Rates and Mechanisms of Coastal Erosion in the Bay of Fundy

芬迪湾海岸侵蚀的速率和机制

• 批准号: RGPIN-2017-04554
• 负责人: Hill, Paul
• 金额: $ 2.33万
• 依托单位: Dalhousie University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=711128
• 关键词: Rates; Mechanisms; Coastal; Erosion; Bay

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.

沿海侵蚀与海平面上升和增加的暴风雨有关，威胁着加拿大和全球的基础设施。 风险模型正在不断发展，以纳入沿海侵蚀的情节性质，但是这些努力建立牢固的，基于证据的风险定义需要经常进行沿海的高分辨率调查，直到最近，这一直是昂贵且逻辑上的困难。 然而，结构 - 运动（SFM）技术的出现使海岸的快速，低成本，准确的调查正在开辟新的途径，以调查发作性侵蚀。 SFM从重叠的照片中构造3-D表面。 该名称来自SFM使用由移动相机收集的图像的能力，其位置在捕获图像时未知。 这种能力使能够使用无人机（UAV）来收集用于SFM沿海形态的SFM重建的照片。 在拟议的研究中，使用无人机用SFM进行低成本重复的沿海调查构成了测量方法的核心。 该研究的具体重点是加拿大芬迪湾的米纳斯盆地的沿海侵蚀的速度和机制。 两个项目将衡量悬崖侵蚀率和控制它们的因素，另一个项目将检查沉积物存储的速率和机制，并在低流排放期间从侧通道中删除。 米纳斯盆地中的悬崖侵蚀威胁着基础设施，但也决定了海床上重要的沉积物质地。 我小组最近的一项研究表明，过去20年中的悬崖撤退率几乎比过去30年大50％。 我计划采用频繁的基于无人机的SFM调查，并结合降雨，风和水位的测量，以研究观察到的沿海撤退率增加的根本原因。 米纳斯盆地中悬浮的沉积物浓度通过影响光场影响水柱中的栖息地。 由于正在研究的原因，冬季的沉积物浓度在冬季增加了五倍。 盆地沉积物的一个潜在来源是在高流排放期间从侧通道侵蚀泥浆。 很难用常规方法估计在高放电事件中释放的沉积物量，因为侧通道中的泥浆对穿越是危险的。 我计划使用新斯科舍省贝尔蒙特河的基于无人机的SFM调查来限制在侧通道中发生重大侵蚀和填充的条件，并限制所涉及的沉积物体积。 加拿大面临着沿海侵蚀的加速率。 拟议的研究将通过制定和实施对沿海形态的低成本测量的新策略来使加拿大受益，这对于建立知情的了解沿海变化的速度和机制至关重要。