Multidisciplinary monitoring and modelling to understand the Holocene landscape evolution of a small upland catchment [abstract]

Scheib, Andreas; Boon, D.; Auton, C.; Williams, J.; Raines, M.; Kuras, O.; Pearson, S.; O Dochartaigh, B.; Kessler, H.. 2008 Multidisciplinary monitoring and modelling to understand the Holocene landscape evolution of a small upland catchment [abstract]. [Lecture] In: International Seminar on Small Catchments 1st meeting of the IAG/AIG Working Group, Miedzyzdroje, Poland, 21-23 April 2008. Adam Mickiewicz University, 27. (Unpublished)

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The British Geological Survey (BGS) is undertaking a holistic multi-disciplinary study of a small upland catchment near Talla Linnfoots in the Southern Uplands, Scotland. The site, which covers about 3.5 km2, is located on the interfluve between two major public water supply reservoirs northeast of Moffat. One of the aims is to develop an integrated 3-dimensional (3D) earth model of the site, which will lead to understanding landscape evolution within the catchment, in response to environmental changes during the past 12.000 years. Geologically, the Talla catchment is dominated by glacial and periglacial deposits overlying resistant Ordovician greywacke bedrock. The valley fill comprises undulating moraines and blanket peat bogs, as well as narrow spreads of alluvium along Talla Water and its headwater tributaries. The lower valley sides are covered with thin colluvium mantling glacial till deposits; steeper rock slopes are mantled in scree. The study consisted of three phases. The first comprised geological, geomorphological and soil surveys. These were followed by multidisciplinary site investigation of the shallow subsurface using several geophysical, geotechnical and intrusive techniques. This was followed by interpretation of the results and development of an attributed 3D geological model. Characterising the ground was achieved using traditional site investigation methods such as geological and soil surveying, trial pitting and borehole drilling, as well as light-weight penetrometer traverses. This was combined with an array of shallow geophysical techniques, including Ground Penetrating Radar (GPR) and Electrical Resistivity Tomography (ERT). These were applied on traverses between boreholes and pits, to gain additional continuous information on lateral extent and thickness of the geology to rockhead and provided a rapid, accurate representation of the shallow subsurface structure, where intrusive data was sparse. The catchment 3D geological model was constructed using “Geological Surveying and Investigation in 3D” (GSI3DTM) software. This utilizes a high resolution (1m cell size) Digital Terrain Model (DTM), created by terrestrial LiDAR survey, linked with mapped geology, borehole, auger hole and geophysical data, to form slices and sections. This approach enabled the geoscientists to construct regularly spaced intersecting cross-sections by correlating boreholes and the outcrops-subcrops of geological units to produce fence diagrams of the area. These can then be variably attributed eg by sediment type, chemical composition, geotechnical properties and permeability etc. Mathematical interpolation between the nodes along the sections and the limits of the units produces a solid model comprising a series of stacked triangulated volume objects. Geophysical sections were used as an additional data source, which enabled the interpretation of measurements in their true 3D positions and improved the accuracy of the model along these traverses. On-going studies at Talla include monitoring of shallow groundwater heads and water chemistry in instrumented shallow boreholes. The eventual aim is to establish a linked model of shallow-groundwater movement and surface drainage through time. Adoption of this type of novel 3D geospatial modelling approach allows geoscientists to visualise, explore and interrogate the landscape evolution of small catchments, such as Talla in three dimensions. It can form an unrivalled template for catchment monitoring.

Item Type: Publication - Conference Item (Lecture)
Programmes: BGS Programmes 2009 > Spatial Geoscience Technologies
Additional Keywords: Talla Earth Observatory
NORA Subject Terms: Earth Sciences
Date made live: 15 Jul 2009 09:10 +0 (UTC)

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