Generation of 2D Riverbed Topography for Digital Elevation Models Using 1D Cross-Section Data

Two-dimensional numerical models in hydraulics often utilize LiDAR-based digital elevation models (DEMs) in order to establish a high-resolution floodplain topography. Conventional LiDAR operates at wavelengths in the near-infrared region, and it is mostly absorbed by water leaving gaps in the generated point cloud data. The lack of underwater topography is also a problem when working with DEMs generated by other methods. Therefore, additional data is required to correctly represent the riverbed topography. One of the data sources that can be used to generate the riverbed topography is the surveyed river cross-sections. Due to the nature of the cross-section data, the measurement points are much closer in the cross-stream direction than in the stream-wise direction. Natural shape of the riverbed also shows a similar anisotropy, such that the topography varies more abruptly in the cross-stream direction. Therefore, special methods are required to generate a realistic riverbed topography using cross-section data. This paper presents techniques that were used to generate riverbed topography using cross-section data, which is then burned into a DEM. First, cross-section points are transformed to a channel-fitted curvilinear coordinate system. The scales in the stream-wise and cross-stream directions are adjusted to account for the anisotropy in the topographic variations. Then, DEM elevations are interpolated in the transformed space using the cross-section points and a set of points along the bank lines extracted from the DEM. The successful use of the method is demonstrated by applying it to generate the two-dimensional riverbed topography for a 187.4-mile-long stretch of Ohio River including man-made structures and natural islands.