\ New Brighton - . '- Preface

Transcription

1 Ot

2 t. ' 't. '- -.. Preface 111s report was wrtten by Bran Caton for the New Brghton Progress Assocaton. t began as a reslt of the Assocaton's reqest to Dr Brce Thorn of the Astralan Natonal nversty and hs sbseqent approach to Professor an Doglas of the nversty of New England. The feld and laboratory work nclded n the report was fnded by the nversty of New England Geography Department whle the athor was a teachng fello\ at that nsttton. The report was wrtten whle the athor was employed at Strt College of Advanced Edcaton. wsh to thank Dr Brce Thorn for sggestng the 1975 feld work and for commentng on the manscrpt and Professor an Doglas for mch encoragement and advce drng earler feld 'ork. thank Yvonne Hdden for help \t h the dagrams and Nan Berrett for typng the fnal copy. ( New Brghton Erosgn Stdy \ New Brghton Ero.n Stdy

3 ::.. \ ' ' ' ).. '. f H = n rn. a - l.... W TABLE OF CONTENTS Secton 1. Secton 2. Secton 3. Secton 4. Secton 5. ntrodcton 11. Backgrond 12. The Problem. Physcal Settng 21. Hastngs Pont to Cape Byron as a coastal nt. 22. Geomorphologcal Hstory. 23. Tdes 24. Waves. Beach Profles '31. Methods.of srvey. 32. Reslts of beach proflng. 33. The effects of the tranng walls. 34. Snnary. Beach Changes from docmentary and photographc Sorces. 41. ntrodcton. 42. The character and relablty of the data. 43. 'Docmentary and photographc coverage. 44. Dscsson. 45. Snnary. 46. Lst of sorces conslted. Smmary Lst of References cted. \1..: Q' )' a Appendx A. Appendx B. Pblshed stdes on groynes. Beach materals..

4 -.'..':.. ' '.'. [. '....:.: a! D! LST or LLSTRATONS Fg. lao lb. Locaton map. Department of Pblc Works hydrographc chart of Brnswck Rver entrance a. Geomorphologcal Map and Locaton of Profle.lnes. 2b. Generalsed cross-sectons across ' the dnes. 2c. Sgnfcant wave heghts at the Gold Coast. 2d. Wave drectons from pblshed Sorces. 2e. Wave vectors. 2f. Wave vectors. 2g. Wave vectors. 3b. Graphcal plot of sand volmes. 3c. Smoothed crve of sand volmes (1-6) 3d. Smoothed crve of sand volmes (7-12) 4a. Locaton map for plots of hstorcal coastal changes. 4b. Photographc coverage. 4c. Varaton n poston of frontal dne throgh tme 1. 4d. Varaton n poston of frontal dne throgh tme 2. 4e. Varaton n poston of frontal dne throgh tme 3. 4f. Bar-grah: Poston of frontal dne g. Bar-graph: Poston of frontal dne h. Bar-grap: Poston of frontal dne

5 ;.;/> ' :';/:: '-::. ';.. ;-'. '.... '......tl.:: - :; ' '/!:: ':t ;;:.\ ;:'f}y!!::?'\; ';; ;/l}?t;j.\.) \>! ){X.- :. 'tr' '- :... ;.< ;.: 'C....'.p....'_' f.'p.r. ('.{O 1;'.. '' -.. '; '.; t.... <. l : <:;:);.r;;;:f]t\ ;.\:{l{t.:1t:t{.:1j1fj1; ---. :l... '.!: :-:-. ;-... f.. : 1')j :'7.o(lr-f''1'l :: \;: : : ':\':;''' ::5; ::t ''r._/:: :'t:.:rt:\.: t:;f;\rt :. ;.' 'V.' j l.t'.'. --:: ': '.';':_ 'c' ;;'-? ' '!...'-r:( 'f'.-:'.j; l.:. '.1...:;{//. :; \' ::-.':l:).::r.:r :;;;l;.!.tl; 1\:;:.';\f11fd.' Secton l. NTRODCTON j 1. j - '\ 11!? ckgrond n late 1962 tlle constrcton of'the Brrswck Rver Tranng Valls as completed by the New Soth \'ales Department of Pblc Works. 111eselvalls ere blt on both sdes of the Brnswck Rver otlet as an attempt to mprove navgaton for the fshng vessels operatng from the town of Brnswck Heads; tllr locaton s s!lown on fg. la. The Nalls are blt of large basalt bolder (dameter to 2 metres) '.and fll;. the sothern wal extends 411 metres. seaward from the prevos foredne n a slghtly. crved algnment approxmately perpendclar to the shore. \. () <'e. \: t.; \ Tle effect of the walls on coastal processes locally s e.. /. central to ths report. Clearly the wa) 1 s act here as fl. (lr 'll jmpct!)cohle- groyne. blockng or dlmmjng...]oral d.:f!.. Both here :l1d at the sma ller tranng walls controllng the moth of the Mooball Creek at Pottsvlle a Hedge of. \ ' an:l ha accll ate? at the sothern s?e of the walls./ lndlcatlng a net drlft to the north. fns drlft of sedment tolvards the north has been observed at many other locatons on the Far North'coast of New Soth Wales and has been careflly docmented at the Qeensland Gold Coast by the Delft Hydralcs Laboratory (Delft'197) and the Qeensland Beach Protecton Athorty (e.g. Patterson and Robnson 1975)..c-; ';;_ j'6l Between the constrcton of the tranng walls n 1962 and the hydrographc srvey made by the Department of Pblc h'orks n October 1964 fg. 1 b the sand trap formed by the sothern wall had flled p. The sx-fathom sobath on ths lwp ndcates the corse of renewed lttoral drft past the moth of the r:ver. T1e movement of s:md ndobtedly contnes today along the rver moth bar whch has proved a danger to local fshermen. 12. The Problem ' The prpose of ths report s to examne the effect of the Brnsl'ckR ver Tranng Walls on eros on and accreton at nearby beaches bt partclarly to the north along the foreshore of NC' Brghton: and Golden 'Sands Estate. Althogh coastal eroson has occrred at other localtes n recent yers Stcl1 as Byron Bay and Gold Coast Cty t s the contenton of the New Brghton Progress Assocaton that at least part 'of the d:lnage at the foreshore. of ther vllage s de to the effects of the tranng walls. n order to test tl1e contenton that eroson at New Bghton s exce]2tonal t s necessary to compare change here wth change t other local beaches l'hch cold not be affected by the walls. For ths reason a coastal nt s defned n

6 . : M l. 1 C!: ' L r -? b rs ;- Secton 1 page 2. secton 21 and measred evdence of beach change for ths nt s presented n the body of the report. There are many pblshed acconts of the effects of groyne-bldng on open coasts wth marked lttoral drft n other parts of the world. Some of these are mentoned n Appendx B. These reports nambgosly sho\ that accreton may be expected on the pdrft sde of a groyne and eroson on the downdrft sde. New Brghton les approxmately between 2 and 3y klometers downdrft of the Brnswck Heads Tranng Walls. Some of the eroson has ndobtedly relted odhe walls the problem s the_magntde of ths_l.o.5.sand how m L!])._:Ef.cts_<?_.!!.@.!1? are alter_at!!. no:_t along the coast frqw-zonstrcton a t.. d...

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8 .. \.;.): ; : -. :. ''.; ) 1 \ l' :'l : ::.t.! '.' ':.' : ;' :..... {-.... '. '-.:....:. \' '.-.t. [j. Secton 2. Physcal Settng r '1 tr a B ' - H f :; ' m [ B : Hastngs Pont to Cape Byron as a coastal nt. The coastal 'nt' or system descrbed here les between the headlands of Hastngs Pont n the north and Cape Byron n the soth (fg.la.). These headlands are otcrops of resstant Palae'ozoc sedmentary and metamorphc rock; they may be vewed as fxed ponts of the coast compartvely lthe affected by short-term flctatons of \nd or wave clmate. Between the headlands the coastlne conssts of a beach of medm to fne qartzose sands. Mnor sold rock otcrops do occr at the beach notably at Black Rock and at the north sde of Brnswck Rver entrance'; none of these otcrops are of sffcent magntde to'exert'an effect on the algnment of the beach. The beach s backed by a lne or lnes of dnes sally less than 1 metres n wdth. Between Pottsvlle and Hastngs Pont at the northern end of the embayment the dnes are qte massve beng 3 metres de and over 12 metres hgh. These dmensons declne towards Wooyng where the hghest dnes are 1 metres and abot 8 metres wde. At Golden Sands jst north of New Brghton t;he dne has declned to a sngle lne 4 metres hgh and only 15 metres across. Nelv Brghton tself s blt on hgher dnes reachng 5 to 8 metres and 15 metres across. For a dstance of abot half a klometre soth of New Brghton the dne has been compleely eroded bt s present agan jst north of the rver. The dnes are massve mmedately soth of the Brnswck tranng wall? narrowng gradally to abot 7 metres wde and 8 metres wde approachng Byron Bay. LandlVard of the lne of dnes s a low swampy -' area parallel to the coast. Soth of Brnswck' Heads ths s a corrdor of varable wdth between the coastal dnes descrbed above 'and the sand rdges of the nner Barrer shown on fg.2a. and descrbed n secton 22. belmv. North of Brnswck Heads the coastal swamps contne nland behnd the dne n a seres 'of embayments shmm on fgre 2a. Aeral photography shows no sand rdges n the swamp here'; excavatons by Prncess Propertes between New Brghton and Wooyng have revealed estarne mds and sands except at the nland permeter of the swamp vhere s'omebeach po.!:s.. ar:e.. f1:'nd. The proxmty and parallelsm of the nner Barrer to the man rampart of the coastal dnes n the sothern half of the embayment sggest that the nner Barrer may make p the'core of the coastal dne here. Ths s not spported by the sand rock otcrops whch are soft and plable and lght

9 ;;::.::':;'1::;;\/ ;{ttft' 11t- 1;sl..... :....\'? : -.!;!.t.'! L D w 'l' P '- g 8 E...' O ' t! S t g. o Secton 2 pa'ge 2. brol\'tl n color appearng to be a Recent formaton. Before Febrary 1974 the man lne of dnes was protected by a small foredne accmlaton whch was beng actvely colonsed by spnfex gras's; ths foredne was 1 to 2 metres hgh and p to 1 metres wde except for the 4 klometres soth of Brtmswck Heads \here very mch wder accmlatons were seen. Except at ths last locaton the fore dne was completely eroded drng cyclone Pam. The general cross-secton form of the dnes s shown by fg.2.b. The plan-shape of the sand beach bet\eer Cape Byron and Hastngs Pont s a shal1w embayment -rvng more sharply at the sothern end whch gves the shape of the Greek letter zeta (Hallgan 197) or a half-heart (Slvester 196). As sch the embayment s one of a seres of 'zeta-crved bays' along the coast' of S.E. Astrala (Langford-Smth and Thorn 1969).. ' t has been shown general1y (Daves 1957; Sl vester 196) that bays of ths shape have developed as an eqlbrm form n response to the oblqe approach of ' the domnent swell. (The persstence of ths plan form s also. shown locally by the parallelsm of the Plestocene nner Barrer dne rdges to the modern beach: see secton' 22. below and fg.2a.). A nmber of ndvdal stdes (e.g. Wrght 197) have shown that N.S.'. beaches are adjsted to the refracted plan of the domnant Soth-Easterly swell. n other words the plan form of the bay nder stdy appears to be an eqlbrm one n as far as t s adjsted to the form of the constrctve Soth-Easterly as modfed by nearshore sbmarne topography. The zeta-crve between Hastngs Pont and Cape Byron s one of the longest on the soth-east Astralan coast beng a 23-mle beach. The headlands whch mark the ends of the bay determne the algnment of the coast and the aspect of the beach bt they do not appear to lmt the lttoral drft of sand. Ths s nferred for the fol1owng reasons. () The weather records (see secton 24. below) and the accmlaton of sand at the tranng wal1s show a marked ne drft to the north bt there s no sgnfcant long-term accmlaton of sand at the northern' end of the bay. The sb-srface component of ths crrent as measred by Delft (197) show varable veloctes reachng a maxmm of '.:.-:::...

10 ;;;;'::'. ::..:.. /.)'::::;';;';;:::;t;f'- -; '/'; /7 L; l>..:4 '..' r.g- o/' 'P o (\ r. '!:..- '.' ':) -P{S BY-. B9 1 O 9OO\ ' l}4m):)\ll S 16 16:117': '... () t :'... '.. ; ':. '. ry 8 t\.} # L. W.....: Dry at '.. 3Y{: ; y:r4!b:: 1 '' 12'2Y:'O'B 14 'S : r<:. 'R.... r R R.... b'7.' 7 2 Y 7 Y 2 S 8' 9Yc \O 41 O?t;.O A.1 na 1'2'tz 13 Y 214Y: : :.EY1'S' 'S 'j\'.t'f>? 7}1 8Ỵ l 9Y.. '. 14 '. '. '.. 9}4loYz r Y414 p. \ '- ' ld Y 2 '. 4'/-.5 8Y 1' t 1Y212 2\12:'2 1 't:.. '.'. \:. \et..8y41 2v:2).d2 \': ;... ' \.'.'\.; 1 ' --. : 6.. fg1])'> V Extract fro;n 3 ' / 6 ; Department of '.' '.. Pblc \'orks hy- \'. : drographc chart; October 1974

11 L _.. :.. -.1(;.'...;.-'.... :-:.!.:::.;. ::.:.... ':.;.. :...:. '.. '::.. '/.'.... ';'(:. :. ;.{;:. ;... l w Secton'2 page 3. ': d '. w W H w ; l /' /... : :; 1/ : ' : approxm<.tely 1ft. per second from ( ()! tme to tme. Pblshed laboratory experments (Sndborg 1956) sggest: that sch veloctes wold be ncompetent to entran qartz' sand.24 to.3 mm. sch as s fond at local beaches. There remans the possblty ' that overhead passage of waves mght ' case movement 6f grans on the sea bed otsde the zone of lttoral drft sffcent to combne wth the Coast crrent to case dsplacement. Ths reol)ans_a.. speclaton however and an n1.tkely possblty. Kng (1972 p:'25-9) con.cldes that movement s sally extremely slow n depths greater than 4 fathoms and nlkely beyond 25 fathoms. Local fshermen report encoterng the sothward crrent no nearer to the coast ' than the 2 fathom lne. There wold appear to be strong geologcal nference'for the long term movement of sand along the north N.S.W. and soth Qeensland coas'ts' becase of the consderable accmlatons of sand at Stradbroke and Moreton s land (Thorn.1974). Looked at n a shorter tme scale modern estmates of sand accmlaton of several mllon cbc yards at Letta Spt (mmedately soth of the Tweed Rver moth) and very rapd northerly drft at the Gold Coast (Delft 197) shows ths phenomenon contnes to-day. } ff. '-' w.j \' \' S A E3 To stll@arse the above secton brefly. t s sggested that the coast from Byron Bay to Hastngs Pont s convenent for the stdy of eroson at Nelv Brghton snce coastal algnment s controlled by the poston of these headlands. Beach plan betleen these fxed ponts has adjsted to the domnant Soth-Easterly swell and as one of a seres of zeta-crve bays appears to be an eqlbrm form. 22. Geomorphologcal Hstory The geomorphologcal evolton of the New Soth Wales coast has been the sbj ect of consderable research effort. Al thogh many problems awat deep-drllng and sand trace nvestgaton the otlne of the development of the coastal landforms may be.. regarded as generally establshed. 't has been smmarsed by Langford-Smth and Thom. (1969) ; '1

12 .: ;!....:. A..: '.'f'' '.j -:: ;..... :; /.' :tf:. of.....j...r.'*- _... at.. ' g Secton 2 page 4. r g. : :!. : 1 r '.. j ( 1 ) 1 The whole coast s bascally a sbmerged one drowned by the Post-glacal rse n sea level. t conssts of a seres of embayments and headlands; where the coast s of moderate or.sbded relef the embayments are o'cctped by bay barrers backed by lagoons or swamps. A doble barrer system of sand rdges has been fond n many embayments. Where ths s flly developed t comprses a landward nner 'Barrer and a seaward Oter Barrer sally separated by a lagoon or s\amp. The nner Barrer s charactersed by a sbded rdge-swale topography wth a relef of p t'o 2 metres and wth a rdge spacng of greater than abot 9 metres. On the Oter Barrer the rdge forms are more prononced where the local relef often exceeds 12 metres and rdge spacng s sally closer than 9 metres.. On the Md-north Coast Den Exter (1974) has reported another' barrer; a gravel Pror barrer n bay-head locatons landward of the nner Barrer. n the area we are concerned wth here only the nner Barrer has been dentfed: ts morphology s clearly vsble on all the seres of avalable aeral photographs and ts locaton s shown on fg.2a. Frther confrmaton of the' dentty of these rdges comes from the otcrop of hard dark mpermeable sandrock n the banks of the Brnswck Man and Soth Arm Rvers where these ct throgh the rdges. Ths sandrock formaton s commonly fond nderlyng the nner Barrer at other locatons. Whle the nner Barrer s fond n the two embayments of low-lyng badly draned land to the soth of Brnswck Heads t s not fond north of that pont to Hastngs Pont. 'The Oter Barrer has not been dentfed n the stdy area althogh t s fond mmedately north at' Cdgen Beach. The establshed explanaton of the Oter Barrer s that t s a Hoocens sand nt whch developed follolng the Post-glacal rse n sea level. lost recent dates for the Oter B'arrer sg'gest 't began to accmlate once sea-level rose to ts present elevaton abot 6 yearsb.p. and accreted rapdly ntl abot 3' years ago (Thom ' 1974). n ths perod mch sand \as avalable n the offshore zone. Drng the perod of accmlaton of the Oter Barrer t appears that the flooded embayments of the N.S.'. coast acted as sedlment traps n the lttoral transport system.. The extent of accmlaton wold depend pon sedment avalablty local lttoral crrents and offshore topography as well as the general algnment of the embayment. n the embayment nder stdy t s reasonable to sppose that sand was avalable for Oter Barrer constrcton snce ths featre s preserved n the small emba)ent of Cdgen Beach

13 . Secton2 page S. ;:t C '... r - ;... ' 14 ' M ' v c' ll W. ;.' B mmedately to the north. t s lkely that the large sze of the embayment has allowed rapd lttoral drft and t has not acted as an effectve sedment trap. Here t appears that the Oter Barrer was ethe;r removed as rapdly 'as t accreted p to 3 B.P. or'sbseqently. Alternatvely sedments of Oter Barrer age cold have by-passed the embayment whch was already flled to plan eqlbrm condtons by mley' Barrer sand. Snce 3 B.P. t appears that the accmlaton of coastal barrers n N.S.W has ceased wth the dmnshment of spples from offshore and from rvers. Thorn (1974) ponts ot that today accreton (other than n the short-term) 's seen at very few ponts along the coast. At rver estares the domnant movement of sand s nto the moth. Ths spply of sand except by means of the eroson of dne storage has fallen. n many northern hemsphere locatons there s evdence of a slght contemporary rse of sea level(eg Kng 1974 pp ) and ths may well be a case of the world-wde trend 'towards coastal eroson. Ths apparently estatc. rse s not sbstantated by East Astralan evdence (dscssed n Thorn 1974) and therefore remans only a possblty n explanng general eroson along the New Soth Wales' coast. ' W thn the g'eologc context otlned above t wold be expected that coastal eroson wold predomnate. Ths cold not be'expected to be a steady process bt a seres of advances and retreats at a varety of tme scales: ' ndvdal storms followed by recovery stormy seasons folloled by a year or two of recovery. The process of eroson s ths an nsdos one and the process of separatng a longterm trend 'from a short term cycle comparable n dffclty to analysng clmatc change. n ths context hstorc records of coastal change become mportant snce changes over a few months or even a year may be temporary and msleadng. From the pblshed works and from local evdence of geomorphologcal hs tory \e may conclde:- (a) (b) Eroson appears to be general along the coast of S.E. Astrala and ths agrees wth the trend of the last 3 years. n the stdy area ths trend s reflected by the absence of an Oter Barrer a formaton whch n many other low embayments of the N.S.W. coast marks a perod x

14 :' M t. - Secton 2 page Tdes of accreton 6 to 3 BC. t s also reflected n the loss of 5 to SO metres of land n the last 1 years sholm by the hstorcal record. X.. -- lr.';. '. : 1! ;;'1. n the Brnswck Heads area the tdal cycle s sem-drnal and shows strong neqalty. Dfferences between hgh and low tdes are freqently of the order of 1. 3m and O.7m on anyone day althogh ths may vary consderably. At 'Brnswck Rver entrance drng the Department of Pblc lorks gagngs of the lowest Sprng tdes were :at 'the level of ndan Sprng Low Water and the hghest 1. 72m. (5.64') above that datm. 'Drn'g the concdence ofsyzgy and pergee n Febrary 1974 a tdal range of 1. 9m. was estmated: ths s lkely to be the hghest astronomc tde the area cold expect ths centry. Perhaps more sgnfcant 'for the topc of ths report' tde levels may vary npredctably de to storm srge. Drng the offshore passage of Tropcal CY'clone Pam n Febrary 1974 a 'srge of approxmately half a metre was estmated (Caton 1975) a fgre n close conformty wth an east coast srvey of tdal levels ndertaken for the Qeensland government (Hopley 1975). Ca'clatons of a lkely srge magntde n the event of a severe cyclone approachng the coast at ths pont sng the emprc formlae of Connor Kraft and Harrs (1957) sggest a srge of 1.5 metres cold well occr. 'At sch a tme accelerated eroson and coastal floodng wold be expected to occr; drng the passage of Pam eroson occrred arond the whole of the bay except the north-facng bay sheltered by Cape Byron. Flood waters nndated the more low-lyng coastal s\amps b'ehnd the dne bt feld observaton'by the ath.or on ths occason sggested thatstorm floodng does not n tself pose a threat to property at New Brghton 24. Waves No nstrmental.recordng of waves wthn the embayment has been carr'ed ot; thogh snce 1965'a daly record of deep water wave heghts and perods has been obtaned by the Qeensland Beach Portecton Athorty by means of a wave-rder! 1

15 .'... '. l.a :. [ - ';;::1. 8 < - '! q tj &5 M. - ' '1.!:l. 9 Secton 2 Page7. boy system at Soth Nobby 4 Mles to'the north. t wold be expected on general gronds that there wold be lttle dfference n' average deep-water wave condtons along 4 mles otopen coast; ths s confrmed by the close agreement between the reslts of wave recordng at Soth Nobby and at Moffat Beach a frthe'r 1 mles along the coast and dscssed n Gorlay (1973). Pblshed sgnfcant wave heghts for Soth Nobby (fg.'2c) show ths coast 'to have energetc cond to'ns at normal tmes (medan H = '1. 22m. (4 ft)) whle storms rase the sgnhcant wave heght to over 3.66m. (12 ft). Drng Tropcal Cyclone Pam (Caton 1975) and drng the easterly gales of ly 1973 t was c'lear that wave set'-p and storm srge were sffcent to completely cover beaches arond the embayment. Althogh the record of wave heghts s only a'valable over a short span of tme t does make clear that these two storms can be regarded as maj or events. The effects of the'se extreme events ere observed and recorded n detal and are reported n secton 32 below. Drecton of wave approach to the beach M...tne s mportant n two respects: t powers lttoral drft and also t ndcates the degree of exposre of the varos locatons and aspects along the beach. ' 'Pblshed records show the domnance of the sotherly component n wnd and wave drecton along ths part of the coast. Fgre 2.d.-A records ' sghtngs of ave drecton n the Tasman Sea ' (Marsden Sqare 48: 3 to 4 S. 145 to 18 E) 1953 to 1961 recorded n the Ocean Wave Statstcs of the Brtsh Natonal Physcal Laboratory (Hogben and Lmb 1967). Fgre 2. d. B sholvs wnd drectons n the mmedate coastal waters recorded by Dtch merchant vessels. Over the perod anary to September 1973 daly lyave drecton was estmated n 22!-z classes by the athor from the synoptc charts of the CommoD\ealth Brea of Meteorology sng the methods set ot n.s. Navy H.O. Pblcaton No. 63 (Person Nemann and ames 196). Over the same perod a daly wave energy ndex was obtaned from' the wave rde'r record sng: E = 41. H T '.

16 .'... :;::!' :. : ;'.... /.:. ''.. --t. t _ :'L_;.. w.. a. '. ' 'd 11 M... Secton 2 page 8. Where: - E = Wave energy n foot ponds per foot of ave crest. T = Wave perod n seconds; record. T from the wave z H = Wave heght n feet; mean wave heght was obtane'd from the H n the wave-rder Slg. record sng the standard converson table n Wega1(196S). Tlese two sets of nformaton \ere sed to constrct \'lave energy' vectors fgs. 2. e f g. for each tme perod between be'ach measrements (see secton. Tle drecton of wave movement was shown by the vector drecton the vector length ws determned by the wave energy ndex. 'The res1 tant s taken to nd'cate the mean drecton of wave power npt and a comparatve measre of ts magntde for each tme-span between beach measrements. For ths short rn of the vector calclatons the strong domnance of ave energy from Soth to East s clearly demonstrated. The comparatve domnance of ndvdal storms n the overall wave energy npt s llstrated by the one example whch occrred at ths tme: the gales of the' frst week of ly '. l - ' S L...

17 .. <:' : ' \;;;;:(. ':;:'T; <1.;.-:- <-.;. : 11:.:r!1:f ;;');/'.:' q HOljgs & 12 Po.nl 1 ( \ 5 K m. -.j 1.. A ]... :1 \ \ /' / / '\ ( ) \ \ -' ' H.\ 1) A.pllH1l1 of nne' Borrer :O( h d 1':.. llldwd of 1(')(.. 11 wrllp.\ t j l ((/olld 1 / r.) r ( '1.' ( p of 'l.' j 3.. ]! ) '_ \\1 \\\ \.:. 1\' \\\ \\\\ \\ \ \' C ope By ( n Fg.2a. Locaton of profles and some geomorphologcal featres.

18 y.? c 'l t n o - ; A Po loeo zoc roc k otcrop._-----._ _.---- dne foredne ' tret' and '. '.m ' 'W.. B nner Bafllel and dge 'j : '\:1 Brnswck 5_Arm R dne foledne..'wt l_.- _ fg.2.b. Generalsed cross-secton.sketch across coastal dnes.. A. locaton: Profle 7 north of tranng walls. B. locaton: Profle 5 soth of walls. ;.. t1 :.

19 . :::.: r -.. Hf';. '': =..:... ;-o.:t: '1#.:-:t 'f ' 'A... t:... (.:-j '..t<t.\ ::.. -t ; ' '.-' '-\ ::;'r!\! ;.'1/:: :... '''' '. r'. :.. '' t' o :'.!.'.. :- 1 '. ;. -. l l ll. <: - ::: <.: - l ::: l <:t ' 9 ' : ' '- o. {)5 1 >1 '5 / TME. A GVEN r '--.. Wve nlo:matfon :eco'rded ra n Agst 1968 to e 'November 1971 at 8 ste 4 1 /2 mles de east rom Brlegh n 155 t. 1 water.. e. g. WAVE HEGHT EXCEEDS 4. Oft. 5% OF THE TME r-... r r-. H.max. (est.)... r t '... r--... r... r '-.... r SGNFCANT WAVE ' HEGHT. (H.sg.) - r-.. '... r-... PERCENTAGE EXCEEDANCE GRAPH... r L 1_- '- _ N WAVE HEGHT (H. 59. or H. max.) S EXCEEDED f.< 4-< '-' +-' \11 oj.-< C) Q) r:\.en +-r-- en +-.-< C1l <ll :: \11 h h <ll +-' <ll +-' h oj p.. \11 +-'''''.e.. lc1l <ll.e.e+-'.o <ll h > c). oj Ol.. 4-< jg\.....;.. -'n ::'A.::.':...'] ::-'::1 ::. :tdl f.n g!:!:.! :?'l''''l W:/l.. ::::E ql!!) -' c -'

20 ''. 1. '... : '..)' -.l t t c M ; A M <> N '' ').q 11 e \ \\ '1 t. ;>;>a '1 l Y v) 1 '. -. t3 w. <> F. t] B ':'! ;. ':':f fg.2.d. Wave drectons from pblshed sorces: A. All reported wave drecton sghtngs n the Tasman Sea from Hogben and Lmb (1967). B. Wave drecton sghtns n adjacent coastal waters by Dtch merchant vessels.

21 ;l{::::.\...: '.1 '!.....-:- ':.. ' ': :.; 11<:;:':'; : r ; '\\: '- ::;;\. ::X '; :.: T'. r' gt;';;:'-?/{:.;:. '!:!'{::'; ;:':' '. ':.: _t '. '.\/..;. t... '! '.>c ;..... >\1.' (:':. s.'..ool c/--no..h'. L '\ fg. 2. e. Wave vectors.

22 L \ r ;. f \ '.1 \ '! -

23 O) ''';... ':'.; t.. ':r..; :... :;.-;.:.. : '. '(... '...:.. ' \.' '- ' ' - - Gl ' a. x... ' c ;..... :::.. ; ':. ' :-. :-:.:'! ''. :'::'.:f'.' ;:wt:... ';;! a Xl ().. M <> > c M :::: <> N :l h... ll > - N O) - N ll ' '... :

24 ... '. t -... j.. Secton 3. BEACH PROFLES 31. ethods of Srvey Drng the perod anary 1973 to Febrary locatons between Cape Byron and Hastngs Pont were repeatedly srveyed n order to montor changes on the sb-aeral beach. Seventeen srveys were made at ths' tme. n September and October 1975 fve of these locatons on three occasons were re-srveyed by members of the New Brghton Progress Assocaton. These 12 profle locatons are located and nmbered on fg.2a. n Febrary 1974 an addtonal profle (A on fg 2a.) was srveyed twce; ths was also re-srveyed three tmes n September and October ;. ; \' All the srveys were made as straght lne traverses from a fxed peg on or behnd the dne to estmate stll water level at the tme of low tde. The profles were arranged n pars to offset the effect of short range flctatons along the beach sch as the movement of csps. Each p'rofle ran across the beach at rght-angles to the coastlne. The srveys n were made sng a telescopc aldade and stada rod; those n 1975 were accomplshed sng the method of Emery (1962). T1e frst seres of profles were calclated and drawn p by hand: the second set were drawn p and calclated by the Strt College compter: programme MA. OLD BEACH. B. NOV All the traverses made were less than 16 m. n length ' and never reqred more than one poston for the telescopc aldade t s thoght from the calclatons that the maxmm vertcal error 'over sch short straght traverses s always less than.3m. Ths error arses almost entrely becase of the practcal dffclty of estmatng stll water level at a hgh-energy. srf beach. Drng hand calclatons of reslts by desk calclator systematc checks were made for operator error n recordng or workng ot reslts. 32. For each profle the form of the beach was drawn p graphcally; also the area between state datm (ndan Sprng Low Water); a vertcal from the marker peg to state datm and the beach profle was calclated. Ths letter was sed as a measre of g;'ln or loss of sand to the sbaeral beach; these qa'nt tes are referred to as 'volmes' n c.metres per north-soth metre of beach. Reslts of Beach Proflng.'Y }j.....' The reslts of 'the beach proflng area smmarsed n tables A and B and n fgs. 3 b c d.. The graphcal plot of change of sand volmes aganst tme (Fg.3b) shows that the overall pattern of beach change s not a seasonal one bt a response to stormy or calm weather. Storms may occr at any tme of the year and as wold be expected.reslt n rapd lowerng and shortenng of the beaches. (See Caton 1975). Recovery drng qeter perods s more slow.

25 9 B H t! l3 ' 'j '. (' / 1-. ;.c- /1 j/ /. Secton 3 page 2. The graphcal plot of sand volmes anary 1973 to Febrary 1974 sggests broadly that profles 3 to '12 ' that s those profles wth a manly easterly component to ther aspect show consderable agreement n drecton and amont of change. Ths s broght ot most clearly 'n 'fgs.''7 c d and where the crves of the graph of sand volmes has been smoothed by takng a movng mean of three tems. Profles 1 and 2 located mmedately north of Cape Byron do not follow the common pattern. Profles 3 to 12 Tlere was a tendency for slght loss from profles 3 to 2 drng the second half of anary throgh Febrary and March; sgnfcant wave heght at ths tme freqently averaged more 'than 1.22 metres (4 feet). Recovery began n Aprl v th wave heghts of 1.1 metres (3.5 feet) and sand gan was most marked drng the frst week of May when wave heghts of 2 feet only were recorded. Most profles showed a slow gan drng ne ntl the storm of the frst' week of ly. Drng ths event H. vales ' wee n excess of 3.5 metre's (1 feet) for Slg. several days and on ly 7th were over 4.88 metres (16 feet) the hghest snce recordng began n Agst The enormos npt of energy nto the lttoral zone made by ths storm s llstrated by the length of the wave vector for theperod on fg. h. All profles 3 to 12 showed sharp loss at ths tme; ths loss was most marked at those locatons where the beaches were stocked above average wth sand at the tme. Followng the storm'of ly 1973 a perod of recovery followe'd' at most locatons arond the bay ntl md-november (srvey 14). Recovery vas mo'st rapd at profles 5 and 6.' ;./'soth of the tranng walls; whle atprofles and _ c'-:': ' located at Golden Sands Estate recovery was delayed' as. ' was the case at profle 12 Hastngs Pont. The delay of r recovery may be an effect of the walls as s dscssed below. / At the begnnng of anary 1974 most profles 2 to 12 were well stocked wth sand; a stormy perod' follolved whch reslted n consderable loss. n late anary and early Febrary the area was affected by the frnge of two cyclones: frst the weak Tropcal tyclonewanda n the second week of anary and then the very ntense Pam on Febrary 6th and 7th. Althogh wave heghts generated by Pam dd not exceed 3.7 metres (12 feet) n the coastal area the very hgh tdes at ths tme combned wth the rogh condtons to reslt n great damage to the dne and foreshore. And at New Brghton and Byron Bay damage to property. The calclated sand volmes at profles and 12 were the lowest n the perod srveyng as shown on fb. 3b.

26 r'... :.':fr..' :...'-;:c.. :\':.'.':';:.:/:.'. 1'A/1; t2(t:;t.;j{{z':.... 1'. t:::l '. W L a B.. 'l;!. j ' j -' Secton 3 page 3. \. ( (Tle other profles ere not srveyed on ths occason becase of the dffclt weather condtons). ' Tle sgnfcance of the narrowness of the lne of dnes mmedately north and soth of New Brghton.was clearly revealed by cyclone Pam. Normally n sch a storm the dne acts as a coastal defence absorbng the mpact of the fnal prsh of the storm aves. Drng the storm the dne was overtopped and breached by aves 'on both sdes of the vllage here the dnes were low and narrow. At these locatons the dnes conssted of a sngle lne of sand hlls poorly stablsed by spnfex. Near Golden Sands estate they stood 2 to 3 metres above the backshore and at the sothern end of New Brghton vllage they stood 1 to 2 metres above the backshore. The poor state of the dne here s a reslt of the falre of these beaches to accmlate sand over a perod of years. As was 'noted n secton 2) above the dnes at ths ste are narrower than at any other pont arond the embayment; t was only at these ponts that the storm breached the dne defence. Ths ths extreme event made clear the mportance of accreton of beaches drng qet weather and also the serosness of the New Brghton staton. t mght be added that the 'wave record reveals that Pam \'1as by no means the most severe event that ths area 'mght expect. An ntense cyclone at the' coast cold well rase a storm tde of eqal magntde and waves 2 to 3 feet hgher. Sch an event cold well remove the vestges of dnes on both sdes of the vllage and case frther property damage. The profles srveyed on and have not been n elded on the swnmary graphs as the tme nterval was too great bt they are lsted n table 2B. Tle averages from both sets of fgres are lsted below:- Averages of Profle Volmes n c.m. per m. Average Profle Average Net Change Nmber Sept. -Oct. '.. : ft :: t r j \ ' ' : :;1..'.. \\.\ : /4 < t t '. (.' l( ;'L.' \ \ C C ' \ 'jl e' ' 12 l5 rr / Nbl'''llC(.V/{ {'(/oo( (t{)l s f at Clearly the general trend of these reslts shows that the perod larch 1974 to September 1975 as one of recovery arond the embayment: 'all the averages except that of profle 7 are mch hgher. n the case of profle 6 pdrft of the Brnswck Tranng Walls the average for September/October 1975 was not only 2% hgher than the prevos average bt hgher than any pre\ros ndvdal vale throghot'the perod of srveyng.

27 .... '-. el.. ' t:] w r 6 - ' B! R ::1. W 6 '. -( ' ' '. t. '. ' c'..: Secton 3 page 4. DOmdrft of the tralnlng walls Profle 7 shows a slght fall n average profle volme. At ths locaton ths s becase of the lack of accmlaton of sand above hgh tde mark: the crest of the dne s lower n 1975 than prevosly and only a small fore dne has accmlated n front of t. Ths the readngs over a tme span of 2 years show the falre of the recovery of the beach downdrft of the walls n marked contrast to the rest of the embayment and especally the p.rofle pdrft of the walls. Whle n tself the smlarty of the tlvo fgres for profle 7 mght not appear mportant the record of earler stqrms llstrates the serosness of lack of accmlaton of sand on the backshore and dne drng sch qet 'petods. The dfference n development on opposte sdes of the ttanng walls s sholvn by the change n poston of the 'dlme face. mmedately north of 'New Brghton t was ct back 7 feet by Cyclone Pam and ths has not been recovered. pdrft of the valls the dne as trmmed back 5 feet by Pam bt has sbseqently ganed 1 feet (see fg. 2 e.). Ths over the perod of one year and 8 months t seems that the comparatve dsplacement of the dne face on ether sde of the tranng walls (l km to soth and 4! km' to the north) amonts to 12 feet. Profles 1 and 2 Fgs 2 bc d can be sed to sggest one frther facet of the lttoral system of the embayment. As was noted above the profles whch have a manly easterly component n ther aspect all tend to gan or lose sand at the same tme. 'HOvever the north' facng profles 1 and 2 'she 1 tered by the headland of Cape Byron behave qte dfferently. Whereas the east-facng beaches respond drectly to wave heght tendng to lose san9 when the deep water wave heghts are greater than 4 feet the reverse apples to the north-facng beaches. They showed ether no change or gan n heavy eather for example the frst week of ly 1973; whereas n the qeter condtons of November and December 1973 they lost sand. Ths featre of the profle record cannot be explaned even n part by a dfference n materal casng varyng adjstments to wave condtons. t s clear from the gran sze analyses (Appendx ) that mean gran szes here are vrtally the same as the rest of the embayment. t appears that the headland and the shallow vater to the north of t case severe dffra cton and re'fracton of waves leadng to extremely rapd onshore movement of materal drng heavy seas from the Soth East. t may well be that t s n sch condtons that sand from the soth moves arond Cape Byron. 33. The Effects of the Tranng Walls t wold be 'expected that f the tranng walls were havng an effect on the movement of sand n the lttoral zone that

28 '. ' :4 w r--.! v:t d!-1 Secton 3 page ' 34. ' ths wold be shown most clearly drng recovery of the beach after a perod of stormy weather. As Slvester (1959) has ponted ot the dverson of 'lttoral crrent nto deeper water by an obstrcton serves to accelerate the movement of sand past the zone downdrft snce the sand s retrned from deeper water frther alongshore.. Al thogh we wold expect sand to be broght ashore all along the beach drng calmer 'weather t wold be lkely that the accelerated northerly movement dcnvndrft of the walls wold case less to accmlate here. Sch an effectwold be most marked mmedatley north of the tranng walls and wold be alternated frther along the coast. ' (l' rled Tle profle 'srveys (Tables A and B) show the perod Febrary 1974 to September 1975 to beone of recovery for the embayment generally. As the averaged fgres on page 4 of ths secton show most clearly ony profle 7 at New Brghton shows no gan. rom_!l1?gerheral consderatons above ths appears to be strong crcmstanfal-evdemce of the walls modfyng lttoral drft n sch a way as to affect the areas downdrft for some \ay along the coast. The mpovershment to the north of the ' Brnswck Heads s n marked contrast to the locaton of greatest gan: pdrft of the walls at profle 6. Smmary ' E:rll () Beach profles at 12 locatons arond the bay were measred on 18 occasons n the perod anary 1973 to Febrary Some of the profles were re-srveyed three tmes n September and October : 1<'... ; H.t rn () The profles wth a manly east-facng orentaton (profles 3 to 12) tended to change together n response to the varaton n wave heght. () f'ol to October 1975 was a perod of recovery for the beaches after a stormy perod clmnatng n Pam n early n the perod of recovery only the New Brghton part of the embayment faled to show gan. t s sggested that ths s de to more rapd lttoral drft north of the walls as well as 'contned accreton for some dstance pdrft of the strctres. '- tlj 1 'j

29 . -' Secton 3 page 6..') : l; :;.--; l g... a F'l. Q m.';j l g.1. :; Profle Nwnber a 111. '/! /! :-! Table A Sand Volwnes at profles n c.metres per metre of beach face; 1973/4 seres srveyed wth.. telescopc aldade v' '; ' _ \ \ 9 ' : 151 ' : \ L313 31S' [ \\ ://;'.'... ) \ :. [.! -:' Srvey Dates Tme Date 1112/1/73 331/1 1516/2 12/3 1617/3 Tme : 'l- \. ** (see below) 12 m f not average becase tme span consderab] longer 115. : 1:- :.\ ' ** l-lean -: drng. Sl.g l!. preceedlng perod. Date 67/4 12/5 1314/5. ':: ; 12/6 3/6 1/7 1112/7 Tme Date 12 45/ / / /1/ /1 17 5/2 17a 7/2 : '!.: L!!

30 1-.' ' '.{.... ' ;;!...;- l: 1 : m r.1.. t Secton 3 page 8. Table B. P 2 r 6 f e 12 N rn b e r Sand volmes at profles n c. metres per metre of.beach face; 1975 seres srveyed sng Emery's method. Date 23 Sept. 3. Sept; 7 Oct \) -

31 .:' AN EB MAR APRL ' MAY.--- LY AG SEP1 OCT NOV. /' DEC AN FE B ' a 2 loa ' '--...' ' /'-'. - --:::--- : m ().' 2 11) a 2 loa a c: z 3 m... --:-... : 2')... j j..--./_-./ - '- --=. ' --==::.' == ::------=-==-'-=----==::::..- a '-.-' ---;--'-' '--' ' ' ' ' '---'-- /'-- ' ' ' /' \_. - '-.-Q c--- : - '... v m. r. 3

32 TM E '-'\ :::: rn - : rn en 2 l 1() o --== ! '':- _a -- -'-' V p7.. '. 2 1 o 2 1 o. _ :::::.. --' -:/_.--:::. -.:: '--:--'.. /---' :----==..:::= : =--:::::-.:- ( ==--: '---=--- - '--' -=----= o 3 2 a A =---. -= A A

33 1'<> w 1 D T E :;; :P :;; O RvCy :P ' Z 1 ; s ' o rt ::r (j) - n c: ' < (j) ' }- + t- o + t- + o - t- o + + }- t ----== = : '.f.:.:;.. ::;> >... ':. ; '. \.'. 1 '; '!:;:\:tr:: '->-.' ' 'E;'.-. --c ' w - ' NMBER T ' A : ' - l>. '- SRVEY '.':;:' f'!t:. l' r '-' ::.'

34 '.;' - j. ' -.' -. lj:f[;b;/{;t1? ; 't;j ;L :--;- --- r't'l' - ' : r- t M > < 5 : (: / L L L L (j-+o-+o- < 4 < 3 < 2.\. - - Fg.3.d. Sand volmes x tme smoothed crves.

35 '. \ '... C ' 1. ' ; 1 l:.. N m M ff.' ; 'j l =- -- (' Secton 4'. ';SEACH CHANGES FROM OOCENTARY AND PHOTOGRAPHC._ -. _./ SORCES.4 l.. n ths secton an attempt s made to place.the very recent eroson at New Brghton wthn the perspectve of coastal change as shown by. docmentary evdence. Agan evdence for the nt of coastlne from Byron Bay to Hastngs Pont 's consdered. Ths s attempted n order to assess the extent to hch eroson at New Brghton has been accelerated by the constrcton of the tranng walls at. Brnswck Heads. 42. The Character and Relablty of the Data.The sorces conslted are lsted n Table at the end of ths secton. The nmbers n the lst are sed as a key to the ponts plotted n fgs. 3c 3d and 3e. 'The majorty of the sorces fall nto 3 grops: l. hydrographc charts 2. property and mnng lease plans 3. aeral photographs From these sorces the poston of the ct face of the dne. backng the beach has been extracted. Ths s marked as a scarp by hachrng on many of the older plans' and s of corse clearly vsble on the aeral photographs. The one excepton to. ths procedre was. the plan of ll3 (sorce 22) whch from Nel Brghton to Hastngs Pont marks Low Water. and sometmes Hgh l'a ter postons on the beach. Becase of the pacty of nformaton north of Wooyng these marks were sed to estmate the poston of the dne n n the case of D fg. 3c (Black Rock) ths may well be sspect. The rocks protect the foreshore here and today the beach s 'exceptonally wde. The poston of the low tde mark 'devates mch more from the general local algnment than does the lne of the dnes. The estmated poston. of the dne n 1956 cold ell have been consderably frther land vard than appears from the estmated poston on graph D and the loss snce ths tme mch less thm appears from the dagram.. The base map sed for plottng was the : 25 seres of the N.S.W. Lands Department. The poston of the face of the dne was measred on the sorce r relaton to some promnent permanent pont dentfable on both the sorce and the base map. Ths was sally a road jncton; althogh bldngs rver jnctons and the hll top mmedately.north of the Brnswck rver moth were also.sed. n the graphs sbseqently plotted at ntervals along the coast the poston of the dne n the 1973 photographs \Vas sed as the zero lne on the graph as ths was the last complete coverage along ths part of the coast. Conversons for scale were made sng representatve fractons. The scale of the vertcal. aeral photographs was calclated sng the procedre otlned n the Amercan Socety of Photogrammetry Manal (p.134).

36 . \ '....:. 'MO ' -'- - ;/ Q 1 t m. ' :: :' B..'.. ' lj tl) ; ;1 :.. secton 4 page 2. Representatve Fracton _ of photograph - Focal length of camera Heght of the arcraft Ths was checked by measrement of known dstances on the photographs. Clearly the scale of the sorces (see Table 1) and the. natre of the procedre make operator error lkely. t s sggested however that ths s mnnal on two conts. Frstly the broad agreement between the reslts at dfferent ponts along the coast. Secondly n the fve mles north of the Brnswck Rver moth the Prncess Propertes hstorcal stdy was avalable as a cross-check: concrrence of reslts was fond. The natre of short-term change n the POSl tln of the dne face has an mportant bearng on the relablty of the data llstrated n' fgs. 3c - h. Wthn. the short term of one or two years the poston of the dne face may vary consderably: where one pont n tme over say ten years s selected by the hstorcal record an erroneos' mpresson may be gven. For example f Commander Howard's srvey of Byron Bay had been ndertaken mnedately after a seaon of storms the poston of the dne face mght \vell be say 1 metres landward of the prevos poston or that acheved after a perod of recovery. Agan ths s llstrated by the varabl ty at' Byron' Bay shown at graph Q (fg.'3e). Here over the perod ' a retreat of 2 metres over one year s recovered the followng year. VelVed n ths context the graphs n fgs. 3c - e. consst ndvdal'ly of only a lne wthn a possble envelope of change whch mght be p to ± 2 metres on ether sde of the lne sholvn dependng on the short-term varaton mmedately precedng the date of the srveyor photography. Whle ths makes :1 general conclsons below possble' t also makes detaled conclsons dffclt to sstan. 43. Docmentary and Photographc Coverage nevtably the hstorcal record s neven n coverage n space and tme. The late 19th centry hydrographc charts were natrally cons trcted wth a vew to the needs of nshore navgaton at the two prncpal ponts of settlement and at Wooyng and at Ne\ -Brghton sbdvson tookplae manly n the perod 1889 to 1921 \'hch s recorded n the plans held by the Lands Department. 'nfortnately smlar plans at the extreme northern end of the bay at Pottsvlle and Hastngs Pont dd not ndcate the poston of the frontal dne or hgh water mark. After 1921 there s a clear gap n the record ntl the Lands' vertcal aeral coverage as far north as New Brghton n May of1947. From ths date onwards records are more freqent.' The most valable were the vertcal aeral photographs of 1958 (sothern half) and 1962 (northern half) also the complete coverage of 1971 and See fg.3b.

37 F m m \ ' n. :.- W 1- W '.. fa ; - - c \ '. '\..;' secton 4 page 3. Tlle long gap from 1921 to 1947 means that even for vell docmented locatons sch as the Brnswck rver moth (fg. 3d K) the mddle secton of the lne of the graph s less than satsfactory. 44. Dscsson of the Reslts of the Hstorcal Search The reslts of the hstorcal' search are smmarsed n fgs. 3a and 3c to h. Overall the trend has been one of erosln: where records exst for 189 the poston of the frontal dne as everywhere seaward of the present lne of dnes. ' At Byron Bay Brnswck Heads and New Brghton ths loss exceeded7 metres. Mch lesser amonts of loss were fond wthn }yronb'!y (fg. 3e graph R) and mmedately soth of l'ooy'lng (fg. 3c. graph F). Ths may be explaned at Byr'on Bay by the change n orentaton of the beach n the c'rve n the extreme sothern end of the bay. Poston R at Mddleton Street Byron Bay Town s the most sotherly of the postons where hstorc change has been examned. T1e modern bea'ch profle srvey (see secton 22) showed that the north-facng beach between the town and Cape Byron sally responded q t'e dfferently to the rest of the Bay to changng weather condtons beng protected by Cape Byron. T1e other locaton of smaller 1'ss soth of Wooyng s ot of agreement wth the nformaton at neghborng ponts E G H and 1. Pont E at Wooyng s mmedately adjacent. Three explanatons are possble for ths dscrepancy: - (a) (b)' (c) The plan of porton 64 (sorce 7 table 1) s erroneos a'nd the plan of porton 75 s correct. The poston of the face of the dne n 1889 s frther sealvard than appears from sorce F. Sorce 15 at Wooytmg s erroneos and sorce 7 s correct: the poston of the frontal dne at Wooyng was not as far sealard as appears from graph E. Ths rases the nterestng possblty that eroson has been mch less marked n the ' northern half of the bay; that s that part of the bay wh ch generally has the more mass've dne barrer. nfortnately ths possbltys not confrmed becase of the lack of records north of Wooyng. W thn the lmts sggested n secton 32 above both' sorces 7 and 15 are correct. Ths there was accreton at ths part of the coast between 1889 and 1914 and sbseqent loss. The last possblty s most consstent wth regard to the docmentary evdence; bt s not consstent wth the generally nform' chage shown along the bay by the modern