New tool for producing two-dimensional river channel topographies from cross sections with large spacing

A new tool is presented that produces two-dimensional (2D) topographic data for a main channel of a river. The returned data can be patched into an existing digital terrain model to overcome the known issue of a main channel bed being misrepresented due to the presence of water at the time of aerial scanning. As input, the tool requires a polyline depicting the channel path and profiles of surveyed transverse sections. Before interpolation, the user must choose the portion (corresponding to just the main channel) of a surveyed section to be used, in order to ensure good consistency with the available terrain model of the floodplains. Sections are linearly interpolated in two nested steps, in which different methods are employed to locate the interpolated sections in space. In the first step, interpolated sections are placed perpendicularly to the channel polyline, whereas in the second step, their planar orientations also are interpolated between known values at other sections. This two-step procedure helps to overcome the paucity of information when the surveyed sections are relatively distant from one another, and also is suitable for creating an appropriate channel bed topography at sharp bends. Some parameters need to be set by the user, the most important of which is the spacing between the sections interpolated in the first step. The tool presented here is available as an editable code from a permanent repository.