Abstract
Prior to a 3-m impoundment in 1976, bedrock comprised 76% of the shoreline of Southern Indian Lake in northern Manitoba. This was reduced to only 14% of the shoreline as the water level rose above the wave-washed zone and flooded into the predominantly fine-grained, frozen overburden materials. Twenty monitoring sites were surveyed annually to determine rates of permafrost melting and solifluction and shoreline erosion. The sequence of shoreline erosion in permafrost materials was found to be cyclic, consisting of melting and undercutting of the backshore zone, massive faulting of the overhanging shoreline, and removal of the melting and fractured debris. Rates of shoreline erosion varied widely, depending on the exposure of the site to wave action and the composition of the backshore materials. At sites in fine-grained frozen silts and clays, representative of over three quarters of the postimpoundment shoreline, rates of retreat of up to 12 m∙yr−1were observed. The total volume of shoreline materials removed varied from less than 1 to over 23 m3∙m shoreline length−1∙yr−1. Clearing of the forested backshore prior to flooding did not affect the erosion rates. The index of erosion based on the hindcast wave energy component perpendicular to the shoreline was 0.00035 m3∙t-m wave energy−1(0.036 m3∙MJ−1). The minimum period of restabilization of the shoreline based on the volume of backshore materials that must be eroded before bedrock conditions are reestablished was estimated to be 35 yr for three quarters of the shoreline surrounding the lake.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
More From: Canadian Journal of Fisheries and Aquatic Sciences
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.