Arc Extract Breakline from DEM
Introduction
This page outlines the method used to take a line feature class, and extract elevations from DEM for input to TUFLOW breaklines. This is useful if you have a hydraulic control, for example a road embankment that you want to ensure is represented in the model. In this method the elevations will be extracted from the DEM. If detailed survey exists this should be used. This can also be used to process a thalweg / creek centre line.
TUFLOW breaklines (2d Z Shape), are a mixture of line and point feature classes. This allows points to be deleted, without deleting the vertices along the line. The process of converting a line feature class, to a point feature class and extracting the elevation. Is a multiple step process and we are looking to implement a python script to automate this. There are two ways of doing this:
Method 1
- Convert line vertices to points
- Extract elevations directly from DEM
This method requires that the line has been digitised at the high or low point that you are trying to represent. The next method, creates a buffer around each points and can be used to extract the maximum / minimum elevation from the DEM within this buffer. This ensures that the control is represented, even if the line does not follow the levee crest or centreline perfectly.
Method 2
The steps involved are:
- Convert line vertices to points
- Create a buffer around each point (specified buffer distance)
- Extract desired elevation statistic (max, min, mean) for each region
- Assign elevation from buffer to point