Piping and pipe blocking impacts on degraded blanket bog hydrology and aquatic carbon

This thesis sought to improve our understanding of soil piping in a heavily degraded headwater blanket peatland in the Peak District of northern England. In particular, it investigated the frequency and extent of piping and the hydrological and erosional contribution of pipeflow to streams, and whether it is possible to moderate streamflow and associated carbon export by blocking pipe outlets. Two distinct types of pipe outlet were identified; head and edge. Head pipe outlets were observed on streambanks with signs of headward retreat and were significantly larger and closer to the peat surface compared to edge pipe outlets that issued onto uniform streambanks. Southwest and west-facing streambanks hosted more than 43 % of the identified pipe outlets. The hydrological responses and associated carbon export for two headwater catchments were compared for nine months before and six months after half of the pipe outlets in one catchment were blocked. Pipeflow was impeded either by inserting a plug-like structure in the pipe-end or by the insertion of a vertical screen at the pipe outlet. Seepage appeared at all blocks, while new pipe outlets were only formed around vertical screens. Pre-blocking, two head pipes accounted for 9.3 % of streamflow compared with 2.0 % for edge pipes. One head pipe accounted for 2.1 % of dissolved organic carbon and 5.8 % of particulate organic carbon stream flux. Water-table level sat much deeper at edge locations than at head locations. The results suggest that impeding pipeflow at pipe outlets did not reduce streamflow and associated aquatic carbon export at the stream scale, but could potentially exacerbate pipe development in streambanks. Therefore, future restoration works in blanket peatlands should prioritise limiting surface runoff inputs to pipe networks, and revegetate bare gullies to reduce the incidence of desiccation on streambanks, to eliminate pipe development.