Template:Canopy Coefficient

Canopy Coefficient

This tool computes a canopy coefficient dataset, consisting of a canopy coefficient for each node in the target grid from a landuse raster. The canopy coefficient dataset can also be thought of as an activity mask. The canopy coefficient terminology comes from the ADCIRC fort.13 nodal attribute of the same name, which allows the user to disable wind stress for nodes directly under heavily forested areas that have been flooded, like a swamp. In essence, the canopy shields portions of the mesh from the effect of wind.

The tool is build to specifically support NLCD and C-CAP rasters, but can be applied with custom rasters as well. The tool has the following inputs/options:

• Input landuse raster – This is a required input parameter and should cover the entire target grid. The user specifies which raster (loaded into the project) will be the used to determine the canopy effect.
• Interpolation option – Select which of the following options will be used for interpolating the canopy coefficient.
  • "Node location" – For this option, the tool finds the landcover raster cell that contains each node in the grid and uses that single cell/pixel to determine the canopy coefficient. The canopy coefficient is set to 1 (active) if the landuse/vegetative classification associated with an pixel type is set to 1 (unprotected) and the coefficient is set to 0 (inactive) if the pixel is of a type that is protected.
  • "Area around node" – When this option is selected, an input field for minimum percent blocked is enabled (described below). For this option, the tool computes the average length of the edges connected to the node being classified. The tool then computes the number of pixels in the area around the node that are protected and the number that are exposed. The node is marked as exposed or protected based on the minimum percent blocked parameter described below. For example, if a node is found to lie in pixel (100,200) of the raster, and the average length of the edges connected to the node is 5 pixels (computed based on the average length of the edge and the pixel size of the raster), then all pixels from (95,195) through (105,205) (100 pixels in all) are reviewed. If more than minimum perent blocked of those pixels are classified as protected, the node is classified as protected.
    • Minimum percent blocked which ignores wind stress – Sets the minimum potential percent of the canopy that will be blocked and ignore the wind stress.
• Target grid – This is a required input parameter. The user specifies which grid/mesh the canopy coefficient dataset will be created for.
• Landuse raster type – This is a required parameter. The user specifies what type the landuse raster is being used.
  • "NLCD" – Sets the landuse raster type to National Land Cover Dataset (NLCD).
  • "C-CAP" – Sets the landuse raster type to Coastal Change Analysis Program (C-CAP).
  • "Other" – Sets the landuse raster type to be set by the user. This adds an option to the dialog.
    • Landuse to canopy coefficient 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.
• Output canopy coefficient dataset – Enter the name for the new canopy coefficient dataset.