Semi-natural Woodland, Merseyside

Geomorphological Survey and Slope Failure Assessment

An extensive but shallow-seated landslip in thick oversteepened high strength glacial till in a steeply incised wooded valley slope with the listric slip detaching on a basal laterally continuous subhorizontal band of saturated sand with a permanent springline. Natural slope recession was ongoing in the area encroaching onto private residential gardens.  Woodland was dominated by Elm which had been decimated with Dutch Elm disease causing die-back of mature trees and loss of support of soils, leading to localised progressive soil creep and mass slope failure.

Evidence of garden waste and construction debris being tipped on to the slope had also overloaded the slope, exacerbating the inherent instability.  An action plan and management strategy was devised including drainage measures, woodland management, replacement planting and communication with local residents with intrusive investigation to assess engineering mitigation requirements.

Distal lobe of debris flow material with dislodged tree and garden wastes transported from top of slope in background.