Predicting Lahar Evolution and Runout Behavior

火山岩是水和火山岩碎片快速流动的混合物，它们造成了一些历史上最严重的火山灾难。火山灰的类型和过程范围很广，主要与水和岩石颗粒的相对体积有关。灾害预测所需的现有模型很好地处理了泥石流的极端行为(洪水和雪崩)，但需要新的模型来涵盖这些复杂现象的广泛中间地带，并包括泥石流的下游演变以及对潜在泥石流路径上的社区和基础设施的影响。松散的火山沉积物上的暴雨，爆炸性喷发的物质与水或冰的混合，或者山顶火山口湖的破裂，都可能引发火山喷发。大多数拉哈尔几乎没有警告信号，因此基本上是不可预测的。这项研究利用了一种几乎是独一无二的情况，即预测新西兰鲁阿佩胡山新填满的火山口湖将发生洪水暴发，并将寻求与圣海伦斯火山进行比较。这项研究由岩石学和地球化学以及EPSCoR项目共同资助，美国和新西兰的科学家、学生和应急管理人员将参与生产一种用户友好的危险预测工具。科学方法包括将现场数据与熔岩流动过程的计算建模相结合。该团队将开发数学方法来描述Lahars的复杂物理过程，以及它们的特征随着它们从源头流出而演变的方式。这个新的模型将是第一个详细处理泥沙和水在岩浆侵位过程中的增加和损失的模型，从而占据了现有质量流模型不能很好地处理的利基。泥沙夹带过程已被发现是导致流量增加许多倍的原因，因此对于了解下游危险的大小显然是重要的。对这两座火山的实地研究将在应用于更广泛种类的火山和火山喷发机制之前，对该模型进行验证。通过将最终产品包装为用户友好的危险预测工具，它旨在弥合Lahar研究人员和可能直接受益于该项目的社区之间的差距。

Lahars are fast-flowing mixtures of water and volcanic rock fragments which have been responsible for some of the worst historical volcanic disasters. There is a wide spectrum of lahar types and processes, mostly linked to the relative volumes of water and rock particles. Existing models, needed for hazard forecasting deal well with the extremes of lahar behavior (floods and avalanches) but new models are needed to cover the wide middle ground for these complex phenomena, and to include the downstream evolution of a lahar and the implications for hazards to communities and infrastructure located in potential lahar pathways. Lahars can be triggered by heavy rainfall on loose volcanic deposits, by mixing of explosively erupted materials with water or ice, or by breakout of a summit crater lake. Most lahars have few warning signs and are thus essentially unpredictable. This study takes advantage of an almost unique situation where a breakout flood is predicted for the newly filled crater lake of Mount Ruapehu in New Zealand and will look to draw comparisons with Mount St Helens. The study, co-funded by the Petrology and Geochemistry and EPSCoR programs, will involve American and New Zealand scientists, students, and emergency managers in the production of a user-friendly hazard forecasting tool.The scientific approach involves integration of field data with computational modeling of lahar flow processes. The team will develop methods of describing mathematically the complex physical processes of lahars, and the manner in which their characteristics evolve as they flow away from source. This new model will be the first to tackle in detail additions and losses of sediment and water during the emplacement of a lahar, thus occupying a niche not well treated by existing mass flow models. Sediment entrainment processes have been found to be responsible for many-fold increases in flow volume, and thus are clearly important for understanding the magnitude of downstream hazard. Field studies at the two volcanoes will provide validation of the model, before application to a wider variety of volcanoes and lahar-triggering mechanisms. By packaging the end product as a user-friendly hazards forecasting tool, it is aimed to bridge the gap between lahar researchers and the communities that may directly benefit from this project.