| Abstract: | This paper describes and analyses the structure and deposits of a large UK peat slide, located at Hart Hope in the North Pennines, northern England. This particular failure is unusual in that it occurred in the winter (February, 1995) and shows excellent preservation of the sedimentary structures and morphology, both at the failure scar and downstream. The slide was triggered by heavy rain and rapid snowmelt along the line of an active peatland stream flush. Detailed mapping of the slide area and downstream deposits demonstrate that the slide was initiated as a blocky mass that degenerated into a debris flow. The slide pattern was complex, with areas of extending and compressive movement. A wave‐like motion may have been set up in the failure. Within the slide site there was relatively little variability in block size (b axis); however, downstream the block sizes decrease rapidly. Stability analysis suggests the area at the head of the scar is most susceptible to failure. A ‘secondary’ slide area is thought to have only been initiated once the main failure had occurred. Estimates of the velocity of the flowing peat mass as it entered the main stream channel indicate a flow velocity of approximately 10 m s?1, which rapidly decreases downstream. A sediment budget for the peat slide estimates the failed peat mass to be 30 800 t. However, sediment delivery to the stream channel was relatively low. About 37% of the failed mass entered the stream channel and, despite moving initially as debris flow, the amount of deposition along the stream course and on the downstream fan is small (only about 1%). The efficiency of fluvial systems in transporting the eroded peat is therefore high. Copyright © 2003 John Wiley & Sons, Ltd. |
