DELINEAT CATCHMENT IN WHITEBOX GAT

                

Download Whitbox GAT from its official site.
Install Java.
Open Whitebox and follow these steps.
You can refer to the video tutorial here.

1. Import DEM in white box format

2. Fill à Hydrological tools | Dem pre-processing | Fill depression

3. Flow direction à Hydrological tools |Flow pointers | D8 flow pointer

4. Flow accumulation à Hydrological tools |Flow Accumulation | D8 and Rho8 flow accumulation

Number of upslope grid cells: if you want to enter grid cells in the threshold value

Specific catchment area: if you want to specify catchment area in the threshold value

5. Extract stream à Stream Network Analysis | Extract stream

Channelization threshold: 100000 à all the cells of raster greater than this value is called stream

Background value: 0 à this value is assigned to all cells of raster which are not part of stream

6. Convert raster stream to vector à Stream Network Analysis | Raster stream to vector

7. Sub-basin à Hydrological tools |Watershed tools| Sub-basins

8. Convert sub-basins raster to vector à Conversion Tools | Raster/Vector conversions | Raster to vector Polygons

9. Create Isobasins à Hydrological tools |Watershed Tools | Isobasin

Target basin size: 100000 (this is cell value because “Number of upslope grid cells” was specified in Flow accumulation and value same as threshold value or other value can also be specified)

10. Snap pour point à Hydrological tools |Watershed Tools | Snap pour points

Snap distance: 100

11. Watershed à raster to vector polygon and calculate areaà Hydrological tools |Watershed Tools| Watershed

12. Convert watershed to polygon à Conversion Tools | Raster/Vector conversions | Raster to vector Polygons

Note: If you want to create only catchment, you can skip steps 7, 8 and 9.