Template:Chezy Friction: Difference between revisions

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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.
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.
===Canopy Coefficient NLCD Mapping Table===
===Chezy Friction NLCD Mapping Table===
{| class="wikitable sortable"
{| class="wikitable sortable"
|+ Canopy Coefficient NLCD Values
|+ Chezy Friction NLCD Values
! Code !! Description !! Canopy
! Code !! Description !! Friction
<!--Use this template to add a new entry:
<!--Use this template to add a new entry:
|-
|-
| Code        || Description                              || Canopy                  
| Code        || Description                              || Friction                  
-->
-->
|-
|-
| 0          || Background                              || 0
| 0          || Background                              || 60
|-
|-
| 1          || Unclassified                            || 0
| 1          || Unclassified                            || 60
|-
|-
| 11          || Open Water                              || 0
| 11          || Open Water                              || 110
|-
|-
| 12          || Perennial Ice/Snow                      || 0
| 12          || Perennial Ice/Snow                      || 220
|-
|-
| 21          || Developed Open Space                    || 0
| 21          || Developed Open Space                    || 110
|-
|-
| 22          || Developed Low Intensity                  || 0
| 22          || Developed Low Intensity                  || 44
|-
|-
| 23          || Developed Medium Intensity              || 0
| 23          || Developed Medium Intensity              || 22
|-
|-
| 24          || Developed High Intensity                || 0
| 24          || Developed High Intensity                || 15
|-
|-
| 31          || Barren Land (Rock/Sand/Clay)            || 0
| 31          || Barren Land (Rock/Sand/Clay)            || 24
|-
|-
| 41          || Deciduous Forest                        || 1
| 41          || Deciduous Forest                        || 22
|-
|-
| 42          || Evergreen Forest                        || 1
| 42          || Evergreen Forest                        || 20
|-
|-
| 43          || Mixed Forest                            || 1
| 43          || Mixed Forest                            || 22
|-
|-
| 51          || Dwarf Scrub                              || 0
| 51          || Dwarf Scrub                              || 55
|-
|-
| 52          || Shrub/Scrub                              || 0
| 52          || Shrub/Scrub                              || 44
|-
|-
| 71          || Grassland/Herbaceous                    || 0
| 71          || Grassland/Herbaceous                    || 64
|-
|-
| 72          || Sedge/Herbaceous                        || 0
| 72          || Sedge/Herbaceous                        || 73
|-
|-
| 73          || Lichens                                  || 0
| 73          || Lichens                                  || 81
|-
|-
| 74          || Moss                                    || 0
| 74          || Moss                                    || 87
|-
|-
| 81          || Pasture/Hay                              || 0
| 81          || Pasture/Hay                              || 66
|-
|-
| 82          || Cultivated Crops                        || 0
| 82          || Cultivated Crops                        || 59
|-
|-
| 90          || Woody Wetlands                          || 1
| 90          || Woody Wetlands                          || 22
|-
|-
| 95          || Emergent Herbaceous Wetlands            || 0
| 95          || Emergent Herbaceous Wetlands            || 48
|-
|-
| 91          || Palustrine Forested Wetland              || 1
| 91          || Palustrine Forested Wetland              || 22
|-
|-
| 92          || Palustrine Scrub/Shrub Wetland          || 1
| 92          || Palustrine Scrub/Shrub Wetland          || 45
|-
|-
| 93          || Estuarine Forested Wetland              || 1
| 93          || Estuarine Forested Wetland              || 22
|-
|-
| 94          || Estuarine Scrub/Shrub Wetland            || 0
| 94          || Estuarine Scrub/Shrub Wetland            || 45
|-
|-
| 96          || Palustrine Emergent Wetland (Persistent) || 0
| 96          || Palustrine Emergent Wetland (Persistent) || 48
|-
|-
| 97          || Estuarine Emergent Wetland              || 0
| 97          || Estuarine Emergent Wetland              || 48
|-
|-
| 98          || Palustrine Aquatic Bed                  || 0
| 98          || Palustrine Aquatic Bed                  || 150
|-
|-
| 99          || Estuarine Aquatic Bed                    || 0
| 99          || Estuarine Aquatic Bed                    || 150
|}
|}
{{-}}
{{-}}
===Canopy Coefficient CCAP Mapping Table===
===Canopy Coefficient CCAP Mapping Table===
{| class="wikitable sortable"
{| class="wikitable sortable"

Revision as of 21:18, 5 August 2021

Chezy Friction

The Chezy Friction tool is used to populate the spatial attributes for the Chezy friction coefficient at the sea floor. A new dataset is created from NLCD, C-CAP, or other land use rasters.

The tool will extract values from the raster object specified by the tool. For each node in the geometry, the "area of influence" is computed for the node. The area of influence is a polygon that represents the area of the geometry around a node. This is computed as the area encompassing the node and half the distance to each of his neighboring nodes. All of the raster values within the area of influence are extracted from the visible raster objects. A composite Chezy friction value is computed taking a weighted average of all the raster values. If the area of the extracted values is less then the area of influence around the node (because the process passed the extent of the raster objects or encountered null values), the default value is used to compute the Chezy friction using the area not represented in the values.

The Chezy Friction tool dialog contains the following options:

  • Input landuse raster – This is a required input parameter and should cover the entire target grid. Specify which raster in the project to use when determining the Chezy friction.
  • 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 in computing the Chezy friction using the area not represented in the values. 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 a value to use as a constant 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.
  • 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

Chezy Friction NLCD Values
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


Canopy Coefficient CCAP Mapping Table

Canopy Coefficient CCAP Values
Code Description Canopy
0 Background 0
1 Unclassified 0
2 Developed High Intensity 0
3 Developed Medium Intensity 0
4 Developed Low Intensity 0
5 Developed Open Space 0
6 Cultivated Crops 0
7 Pasture/Hay 0
8 Grassland/Herbaceous 0
9 Deciduous Forest 1
10 Evergreen Forest 1
11 Mixed Forest 1
12 Scrub/Shrub 0
13 Palustrine Forested Wetland 1
14 Palustrine Scrub/Shrub Wetland 1
15 Palustrine Emergent Wetland (Persistent) 0
16 Estuarine Forested Wetland 1
17 Estuarine Scrub/Shrub Wetland 0
18 Estuarine Emergent Wetland 0
19 Unconsolidated Shore 0
20 Barren Land 0
21 Open Water 0
22 Palustrine Aquatic Bed 0
23 Estuarine Aquatic Bed 0
24 Perennial Ice/Snow 0
25 Tundra 0


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