Update vegetation parameters in constants.py (#250)

* Update vegetation parameters in constants.py

Removes unused V_Lat parameter
solves #120 
Changes default for veg_min_elevation to -10 to avoid unwanted use of this functionality.

* Update aeolis/constants.py

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

---------

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Author: Sierd

aeolis/constants.py

@@ -300,7 +300,6 @@
     'hveg_max'                      : 1.,                 # [m] Max height of vegetation
     'dzb_opt'                       : 0.,                 # [m/year] Sediment burial for optimal growth
     'V_ver'                         : 0.,                 # [m/year] Vertical growth potential
-    'V_lat'                         : 0.,                 # [m/year] Lateral growth
     'germinate'                     : 0.,                 # [1/year] Possibility of germination per year
     'lateral'                       : 0.,                 # [1/year] Posibility of lateral expension per year
     'veg_gamma'                     : 1.,                 # [-] Constant on influence of sediment burial
@@ -332,7 +331,7 @@
     'alfa'                          : 0,                  # [deg] Real-world grid cell orientation wrt the North (clockwise)
     'dune_toe_elevation'            : 3,                  # Choose dune toe elevation, only used in the PH12 dune erosion solver
     'beach_slope'                   : 0.1,                # Define the beach slope, only used in the PH12 dune erosion solver
-    'veg_min_elevation'             : 3,                  # Choose the minimum elevation where vegetation can grow
+    'veg_min_elevation'             : -10.,               # Minimum elevation (m) where vegetation can grow; default -10 disables restriction (allows vegetation everywhere). Set to a higher value to enforce a minimum elevation for vegetation growth.
     'vegshear_type'                 : 'raupach',          # Choose the Raupach grid based solver (1D or 2D) or the Okin approach (1D only)
     'okin_c1_veg'                   : 0.48,               #x/h spatial reduction factor in Okin model for use with vegetation
     'okin_c1_fence'                 : 0.48,               #x/h spatial reduction factor in Okin model for use with sand fence module