Quadratic Friction Tool

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