Spatial data pre-processor

The spatial data pre-processor offers a range of tools that can be used to manipulate spatial data.

Plugin file:

C:\Program Files\eWater\Source version\Plugins\RiverSystem.Plugins.SpatialDataPreProcessor.dll

QuickRemap

The QuickRemap tool allows the grid codes of a raster file to be changed in an easy manner by changing the values in the table and running the tool to get a new raster:

• Drag and drop a raster into the src box. This is the source raster from which remapping will be done;
• Enter the modified grid codes that map to certain layers within the raster. For example, a forest layer in a land use map may have a grid code of 3. If a scenario is required where the forest is cleared for horticulture, the grid code may need to be changed to 5, to signify that it is a Horticulture FU.
• Click Run and the remapped raster appears in the dest box. This can be saved to disk.

CreateMask

The CreateMask tool creates a new raster of the same dimensions as the source raster with grid cell values that equal the mask value. Therefore, all non-null values in the raster grid are replaced with the maskValue parameter. This can be done as follows:

• Drag and drop a raster into the src pane. This is the source raster from which remapping will be done;
• Enter a value for maskValue, which will replace all the non-null values in the raster grid. For example, a maskValue of 1 (default) will produce a new raster with the value of 1 in all cells that are not null values; and
• Click Run and the new mask raster appears in the dest pane. This can be saved to disk.

CookieCut

The CookieCut tool allows a portion of a larger raster to be "cut out" and a new raster produced. This may be useful when you only need a small segment of a large land use or DEM file.

• Drag and drop the raster that a segment is to be "cut" from into the "dough" pane;
• In the cutter pane drag and drop the raster that will mark the dimensions or border of the new raster; and
• Click Run and the new segment raster is displayed in the cookie pane and can be saved using the Save icon to the left of the Cookie pane.

SelectColumns FromVectors

The SelectColumnsFromVectors tool extracts a particular attribute column from a vector map (ie. shape file) and creates a new vector map based on the selected attribute.

1. Drag and drop a vector file (such as a shape file) into the sourceData pane. A list of attributes is displayed. To display the spatial extent of the attribute, select the attribute name in the sourceData pane. The number of the attribute column is displayed under Hide.
2. Set the attribute column number in the entryToTake pane. In the example shown a value of 1 corresponds to the GRIDCODE attribute column.
3. Click Run. The resulting vector map is displayed in the destinationData window, which contains only the attribute in the column corresponding to the value specified in entryToTake.

Sub-catchment Union

The Sub-catchmentUnion tool joins all sub-catchments in a sub-catchment raster into a single catchment area:

1. Drag and drop a sub-catchment raster into the src pane.
2. Click BI. The resulting catchment raster is displayed in the dest pane and can be saved by clicking Save.

HazardMap Scaling

Hazard maps are useful for informing catchment and land managers of those parts of the landscape that are most vulnerable to certain environment hazards, such as soil erosion or salinity. Scaling the Event Mean Concentration (EMC) and the Dry Weather Concentration (DWC) values using an erosion hazard map allows areas with "hazardous" land uses (eg. highly grazed areas can be susceptible to higher levels of soil loss) to reflect the expected constituent magnitudes in such areas.

EMC and DWC parameters are determined from analysis of water quality data and are given as a minimum, median and maximum for each land use - but can be considered to apply to that land use only if it has a median erosion hazard. If the erosion hazard is above or below the median, the DWC and EMC need to be modified for that land use in that particular location. The erosion hazard map is defined as a weighted sum of the Universal Soil Loss Equation (USLE) and gully density maps (these can be generated using eWater SedNet). The weights are chosen by the user but are conceptually a function of the sediment delivery ratio (SDR). The default values are 1.5 and 0.05 for gully density and USLE respectively.

The erosion hazard map is used to compute the median, min and max values for each land use across the whole catchment, and for each land use within each sub-catchment. So, for every sub-catchment and every land use within each sub-catchment, there is a value of min, median and max erosion hazard.

The EMC and DWC values applied to a particular land use in a particular sub-catchment is computed from the ratio of sub-catchment to global values multiplied by the global EMCs and DWCs for each land use. This can be best illustrated via the hypothetical example where Table 1 for tree and grass EMCs for each sub-catchment is computed by using Table 2 and Table 3 to linearly scale Table 4.

Table 1. Derived event mean concentrations (example values)

Table 2. Erosion hazard (example values)

The basic approach to scaling EMC and DWC values using a hazard map is as follows:

• Choose Configure » Constituent Models » Parameters...;
• Choose Scale EMCs and DWCs using Hazard Map from the Available Methods drop-down menu.
• The sub-catchment and functional unit maps will automatically be displayed in the second and third boxes with the hazard map box initially blank.
• Drag and drop a hazard map into the blank window.
• Click on the Parameter tab. The Output, Constraint and State tabs can be ignored, as they are automatically generated by Source.
• Select the Constituent type from the Select Element drop-down menu (eg. TSS).
• Manually enter or load a text file containing functional unit name, minimum median and maximum EMC values for each corresponding functional unit type. An example is given in Figure for EMC values. Repeat for DWC window.
  • Percentile - specifies the percentile bound for generating the regional hazard statistics visible under the State tab;
  • Processing cell size - this parameter can be ignored. The ProcessingCellSize is used when rasterising the FU land use and Hazard maps, and is set to a default of 100, which is 100 meters wide (and high). A smaller the size results in a finer the scale for spatial scaling of erosion hazard values, but processing will take longer; and
  • Use FU areas - this parameter can be ignored as it is automatically generated and requires no input from the user.
• Click Run;
• When processing is complete the green progress bar at the bottom of the screen will have moved across;
• If more than one constituent type is listed, then a new constituent must be selected from the drop down list at the top of the screen. A new set of corresponding EMC/DWC values need to be loaded to correspond to the new constituent selected; and
• Select Close when appropriate EMC/DWC values have been assigned for all constituents.

StreamOrder Lengths

The StreamOrderLengths tool gives a summary of the lengths (in meters) of the river reaches and streams for each sub-catchment so that management tasks, such as riparian buffer zones, can be applied to specific stream orders within sub-catchments.

Select Tools » Plugins » RiverSystems.Plugins.SpatialDataPreProcessor » StreamOrderLengths. The Stream Order Lengths window appears:

• Drag and drop a stream order raster into the StreamOrderRaster pane;
• Drag and drop the sub-catchment map into the Sub Catchment Raster pane;
• Adjust the sinuosity factor if necessary (default value is 1.25);
• Click Create to create a table summarising the stream orders and lengths per sub-catchment; and
• Click Save to save the table. Source saves this as a tab-delimited file (.txt).

ExtractRaster

The ExtractRaster tool allows a spatial layer to be extracted from a raster. Therefore, if grid code 3 is entered in the val box, then all grid codes referenced as 3 will be extracted from the source raster (src).

• Drag and drop a raster to the src box;
• Enter the grid code value of the layer that is to be extracted; and
• Click Run. The extracted raster is displayed in the Output tab.