A proposed acoustic monitoring solution for observing suspended sediments during intense storm events causing coastal erosion in the Western Canadian Arctic

Declining Arctic sea-ice cover and increases in fetch are increasing the risk of wave-driven erosion of coastlines and storm surges, which can affect communities and regional coastal ecosystems in the Western Canadian Arctic. Storm-induced flooding and wave erosion action are caused by strong, persistent northwesterly wind forcing, and are active processes during the summer and fall. Delayed freeze-up attributed to climate change maintains fetch into October, where an increasingly baroclinic atmospheric environment may enhance storm development and commensurate impacts on shorelines. This can result in sharp rates of coastal erosion during intense storms, and transport and deposition of coastal sediments. Although coastal ecosystems rely on sedimentation and salinization from small floods, large storm inundations can cause salinization of freshwater ponds and non-saline meadows, damage vegetation along the margins of permafrost plateaus, and melt subterranean permafrost, causing underground hollows subject to collapse.

We present a concept for monitoring rates of coastal erosion through bottom-looking mooring observations of acoustic backscatter from suspended sediment during intense Arctic storms in shallow Arctic waters to study large erosion events impacting the community of Tuktoyaktuk, NWT, as well as at locations throughout the Western Canadian Arctic (e.g. Pelly Island, NWT, Mackenzie Delta). The Multi-frequency Ultrasonic Device (MUD™) is based on ASL's successful Acoustic Zooplankton Fish Profiler (AZFP). The MUD and AZFP echosounders can be configured with up to four frequencies ranging from 38 kHz to 2 MHz. The MUD prototype is based on a set of higher frequencies (200 kHz, 769 kHz, 1.2 MHz and 2.0 MHz) that will allow for a broad range of particle size discrimination. While the AZFP is a high gain device for low scattering conditions and the greatest possible range, the MUD echosounder is a lower gain system that is being tuned to work in higher backscatter regimes such as high concentration of suspended sediment. The MUD has successfully detected coastal turbidity flows in a previous deployment in Bute Inlet, B.C., Canada.