[MTT35-P04] Making of a 3D model of a gravel river bed by combining a DSM with near surface resistivity profiles.
Keywords:DSM, River bed, Kinu River, 3D model, Resistivity
The aerial photos were processed using Agisoft Photoscan Professional to create an orthophoto and a DSM with a resolution of 4.8 cm and 9.6 cm respectively. Regretfully, we could not locate them onto the local coordinate system for a half year due to postseismic displacements associated with the 2011 East Japan Earthquake. We re-positioned 6 GCPs which had been set in the site in June 2011 after reopening of GPS stations situated in Kanto Plain, and projected the photogrammetric results on the plane rectangular coordinate system Zone IX through JGD2011 revised in October 2011. Control points of resistivity survey lines were also referenced to the same system, and the geo-referenced resistivity sections were imported in commercial 2D/3D visualization systems (Surfer 15 and Voxler 4 provided by Golden Software). Finally we created a 3D near surface geoscientific model of the gravel river bed of Kinu River.
The constructed 3D geoscientific model clearly mapped a micro-geomorphology of the gravel river bed, especially a trace of distributary channels. Geo-referenced resistivity sections were concordant well with micro-geomorphology. For example, remnant channels traced in the high-water surface were imaged as low resistivity anomaly. In contract, a dune in the low-water surface was imaged as relatively high resistivity zone through parallel survey lines. The 3D model and field observations showed the river bed consisted of thick coarse-grained fluvial sediments and conductivity of pore water was relatively low or resistivity was high due to the infiltration of fresh water in the surficial layers.