﻿438 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  the 
  Heine, 
  the 
  Khone, 
  the 
  Loire, 
  the 
  Garonne 
  and 
  other 
  import- 
  

   ant 
  rivers 
  resulted 
  in 
  a 
  decision 
  not 
  to 
  carry 
  out 
  the 
  numerous 
  

   reservoirs 
  which 
  had 
  been 
  proposed, 
  owing 
  to 
  the 
  uncertainty 
  

   and 
  doubtful 
  efficacy 
  of 
  their 
  action 
  in 
  floods. 
  

  

  Further 
  investigations 
  were 
  made 
  after 
  the 
  inundations 
  of 
  

   1875. 
  These 
  latter 
  observations 
  show 
  that 
  in 
  the 
  case 
  of 
  the 
  

   Garonne, 
  a 
  reservoir 
  capacity 
  of 
  about 
  20,000,000,000 
  cubic 
  feet 
  

   would 
  be 
  required 
  to 
  protect 
  Toulouse, 
  and 
  one 
  of 
  50,000,000,000 
  

   to 
  60,000,000,000 
  cubic 
  feet 
  to 
  protect 
  Agen 
  and 
  the 
  rest 
  of 
  the 
  

   basin. 
  Unfortunately, 
  the 
  capacity 
  of 
  the 
  reservoirs 
  which 
  could 
  

   be 
  constructed 
  in 
  the 
  upper 
  valley 
  of 
  the 
  Garonne 
  would 
  amount 
  

   to 
  only 
  about 
  one-sixth 
  of 
  that 
  required 
  for 
  protecting 
  Toulouse. 
  

   The 
  investigations 
  led 
  to 
  similar 
  conclusions 
  in 
  the 
  case 
  of 
  the 
  

   lower 
  Garonne, 
  and 
  the 
  other 
  principal 
  river 
  basins 
  in 
  France. 
  1 
  

  

  In 
  one 
  particular 
  the 
  French 
  engineers 
  seem 
  to 
  have 
  been 
  far 
  

   from 
  right 
  in 
  their 
  investigation 
  of 
  the 
  utility 
  of 
  storage 
  reser- 
  

   voirs. 
  Thus 
  the 
  statement 
  is 
  made 
  that 
  such 
  reservoirs, 
  to 
  be 
  

   useful 
  against 
  floods, 
  must 
  be 
  kept 
  empty 
  throughout 
  the 
  whole 
  

   season 
  when 
  floods 
  may 
  occur. 
  This, 
  perhaps, 
  may 
  be 
  true 
  in 
  

   France, 
  but 
  it 
  is 
  not 
  true, 
  under 
  the 
  different 
  conditions 
  of 
  rain- 
  

   fall, 
  in 
  a 
  number 
  of 
  cases 
  in 
  the 
  State 
  of 
  New 
  York. 
  Possibly, 
  

   the 
  French 
  engineers 
  overlooked 
  the 
  moderating 
  effect 
  of 
  a 
  reser- 
  

   voir, 
  with 
  large 
  water 
  surface, 
  upon 
  a 
  flood 
  even 
  when 
  the 
  

   reservoir 
  is 
  filled 
  to 
  the 
  flow-line. 
  The 
  writer 
  has 
  discussed 
  this 
  

   question 
  extensively 
  in 
  his 
  several 
  reports 
  to 
  the 
  State 
  Engineer 
  

   and 
  Surveyor, 
  and 
  also 
  in 
  his 
  report 
  to 
  the 
  Board 
  of 
  Engineers 
  

   on 
  Deep 
  Waterways, 
  and 
  a 
  computation 
  is 
  given 
  in 
  connection 
  

   with 
  floods 
  on 
  Genesee 
  river 
  which 
  shows 
  that 
  even 
  under 
  the 
  

   adverse 
  condition 
  of 
  water 
  at 
  the 
  crest, 
  the 
  temporary 
  storage 
  

   on 
  the 
  water 
  surface 
  is 
  in 
  most 
  cases 
  great 
  enough 
  to 
  practically 
  

   double 
  the 
  time 
  of 
  a 
  flood 
  and 
  hence 
  to 
  greatly 
  decrease 
  its 
  de- 
  

   structive 
  effect. 
  The 
  conclusion 
  on 
  this 
  head, 
  therefore, 
  is 
  that 
  

   an 
  extreme 
  flood, 
  which 
  would 
  not 
  be 
  effectually 
  mitigated, 
  even 
  

   though 
  a 
  reservoir 
  were 
  full, 
  would 
  occur 
  not 
  oftener 
  than 
  once 
  

   in 
  a 
  century. 
  

  

  Flood 
  warnings. 
  Since 
  the 
  flood 
  wave 
  in 
  a 
  river 
  is 
  progres- 
  

   sive, 
  some 
  idea 
  can 
  be 
  formed 
  in 
  advance 
  as 
  to 
  the 
  stages 
  of 
  

  

  l 
  Annates 
  des 
  Ponts 
  et 
  Chanssees, 
  sixth 
  series, 
  Vol. 
  II, 
  1881, 
  p. 
  5, 
  trans- 
  

   lation 
  in 
  Proc. 
  Inst. 
  C. 
  E. 
  

  

  