Holocene modification of sediment-mantled hillslopes in the English Lake District

As part of a growing body of literature focusing on Holocene landscape change in upland Britain, attention has been drawn to periodic remobilization of hillslope sediment stores by hillslope processes, especially debris flow activity and gullying, possibly associated with anthropogenic activity, exceptional rainstorms, and/or longer-term climatic changes (e.g. Chiverrell et al., 2007; Curry et al., 2007; Ballantyne, 2008). At susceptible sites this activity occurred intermittently throughout the Holocene, long after the cessation of initial paraglacial adjustment, there is geomorphological evidence for more frequent and extensive debris flow activity within the past few centuries. The overall temporal pattern and causes, however, remain unclear, largely because of a paucity of dating evidence from a relatively small number of (mostly Scottish) sites. Notably, the debris flow record for the English Lake District has received little attention. Further, most published dates are confined to the last few thousand years - probably a sampling artefact, as most dated debris cones have been sampled to depths of only 1-3 m. The aim of this research is to establish the age and causes of hillslope erosion at several sites in the Lake District. The timing of reworking events is of fundamental importance, in evaluating competing hypotheses for the causation of enhanced hillslope activity. In the Eastern Lakes, several small lakes and slope-foot peat bogs are directly fed by debris flows at the foot of steep, gullied slopes. These sites are expected to yield a promising record of intermittent inwashing of minerogenic sediment from the adjacent slopes. Radiocarbon dating of organic-rich sediment intercalated with reworked deposits within such basins could return a high resolution chronology of debris flow activity.The programme includes (i) aerial photograph consultation and field mapping to assess the extent of slope erosion at the sites; (ii) coring and removal of intact lacustrine, peat bog and debris cone sediments; (iii) particle-size and mineral magnetic analyses of the minerogenic sediments to establish their origin; and (iv) palynological analysis and radiocarbon dating of organic-rich sediments to address questions regarding timing and causes of erosion.