﻿LAND 
  USE 
  — 
  LOWDERMILK 
  423 
  

  

  to 
  steep 
  gradients 
  as 
  forests 
  were 
  cleared 
  away. 
  These 
  mountains 
  had 
  

   been 
  sculptured 
  by 
  glaciers 
  of 
  the 
  Ice 
  Age 
  into 
  deep 
  gorges 
  bordered 
  

   by 
  hanging 
  valleys, 
  which 
  set 
  the 
  stage 
  for 
  torrential 
  debris 
  floods 
  as 
  

   slopes 
  were 
  cleared 
  of 
  forests 
  for 
  cultivation 
  or 
  heavily 
  grazed. 
  

  

  France 
  and 
  Italy 
  have 
  been 
  engaged 
  for 
  many 
  years 
  in 
  the 
  control 
  

   of 
  debris 
  floods 
  in 
  mountain 
  valleys. 
  France 
  has 
  carried 
  out 
  for 
  60 
  

   years 
  a 
  comprehensive 
  program 
  of 
  works, 
  with 
  notable 
  achievements. 
  

   The 
  experience 
  of 
  60 
  years 
  of 
  such 
  works 
  is 
  especially 
  valuable 
  in 
  meet- 
  

   ing 
  the 
  increasing 
  hazards 
  of 
  floods 
  in 
  mountainous 
  areas 
  of 
  the 
  New 
  

   World. 
  Debris 
  floods 
  bury 
  fields, 
  orchards, 
  and 
  villages 
  in 
  valley 
  

   floors, 
  interrupt 
  communication, 
  and 
  destroy 
  livestock 
  and 
  human 
  life. 
  

   Losses 
  over 
  the 
  past 
  century 
  have 
  reached 
  enormous 
  figures 
  and 
  have 
  

   stimulated 
  brilliant 
  engineering 
  and 
  remarkable 
  measures 
  of 
  erosion 
  

   control 
  and 
  revegetation. 
  

  

  Correction 
  of 
  mountain 
  torrents 
  is 
  most 
  economically 
  and 
  effectively 
  

   carried 
  out 
  as 
  a 
  gigantic 
  chess 
  game. 
  It 
  is 
  man 
  against 
  nature, 
  where 
  

   man 
  may 
  perchance 
  delay 
  the 
  inevitable 
  long 
  enough 
  for 
  his 
  purposes. 
  

   It 
  takes 
  time 
  and 
  daring 
  as 
  well 
  to 
  play 
  this 
  game, 
  in 
  addition 
  to 
  

   minute 
  study 
  of 
  natural 
  forces 
  at 
  work. 
  As 
  the 
  torrent-control 
  

   engineer 
  builds 
  each 
  structure 
  he 
  waits 
  to 
  observe 
  the 
  responses 
  of 
  

   natural 
  forces. 
  These 
  in 
  turn 
  determine 
  his 
  next 
  move, 
  whether 
  to 
  

   build 
  another 
  structure, 
  or 
  reinforce 
  existing 
  works, 
  until 
  in 
  due 
  time 
  

   he 
  is 
  successful 
  in 
  checkmating 
  torrential 
  floods. 
  The 
  high 
  costs 
  of 
  

   the 
  control 
  of 
  torrents 
  are 
  justified 
  by 
  the 
  protection 
  of 
  valley 
  lands 
  

   from 
  damage, 
  by 
  the 
  reduction 
  of 
  debris 
  accumulations 
  in 
  stream 
  

   channels, 
  as 
  a 
  safeguard 
  against 
  rising 
  water 
  tables 
  and 
  marshy 
  condi- 
  

   tions 
  in 
  high-value 
  alluvial 
  lands, 
  and 
  by 
  saving 
  life. 
  

  

  Two 
  essential 
  principals 
  are 
  followed 
  in 
  all 
  torrent-control 
  works 
  : 
  

   establishment 
  of 
  base 
  levels 
  of 
  cutting 
  in 
  torrent 
  channels 
  with 
  per- 
  

   manent 
  check 
  dams, 
  and 
  revegetation 
  of 
  the 
  catchment 
  area. 
  Similar 
  

   work 
  has 
  been 
  done 
  in 
  Bavaria 
  in 
  southern 
  Germany, 
  but 
  it 
  was 
  not 
  

   possible 
  for 
  me 
  to 
  continue 
  the 
  projected 
  survey 
  into 
  Germany 
  because 
  

   of 
  the 
  outbreak 
  of 
  war 
  in 
  that 
  fateful 
  September. 
  

  

  FIXATION 
  OF 
  SAND 
  DUNES 
  

  

  Problems 
  of 
  water-erosion 
  control 
  are 
  most 
  common 
  on 
  sloping 
  

   lands, 
  but 
  those 
  of 
  wind-erosion 
  control 
  most 
  often 
  occur 
  on 
  flat 
  lands. 
  

   Sand 
  dunes 
  have 
  been 
  formed 
  in 
  semiarid 
  regions 
  by 
  the 
  sorting 
  effect 
  

   of 
  wind 
  erosion 
  of 
  cultivated 
  lands. 
  The 
  wind 
  sorts 
  dry 
  soils, 
  lifting 
  

   the 
  fine 
  and 
  fertile 
  particles 
  to 
  blow 
  them 
  away 
  in 
  dust 
  clouds, 
  whereas 
  

   the 
  heavier 
  particles 
  as 
  sand 
  are 
  left 
  behind 
  to 
  form 
  hummocks 
  and 
  

   finally 
  active 
  sand 
  dunes. 
  Usually 
  former 
  farm 
  lands 
  of 
  the 
  Old 
  

   World 
  so 
  damaged 
  have 
  been 
  abandoned 
  and 
  left 
  to 
  their 
  fate 
  (8). 
  

  

  In 
  southwestern 
  France 
  the 
  government 
  has 
  carried 
  out 
  the 
  classic 
  

   and 
  greatest 
  achievement 
  in 
  the 
  fixation 
  of 
  a 
  vast 
  area 
  of 
  a 
  "moist 
  

  

  