Quadratic Friction Tool

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Quadratic Fiction

The Quadratic Friction tool creates a new scalar dataset that represents the spatially varying quadratic 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.

The tool will combine 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 quadratic friction coefficient 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 quadratic friction coefficient at the node.

The Quadratic Friction tool dialog contains the following options:

Input Parameters

  • Input landuse raster – This is a required input parameter. Specify which raster in the project to use when determining the quadratic 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 quadtratic 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 quadratic friction dataset will be created for.
  • Default quadtratic friction option – Set the default value to use in computing the quadtratic friction using the area 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 quadtratic friction value – Enter the constant value to use as a default value.
    • Default quadtratic 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 Paramters

  • Output quadtratic friction dataset – Enter the name for the new quadtratic friction dataset.

If the landuse type is chosen as NLCD or C-CAP, the default values below are used in the calculation. If there is a different landuse raster type, or wishing to use values that differ from the defaults, specify the raster type as "Custom" and provide a CSV file with the desired values.

Quadratic Friction NLCD Mapping Table

Quadratic Friction NLCD Values
Code Description Friction
0 Background 0.002
1 Unclassified 0.002
11 Open Water 0.0018
12 Perennial Ice/Snow 0.00046
21 Developed Open Space 0.0018
22 Developed Low Intensity 0.011
23 Developed Medium Intensity 0.046
24 Developed High Intensity 0.1
31 Barren Land (Rock/Sand/Clay) 0.037
41 Deciduous Forest 0.046
42 Evergreen Forest 0.055
43 Mixed Forest 0.046
51 Dwarf Scrub 0.0073
52 Shrub/Scrub 0.011
71 Grassland/Herbaceous 0.0053
72 Sedge/Herbaceous 0.0041
73 Lichens 0.0033
74 Moss 0.0028
81 Pasture/Hay 0.005
82 Cultivated Crops 0.0062
90 Woody Wetlands 0.046
95 Emergent Herbaceous Wetlands 0.0092
91 Palustrine Forested Wetland 0.046
92 Palustrine Scrub/Shrub Wetland 0.01
93 Estuarine Forested Wetland 0.046
94 Estuarine Scrub/Shrub Wetland 0.01
96 Palustrine Emergent Wetland (Persistent) 0.0092
97 Estuarine Emergent Wetland 0.0092
98 Palustrine Aquatic Bed 0.001
99 Estuarine Aquatic Bed 0.001


Quadratic Friction CCAP Mapping Table

Quadratic Friction CCAP Values
Code Description Friction
0 Background 0.002
1 Unclassified 0.002
2 Developed High Intensity 0.1
3 Developed Medium Intensity 0.046
4 Developed Low Intensity 0.011
5 Developed Open Space 0.0018
6 Cultivated Crops 0.0062
7 Pasture/Hay 0.005
8 Grassland/Herbaceous 0.0053
9 Deciduous Forest 0.046
10 Evergreen Forest 0.055
11 Mixed Forest 0.046
12 Scrub/Shrub 0.011
13 Palustrine Forested Wetland 0.046
14 Palustrine Scrub/Shrub Wetland 0.01
15 Palustrine Emergent Wetland (Persistent) 0.0092
16 Estuarine Forested Wetland 0.046
17 Estuarine Scrub/Shrub Wetland 0.01
18 Estuarine Emergent Wetland 0.0092
19 Unconsolidated Shore 0.002
20 Barren Land 0.037
21 Open Water 0.0018
22 Palustrine Aquatic Bed 0.001
23 Estuarine Aquatic Bed 0.001
24 Perennial Ice/Snow 0.00046
25 Tundra 0.002