Temporal characteristics and controls on landsliding in glacial tills

This investigation seeks to examine the conditions that lead to hysteresis in landslide movement in response to pore-pressure changes in a glacial till landslide complex. Fieldwork has been conducted to understand the relationship between pore-pressure change and the resultant movement rate and style. The study area is a north-facing coastal bluff containing materials comprising of a sequence of glacial deposits. The resulting landslide complex displays seasonal movements, associated with rotational failures, sliding and deterioration of the failed mass into complex mudslides. Movement is dominated both by ground water variations from precipitation inland, and marine undercutting of the toe. A 200 m section of the complex landslide at Upgang beach in Whitby, UK, has been intensively instrumented in order to understand the conditions under which the landslide movement initiates and then subsides. Initial results indicate that while creep occurs continually at the upper section, rotational slips are dominant during periods of high groundwater level. More needs to be done to have a better understanding of the hysteresis relationship between groundwater level and rate of movement. This paper is merely the starting point. Moving forwards, more heavy and intensive rainfall events need to be recorded before further analysis and conclusions, if any, can be achieved.