NATURAL HAZARDS OF SHORELINE BLUFF EROSION - A CASE-STUDY OF HORIZON VIEW, LAKE HURON

Assessment of hazard of erosion of shoreline bluffs requires an unders tanding of the natural processes and human use in these high risk area s. As an important component associated with erosion and natural evolu tion of bluff shorelines, alongshore sediment transport is an essentia l process in defining the hazard associated with bluff erosion. The ob jective of this study is the integration of an understanding of alongs hore sediment transport into a proposed management framework for cohes ive bluff shorelines. A study of a ten kilometre area along the southe astern 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 d ominant sediment transport is north to south alongshore, the pattern o f wave refraction during south and southwest waves, suggests frequent northward transport of material from the 30 meter high bluffs at the s ite. 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 po tential for continued bluff erosion and the study results suggest that when combined with other factors such as wave energy, bluff morpholog y, 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 un derstanding the natural hazard of bluff erosion in developed coastal a reas. A management framework for cohesive bluffs attempts to integrate an understanding of natural processes with human uses and land use po licies in order to identify, assess and select a preferred management option reflecting this understanding.