Natural hazards of shoreline bluff erosion: a case study of Horizon View, Lake Huron

Abstract

Assessment of hazard of erosion of shoreline bluffs requires an understanding of the natural processes and human use in these high risk areas. As an important component associated with erosion and natural evolution bluff shorelines, alongshore sediment transport is an essential process in defining the hazard associated with bluff erosion. The objective of this study is the integration of an understanding of alongshore sediment transport into a proposed management framework for cohesive bluff shorelines. A study of a ten kilometre area along the southeastern Lake Huron shoreline, at the cottage community of Horizon View, north of Goderich, Ontario examines the natural and human components which have led to the development of bluff erosion hazards. Although dominant sediment transport is north to south alongshore, the pattern of wave refraction during south and southwest waves, suggests frequent northward transport of material from the 30 meter high bluffs at the site. Examination of beach sediments and bluff conditions support this finding and indicate long term sediment supply and bluff instability. Planning of future development at this location must appreciate the potential for continued bluff erosion and the study results suggest that when combined with other factors such as wave energy, bluff morphology, groundwater conditions, vegetation cover, land uses and impacts of fluctuating lake levels, studies of alongshore sediment transport can be a useful tool to assist in management of cohesive coastlines and understanding the natural hazard of bluff erosion in developed coastal areas. A management framework for cohesive bluffs attempts to integrate an understanding of natural processes with human uses and land use policies in order to identify, assess and select a preferred management option reflecting this understanding.