Next-generation Forecasting of Hazards Offshore from River Deltas

“NERC：刘易斯贝利：NE/L002531/1“我们的首要目标是更好地了解触发河口近海沉积物海底雪崩（称为浊流）的过程。通过分析触发机制，我们的目标是建立一个模型，可以预测浊流活动，并适用于全球河流三角洲。这些沉积物流动的力量可能非常强大（速度高达20米/秒），并可移动很长的距离（100公里）。因此，浊流对海底基础设施，如石油和天然气管道和电信电缆构成重大危险。在当前的封锁和远程工作世界中，我们从未如此依赖互联网。即使流速为1-2米/秒的较弱水流也会严重损坏海底设备，使减灾工作变得具有挑战性，而且成本非常高（每公里数百万美元）。因此，提高我们对流动的频率和时间的理解对于评估这些额外成本是必要的至关重要。浊流的破坏性意味着只有很少的地方能直接测量到大量的水流。因此，导致流动触发的机制仍然知之甚少。最近的监测已经取得了进展，使用沿着流动路径停泊的仪器来精确测量浊流时间，以与潜在的触发器进行比较。在加拿大不列颠哥伦比亚省的偏远峡湾三角洲环境中进行的分析表明，浊流优先发生在河流流量升高期间的低潮。新的多元统计方法（即分析多个变量的综合影响）量化了河流流量和水位的相对作用。利用这种关系，它已经可以成功地预测近90%的浊流活动。然而，这种分析是基于在相对较短的时间段（几个月）内获得的数据，因此可能会错过更长的（季节-年度）流量活动周期。也不知道在扩大规模并应用于水下活动对沿海社区和关键海底基础设施构成更大危害的主要河流时，河流流量和水位的相对作用如何变化。该项目将使用加拿大政府资助的开创性的维多利亚海底实验网络有线观测台提供的长期监测数据集，该观测台自2008年以来一直在记录不列颠哥伦比亚省弗雷泽河三角洲近海异常详细的数据。利用此资料，结合以往直接测量的浊流，本计画的目的是：（1）了解流量与潮汐在不同尺度河流系统中对浊流触发的作用。(2)开发一个可应用于全球河流三角洲系统的浊流发生预测模型。(3)了解气候变化对浊流频率和时间的潜在影响。我们的研究结果将有利于未来的海底基础设施，包括石油和天然气管道和电信电缆的地质灾害评估。浊流预测模型的开发将帮助我们了解水流的频率和时间以及对海底基础设施的风险。这样的预测还可以有助于电缆或管道路由的未来规划。

"NERC : Lewis Bailey : NE/L002531/1"Our overarching aims is to better understand the processes that trigger submarine avalanches of sediment, known as turbidity currents, offshore from river mouths. By analysing triggering mechanisms, we aim to build a model that can forecast turbidity current activity, and be applied to river deltas globally. These sediment flows can be exceptionally powerful (velocities of up to 20 m/s) and travel for long (100s km) distances. Therefore, turbidity currents pose a significant hazard to seafloor infrastructure such as oil and gas pipelines and telecommunication cables. We have never been more reliant on the internet in the current world of lockdowns and remote working. Even weaker flows travelling at speeds of ~1-2 m/s can severely damage seafloor equipment making hazard mitigation be re-routing challenging and very expensive ($millions per km). Improving our understanding of the frequency and timing of flows is therefore critical to asses where these extra costs are a necessity. The destructive nature of turbidity currents means there are very few sites where a significant number of flows have been directly measured. Therefore, the mechanisms that result in flow triggering still remain poorly understood. Recent monitoring has made advances using instruments moored along flow paths to precisely measure turbidity current timing to compare with potential triggers. Analysis in remote fjord-delta settings in British Columbia, Canada, have shown turbidity currents preferentially occur at low tide during periods of elevated river discharge. Novel multivariate statistical methods (i.e. analysing the combined effect of multiple variables) have quantified the relative role of river discharge and water level. Using this relationship, it has been possible to successfully predict almost 90% of turbidity current activity. However, this analysis is based on data acquired over relatively short-time periods (months), and therefore may miss longer (seasonal-yearly) cycles of flow activity. It is also unknown how the relative roles of river discharge and water level vary when upscaled and applied to major rivers where underwater events pose a much greater hazard to coastal communities and critical seafloor infrastructure. The project will use longer-term monitoring datasets that have been made possible by the pioneering Canadian Government-funded Victoria Experimental Network Under the Sea (VENUS) cabled observatory, which has been recording unusually detailed data offshore the Fraser River Delta, British Columbia, since 2008. Using this dataset combined with previous direct measurements of turbidity currents the project aims are to:(1) Understand how the roles of discharge and tide for turbidity current triggering vary at different scale river systems.(2) Develop a predictive model for turbidity current occurrence that could be applied to river delta systems globally. (3) Understand the potential effects of climate change on the frequency and timing of turbidity currents. Our results will benefit future geohazard assessments for seafloor infrastructure including oil and gas pipelines, and telecommunication cables. The development of a turbidity current forecasting model will help us understand the frequency and timing of flows and the risk to seafloor infrastructure. Such forecasting can also contribute to future planning of cable or pipeline routing.