Quantifying the spatial distribution of sediment transport in an experimental gully system using the morphological method |
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Authors: | Wen Dai Liyang Xiong Gilles Antoniazza Guoan Tang Stuart N. Lane |
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Affiliation: | 1. Key Laboratory of Virtual Geographic Environment (Nanjing Normal University), Ministry of Education, Nanjing, China;2. Institute of Earth Surface Dynamics (IDYST), University of Lausanne, Lausanne, Switzerland;3. Key Laboratory of Virtual Geographic Environment (Nanjing Normal University), Ministry of Education, Nanjing, China School of Geography, Nanjing Normal University, Nanjing, China Jiangsu Centre for Collaborative Innovation in Geographical Information Resource Development and Application, Nanjing, China |
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Abstract: | Whilst time-series of sediment transport in gullies in both laboratory experimental and field settings can be determined through instrumentation, quantifying the spatial distribution of transport rates remains challenging. The morphological method, which was proposed for estimating bed-material transport in both one- and two-dimensions in rivers, provides an alternative. Here, we developed this method for gully systems. A laboratory catchment was used to simulate gully erosion. High-resolution topographical data were acquired by close-range digital photogrammetry. Morphological changes were determined using high-resolution topographic data and an associated level of detection. Based on measured morphological changes, one-dimensional (1D) and two-dimensional (2D) sediment transport rates were calculated via cross-section by cross-section routing (1D) and cell by cell routing (2D). The 1D application provided a general trend of longitudinal variation of sediment transport for the whole gully system, increased gradually from zones of headward extension to a zone downstream where erosion and deposition were in balance, and sediment transport rates less variable in space. For the 2D application, hydrological and blended hydrological-hydraulic routing solutions were compared. We found that the level of negative transport was insensitive to whether or not a blended hydrological-hydraulic routing was used and that results from applying the hydrological routing throughout were not significantly degraded. We also found that consideration should be given to spatial and temporal resolution of the topographic data. The 2D application provided spatial patterns of sediment transport that vary with gully evolution. The main gully remained a high transport corridor but branch transport became more important through time. The framework we report provides an additional tool for both experimental and field quantification of the spatial patterns of sediment transport in gullies; and quantification of how these patterns change under different forcing factors. |
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Keywords: | 1D and 2D transport rates gully erosion and deposition morphological change detection sediment routing spatial pattern of sediment transport the morphological method |
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