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Quantifying the Delivery & Dispersal of Landslide-Derived Sediment to the Dart River, New Zealand

量化交付

基本信息

批准号：
NE/M005054/1
负责人：
James Brasington
金额：
$ 6.62万
依托单位：
Queen Mary University of London
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2014
资助国家：
英国
起止时间：
2014 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FM005054%2F1
关键词：
Quantifying Delivery Dispersal Landslide Derived

项目摘要

Following heavy rainfall on the 4/1/14, a major debris flow at Slip Stream (44.59 S 168.34 E) introduced >10^6 m^3 of sediment to the Dart River valley floor in NZ Southern Alps (S. Cox, pers. comm). Runout over the existing fan dammed the Dart River causing a sudden drop in discharge downstream. This broad dam was breached quickly, however the loss of conveyance has since impounded a 4 x 1 km lake with depths that exceed 20 m. This event presents a rare and unprecedented opportunity to study the impacts of a discrete, high magnitude 'sediment pulse', remarkable in its capacity to dam a large river in flood (peak discharge during the event was recorded at ~790 m^3/s). Quantifying the impact of this disturbance on the form and stability of the receiving body, the Dart River, will advance our understanding of how such low frequency geophysical events shape the evolution of large alpine rivers and will create a vital baseline for future research that seeks to test theories of how such large bed wave propagates and disperse sediment downstream. The impact of this pulse also elevates the risks posed by natural hazards in the region. Enhanced sediment transport has the potential to raise riverbed levels, destabilise floodplain assets, reduce standards of flood protection, increase the risk of channel avulsion and impact on freshwater and riparian ecology with a legacy that long outlasts the initial disturbance. Locally, this event may result in rapid advance of the Dart-Rees delta into Lake Wakatipu threatening the lakeshore communities of Glenorchy and Kinloch. The assessment of how large fluvial sediment pulses migrate, disperse and condition such hazards will offer key insights that may be transferable to other dynamic alpine settings. However, in order to constrain this event effectively, an initial topographic and sedimentological survey must be undertaken urgently, in the immediate aftermath of the event, to enable robust quantification of the sediment pulse and the existing channel morphology. This research aims to advance this goal by seeking to: develop a unique baseline dataset that will be used to quantify the delivery and dispersal of sediment inputs from the Slip Stream landslide, from its source at Te Koroka to its sedimentary sink in Lake Wakatipu. Using a combination of aerial, terrestrial and bathymetric surveying, we will acquire two synoptic, system-wide snapshots of this highly charged sediment cascade that record the 3d morphology and sedimentology of the interlinked components of the sediment transfer system. Surveys will be undertaken in April 2014 and then one year later in March 2015, following the annual summer floods that dominate fluvial sediment transport in the region. The first survey will establish the initial state of the system and so create the opportunity to quantify the downstream pattern of sediment storage and transport through comparison with the second and any subsequent re-surveys direct differencing of Digital Elevation Models. The simultaneous bathymetric surveys of the upstream impounded lake and the delta morphology will provide constraints on sediment flux across the boundaries of the study area, enabling closure of the coarse sediment budget. The combined results of these two survey campaigns will create an unparalleled dataset to help frame and test hypotheses that seek to explain the dispersal of major sediment pulses within rivers.

继2014年4月1日的强降雨之后，滑流（44.59 S 168.34 E）的一场主要泥石流将超过10^6 m^3的沉积物带到了新西兰南阿尔卑斯山（S.考克斯，人）。现有风机上的溢流堵塞了达特河，导致下游流量突然下降。这座宽阔的大坝很快就被冲垮了，然而，由于失去了运输能力，一个4x 1公里的湖泊被蓄水，深度超过20米。这一事件提供了一个罕见的和前所未有的机会来研究一个离散的，高强度的“沉积物脉冲”的影响，其显着的能力，以大坝的洪水（在事件期间的峰值流量记录在约790 m^3/s）。量化这种干扰的形式和稳定性的接收体，达特河的影响，将推进我们的理解，这种低频率的地球物理事件如何塑造大型高山河流的演变，并将创建一个重要的基线，为未来的研究，旨在测试理论如何这样大的床波传播和分散沉积物下游。这一脉动的影响也增加了该区域自然灾害造成的风险。泥沙输移的增加有可能提高河床水位，破坏洪泛区资产的稳定，降低防洪标准，增加河道撕裂的风险，并对淡水和河岸生态产生影响，其影响比最初的扰动持续时间更长。在当地，这一事件可能导致达特-里斯三角洲迅速进入瓦卡蒂普湖，威胁到格伦诺奇和金洛克的湖岸社区。大型河流沉积物脉冲迁移，分散和条件的评估将提供关键的见解，可能会转移到其他动态高山设置。然而，为了有效地限制这一事件，必须在事件发生后立即紧急进行初步地形和沉积学调查，以便对沉积物脉冲和现有河道形态进行可靠的量化。本研究旨在通过以下方式推进这一目标：开发一个独特的基线数据集，用于量化滑流滑坡从Te Koroka源到瓦卡蒂普湖沉积汇的沉积物输入的输送和分散。综合运用航空、陆地和水深测量，我们将获得这一高度带电的沉积物级联的两个天气学、系统范围的快照，记录沉积物传输系统相互关联的组成部分的三维形态和沉积学。调查将于2014年4月进行，一年后的2015年3月，即每年夏季洪水主导该区域河流沉积物迁移之后进行。第一次调查将建立系统的初始状态，从而创造机会，通过与第二次调查和任何后续的重新调查进行比较，量化沉积物储存和运输的下游模式。同时水深测量的上游蓄水湖和三角洲形态将提供限制沉积物通量的边界的研究区，使关闭的粗沉积物预算。这两项调查活动的综合结果将创建一个无与伦比的数据集，以帮助框架和测试试图解释河流内主要沉积物脉冲分散的假设。