﻿Campbell. 
  — 
  On 
  Beach 
  Protection, 
  147 
  

  

  Works, 
  having 
  for 
  their 
  ohject 
  the 
  protection 
  of 
  the 
  sea-beach, 
  should 
  

   divide 
  the 
  destructive 
  and 
  progressive 
  actions 
  of 
  the 
  waves. 
  This 
  require^ 
  

   ment 
  is 
  fulfilled 
  by 
  piled 
  and 
  planked 
  groynes, 
  constructed 
  at 
  right 
  angles 
  

   to 
  the 
  shore 
  line, 
  their 
  tendency 
  being 
  to 
  collect 
  and 
  retain 
  the 
  sand 
  and 
  

   shingle. 
  When 
  the 
  waves 
  approach 
  the 
  shore 
  exactly 
  at 
  right 
  angles, 
  the 
  

   groynes 
  will 
  have 
  their 
  minimum 
  effect, 
  as 
  no 
  progressive 
  action 
  exists. 
  

   The 
  constant 
  shifting 
  of 
  the 
  beach, 
  however, 
  at 
  Hokitika, 
  either 
  to 
  the 
  north 
  

   or 
  south, 
  shows 
  that 
  an 
  oblique 
  direction 
  usually 
  prevails. 
  Groynes 
  have 
  

   been 
  found 
  to 
  be 
  most 
  successful 
  in 
  similar 
  cases 
  of 
  encroachment 
  on 
  the 
  

   coasts 
  of 
  Great 
  Britain. 
  In 
  the 
  Baltic, 
  a 
  double 
  row 
  of 
  piles 
  has 
  been 
  found 
  

   to 
  succeed 
  ; 
  while 
  on 
  the 
  Dutch 
  coast 
  groynes 
  are 
  constructed 
  of 
  fascines, 
  

   where 
  the 
  dykes 
  are 
  more 
  than 
  iisually 
  exposed 
  to 
  the 
  waves. 
  The 
  Enghsh 
  

   practice 
  is 
  to 
  drive 
  the 
  piles 
  from 
  one-half 
  to 
  two-thirds 
  of 
  their 
  length 
  in 
  

   the 
  sand 
  or 
  shingle, 
  either 
  in 
  pairs, 
  placing 
  planking 
  between 
  them, 
  or 
  to 
  

   have 
  a 
  pile 
  on 
  alternate 
  sides 
  of 
  the 
  planking. 
  Sheet-piling 
  would 
  be 
  

   particularly 
  advantageous, 
  and 
  is 
  shown 
  in 
  figs. 
  1 
  and 
  2, 
  which 
  closely 
  

   resembles 
  a 
  design 
  by 
  Mr. 
  E. 
  Pickwell, 
  A.I.C.E. 
  With 
  main 
  piles 
  27 
  feet 
  

   long, 
  and 
  sheet 
  piles 
  15 
  feet 
  long, 
  the 
  rate 
  per 
  yard 
  run 
  would 
  be 
  15 
  lin. 
  

   feet 
  main 
  piles, 
  3 
  CBM 
  timber 
  in 
  planking, 
  sheet 
  piles, 
  and 
  waling, 
  511bs, 
  

   ironwork 
  in 
  bolts 
  and 
  301bs. 
  in 
  shoes. 
  With 
  planking 
  only, 
  the 
  quantity 
  per 
  

   yard 
  run 
  would 
  be 
  15 
  lin. 
  feet 
  main 
  piles, 
  1 
  CBM 
  timber 
  in 
  planking 
  and 
  

   401bs. 
  ironwork 
  in 
  bolts 
  and 
  81bs. 
  in 
  shoes. 
  

  

  To 
  protect 
  the 
  beach 
  from 
  opposite 
  Camp 
  Street 
  to 
  Hampden 
  Street, 
  a 
  

   distance 
  of 
  770 
  yards, 
  six 
  groynes, 
  each 
  Q6 
  lin. 
  yards 
  in 
  length, 
  might 
  be 
  

   placed 
  every 
  154 
  yards. 
  Their 
  cost 
  would 
  be 
  about 
  £3,000. 
  With 
  the 
  

   foreshore 
  thus 
  protected 
  a 
  Une 
  of 
  scrub 
  and 
  saplings 
  could 
  be 
  placed 
  with 
  

   advantage 
  along 
  the 
  beach. 
  The 
  cost 
  would 
  be 
  about 
  £500. 
  

  

  As 
  instances 
  of 
  the 
  successful 
  conservation 
  of 
  foreshores 
  by 
  groynes, 
  it 
  

   may 
  be 
  mentioned 
  that, 
  at 
  Spurn 
  Point 
  in 
  Yorkshire,* 
  piled 
  and 
  planked 
  

   groynes 
  were 
  used 
  by 
  Sir 
  John 
  Coode, 
  and 
  in 
  four 
  years 
  the 
  line 
  of 
  bent 
  

   grass 
  had 
  extended 
  200 
  feet 
  to 
  seaward, 
  covering 
  many 
  drift 
  banks 
  ; 
  also 
  at 
  

   Withernsea,t 
  in 
  the 
  same 
  neighbourhood, 
  some 
  groynes 
  300 
  to 
  350 
  feet 
  

   long 
  were 
  constructed 
  200 
  yards 
  a]part 
  by 
  Mr. 
  Pickwell 
  ; 
  the 
  piles 
  at 
  first 
  

   stood 
  ten 
  feet 
  above 
  the 
  beach 
  at 
  the 
  land 
  end 
  and 
  six 
  feet 
  at 
  the 
  sea 
  end, 
  

   the 
  upper 
  five 
  planks 
  were 
  added 
  as 
  the 
  beach 
  accumulated, 
  and 
  in 
  four 
  

   years 
  the 
  groynes 
  were 
  nearly 
  covered 
  ; 
  at 
  Eastbourne 
  and 
  Folkestone 
  

   groynes 
  of 
  similar 
  construction 
  have 
  been 
  successfully 
  used 
  ; 
  at 
  the 
  former 
  

   place 
  they 
  were 
  constructed 
  150 
  yards 
  apart, 
  the 
  piles 
  were 
  driven 
  in 
  pairs 
  

   with 
  two 
  walings 
  and 
  a 
  centre 
  row 
  of 
  closely 
  driven 
  sheet-piles 
  six 
  inches 
  

  

  *Proc. 
  Inst. 
  C.E., 
  Vol. 
  XXVUL, 
  p. 
  503. 
  

   t 
  Proo. 
  Inst. 
  C.E., 
  Vol. 
  LI., 
  p. 
  206. 
  

  

  