diff --git a/grass/hydrology.html b/grass/hydrology.html index f18c14b..71930ff 100644 --- a/grass/hydrology.html +++ b/grass/hydrology.html @@ -54,8 +54,8 @@

Compute flow direction, flow accumulation and subwatersheds

Generate relief shaded map of basins - and display extracted streams along with the official Wake county streams (red): -How do the derived streams compare with the official stream map?
+ and display extracted streams along with the official Wake county streams (red).
+How do the derived streams compare with the official stream map? How can you modify the mapcalc expression to make stream origins fit better with the official stream map? @@ -108,11 +108,12 @@

Create map of DEM depressions

Derive contributing area for a given outlet

-Set region to the high resolution study area and zoom to it: +Set region to the high resolution study area and zoom to it, +compute flow accumulation, flow direction and basins with 15000 cells threshold:

 g.region rural_1m -p
-r.watershed -as elevation=elev_lid792_1m threshold=5000 accumulation=accum_5K drainage=draindir_5K basin=basin_5K
+r.watershed -as elevation=elev_lid792_1m threshold=15000 accumulation=accum_15K drainage=draindir_15K basin=basin_15K
 

@@ -121,40 +122,36 @@

Derive contributing area for a given outlet


 d.erase
 d.rast ortho_2001_t792_1m
-d.rast accum_5K values=1500-1000000
+d.rast accum_5K values=1000-1000000
 

-Identify outlet on the extracted stream. -

-Create a vector map with the point east=638845.52 north=220085.26 (download the text file) -that has accum_5K=224510. - -


-v.in.ascii input=outlet_point.txt output=outletA30 separator=space
-d.vect outletA30 color=yellow
-
- -

-Delineate the contributing area associated with this outlet and convert it to vector format: +Delineate contributing area (watershed) associated with an outlet located +on the extracted stream and convert it to vector format:


 r.water.outlet input=draindir_5K output=basin_A30 coordinates=638845.52,220085.26
 r.to.vect -s basin_A30 output=basin_A30 type=area
+v.in.ascii input=outlet_point.txt output=outletA30 separator=space
 

-Display watershed boundary along with contours.
-Compute the watershed area (category 1)
+Display watershed boundary along with contours and +compute the watershed area (category 1)


+d.erase
 d.vect basin_A30 type=boundary color=green width=2
 r.contour elev_lid792_1m output=elev_lid792_cont_1m step=1 minlevel=104
 d.vect elev_lid792_cont_1m color=white
+d.vect outletA30 color=yellow
 d.out.file watershedA30
 r.report basin_A30 unit=h,a
 
+What is the delineated watershed area [ha] ?
+Optional: How would you compute average slope of this contributing area? +

Assess and mitigate impact of the road on flowrouting

Compare the extracted streams (accum > 1500) with official stream data: