Chapter 6 - Peat landslides

Abstract

Peat landslides form a distinct suite of slope failures which are characteristic of landscapes where organic soils dominate. Six main types of peat mass movement are recognised: bog burst, bog flow, bog slide, peat slide, peaty-debris slide and peat flow. Such failures have been prevalent in the British Isles, but their occurrence globally is far more widespread than hitherto reported. Peat has distinct geotechnical properties that influence its stability and govern the range of impacts of landslide events. Geotechnically peat is a low-density, organic-rich, nonmineral soil which has a high water content, significant fibre content, high voids ratio, high compressibility and low shear strength. Peat landslides cause significant environmental impacts at-a-site and their runout is far travelled causing considerable downstream devastation to infrastructure and stream habitats. Peat landslides triggered by construction in upland areas demonstrate the importance of surface and sub-surface drainage and surface loading in contributing to failure. Although the general mechanisms of peat failure are now well understood, considerable uncertainties remain, associated with determining geotechnical properties of peat, adequately assessing the hydrological conditions relating to peat instability and establishing long-term magnitude–frequency relationships.