```r
# environmental predictors: catchment slope and catchment area
ep = run_qgis(alg = "saga:sagawetnessindex",
              DEM = dem,
              SLOPE_TYPE = 1, 
              SLOPE = tempfile(fileext = ".sdat"),
              AREA = tempfile(fileext = ".sdat"),
              load_output = TRUE,
              show_output_paths = FALSE)
```