anchor.diff:          md%domains(1)%boundary_subroutine => boundary_stage_transmissive_normal_momentum
       case('boundary_stage_transmissive_momentum')
           md%domains(1)%boundary_subroutine => boundary_stage_transmissive_momentum
  -    !case('boundary_stage_transmissive_momentum_sponge')
  -    !    md%domains(1)%boundary_subroutine => boundary_stage_transmissive_momentum_sponge
       case('flather_with_vh_from_continuity')
           md%domains(1)%boundary_subroutine => flather_boundary
       case('flather_with_vh_equal_zero')
  
positive.code: 
          !
          ! The DEM needs to be 'fixed' in a few places where bridges remain. Google earth    
          ! suggests the bridges should not strongly impede the flow. So based on checks of teh DEM, ....
          !
          ! pol1 should have a value about -6.0
          !
  
negative.code:             case('boundary_stage_transmissive_momentum')
                  ! Do nothing, because we do not need uh/vh.
                  stage_uh_vh_elev(2:3) = 0.0_dp 
  
              case('flather_with_vh_equal_zero') 
                  ! This absorbs, but also distorts the stage at the boundary too much when
  