Height above channel.
Height above channel. How does one determine height above a channel using a DEM? This may seem straight forward: there are well-established methods for tracing channel courses over a DEM, and once we have the channel locations, we can measure the difference in elevation between the channel and any point on the valley floor. In implementing such a scheme, however, several questions arise: Which point in the channel should we use? DEM data are noisy, particularly for lidar in wide channels where there are no reflections (water absorbs the infrared laser signal) and areas with tree cover. What is the appropriate elevation for a point in a channel with noisy DEM data? Which point in the channel? In NetMap, we currently use a distance-weighted mean of all channel elevations within a certain distance of each valley-floor point, which I’ll illustrate, but first I want to discuss several other approaches that might seem at first like good options, but don’t always...
