Development of an Anisotropic Spatial Interpolation Method for Velocity in the Meandering River Channel

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Hojun You, Dongsu Kim, Geunsoo Son

Thursday 2 july 2015

14:50 - 15:05h at Oceania Foyer (level 0)

Themes: (T) Water resources and hydro informatics (WRHI), (ST) Surface and subsurface flow interactions

Parallel session: 12L. Water resources - Flow interactions

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Understanding of the two-dimensional velocity field is crucial in terms of analyzing various hydrodynamic and fluvial processes in the riverine environments. Until recently, many numerical models have played major roles of providing such velocity field instead of in-situ flow measurements, because there were limitations in instruments and methodologies suitable for efficiently measuring in the broad range of river reaches. In the last decades, however, the advent of modernized instrumentations started to revolutionize the flow measurements. Among others, acoustic Doppler current profilers (ADCPs) became very promising especially for accurately assessing streamflow discharge, and they are also able to provide the detailed velocity field very efficiently. Thus it became possible to capture the velocity field only with field observations. Since most of ADCPs measurements have been mostly conducted in the cross-sectional lines despite their capabilites, it is still required to apply appropriate interpolation methods to obtain dense velocity field as likely as results from numerical simulations. However, anisotropic nature of the meandering river channel could have brought in the difficulties for applying simple spatial interpolation methods for handling dynamic flow velocity vector, since the flow direction continuously changes over the curvature of the channel shape. Without considering anisotropic characteristics in terms of the meandering, therefore, conventional interpolation methods such as IDW and Kriging possibly lead to erroneous results, when they dealt with velocity vectors in the meandering channel. Based on the consecutive ADCP cross-sectional measurements in the meandering river channel, the present study attempts to develop a specialized velocity interpolation framework and an ArcGIS-based software named A-VIM, which encompassed anisotropic or multi-directional reference ranges following the varying streamwise direction as well as channel geometry. For this purpose, the geographic coordinate with the measured ADCP velocity was converted from the conventional Cartesian coordinate (x,y) to a curvilinear coordinate (s,n). The results from application of A-VIM showed significant improvement in accuracy as much as 41.5% in RMSE. This research was supported by a grant (14RDRP-B076508-01-000000) from the Jeju Regional Infrastructure Technology Development Center Program, funded by Ministry of Construction & Transportation of Korean government.