variation in riverbed levels and channel position for flood risk, geomorphological processes are commonly overlooked in flood risk mapping. In the Philippines, rivers are particularly dynamic; risks arising from sedimentation and erosion need to be assessed and incorporated into flood risk management to mitigate the impact of flooding on welfare and the economy. This project aims to: (i) develop a national-scale catchment characteristics database, and associated river geometry relations, to assess the susceptibility of different catchments to morphological change impacts on flood hazard; and (ii) assess flood hazards arising from morphological change associated with variations in sediment supply and the influence of lateral constraints on channel morphological adjustment. To achieve the first aim we will use national scale topographic models and repeat satellite imagery to assess fluvial and landscape characteristics to identify indicators of enhanced channel mobility and sediment transport, with outputs available from a river centreline Geographic Information System with data points every 1 km along the Philippines river network. This national scale dataset will be used by project partners to assess and plan infrastructure developments. To achieve the second aim we will generate repeat, high-resolution Digital Elevation Models (DEMs) of the Pinacanauan de Ilagan River and the Bacarra Rivers, from airborne Light Detection and Ranging (LiDAR) and bathymetric surveys. We will difference these DEMs to map patterns of erosion and deposition during a wet season, and calculate a sediment budget for each river. The DEMs and sediment budget will then be used to parameterise and assess hydro- and morpho-dynamic models that will be used to investigate changes in flood risk due to morphological change. This framework will be used, by project partners, to guide river and flood management in the Pinacanauan de Ilagan and the Bacarra catchments. The framework will also be transferable to other rivers in the Philippines, and farther afield in SE Asia and beyond.This proposal forges a partnership between the University of the Philippines (UP) Diliman, the University of Glasgow, four Filipino project partners, and project partner Prof Brierley (University of Auckland). Specifically, the Philippine project partners are: the Mines and Geosciences Bureau; the Department of Public Works and Highways; and two Local Government Units in the study catchments, namely City of Ilagan and Municipality of Vintar. The project brings together UP Diliman's expertise in geomatics with the University of Glasgow's expertise in fluvial geomorphology and numerical modelling, to undertake research that will shed light on the morphodynamics of tropical rivers and produce tools that will be used for sustainable fluvial flood management in the Philippines.