In the January 2016 Newsletter, we presented one way to accomplish river flattening using TerraModeler. In this article, we introduce an updated approach to this process, which should be more efficient.
Hydro-flattening is a common requirement when it comes to delivering surface models to the U.S. Geological Survey (USGS) National Elevation Dataset (NED). According to the USGS LIDAR Base Specification version 1.2, a hydro-flattened surface refers to a specific kind of digital elevation model (DEM) that is required for inclusion in the NED. Hydrologically flattened waterbodies, streams, rivers, and other water surfaces should be flat and level from bank-to-bank. Rivers and streams should follow a downhill water surface, which would reflect the more natural behavior of the environment.
There are different methods a user can employ to create hydro-flattened surfaces. The method outlined within this article is only one of those options. In this suggested method, breaklines will be created to represent river flattening and then used to enforce the surface, resulting in a flattened surface from bank to bank which flows in the downstream direction.