﻿HYDROLOGY 
  OF 
  NEW 
  YORK 
  44 
  < 
  

  

  area 
  in 
  modifying 
  the 
  effect 
  of 
  an 
  extreme 
  flood, 
  reference 
  may 
  be 
  

   made 
  to 
  fig. 
  35, 
  in 
  which, 
  with 
  time 
  as 
  abscissas 
  and 
  runoff 
  as 
  

   ordinates, 
  the 
  runoff 
  record 
  of 
  Genesee 
  river 
  for 
  May 
  18-23, 
  1894, 
  

   has 
  been 
  plotted. 
  The 
  lower 
  curve 
  of 
  that 
  figure 
  may 
  be 
  taken 
  as 
  

   representing 
  approximately 
  the 
  law 
  of 
  the 
  runoff 
  of 
  any 
  generally 
  

   distributed 
  heavy 
  rainfall 
  on 
  the 
  catchment 
  area 
  of 
  this 
  stream. 
  

   In 
  making 
  this 
  statement 
  it 
  is 
  not 
  overlooked 
  that 
  flood-flows 
  at 
  

   other 
  seasons 
  of 
  the 
  year 
  may 
  differ 
  somewhat 
  in 
  their 
  movement 
  

   from 
  that 
  of 
  May, 
  181)4. 
  Inasmuch 
  as 
  the 
  rapidity 
  and 
  intensity 
  

   of 
  the 
  runoff 
  of 
  any 
  given 
  stream 
  depend 
  largely 
  upon 
  the 
  topog- 
  

   raphy, 
  the 
  statement 
  may 
  be 
  made 
  that 
  the 
  general 
  law 
  of 
  move- 
  

   ment 
  of 
  floods 
  in 
  the 
  Genesee 
  river 
  is 
  indicated 
  by 
  the 
  lower 
  curve 
  

   of 
  fig. 
  35. 
  With 
  this 
  understanding 
  we 
  may 
  assume 
  any 
  other 
  run- 
  

   off 
  and 
  construct 
  the 
  approximate 
  curve 
  by 
  drawing 
  it 
  generally 
  

   parallel 
  to 
  the 
  curve 
  of 
  the 
  actually 
  observed 
  case. 
  In 
  this 
  way 
  

   the 
  upper 
  curve 
  of 
  fig. 
  35, 
  representing 
  the 
  curve 
  of 
  a 
  flood 
  one 
  

   and 
  one-half 
  times 
  greater 
  than 
  that 
  of 
  May, 
  1894, 
  has 
  been 
  pro- 
  

   duced, 
  slight 
  irregularities 
  of 
  the 
  lower 
  curve 
  having 
  been 
  neg- 
  

   lected 
  in 
  projecting 
  the 
  upper 
  one. 
  

  

  A 
  flood-flow 
  one 
  and 
  one-half 
  times 
  as 
  great 
  as 
  that 
  of 
  May, 
  1894. 
  

   which 
  culminated 
  in 
  a 
  maximum 
  of 
  about 
  42,000 
  cubic 
  feet 
  per 
  

   second 
  at 
  3.30 
  a. 
  in. 
  of 
  May 
  21, 
  gives 
  a 
  maximum 
  of 
  63,000 
  cubic- 
  

   feet 
  per 
  second, 
  the 
  movement 
  of 
  which 
  would 
  be, 
  under 
  the 
  

   assumptions, 
  substantially 
  as 
  in 
  the 
  upper 
  curve 
  of 
  fig. 
  35. 
  As 
  

   to 
  the 
  probability 
  of 
  a 
  maximum 
  flood-flow 
  of 
  63,000 
  cubic 
  feet 
  

   per 
  second 
  on 
  the 
  upper 
  Genesee 
  catchment 
  area, 
  the 
  case 
  of 
  the 
  

   neighboring 
  Chemung 
  river 
  may 
  be 
  cited, 
  where 
  a 
  flood-flow 
  of 
  

   67.1 
  cubic 
  feet 
  per 
  second 
  per 
  square 
  mile 
  occurred 
  in 
  June, 
  1898. 
  

   This 
  figure 
  applied 
  to 
  the 
  upper 
  Genesee 
  would 
  give 
  a 
  possible 
  

   maximum 
  runoff 
  of 
  71,126 
  cubic 
  feet 
  per 
  second. 
  

  

  Flood 
  of 
  1896. 
  The 
  flood 
  of 
  April, 
  1896, 
  came 
  very 
  near 
  reach- 
  

   ing 
  the 
  danger 
  limit 
  — 
  so 
  near, 
  indeed, 
  that 
  it 
  is 
  now 
  the 
  opinion 
  

   of 
  many 
  thinking 
  citizens 
  of 
  Rochester 
  that 
  the 
  regulation 
  

   afforded 
  by 
  the 
  proposed 
  storage 
  dam 
  at 
  Portage 
  may 
  not 
  be 
  

   sufficient 
  to 
  fully 
  protect 
  the 
  city 
  from 
  a 
  repetition 
  of 
  the 
  disaster 
  

   of 
  1865. 
  If 
  the 
  river 
  were 
  to 
  again 
  rise 
  to 
  the 
  hight 
  attained 
  in 
  

   that 
  year, 
  the 
  damage 
  would 
  inevitably 
  be 
  several 
  times 
  greater 
  

   than 
  occurred 
  then. 
  

  

  