Morphodynamics and sedimentology of the tidally-influenced fluvial zone (TIFZ)

全球所有流入海洋的河流都有一个长达数百公里的区域，它是河流和潮汐环境之间的过渡地带(这里称为潮汐影响河流区，简称TIFZ)。这一地区是地球表面最复杂的环境之一，因为它是一个河流流量和潮流都很大的地区，这些竞争力量每天、季节和每年都会发生变化。这些区域对人类很重要，并形成了一些人口密度最高的区域：它们在当今具有重要的战略意义，因为这些区域处于航运、水产养殖、填海造地和自然保护等相互竞争的需求的交界处。因此，为了更好地维护、管理和保护这些脆弱区域，我们必须了解这些区域如何变化以及为什么变化，以及控制这种变化的因素是什么。此外，古代TIFZ的沉积物可能含有大量碳氢化合物，这越来越成为许多能源公司的目标。例如，阿萨巴斯卡油砂形成了地球上最大的石油储量，这些沥青焦油与古老的TIFZ沉积物锁在一起。因此，当试图从这种古老的碳氢化合物储集层中提取最大数量的石油(或天然气)时，了解这种TIFZ沉积物的内部性质是至关重要的--我们需要知道是什么控制了这些储集层的几何和内部特征，从而更好地规划了高效和最大限度的碳氢化合物提取策略。因此，现代和古代TIFZ环境中的所有这些兴趣都取决于对这些地区的流体流动的详细了解，这些流动如何输送其沉积物，以及这些环境的形态(或形态)如何随着时间的变化而变化。然而，由于在如此复杂和动态的环境中工作是非常困难的，几乎没有高分辨率的、具有空间代表性的野外数据集，而且对这种TIFZ矿床的内部沉积结构的诊断工作也非常少。此外，虽然在河口水流和泥沙输移的数学模型方面取得了进展，但这些模型在很大程度上仍未得到检验。因此，迫切需要通过对TIFZ的流动、形态和沉积物运动的综合研究，将TIFZ的过程和沉积联系起来，以量化关键的过程以及这些过程如何在地下沉积记录中表现出来。这项建议概述了一项综合的实地和数学模型研究，旨在利用实地调查和数学建模方面的最新技术，实现我们对TIFZ的理解的阶段性变化。这些技术将产生无与伦比的高分辨率水深测量、水流、沉积物输送和沉积结构数据集，然后将用于构建和验证TIFZ的新数值模型。这最终将能够评估与TIFZ有关的关键未知数，例如这种环境在与海平面变化相关的潮汐和河流贡献的变化情景下如何演变，以及是否有可能区分“河流”和“潮汐”影响的沉积。这些结果将改变我们对这些TIFZ带在现代环境中的行为的理解，并关键地改变这些变化在古代沉积序列中可能被识别的方式。

All rivers across the globe that exit to the ocean contain a zone, which can be 100s of kilometres long, which is transitional between river and tidal environments (termed here the Tidally-Influenced Fluvial Zone, or TIFZ). This zone is one of the most complex environments on the surface of the Earth because it is an area where both river flow and tidal currents are significant, and these competing forces vary daily, seasonally and annually. These regions are important to mankind and form some of the areas of highest population density: they are strategically important in the present day because these zones are at the interface of competing demands for shipping, aquaculture, land reclamation and nature conservation. Thus in order to better maintain, manage and protect these fragile zones, we must understand how and why these regions change and what factors control such change. Additionally, the sediments of ancient TIFZ's may contain significant volumes of hydrocarbons which are increasingly the target for many energy companies. For example, the Athabasca oil sands form the largest petroleum deposit on Earth and these bitumen tars are locked up with ancient TIFZ sediments. Understanding the internal nature of such TIFZ sediments is thus of paramount importance when attempting to extract the maximum quantity of oil (or gas) from such ancient hydrocarbon reservoirs - we need to know what controls the geometry and internal characteristics of these reservoirs, and thus better plan efficient and maximal hydrocarbon extraction strategies. Thus all of these interests in both modern and ancient TIFZ environments depend on a detailed knowledge of the fluid flows in these areas, how such flows transport their sediment and critically how the form (or morphology) of these environments changes through time. However, due to the extraordinary challenges of working in such a complex and dynamic environment, few high-resolution, spatially-representative, field datasets exist and remarkably little work has been undertaken on the diagnostic internal sedimentary structure of such TIFZ deposits. Additionally, whilst there has been progress on the mathematical modelling of estuarine flow and sediment transport, these models remain largely untested. There is therefore a pressing need to link the processes and deposits of the TIFZ through an integrated study of their flow, morphology and sediment movement to quantify the key processes and how these are represented within the subsurface sedimentary record. This proposal outlines an integrated field and mathematical modelling study that seeks to achieve a step-change in our understanding of the TIFZ, using the very latest techniques in field survey and mathematical modelling. These techniques will yield unrivalled high-resolution datasets of bathymetry, flow, sediment transport and sedimentary structure that will then be used to construct and validate new numerical models of the TIFZ. This will ultimately allow evaluation of key unknowns with respect to the TIFZ, such as how such environments evolve under changing scenarios of tidal and fluvial contributions associated with sea-level change, and whether it is possible to differentiate between 'fluvial' and 'tidally' influenced deposits. Such results will transform our understanding of how such TIFZ zones behave in modern environments and critically how these changes may be recognized within ancient sedimentary successions.