MONITORING METHOD OF RIVER MORPHOLOGY AROUND RIVER STRUCTURE USING ESTIMATED ELEVATION WITH SATELLITE IMAGES AND OBSERVED RIVER WATER LEVEL

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  • 人工衛星画像と河川観測水位を用いた河川構造物周辺地形の推計

Abstract

<p> River bank erosion is the major issue along large rivers such as Brahmaputra in Bangladesh. This study is aimed to develop the method for estimating river morphology along river bank to monitor movement of sand bars and erosion near river structures. The method combines satellite imagery, which is used to estimate water extent, and observed water level. Elevation of each pixel is estimated with several water level gauges and merged with an inverse distance weight method to consider slope of water surface. Developed method was applied to Brahmaputra river. This study used Sentinel-1 satellite images with Synthetic Apeture Radar (SAR) and optical satellite Sentinel-2 with MultiSpectral Instrument (MSI), both operated by European Space Agency. By comparison between observed and estimated cross section, the developed method effectively captured shape of river cross section. The results demonstrate that this method is used to detect sand bars movement and scouring around river structures. However when the method is applied to relatively small scale phenonmenum of less than 100 meter horizontally, applicability is affected by several factors including availability of satellite images influenced by cloud cover, observation frequency, and range of water fluctuation. These factors should be considered when practical application is considerd.</p>

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