MODELLING RAPID LANDSCAPE CHANGE DUE TO OUTBURST FLOODS

该项目的目的是模拟流动床的相互作用在一个突出的洪水。爆发性洪水是水和沉积物的突然释放和推进波，其峰值流量通常比常年流量大几个数量级。天然源（即不包括人造水坝的决口）引发的常见突发洪水包括冰川湖和冰碛湖、淡水堤坝和堤坝决口、火山碎屑坝、山体滑坡、雪崩、海岸海湾坝以及树木或植被坝引发的洪水。虽然这些危险听起来很奇特，但突发洪水危险经常被纳入城市、沿海和山区等地区的风险评估。爆发洪水的危险主要是由于直接的影响，造成的正面浪涌波，从碎片内的流体，并从质量和一致性的流动。一些次级影响也造成危害，包括沉积物的广泛沉积和支流阻塞。由于突发洪水，造成最大危害之一的是迅速的景观变化，这是泥沙的移动和重新分布。因此，该项目的一个特别重点是确定水动力和沉积特征的参数，特别是水深、流速、河床剪切应力、能量和动力、沉积物分选、粒度分布和结构。水动力学和沉积特性的突出洪水过程将获得使用充分参数化和验证实验室水槽建模，这提供了一个迄今为止尚未开发的机会，研究水和沉积物之间的复杂的相互作用，突出洪水。明确量化的水沙过程中突发性洪水是必不可少的几个原因：1。洪水爆发在世界各地都有发生，是对生命、财产和基础设施的自然危害。2.尽管所有突发洪水都是水和沉积物的混合，但完全整合这两个过程的模型尚未报道。3.虽然突发洪水的来源和触发机制是众所周知的，但流动行为却不是，主要是因为直接测量这种突然，强大和快速变化的流动的固有问题。因此，目前对流动特性的预测非常有限。3.只有在充分了解控制水流行为的过程时，才能制定突发洪水缓解措施;即参数化和建模，并根据真实世界的数据验证该模型。这些标准必须产生于一个综合的和可持续的设计方法。4.随着气候变化，气温和降水模式有真实的可能发生变化，导致冰湖溃决和滑坡引发的溃决发生频率增加，冰川引发的洪水溃决规模增加。5.大多数突发洪水都来自天然湖泊，否则这些湖泊就是一种水资源，如果有适当的管理解决方案，它们就可以保持这种状态。这个项目是非常及时的，因为最近爆发的洪水从Sólheimajökull（冰岛）和预测的火山口湖洪水从Mt Ruapehu（新西兰）的限制与精确的事件前和事件后的调查，提供迄今无法获得的数据模型参数化和验证。后者还将以GNS Science和Massey大学正在开发的最先进的传感器系统为特征，以产生关于流动行为和水力参数的时间序列数据。该项目显然将为自然灾害风险中心的使命作出重大贡献，提供量化数据，促进对自然灾害解决办法的了解和支持，这将给工业和公共部门带来经济和社会效益，并吸引来自若干学科和国家的优秀研究人员参与。

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.