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Title: Inter-relationships between soil pipes and landslides in a small upland catchment, Llyn Brianne region, Mid-Wales
Author: Robinson, D. H.
Awarding Body: University College of Swansea
Current Institution: Swansea University
Date of Award: 1995
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The thesis examined the inter-relationships between soil pipes and landslides in a small upland catchment in the Llyn Brianne region of Mid-Wales. The research was stimulated by the occurrence of a slide after an extreme rainfall event on 17-18/10/87 in which soil pipes found draining into the landslide scar were thought to have promoted instability. The thesis (1) mapped the distribution of pipes and landslides in the catchment; (2) investigated the influence of pipes and pipeflow on water table depths and pore water pressures at two instrumented piped sites, one failed and one unfailed; and (3) assessed the role of pipes and landslides on the evolution of the catchment. The process study showed that the influence of soil pipes was very site-specific. Pipes enabled subsurface stormflow to reach both sites quickly. At the failed site, however, this subsurface water built up in a boggy hollow behind the headwall of the landslide allowing critical pore water pressures to develop whereas the perennially flowing pipe network at the unfailed site drained subsurface flow through the site and improved stability. Pipes and landslides were found to be linked within the catchment. Pipes were mapped using traditional survey techniques, dye tracing and an application of the geophysical technique of resistivity. In combination with remote sensing imagery this proved a successful and objective approach to pipe mapping. From stratigraphic evidence and Mid-Wales Holocene data a speculative chronology of catchment development was proposed. Two episodes of instability were suggested: solifluction and landsliding during the Loch Lomond Stadial and immediately after deforestation (2700 yrs BP). During the subsequent Sub-Atlantic period (2500 yrs BP) the catchment has been subjected to extensive peat development and periodic landsliding as a consequence of extreme rainfall events.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available