﻿i82 
  Geological 
  Survey 
  of 
  Louisiana 
  [Sect. 
  

  

  There 
  are 
  very 
  marked 
  rapids 
  in 
  Bowman's 
  chute, 
  just 
  above 
  

   where 
  it 
  joins 
  Middle 
  bayou 
  and 
  the 
  "Ditch" 
  forming 
  Cross 
  

   bayou. 
  

  

  Formafioti 
  of 
  waterfalls 
  and 
  rapids. 
  — 
  During 
  the 
  raft 
  period 
  

   many 
  of 
  the 
  old 
  stream 
  channels 
  were 
  covered 
  by 
  lakes. 
  The 
  

   sediment 
  deposited 
  in 
  these 
  lakes 
  often 
  more 
  than 
  filled 
  parts 
  of 
  

   the 
  old 
  channels 
  so 
  that 
  after 
  the 
  removal 
  of 
  the 
  raft 
  and 
  the 
  

   partial 
  drainage 
  of 
  the 
  lakes 
  the 
  streams 
  were 
  forced 
  to 
  cut 
  new 
  

   channels. 
  It 
  would 
  sometimes 
  happen 
  that 
  a 
  stream 
  thus 
  forced 
  

   out 
  of 
  its 
  channel 
  would 
  find 
  itself 
  superimposed 
  on 
  the 
  older 
  

   blue 
  clays 
  or 
  on 
  projecting 
  points 
  of 
  the 
  adjoining 
  Eocene 
  clays. 
  

   Such 
  a 
  stream 
  may, 
  in 
  its 
  course, 
  find 
  its 
  way 
  back 
  into 
  a 
  portion 
  

   of 
  the 
  old 
  stream 
  bed 
  which 
  has 
  not 
  been 
  filled. 
  The 
  fall 
  thus 
  

   developed 
  on 
  the 
  bank 
  of 
  the 
  former 
  stream 
  will 
  wear 
  rapidly 
  

   back 
  through 
  the 
  alluvium 
  till 
  the 
  face 
  of 
  the 
  blue 
  clay 
  is 
  

   reached. 
  At 
  this 
  point, 
  if 
  there 
  is 
  a 
  layer 
  of 
  harder 
  clay 
  under- 
  

   laid 
  by 
  softer 
  material, 
  the 
  waterfall 
  will 
  maintain 
  itself 
  and 
  

   gradually 
  wear 
  back 
  until 
  the 
  lake 
  formed 
  by 
  the 
  daming 
  of 
  the 
  

   old 
  stream 
  channel 
  is 
  reached. 
  If 
  the 
  clay 
  is 
  a 
  uniform 
  mass 
  

   the 
  face 
  of 
  the 
  falls 
  will 
  be 
  worn 
  off 
  and 
  rapids 
  produced. 
  

  

  In 
  this 
  region 
  the 
  same 
  result 
  could 
  be 
  produced 
  without 
  the 
  

   formation 
  of 
  a 
  waterfall 
  by 
  the 
  tumbling 
  of 
  the 
  stream 
  over 
  the 
  

   old 
  stream 
  bank. 
  If 
  the 
  old 
  channel 
  has 
  been 
  completely 
  filled 
  

   the 
  water 
  will 
  flow 
  in 
  the 
  lowest 
  part 
  of 
  the 
  adjacent 
  land; 
  part 
  

   of 
  its 
  bed 
  being 
  of 
  alluvial 
  material 
  and 
  part 
  possibly 
  of 
  the 
  

   older 
  clays. 
  As 
  the 
  river 
  erodes 
  its 
  channel 
  the 
  side 
  streams 
  

   would 
  tend 
  to 
  do 
  likewise 
  and 
  would 
  soon 
  cut 
  ample 
  channels 
  

   through 
  the 
  alluvium 
  lying 
  between 
  the 
  older 
  clays 
  and 
  the 
  

   river, 
  leaving 
  the 
  less 
  easily 
  eroded 
  clays 
  to 
  form 
  rapids 
  and 
  

   waterfalls 
  in 
  the 
  channel. 
  

  

  In 
  the 
  case 
  of 
  the 
  rapids 
  at 
  Albany 
  flats 
  the 
  ancient 
  channel 
  

   was 
  evidently 
  to 
  the 
  north 
  of 
  the 
  present 
  channel. 
  This 
  old 
  

   channel 
  was 
  filled 
  with 
  sediment 
  brought 
  down 
  by 
  the 
  outlet 
  

   bayous. 
  When 
  the 
  raft 
  was 
  removed 
  the 
  stream 
  occupied 
  the 
  

   lowest 
  land, 
  which, 
  since 
  the 
  greater 
  part 
  of 
  the 
  filling 
  was 
  on 
  

   the 
  northern 
  side 
  of 
  Sodo 
  lake, 
  was 
  along 
  the 
  base 
  of 
  the 
  hills. 
  

   Here 
  the 
  stream 
  found 
  hard 
  blue 
  Eocene 
  clays. 
  The 
  rapid 
  erosion 
  

   of 
  the 
  alluvial 
  material 
  between 
  these 
  clays 
  and 
  the 
  river 
  left 
  them 
  

  

  