Soil erosion risk along a buried hydrocarbon pipeline in Scotland

  • Kayleigh Kats

Student thesis: Master's ThesisMaster of Science

Abstract

Onshore buried pipelines are potentially at risk of soil erosion by heavy rainfall events that may decrease pipeline cover and increase the risk of pipeline failure. The National Grid gas pipeline that runs throughout Scotland was studied in relation to the number and change in heavy (≥4 mm/h) rainfall events per annum at three locations (Dyce, Leuchars and Eskdalemuir) along the pipeline route. Eskdalemuir experienced more than double the number of heavy rainfall events per year with a mean value of 30, compared to Dyce at 11 and Leuchars at 9. The number of rainfall events was highly variable, with the 2015 winter period alone at Eskdalemuir experiencing 21 heavy rainfall events. The G.I.S. analysis of the pipeline showed that 740 km of the 1611 km length of the pipeline was classified as arable land cover. Crop records attributed to 531 km of the pipeline length to spring and winter cereals, oilseed rape and potatoes sown in light-textured loamy soils. These arable soils are relatively vulnerable to soil erosion and are located mainly in the (drier) North of the pipeline route. The much wetter Eskdalemuir region, in the south west, is much less agriculturally active but also has steeper slopes.

Eskdalemuir was selected to evaluate ground displacement using Sentinel-1 radar imagery as this area experiences intense rainfall events and is in elevated terrain and erosion of even a few metres of pipeline is a potentially serious hazard. Fifty-four image pairs were processed for the winter periods of 2015 to 2018: the top 10% of ground displacement points along the pipeline route ranged from -43mm to -11 mm and indicated locations where significant erosion may have occurred. Ground displacements immediately above the pipeline appeared similar to those on either side of the pipeline corridor. Risk factors (slope, soil grouping and land use) were mapped to compare with a published European soil erosion risk map and the ground displacements map. The G.I.S-based risk mapping and monitoring of ground displacement all indicated areas of potential concern, but showed few areas of complete agreement. Whilst all methods highlight areas at risk they mainly indicate sites that require field visits for local assessment of soil conditions.
Date of Award2022
Original languageEnglish
SupervisorGlyn Bengough (Supervisor) & Andrew Black (Supervisor)

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