docs: def _writeOptionalXsecCards(self, fileObject, xSec, replaceParamFile):
          """
          Write Optional Cross Section Cards to File Method
          """
          if xSec.erode:
              fileObject.write('ERODE\n')
  
          if xSec.maxErosion != None:
              fileObject.write('MAX_EROSION    %.6f\n' % xSec.maxErosion)
  
          if xSec.subsurface:
              fileObject.write('SUBSURFACE\n')
  
          if xSec.mRiver != None:
              mRiver = vwp(xSec.mRiver, replaceParamFile)
              try:
                  fileObject.write('M_RIVER        %.6f\n' % mRiver)
              except:
                  fileObject.write('M_RIVER        %s\n' % mRiver)
  
          if xSec.kRiver != None:
              kRiver = vwp(xSec.kRiver, replaceParamFile)
              try:
                  fileObject.write('K_RIVER        %.6f\n' % kRiver)
              except:
                  fileObject.write('K_RIVER        %s\n' % kRiver)