MODELLING RAPID LANDSCAPE CHANGE DUE TO OUTBURST FLOODS

该项目的目的是模拟突发性洪水中的水流-河床相互作用。暴发洪水是一种水和泥沙的突然释放和推进波，其峰值流量通常比常年水流大几个数量级。来自自然来源(即不包括人工堤坝决口)的常见暴发洪水包括冰川和冰河蓄水湖泊、淡水堤坝和堤坝决口、火山碎屑坝、滑坡、雪崩、沿海海湾堤坝以及树木或植被堤坝造成的洪水。例如，尽管这些灾害听起来很奇怪，但暴发的洪水灾害经常被纳入城市、沿海和山区的风险评估。突发性洪水灾害主要是由正面涌浪引起的直接影响、来自水流体内的泥石流以及水流的质量和一致性造成的。一些次生影响也造成了危险，包括广泛的泥沙沉积和支流堵塞。正是由于泥沙的动员和重新分配，导致了快速的地貌变化，这是突发洪水造成的最大危害之一。因此，该项目的一个特别重点将是对水动力和沉积特征进行参数化；特别是水流深度、流速、河床剪应力、能量和功率、沉积物分类、粒度分布和结构。将使用完全参数化和经过验证的实验室水槽模型来获得突发性洪水过程的水动力和沉积特征，这为研究突发性洪水中水和泥沙之间的复杂相互作用提供了一个迄今尚未开发的机会。由于以下几个原因，明确量化突发性洪水中的水沙过程是至关重要的：1.突发性洪水发生在世界各地，是对生命、财产和基础设施的自然危害。2.虽然所有暴发洪水都是水和泥沙的混合物，但完全整合这两个过程的模型尚未报道。3.虽然暴发洪水的来源和触发机制是众所周知的，但水流行为并不是众所周知的，这主要是因为直接测量这种突然、强大和快速变化的水流的固有问题。因此，目前对流动特性的预测非常有限。3.只有当很好地理解了控制水流行为的过程时，才能产生缓解暴洪的措施；即，对该模型进行参数化和模型化，并根据真实世界的数据对该模型进行验证。这些标准必须源于一种综合和可持续的设计方法。4.随着气候变化，气温和降水模式的变化很有可能导致冰川湖暴发和滑坡引发的暴发的频率增加，以及降雨引起的暴发洪水的规模增加。5.大多数暴发洪水来自天然湖泊，否则这些湖泊就是水资源，如果有适当的管理办法，可以保持这种情况。这个项目非常及时，因为最近来自冰岛S的暴发洪水和预测的来自新西兰鲁阿佩胡山的火山口湖洪水都受到精确的事前和事后调查的约束，这些调查为模型的参数化和验证提供了迄今为止无法获得的数据。后者的特点还包括GNS Science和梅西大学正在开发的最先进的传感器系统，以产生关于水流行为和水力参数的时间序列数据。该项目显然是对NERCS使命的重大贡献，它将通过提供量化数据来促进对自然灾害解决方案的知识和支持，这将对工业和公共部门产生经济和社会效益，并通过聘请来自几个学科和国家的优秀研究人员。

The aim of this project is to model flow-bed interactions within an outburst flood. Outburst floods are a sudden release and advancing wave of water and sediment, with a peak discharge that is often several orders of magnitude greater than perennial flows. Common outburst floods from natural sources (i.e. excluding breaches of man-made dams) include those from glacial and moraine-impounded lakes, freshwater dyke and levee bursts, volcanic debris dams, landslides, avalanches, coastal bay-bars, and those from tree or vegetation dams. Although these hazards sound exotic, outburst flood hazards are regularly incorporated into risk assessments for urban, coastal and mountainous areas, for example. Outburst flood hazards are primarily due to direct impacts, caused by a frontal surge wave, from debris within a flow body, and from the mass and consistency of the flows. A number of secondary impacts also pose hazards, including widespread deposition of sediment and blocked tributary streams. It is rapid landscape change, which is achieved the mobilization and redistribution of sediment that causes one of the greatest hazards due to outburst floods. Thus a particular focus of this project will be to parameterise hydrodynamic and sedimentary characteristics; particularly flow depth, velocity, bed shear stress, energy and power, sediment sorting, grain size distribution and architecture. Hydrodynamic and sedimentary characteristics of outburst flood processes will be obtained using fully parameterised and validated laboratory flume modelling, which offers a hitherto untapped opportunity for examining complex interactions between water and sediment within outburst floods. Explicit quantification of water-sediment processes within outburst floods is essential for several reasons: 1. Outburst floods occur worldwide and are a natural hazard to life, property and infrastructure. 2. Although all outburst floods are a mix of water and sediment, models that fully integrate both processes are unreported. 3. Whilst sources of outburst floods and trigger mechanisms are well known, flow behaviour is not, largely because of the inherent problem of directly measuring such sudden, powerful and rapidly-varying flows. Prediction of flow character is therefore currently very limited. 3. Outburst flood mitigation measures can only be produced when processes governing flow behaviour are well understood; i.e. parameterised and modelled, and that model is validated against real-world data. These criteria must arise from an integrated and sustainable design approach. 4. With climate change, there is a very real potential for alterations in air temperature and precipitation patterns to cause an increased frequency of glacial lake outbursts and landslide-triggered outbursts, and an increased magnitude of rainfall-induced outburst floods. 5. Most outburst floods are sourced from natural lakes that are otherwise a water resource, and with appropriate management solutions can remain so. This project is extremely timely because recent outburst floods from Sólheimajökull (Iceland) and the predicted Crater Lake flood from Mt Ruapehu (New Zealand) are constrained with precise pre- and post-event surveys that provide hitherto unobtainable data for model parameterisation and validation. The latter will also be characterised by a state-of-the-art sensor system under development by GNS Science and Massey University to yield time-series data on flow behaviour and hydraulic parameters. This project will clearly be a substantial contribution to NERCs mission by providing quantitative data to advance knowledge and support for natural hazard solutions, which will be of economic and social benefit to industry and to the public sector, and by engaging excellent researchers from several disciplines and countries.