Rates and Mechanisms of Coastal Erosion in the Bay of Fundy

与海平面上升和风暴增加相关的海岸侵蚀威胁着加拿大和全球的基础设施。风险模型正在演变，以纳入海岸侵蚀的偶发性质，但这些建立更牢固、基于证据的风险定义的努力需要对海岸进行频繁、高分辨率的调查，直到最近，这些调查都是昂贵的，而且在后勤上很困难。然而，运动构造（SfM）技术的出现使得对海岸进行快速、低成本、准确的调查成为可能，这为调查间歇性侵蚀开辟了新的途径。***SfM从重叠的照片构建三维表面。这个名字来自于SfM使用移动相机收集的图像的能力，这些图像在图像捕获时是未知的。这种能力使无人驾驶飞行器（uav）能够收集照片，用于沿海形态的SfM重建。使用无人机与SfM进行低成本的重复海岸调查构成了拟议研究中测量方法的核心。***研究的具体重点是加拿大芬迪湾米纳斯盆地海岸侵蚀的速率和机制。两个项目将测量悬崖侵蚀率和控制侵蚀率的因素，另一个项目将检查在低流量和高流量期间侧河道沉积物储存和移走的速率和机制。***米纳斯盆地的悬崖侵蚀威胁着基础设施，但它也决定了海底生态重要的沉积物质地。我小组最近的一项研究表明，过去20年的悬崖退缩率比之前30年高出近50%。我计划采用频繁的基于无人机的SfM调查，结合降雨、风和水位的测量来调查观察到的沿海退缩速度增加的潜在原因。***米纳斯盆地悬浮泥沙浓度通过影响光场影响水柱生境。沉积物浓度在冬季增加了五倍，原因正在调查中。盆地沉积物的一个潜在来源是在高流量期间从侧面渠道侵蚀的泥浆。常规方法很难估计在高流量事件期间释放的沉积物体积，因为侧通道中的泥浆穿越是危险的。我计划对新斯科舍省的贝尔蒙特河进行基于无人机的SfM调查，以限制在侧河道发生严重侵蚀和填充的条件，并限制所涉及的沉积物体积。加拿大正面临海岸侵蚀加速的问题。拟议的研究将通过制定和执行低成本沿海形态调查的新战略使加拿大受益，这对于建立对沿海变化速度和机制的知情了解至关重要。*****

Coastal erosion associated with rising sea levels and increased storminess threatens infrastructure in Canada and around the globe. Models of risk are evolving to incorporate the episodic nature of coastal erosion, but these efforts to establish firmer, evidence-based definitions of risk require frequent, high-resolution surveys of the coast, which until recently have been costly and logistically difficult. The emergence of Structure-from-Motion (SfM) technology, however, enables rapid, low-cost, accurate surveys of the coast, which is opening new avenues for investigation of episodic erosion. ***SfM constructs 3-D surfaces from overlapping photographs. The name comes from the ability of SfM to use images collected by a moving camera with positions that are unknown at the time of image capture. This ability has enabled the use of unmanned aerial vehicles (UAVs) for collection of photographs for SfM reconstruction of coastal morphology. The use of UAVs to conduct low-cost repetitive coastal surveys with SfM forms the core of the measurement approach in the proposed research.***The specific focus of the research is on rates and mechanisms of coastal erosion in the Minas Basin of the Bay of Fundy, Canada. Two projects will measure cliff erosion rates and the factors that control them, and another will examine rates and mechanisms of sediment storage and removal from side channels during periods of low and high stream discharge.***Cliff erosion in the Minas Basin threatens infrastructure, but it also determines the ecologically important sediment texture of the seabed. A recent study in my group showed that cliff retreat rates over the past 20 years are almost 50% larger than during the previous 30 years. I plan to employ frequent UAV-based SfM surveys, combined with measurements of rainfall, wind, and water level to investigate the underlying causes of observed increases in the rate of coastal retreat.***Suspended sediment concentration in the Minas Basin affects habitat in the water column by influencing the light field. Sediment concentration increases fivefold in the winter for reasons that are under investigation. One potential source of sediment to the Basin is erosion of mud from side channels during periods of high stream discharge. It is difficult to estimate volumes of sediment released during high discharge events with conventional methods, because the muds in side channels are dangerous to traverse. I plan to use UAV-based SfM surveys of the Belmont River in Nova Scotia to constrain conditions under which significant erosion and infilling occur in side channels and to constrain the volume of sediment involved.***Canada is faced with accelerating rates of coastal erosion. The proposed research will benefit Canada by developing and implementing new strategies for low-cost surveying of coastal morphology that are essential to building informed understanding of the rates and mechanisms of coastal change.*****