Template:Chezy Friction
Chezy Friction
The Chezy Friction tool creates a new scalar dataset that represents the spatially varying Chezy friction coefficient at the sea floor. The tool is built to specifically support NLCD and C-CAP rasters with built in mapping values, but can be applied with custom rasters or custom mapping as well. Tables containing the default parameter values for these raster types are included below.
The tool combines values from the pixels of the raster object specified as a parameter for the tool. For each node in the geometry, the "area of influence" is computed for the node. The area of influence is a square with the node at the centroid of the square. The size of the square is the average length of the edges connected to the node in the target grid. All of the raster values within the area of influence are extracted from the specified raster object. A composite Chezy friction value is computed taking a weighted average of all the pixel values. I a node lies outside of the extents of the specified raster object, the default value is used as the Chezy friction coefficient at the node.
Input Parameters
- Input landuse raster – This is a required input parameter. Specify which raster in the project to use when determining the Chezy friction coefficients.
- Landuse raster type – This is a required parameter. Specify what type of landuse raster to use.
- "NLCD" – Sets the landuse raster type to National Land Cover Dataset (NLCD). A mapping table file for NLCD can be found here and down below.
- "C-CAP" – Sets the landuse raster type to Coastal Change Analysis Program (C-CAP). A mapping table file for C-CAP can be found here and down below.
- "Other" – Sets the landuse raster type to be set by the user. This adds an option to the dialog.
- Landuse to Chezy friction mapping table – The Select File... button will allow a table file to be selected. The entire file name will be displayed in the text box to its right.
- Target grid – This is a required input parameter. Specify which grid/mesh the canopy coefficient dataset will be created for.
- Default Chezy friction option – Set the default value to use for the Chezy friction coefficient for nodes not lying inside the specified raster object. This can be set to "Constant" to use a constant value or set "Dataset" to select a dataset to use.
- Default Chezy friction value – Enter the constant value to use as a default value.
- Default Chezy friction dataset – Select a dataset to use as a default value.
- Subset mask dataset – This optional option allows using a dataset as a subset mask. Nodes not marked as active in this dataset are assigned the default value.
Output Parameters
- Output Chezy friction dataset – Enter the name for the new Chezy friction dataset.
If the landuse type is chosen as NLCD or C-CAP, the following default values below are used in the calculation. If there are different landuse raster types, or wishing to use values that differ from the defaults, specify the raster type as Custom and provide in CSV file with the desired values.
Chezy Friction NLCD Mapping Table
| Code | Description | Friction |
|---|---|---|
| 0 | Background | 60 |
| 1 | Unclassified | 60 |
| 11 | Open Water | 110 |
| 12 | Perennial Ice/Snow | 220 |
| 21 | Developed Open Space | 110 |
| 22 | Developed Low Intensity | 44 |
| 23 | Developed Medium Intensity | 22 |
| 24 | Developed High Intensity | 15 |
| 31 | Barren Land (Rock/Sand/Clay) | 24 |
| 41 | Deciduous Forest | 22 |
| 42 | Evergreen Forest | 20 |
| 43 | Mixed Forest | 22 |
| 51 | Dwarf Scrub | 55 |
| 52 | Shrub/Scrub | 44 |
| 71 | Grassland/Herbaceous | 64 |
| 72 | Sedge/Herbaceous | 73 |
| 73 | Lichens | 81 |
| 74 | Moss | 87 |
| 81 | Pasture/Hay | 66 |
| 82 | Cultivated Crops | 59 |
| 90 | Woody Wetlands | 22 |
| 95 | Emergent Herbaceous Wetlands | 48 |
| 91 | Palustrine Forested Wetland | 22 |
| 92 | Palustrine Scrub/Shrub Wetland | 45 |
| 93 | Estuarine Forested Wetland | 22 |
| 94 | Estuarine Scrub/Shrub Wetland | 45 |
| 96 | Palustrine Emergent Wetland (Persistent) | 48 |
| 97 | Estuarine Emergent Wetland | 48 |
| 98 | Palustrine Aquatic Bed | 150 |
| 99 | Estuarine Aquatic Bed | 150 |
Chezy Friction CCAP Mapping Table
| Code | Description | Friction |
|---|---|---|
| 0 | Background | 60 |
| 1 | Unclassified | 60 |
| 2 | Developed High Intensity | 15 |
| 3 | Developed Medium Intensity | 22 |
| 4 | Developed Low Intensity | 44 |
| 5 | Developed Open Space | 110 |
| 6 | Cultivated Crops | 59 |
| 7 | Pasture/Hay | 66 |
| 8 | Grassland/Herbaceous | 64 |
| 9 | Deciduous Forest | 22 |
| 10 | Evergreen Forest | 20 |
| 11 | Mixed Forest | 22 |
| 12 | Scrub/Shrub | 44 |
| 13 | Palustrine Forested Wetland | 22 |
| 14 | Palustrine Scrub/Shrub Wetland | 45 |
| 15 | Palustrine Emergent Wetland (Persistent) | 48 |
| 16 | Estuarine Forested Wetland | 22 |
| 17 | Estuarine Scrub/Shrub Wetland | 45 |
| 18 | Estuarine Emergent Wetland | 48 |
| 19 | Unconsolidated Shore | 60 |
| 20 | Barren Land | 24 |
| 21 | Open Water | 110 |
| 22 | Palustrine Aquatic Bed | 150 |
| 23 | Estuarine Aquatic Bed | 150 |
| 24 | Perennial Ice/Snow | 220 |
| 25 | Tundra | 60 |
Current Location in Toolbox
Datasets/Chezy Friction
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