Next-generation Forecasting of Hazards Offshore from River Deltas

河流三角洲近海灾害的下一代预测

• 批准号: NE/V021095/1
• 负责人: Ivan Haigh
• 金额: $ 1.12万
• 依托单位: University of Southampton
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2021
• 资助国家: 英国
• 起止时间: 2021 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FV021095%2F1
• 关键词: Next; generation; Forecasting; Hazards; Offshore

"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.

“NERC：Lewis Bailey：NE/L002531/1”我们的首要目标是更好地了解在河口近海引发海底沉积物雪崩的过程，即所谓的浑浊流。通过对触发机制的分析，我们的目标是建立一个能够预测浊流活动的模型，并将其应用于全球河流三角洲。这些泥沙流可以非常强大(速度高达20米/S)，并可以移动很长(100公里)的距离。因此，浊流对油气管道和通信电缆等海底基础设施构成重大危险。在当前的封锁和远程工作的世界里，我们从未像现在这样依赖互联网。即使较弱的水流以约1-2米/S的速度行进，也会严重损坏海底设备，使减灾改道具有挑战性，而且非常昂贵(每公里数百万美元)。因此，提高我们对流动频率和时间的了解，对于评估哪些地方需要这些额外成本至关重要。浑浊流的破坏性意味着很少有直接测量到大量水流的地点。因此，导致流触发的机制仍然知之甚少。最近的监测取得了进展，使用停泊在流动路径上的仪器来精确测量浑浊电流定时，以与潜在触发因素进行比较。对加拿大不列颠哥伦比亚省偏远峡湾三角洲环境的分析表明，浊流优先出现在河流流量上升时期的低潮时期。新的多变量统计方法(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。利用这个关系式，可以成功地预测近90%的浑浊电流活度。然而，这种分析是基于在相对较短的时间段(月)内获得的数据，因此可能会错过较长的(季节性-年度)流动活动周期。同样未知的是，当河流流量和水位的相对作用扩大并应用于对沿海社区和关键海底基础设施构成更大危险的主要河流时，它们的相对作用如何变化也是未知的。该项目将使用加拿大政府资助的开创性的海底维多利亚实验网络(Venus)有线天文台提供的长期监测数据集，该天文台自2008年以来一直在不列颠哥伦比亚省弗雷泽河三角洲近海记录异常详细的数据。利用这一数据集，结合以往对浊流的直接测量，该项目的目的是：(1)了解流量和潮汐对触发浊流的作用在不同尺度的水系中是如何变化的。(2)建立一个可以应用于全球河流三角洲系统的浑浊发生预测模型。(3)了解气候变化对浑浊流频率和时间的潜在影响。我们的结果将有助于未来对海底基础设施进行地质灾害评估，包括石油和天然气管道以及电信电缆。浊流预报模型的开发将有助于我们了解水流的频率和时间以及对海底基础设施的风险。这样的预测也有助于电缆或管道布线的未来规划。