SHArC - Working Principles

Working principles

Cover HSI: Substrate

A dmean Raster is needed in the RiverArchitect/01_Conditions/CONDITION/ folder. If this box is checked, a substrate_hsi Raster is created in RiverArchitect/SHArC/HSI/CONDITION/. The applied Habitat Suitability Curves can be adapted by clicking on the Edit HSCs button.

Cover HSI: Boulder

A boulder shapefile containing polygons with boulder sizes (diameters) needs to be available in RiverArchitect/SHArC/Cover/CONDITION/. The polygons need to be manually delineated for the entire region of interest. The module will convert boulder size information into a Raster and retain boulders with a size larger than a threshold value. Areas, where the boulder presence covers more than 30\% of the surface get assigned an HSI value of 0.5. Both the 30\% surface ratio and the associated HSI of 0.5 can be changed for every Physical Habitat for fish species and lifestages.

Cover HSI: Cobble

A cobble Raster containing substrate sizes (cobble diameters) needs to be available in RiverArchitect/SHArC/HSI/CONDITION/. The module will evaluate the percentage of area that is covered with cobble larger than a threshold value (grain size). Areas, where the percentage area covers more than 30\% of the surface get assigned an HSI value of 0.3. Both the 30\% surface ratio and the associated HSI of 0.3 can be changed for every Physical Habitat for fish species and lifestages.

Cover HSI: Streamwood

A streamwood shapefile containing polygons with single wood elements needs to be available in RiverArchitect/SHArC/HSI/CONDITION/. The module draws polygons with a user-defined radius around the streamwood polygons and assigns a value of 1 to these polygons. The new polygons are converted into a Raster and an HSI value of 0.3 is assigned to 1-pixels. The user-defined radius and the associated HSI of 0.3 can be changed for every Physical Habitat for fish species and lifestages.

Cover HSI: Vegetation

A plantings shapefile containing polygons with single plants needs to be available in RiverArchitect/SHArC/HSI/CONDITION/. The module draws polygons with a user-defined radius around the plant polygons and assigns a value of 1 to these polygons. The new polygons are converted into a Raster and an HSI value of 0.3 is assigned to 1/pixels. The user-defined radius and the associated HSI of 0.3 can be changed for every Physical Habitat for fish species and lifestages.

Cover HSI combination methods

The cover Rasters are combined by selecting the maximum value of the superposition of applied cover types: covHSI = arcpy.sa.Float(arcpy.sa.CellStatistics(applied_covers, ”MAXIMUM”, ”DATA”)), where applied_covers is a list of arcpy.Raster()s of applied cover types.

Usable habitat area calculation

The usable area is measured by converting cHSI Rasters to polygon shapefiles using arcpy.RasterToPolygon_conversion(cHSI, polygon_shp, ”NO_SIMPLIFY”). The area of single polygons is calculated by arcpy.CalculateGeometryAttributes_management(polygon_shp, geometry_property=[["F_AREA", "AREA"]], area_unit=self.area_unit). The polygon areas are summed up in a loop over the polygons (with arcpy.da.UpdateCursor(polygon_shp, ”F_AREA”)as cursor: for row in cursor: area += float (row[0])). The area variable contains the usable habitat area for every discharge-related cHSI Raster and it is eventually written in column G of CONDITION_FILI.xlsx.