subroutine ranrou(
     *  csfsil, csfsan,
     *  bszrr, bszrro,
     *  cumpa, dcump, cf2cov, csvroc)

c     + + + ARGUMENT DECLARATIONS + + +
      real csfsil, csfsan
      real bszrr, bszrro,
     *  cumpa, dcump, cf2cov, csvroc

c     + + + LOCAL VARIABLES + + +

      real arr, crr

c     + + + LOCAL DEFINITIONS + + +
c
c   arr       - regression coef. to calc. random roughness
c   crr       - regression coefficient for random roughness decrease
c   csfsan    - top layer fraction of sand.
c   csfsil    - top layer fraction of silt.
c   csvroc    - soil volume fraction of rock in top layer

c  RANDOM ROUGHNESS SECTION:
c     calc. reg. coefficients (eq. S-12, S-13)
      arr = 91.08 + 765.8 * csfsil
      crr = 0.53 + 4.66 * csfsan - 3.8 * csfsan**1.5
     &      - 1.22*(csfsan)**0.5
c     calc. apparent precip. (eq. S-11 is S-14 solved for a bare surface)
C     changed * to ** to conform to equ S-10
c     erosion could make bszrr > bszrro so insert fix - LH
      if(bszrr .ge. bszrro) then
         cumpa = 0.0
         bszrro = bszrr
      else
         cumpa = arr * (-log(bszrr / bszrro)) ** (1.0 / crr)
      end if

c     update random roughness (eq. S-14)
C *** debugging fix

      if ((cumpa + (1.0 - csvroc) * cf2cov * dcump)/arr
     *  .lt. 0.) then
         bszrr = bszrro
c         write(*,*) 'soil: debugging fix executed 1'
c         write(*,*) '  cumpa, dcump, cf2cov, arr, csvroc ',
c     *            cumpa, dcump, cf2cov, arr, csvroc
      else
C *** end of debugging fix
C ***      write(*,*) ' crr ', crr
         bszrr = bszrro * exp(-((cumpa + (1.0 - csvroc)*
     *     cf2cov*dcump) /arr)**crr)
      endif
      if ( bszrr .lt. 2.0) bszrr = 2.0
      end