WATERSHED DELINEATION IN QGIS | DERIVING STREAM NETWORK AND ADDING OUTLET POINT | STEP BY STEP PROCEDURE | QGIS SOFTWARE

STEPS:
  • OPEN QGIS
  • OPEN NEW PROJECT
  • IN MENU TOOLBAR CLICK ON LAYER à ADD LAYER à ADD RASTER LAYER à BROWSE USING THE THREE DOTS à SELECT GEOTIFF FILE à CLICK ON OPEN à ADD à CLOSE
  • IN MENU TOOLBAR à PLUGINS à MANAGE AND INSTALL PLUGINS à QUICKMAPSERVICES à INSTALL PLUGIN à CLOSE



  • IN MENU TOOLBAR à WEB à OSM à OSM STANDARD
  • RIGHT CLICK ON THE ADDED LAYER à CLICK ON PROPERTIES à INFORMATION
  • CHECK THE PROJECTION SYSTEM
  • IF PROJECTION SYSTEM IS NOT UTM OR ANY OTHER LOCAL PROJECTION SYSTEM (i.e. IF CRS IS GEOGRAPHIC AND UNIT IS IN DEGREES) THEN à IN MENU TOOLBAR CLICK ON RASTER à PROJECTIONS à WARP (REPROJECT) à IN TARGET CRS (OPTIONAL) CLICK ON THE BROWSE ICON à UNTICK NO CRS à IN FILTER SEARCH FOR WGS 84 UTM 45N (HERE 45N IS THE ZONE) à CLICK ON OK à RUN




  • IN STATUSBAR LEFT CLICK ON EPSG:4326 à UNTICK NO CRS à IN FILTER SEARCH FOR WGS 84 UTM 45N à CLICK ON APPLY à CLICK ON OK
  • IN MENU TOOLBAR à PROCESSING à TOOLBOX à SEARCH FILL SINKS (WANG & LIU) à DOUBLE CLICK ON FILL SINKS (WANG & LIU) à IN DEM SELECT REPROJECTED à CLICK ON RUN à CLOSE


  • IN PROCESSING TOOLBOX à SEARCH STRAHLER ORDER à DOUBLE CLICK ON STRAHLER ORDER à IN ELEVATION SELECT FILLED DEM à CLICK ON RUN à CLOSE


  • IN MENU TOOLBAR à CLICK ON RASTER à RASTER CALCULATOR à IN RASTER BANDS DOUBLE CLICK ON STRAHLER ORDER@1 à IN OPERATORS SELECT >= à THEN INPUT VALUE (FOR THIS CASE 6 ‘NOTE: THIS VALUE DEPENDS ON THE CLASSES OF YOUR STRAHLER ORDER’) à IN RESULT LAYER CLICK ON THE THREE DOTS IN OUTPUT LAYER GIVE A FILE NAME AND SAVE à CLICK ON OK
  • IN LAYERS YOU WILL FIND YOUR SAVED FILE à RIGHT CLICK ON THAT à PROPERTIES à TRANSPERENCY à INPUT ‘0’ IN ADDITIONAL NO DATA VALUE
  • IN PROCESING TOOLBOX SEARCH CHANNEL à DOUBLE CLICK ON CHANNEL NETWORK AND DRAINAGE BASINS à IN ELEVATION SELECT FILLED DEM à IN THRESOLD (INPUT THE VALUE USED IN RASTER CALCULATOR) FOR THIS CASE THRESOLD WILL BE 6 à UNTICK ALL THE OPEN OUTPUT FILE AFTER RUNNING ALGORITHM EXCEPT “CHANNELS” à RUN à CLOSE


  • FIND THE COORDINATES OF THE POINT à IN MENU TOOLBAR à CLICK ON INFO ICON à IN PROCESSING TOOLBOX FIND BAND 1 IN IDENTIFY RESULTS
  • IN PROCESSING TOOLBOX SEARCH UPSLOPE à DOUBLE CLICK ON UPSLOPE AREA à TARGET AREA WILL BE: FILLED DEM à COPY THE VALUE 1 AND 2 FROM THE IDENTIFY RESULTS AND PASTE IT IN TARGET X COORDINATE AND TARGET Y COORDINATE RESPECTIVELY à ELEVATION AS FILLED DEM à METHOD AS [0] DETERMINISTIC 8 à RUN à CLOSE


  • IN MENU TOOLBAR à RASTER à POLYGONIZE (RASTER TO VECTOR) à INPUT LAYER WILL BE: UPSLOPE AREA à RUN à CLOSE


  • RIGHT CLICK ON VECTORIZED à OPEN ATTRIBUTE TABLE à CLICK ON TOGGLE EDITING à DELETE FEATURES WITH DN ‘0’ à SAVE EDITS
  • IN PROCESING TOOLBOX SEARCH CHANNEL à DOUBLE CLICK ON CHANNEL NETWORK AND DRAINAGE BASINS à IN ELEVATION SELECT FILLED DEM à IN THRESOLD (INPUT THE VALUE USED IN RASTER CALCULATOR) FOR THIS CASE THRESOLD WILL BE 6 à UNTICK ALL THE OPEN OUTPUT FILE AFTER RUNNING ALGORITHM EXCEPT “CHANNELS” à RUN à CLOSE
  • IN PROCESSING TOOLBOX à SEARCH POLYGON CLIPPING à DOUBLE CLICK ON POLYGON CLIPPING à SELECT VECTORIZED IN CLIP FEATURES AND CHANNELS IN INPUT FEATURES à IN OUTPUT FEATURES CLICK ON BROWSE AND SAVE FILE à RUN à CLOSE
  • TO CREATE OUTLET POINT:   IN MENU TOOLBAR CLICK ON LAYER à CREATE LAYER à NEW SHAPEFILE LAYER à GIVE FILENAME AS OUTLET, GEOMETRY TYPE: POINT, CHANGE CRS à CLICK ON OK à IN THE ADDED LAYERS à RIGHT CLICK ON OUTLET LAYER à TOGGLE EDITING à ON TOP IN DATA SOURCE MANAGER TOOLBAR à CLICK ON ADD POINT FEATURE à FIND THE LOCATION OF YOUR OUTLET POINT AND CLICK ON THAT LOCATION à SAVE LAYER EDITS




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