depth_grad.f90

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!/---------------------------------------------------------------------------/
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!/===========================================================================/

!==============================================================================|
!     CALCULATE THE GRADIENT OF THE WATER DEPTH WITH X ANDY                    |
!==============================================================================|

   SUBROUTINE depth_gradient      

!==============================================================================|
   USE all_vars
   USE mod_par

   IMPLICIT NONE
   REAL(SP) :: PHPX,PHPY,F1
   INTEGER  :: I,J,I1,I2
!==============================================================================|

!----------CALCULATE DERIVATIVES OF DEPTH WITH X AND Y AT NODES----------------!

   DO i=1,m
     phpx = 0.0_sp ; phpy = 0.0_sp
     DO j=1,ntsn(i)-1
       i1 = nbsn(i,j)
       i2 = nbsn(i,j+1)
       f1 = 0.50_sp*(h(i1)+h(i2)) 
       phpx = phpx + f1*(vy(i1)-vy(i2))
       phpy = phpy + f1*(vx(i2)-vx(i1))
     END DO
     phpx = phpx/art2(i)
     phpy = phpy/art2(i)

     IF(phpx==0.0_sp .AND.  phpy ==0.0_sp)THEN
       sita_gd(i) = 0.0_sp ; phpn(i) = 0.0_sp
     ELSE
       sita_gd(i) = atan2(phpy,phpx)
       phpn(i)    = sqrt(phpy*phpy+phpx*phpx)
     END IF

   END DO


   RETURN
   END SUBROUTINE depth_gradient
!==============================================================================|