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How does ArcGIS calculate curve numbers?
In the Compute GIS Attributes dialog, select the SCS Curve Number option. Select the coverage or GIS layers to use for the calculation. Import the land use table file by clicking the Import button and selecting the land use table text file. Once your options are set, click OK to generate your curve numbers.
How do you calculate a curve number?
The weighted CN is calculated by taking the sum of each CN value multiplied by its fraction of the total subcatchment area. The sum is (usually) rounded to the nearest whole number, as described below. The rounded result is used for all calculations and reports.
What is a CN grid?
The Curve Number (CN) method is a widely used procedure for estimating precipitation excess/loss that takes into effect land use and soil types. Each each grid cell within a subbasin receives its own precipitation and losses/excess are computed based on the grid cell’s CN value.
What does a higher curve number mean?
has a range from 30 to 100; lower numbers indicate low runoff potential while larger numbers are for increasing runoff potential. The lower the curve number, the more permeable the soil is. As can be seen in the curve number equation, runoff cannot begin until the initial abstraction has been met.
What is soil curve number?
The SCS curve number method is a simiple, widely used and efficient method for determining the approxient amount of runoff from a rainfall even in a particular area. The curve number is based on the area’s hydrologic soil group, land use , treatment and hydrologic condition.
How do you find the composite number in a curve?
The composite CN is calculated as the weighted average of the initial CN values of vegetation, impervious surface and soil fractions. With this composite CN method, surface runoff is then simulated under the 57 mm and 81 mm precipitation for the study area.
Can you use a raster calculator in ArcPy?
Builds and executes a single Map Algebra expression using Python syntax in a calculator-like interface. The Raster Calculator tool is intended for use in the application only as a GP tool dialog box or in ModelBuilder. It is not intended for use in scripting and is not available in the ArcPy Spatial Analyst module.
How are variables connected to the raster calculator?
Variables are connected to the Raster Calculator tool when they are selected from the list of variables. All variables are automatically listed in the Variable list inside the tool. When a dataset or variable is used in the expression, a link between the variable and the tool will be created.
Do you need to put the output raster name in an expression?
You do not need to put the output raster name or the = sign in the expression because the output name is specified in the Output raster parameter. You do not need to cast input data as a Raster object when using operators. You can easily clip a raster dataset by setting the extent environment and specifying the input raster name in the expression.
What happens if you delete a variable in ArcGIS Pro?
If you delete the connection to a variable, the variable is not removed from the expression. You should not rename a variable that is connected to the tool, since the variable will not be renamed within the expression. If you do so, the expression will be invalid.