HR: 08:15h
AN: H51L-02    [Abstracts]
TI: Modelling Braided River Morphodynamics With Terrestrial Laser Scanning
AU: * Brasington, J
EM: james.brasington@aber.ac.uk
AF: Centre for Catchment and Coastal Research, University of Wales Aberystwyth, Aberystwyth, SY23 3GD, United Kingdom
AU: Wheaton, J M
EM: joe.wheaton@aber,ac,uk
AF: Centre for Catchment and Coastal Research, University of Wales Aberystwyth, Aberystwyth, SY23 3GD, United Kingdom
AU: Vericat, D
EM: dvv@aber.ac.uk
AF: Centre for Catchment and Coastal Research, University of Wales Aberystwyth, Aberystwyth, SY23 3GD, United Kingdom
AU: Hodge, R
EM: rebecca.hodge@ges.gla.ac.uk
AF: Department of Geographical and Earth Sciences, University of Glasgow, Glasgow, G12 8QQ, United Kingdom
AB: Advances in topographic survey and terrain modelling have enabled a revolution in the study in the fluvial morphodynamics in the last decade. Prior to the advent of electronic tacheometry in the 1990s, the analysis of channel dynamics was typically inferred from a combination of cross-section surveys and planform mapping. Distributed surveys acquired with GPS or EDMs enabled this analysis to be dimensionally extended and the pattern and magnitude morphodynamics elucidated in 3D; in particular through DTM differencing. Continuing developments in survey technology are now posed to reset this field once again. Now no longer confined to the laboratory, ruggedized laser scanners are capable of acquiring between 4-50,000 observations per second, at ranges exceeding 100 m. This latest development creates the potential for typical reach-scale (1-10 km) topographic datasets to rise in size by 7 orders of magnitude (hundreds to billions of points) in the coming years. Terrestrial Laser Scanning (TLS) offers a wealth of opportunities to better monitor fluvial systems; improving models of cut-and-fill, roughness and enhancing the prospect for ever more detailed parameterizations for fluid models. While this technology enables the creation of ‘virtual facsimiles' of landscapes, the demands of storing, processing and modelling geomorphological products from such data requires a wholesale reappraisal of our data management and modelling methods. Here we outline a field-to-product methodology for TLS of fluvial systems using data from two annual surveys of a 1 km reach of the River Feshie, Scotland. These surveys delivered 3D point cloud datasets, incorporating over 200 million xyz observations, with median spatial densities of over 1000 pts/m2. The surveys were fixed to a GPS-based control network, including over 200 coincident tie- points to register multiple setups to a global coordinate system (RMS errors 0.002-0.011 m). Modelling reach-scale geometries from such dense point clouds poses a non-trivial computational problem and required the development of a bespoke spatial filtering toolbox. This was designed to allow intelligent decimation of TLS data and extract multi-resolution and statistical data suitable for describing bar-scale morphologies over the entire reach, whilst retaining grain-scale information. We use this toolbox to explore the precision and reliability of a morphological sediment budget for the study reach, following a 10 year flood in November 2006. The results are benchmarked against a traditional survey/DTM methodology based on GPS data.
UR: http://www.aber.ac.uk/iges/staff/brasingtonjames.shtml
DE: 0520 Data analysis: algorithms and implementation
DE: 1825 Geomorphology: fluvial (1625)
DE: 1855 Remote sensing (1640)
DE: 1862 Sediment transport (4558)
DE: 1895 Instruments and techniques: monitoring
SC: Hydrology [H]
MN: 2007 Fall Meeting