﻿HYDROLOGY 
  OF 
  NEW 
  YORK 
  4Jo 
  

  

  the 
  bed, 
  together 
  with 
  the 
  alluvial 
  banks, 
  permit 
  of 
  sudden 
  and 
  

   extensive 
  changes 
  in 
  channel 
  location 
  at 
  times 
  of 
  floods. 
  This 
  

   concavity 
  of 
  profile, 
  with 
  its 
  resulting 
  diminution 
  of 
  velocity, 
  is 
  one 
  

   of 
  the 
  potent 
  factors 
  in 
  the 
  causation 
  of 
  floods, 
  since 
  it 
  permits 
  

   flood 
  waters 
  to 
  be 
  brought 
  to 
  points 
  having 
  sharp 
  concavities 
  of 
  

   profile 
  or 
  abrupt 
  flattening 
  of 
  grades 
  more 
  rapidly 
  than 
  the 
  chan- 
  

   nel 
  will 
  carry 
  the 
  same 
  away, 
  producing 
  at 
  such 
  points 
  temporary 
  

   accumulations 
  of 
  water 
  with 
  an 
  attendant 
  overflow. 
  

  

  It 
  is 
  not 
  to 
  be 
  understood 
  that 
  the 
  profile 
  of 
  any 
  stream 
  is 
  a 
  

   perfectly 
  smooth 
  concave 
  curve, 
  nor 
  that 
  the 
  grades 
  grow 
  

   progressively 
  flatter 
  without 
  interruption 
  as 
  one 
  passes 
  down 
  

   stream. 
  Local 
  causes 
  interfering 
  with 
  regularity 
  of 
  flow, 
  and 
  

   geological 
  formations 
  interfering 
  with 
  the 
  vertical 
  erosion 
  of 
  

   channels, 
  cause 
  interruptions 
  in 
  the 
  regularity 
  of 
  the 
  concave 
  

   profile. 
  The 
  Genesee 
  river 
  is 
  a 
  characteristic 
  type 
  of 
  this 
  inter- 
  

   ruption 
  by 
  geological 
  causes. 
  Whatever 
  the 
  regularity 
  or 
  irregu- 
  

   larity 
  of 
  the 
  profile 
  may 
  be, 
  however, 
  it 
  is 
  safe 
  to 
  expect 
  that 
  if 
  

   floods 
  occur 
  at 
  all 
  on 
  a 
  stream, 
  they 
  are 
  more 
  certain 
  to 
  occur 
  

   where 
  the 
  stream 
  slope 
  grows 
  suddenly 
  or 
  decidedly 
  flatter 
  or 
  

   where 
  extensive 
  local 
  obstructions 
  or 
  restrictions 
  occur. 
  1 
  

  

  In 
  order 
  to 
  correct 
  the 
  excessive 
  flows 
  produced 
  by 
  the 
  fore- 
  

   going 
  conditions 
  the 
  stream 
  may 
  be 
  trained 
  or 
  regulated 
  in 
  a 
  

   number 
  of 
  ways; 
  such 
  training 
  is 
  commonly 
  called 
  river 
  regula- 
  

   tion 
  or 
  river 
  conservancy. 
  

  

  Antiquity 
  of 
  river 
  regulation 
  or 
  conservancy. 
  Eiver 
  regulation, 
  

   or 
  river 
  conservancy, 
  is 
  very 
  old, 
  and 
  there 
  is 
  scarcely 
  a 
  phase 
  of 
  

   it 
  that 
  has 
  not 
  been 
  considered 
  at 
  some 
  time 
  in 
  the 
  Old 
  World. 
  

   The 
  Chinese 
  rivers, 
  particularly 
  the 
  Hoang-ho, 
  were 
  regulated 
  by 
  

   dykes 
  and 
  embankments 
  over 
  4000 
  years 
  ago. 
  The 
  same 
  is 
  true 
  

   of 
  the 
  Euphrates 
  and 
  many 
  other 
  rivers 
  on 
  which 
  were 
  situated 
  

   the 
  cities 
  of 
  the 
  ancient 
  world. 
  This 
  statement 
  is 
  specially 
  true 
  

   of 
  the 
  river 
  Tiber, 
  at 
  Rome. 
  In 
  the 
  year 
  53 
  B. 
  C. 
  — 
  1957 
  years 
  

   ago 
  — 
  a 
  proposition 
  was 
  brought 
  forward 
  in 
  the 
  Roman 
  senate 
  for 
  

   moderating 
  the 
  frequent 
  inundations 
  of 
  this 
  stream, 
  which 
  re- 
  

   sulted 
  in 
  the 
  appointment 
  of 
  five 
  senators 
  as 
  a 
  river 
  conservancy 
  

   commission, 
  to 
  whom 
  was 
  assigned 
  the 
  task 
  of 
  so 
  regulating 
  the 
  

   volume 
  of 
  water 
  in 
  the 
  river 
  that 
  there 
  might 
  be 
  " 
  no 
  deficiency 
  

  

  lAbstract 
  from 
  the 
  Report 
  of 
  the 
  Water 
  Storage 
  Commission. 
  

  

  