Construct Depression Hierarchy
Description
Identifies closed contours in the DEM, their nested structure, and defines attributes identifying position of the contour within the nested contour structure. Several criteria are used to define the closed contours:
- Contour value. Defined by the user specified Base Contour (minimum elevation to be considered) and Contour Interval (spacing between contours).
- Closeness of the contour line. A contour line is considered closed if the starting and ending point of the line are within 0.01 map units (this is a hard-coded value).
- Length of the contour line. A contour polygon is deemed viable if its length (perimeter) is longer than 40 map units.
- Area of closed contour polygon. A contour polygon is deemed viable if its area is greater than user specified minimum area (defined in number of DEM cells).The output of the function is a polygon feature class representing closed contours within the DEM. The following attributes are created for each contour polygon:HydroID unique identifier for each contour polygon.Contour contour elevation (in DEM units) of the polygon.SINKLEVEL number indicating nesting level of the polygon. Value of 1 indicates top level in the nested structure, 2 one level below, etc. Negative values indicate seed (terminal) level within nested structure, that is, there will be no other polygons contained within that polygon (with lower elevation). Thus value of -1 indicates an isolated contour polygon (one that is not contained by any other contour nor is containing any other contour polygons).PID HydroID of the contour polygon directly containing the polygon. <NULL> value indicates a root (top) polygon in a nested contour tree structure.ROOTID HydroID of root (top) contour polygon containing this polygon. <NULL> value indicates a root (top) polygon in a nested contour tree structure.The input DEM can be any DEM type but using the smooth depression DEM generated by the Extract Smooth Depression DEM tool will provide better performance and more streamlined contour representation.The methodology and initial code were developed by Dr.Qiusheng Wu (Wu Q., Liu H., Wang S., Yu B., Beck R., Hinkel K., 2015. A localized contour tree method for deriving geometric and topological properties of complex surface depressions based on high-resolution topographical data. International Journal of Geographical Information Science, 29 (12), 20412060. doi/full/10.1080/13658816.2015.1038719).
Usage
Parameters
| Direction | Type | Parameter Name | Data Type | Dialog Reference |
|---|---|---|---|---|
| Input | Required | Input DEM | GPRasterLayer | DEM raster that will be used to identify depression hierarchy. This can be any DEM type but using the smooth depression DEM generated by the “Extract Smooth Depression DEM” tool will provide better performance and more streamlined contour representation. |
| Input | Required | Contour Interval | GPDouble | |
| Input | Required | Base Contour | GPDouble | |
| Input | Required | Minimum Area (number of cells) | GPDouble | |
| Output | Required | Output Closed Contour FC | GPFeatureLayer |