Assessment of Storm Surge History as Recorded by Driftwood in the Mackenzie Delta and Tuktoyaktuk Coastlands, Arctic Canada

Abstract

The southern Beaufort coastline in Canada experiences significant storm surge events that are thought to play an important role in coastal erosion and influence permafrost dynamics. Unfortunately, many of these events have not been documented with tide gauge records. In this paper, we evaluate coastal driftwood accumulations as a proxy for estimating maximum storm surge heights and the history of these events. We use historical air photos and data derived from Unoccupied Aerial Vehicle (UAV) imagery to resurvey four coastal stranded driftwood study sites that were first appraised in 1985–86 and assess two new regional sites in the Mackenzie Delta. Maximum storm surge heights were found to be similar to observations carried out in the 1980s, however, we refine the elevations with more accuracy and reference these to a vertical datum appropriate for incorporating into sea level hazard assessments. Detailed mapping, historical air photo comparisons and the UAV acquired imagery at a site close to Tuktoyaktuk demonstrate that the highest storm surge at this site (1.98 m CGVD2013) occurred in association with a severe storm in 1970. This event shifted driftwood and floated material slightly upslope from an older event thought to occur in 1944 that reached 1.85 m (CGVD2013) elevation. The quality and accuracy of the high-resolution Digital Surface Model (DSM) and orthophoto derived from Structure from Motion (SfM) processing of the UAV photographs allowed mapping of four distinct stratigraphic units within the driftwood piles. Based on variations in anthropogenic debris composition, weathering characteristics and history of movement on aerial photographs, we conclude that no storm surge events at Tuktoyaktuk have exceeded ∼1.3 m (CGVD2013) since 1970. While there has been some speculation that ongoing climate change may lead to more frequent large magnitude storm surges along the Beaufort coast, our study and available tide gauge measurements, suggest that while moderate elevation storm surges may be more frequent in the past several decades, they have not approached the magnitude of the 1970 event.

Assessing Numerical Model Skill at Simulating Coastal Flooding Using Field Observations of Deposited Debris and Photographic Evidence

“…Debris transport and deposition are affected by the physical properties of the debris, shoreline characteristics, and hydrodynamics [50][51][52]. In this study, sea wrack and shoreline debris were used to support model skill assessment, assuming that they represent a proxy for peak water level elevation and flood extent, following similar assumptions by others [8,[26][27][28][29][30]. Future research addressing the processes and mechanisms underlying the transport and deposition of specific debris types in different coastal settings would help to clarify linkages between water levels and deposits of debris, and their utility to support coastal flood hazard assessment.…”

“…In addition, a qualitative assessment of model skill was conducted through a comparison with photographic and video evidence. Where adequate observational data exist, deposited debris such as driftwood and sea wrack have been used to support analyses related to coastal flooding [8,[26][27][28][29][30]. Didier et al [8] used debris lines to evaluate coastal flood extent, as well as predictive accuracy of wave runup estimations, for the community of Maria, Québec; Maria is located approximately 100 km northwest of the Acadian Peninsula.…”