I I I BANK EROSION STUDY I I I I I I I I I I I :~ I

I ~ . ~ PUBliC I · ---.. WORKS ~ .., I Council EstuarIes Be environment Polley Branch t II I; TOlllaga River I Bank Erosion Study I I I I I I I

"I II t I I, REPORf No. 93031 ISBN No. 0731010035 I November 1994 I I I

I FOREWORD ErosIOn of the TomakIn SpIt IS perpetual Presently there IS concern by Eurobodalla J; CouncIl and local resIdents that the Tomaga RIver may break through the SPIt Into Broulee Bay at TomakIn Beach I ThIS report examInes the hlstoncal changes to the Tomaga RIver bank from 1962 to 1993 The extent and state of erOSIOn has been analysed and future trends predIcted enablIng the development of management optIOns and to gIve Eurobodalla CouncIl I an IndIcatIOn of when "breakout" may occur

The study has been undertaken by the NSW PublIc Works, Estuary Management I SectIOn for Eurobodalla CouncIl as part of ItS role In proVIdIng techmcal assIstance and to develop engIneerIng SolutIons to assIst CouncIls In managIng estuary r problems ThIS report was prepared by the Estuary Management SectIon, Estuanes and 'I EnvIronment PolIcy Branch, McKell BUIldIng, 2-24 Rawson Place, I I I

"I 11 t I I I I I t I SUMMARY The study area concentrates on Tomakm Beach sand SpIt approxImately 400m north , of the entrance to the Tomaga RIver Tomakm Residents & Ratepayers AssociatIOn and Eurobodalla Council have expressed concern about the ongomg erosIOn of the Tomakm SPit (see AppendIx A for correspondence) Based on photogrammetnc I analysIs of histoncal aenal photography the Spit has receded up to 20m m places over the past 30 years Consequently there IS the threat of the nver breakmg through II the SPit mto Broulee Bay at some time m the future ThiS mvestlgatIOn has been camed out to examme the rate of erOSIOn of the SPit and to develop management optIOns to protect the SPit from a possible future "breakout" I Careful consIderatIOn has been gIven to the surroundmg environment and the processes causmg the Spit to erode I The study mvestIgation mvolved photogrammetnc analysIs of the SPIt over a 31 year penod between 1962 to 1993 and extensIve sedIment sampling and testmg I The scarp on the outer bend of Tomaga River was estimated to have receded by up to 20m m places at varymg rates rangmg from 0 3 to 1 3 metres/year (see Figure 2.9) I The strong curvature of the nver near the eroSIOn site causes a concentratIOn of flow agamst the outsIde of the bend, resultmg m mcreased velOCities ThIS m tum leads to mcreased sedIment carrymg capacity causmg erosIOn of the outside bend Sediment Ii can be moved both up and downstream or across nver onto the shoals on the outsIde bend ThiS IS an ongomg process and IS attnbutable to natural nver mIgratIOn FIgure I 3.2 shows the conceptual sedIment flowpaths wlthm the study area Although there IS no ImmedIate threat of "breakout", should It be allowed to occur It IS likely that the eXlstmg entrance would shoal thereby affectmg boatmg naVIgatIOn , and the permIssIve occupancIes along the waterfront at Mossy Pomt The "breakout" would also result m the loss of Telecom commUnICatIOn servIces and create an hydraulically unstable second entrance It IS unlikely that a breakthrough would ever I be allowed to happen, and If It were ever lIkely, then corrective actIOn may be taken to prevent It

I; To determme sedIment clasSIfIcatIOn throughout the study area, sedIment sampling was camed out on the 14th July, 1993 ExtenSive samplmg of the Tomakm SPIt and the adjacent Tomaga River entrance shoals were conducted CompatIbIlity of these t sediments would determme how successful "Sand Nounshment" of the SPIt would be as a soft approach m the management of the eroSIOn

I From the mveStIgatIOn three management optIOns were IdentIfied I Cl Option A - "Do Nothmg" Cl Option B - Sand Nourzshment and I Cl Option C - Placed Rock The management optIOns are dIscussed m detail m SectIOn 4 With the cost estimates set out III AppendIx C Table SI summaries the optIOns and hIghlights some I advantages and dIsadvantages associated WIth each optIOn I II I

Option A - "Do Nothmg" simply means that no bank protectIOn works be carned out I and the erosIOn allowed to contInue Usmg hlstoncal nver behavIOur as an mdlcator, It IS predicted that the SPit may naturally "breakout" In approximately 30 years time i II ThiS IS an estimate based on average past behavIOUr. The frequency and size of nver floods and storm events over thiS penod may alter the erosIOn process Based on hlstoncal InformatIOn there IS no Immediate threat of breakout through the SPit ,I However, erosIOn IS expected to contInue with the consequent loss of sand from the dunes

II Option B - Sand NouTlshment mvolves the dredgmg of some 30,OOOm3 of compatible sand from the adjacent mner nver shoal, to restore the eroded scarp to that eXlstmg m 1962 ThiS Will create an approximate additIOnal 30 year buffer ThiS I optIOn has added advantages, as It Will blend Into the surroundIng environment, and the sediment on the adjacent shoal IS compatible to use for nounshIng the erodmg scarp The accesslblhty and abundance of the sand make It an attractive optIOn from I an envHonmental viewpoInt Through dredgIng the shoal, the OppOrtUllity anses to reshape the channel to Improve navigatIOn If protectIOn of the sand Spit IS to be undertaken, the sand nounshment optIOn IS recommended as the preferred short term I optIOn OngoIng mamtenance of noun shed sand Will be reqUIred to mamtam the buffer

I' Option C - Placed Rock reqUIres some 4,250 tonnes of placed rock which IS readily avaIlable from Pubhc Works Bodalla Quarry ThiS Will provide long term protectIOn to the sand Spit The disadvantages of usmg rock protectIOn are the Visual aesthetics I, of the rock wall compared With the natural enVHonment and the high capital cost up front Ongomg funds would also be needed to cover mamtenance of the structure m I the future

In the short term It IS recommended that counCil undertake remedial works to reduce II the nsk of a breakthrough In the foredune at ItS narrowest and most vulnerable pomt (Figure 2 5, profile No 6 ) ThiS would mclude fencmg and slgnpostmg of the ,I degraded area to discourage pedestnan traffic usmg It as a thoroughfare The mmor "blowout" could be topped up With fill sand and stablhsed With appropnate vegetation to reduce the potential for the nver to breakthrough Mmlmal disturbance I to the eXlstmg vegetation should be ensured dunng constructIOn of these works

Based on hlstoncal bank movements It IS estimated that It Will take up to IJ approximately 30 years before the Tomaga River breaks through the sand Spit In view of thiS estimate It IS suggested that Eurobodalla CounCil at thiS time adopt the "do nothIng" optIOn and regularly mOllitor the erosIOn of the sand Spit to aid In any I future deCISIOns The fmal deCISIOn rests With CounCil and needs to be based on I SOCial (nsk), economic and environmental factors I I I III I I

Table Sl I Summary Of Management Options I t " A ... No capital outlay Do Nothing Bank will contmue to erode I' $0 ...... RelocatIOn of Telecom services ... Possible break through of Spit B I ... Abundant sand supply readily available Nourishment $275,000 ... Blends mto the natural environment ... Creates at least a 30 year buffer I ... Improved channel navigatIOn ... Will reqUIre toppmg up of sand C ... Reduced aesthetics from rock revetment I Placed Rock ... May have mcreased environmental Impacts from $200,000 constructIOn ... ReqUIres mamtenance I ... Arrests scarp movement I J I, I t I I I I I IV I I' TABLE OF CONTENTS I Page No FOREWORD ...... I I SUMMARY ...... 11 t 1. INTRODUCTION ...... 1 I' 2. PHOTOGRAMMETRIC ANALYSIS ...... 2 2 1 Methodology...... 2 22 RIver Scarp AnalYSIS...... 3 I 2.3 DISCUSSIOn of Results...... 5

Ii 3. SEDIMENT DYNAMICS ...... 6

, 3 I Sedunent Samplmg ...... 6 32 SedIment ClassIficatIOn ...... 6 I 33 Nounshment Sources .... 8 I 4. MANAGEMENT OPTIONS ...... 9 4.1 Option A Do Nothmg 9 4.2 StabIlIsatIOn works ...... 10 I 4.2 1 Option B Nounshment . 10 4 2 2 Option C . Placed Rock . 11 43 Cost EstImates .. 11 I 4.4 Recommendations. 11

5. RECOMMENDATIONS ...... 12

6. REFERENCES...... 12

7. ACKNOWLEDGMENTS ...... 13

APPENDIX A Correspondence

APPENDIXB Sedunent SamplIng ExercIse, 14th July 1993 I APPENDIXC Cost Estimates of Management Options I v I t LIST OF TABLES

" I Table SI Summary of Management OptIons Table 2.1 Summary of Photogrammetnc Data I Table 2 2 Photogrammetrtc Accuracy I' Table 2.3 Shorehne PosltIon RelatIve To 1962 Table 2.4 Shorelme Movement (m)

I' Table 25 EroslOn Rate (metres/year) I Table 41 Summary of Management OptIons ,I LIST OF FIGURES Flgure 1 1 General LocatIon Map of the Study Area I Figure 1 2 LocahtyMap I Flgure 2.1 Landform details 1962 Flgure 2 2 Landform detalls 1972 I: Flgure 2 3 Landform detalls 1980 Flgure 2 4 Landform detalls 1993

I Flgure 2 5 Scarp Companson 1962 to 1993 t Flgure 2 6 Promes 1 to 4 Flgure 2 7 Promes 5 to 7 I Figure 2.8 Promes 8 to 10 Flgure 2 9 Scarp EroslOn AnalYSlS

I Figure 3 1 Sedlment Samplmg LocatIons I Flgure 3.2 Conceptual Sedlment Flow Paths I Flgure 4 1 Managements OptIons B & C I I I Vl I I LIST OF PLATES I Plate 1 Aenal Photography of Study Area - 1962 Plate 2 Aenal Photography of Study Area - 1972 I Plate 3 Aenal Photography of Study Area - 1980 I Plate 4 Aenal Photography of Study Area - 1993 I II I I I I I I ~ a, I I I I I VIl NSW Public Works REPORT No. I & TOMAGA RIVER BANK EROSION STUDY 93031 I I I I I I I I I I I I I I I ells I I

. ,. 1 : I eneral Location Map the Area I Figure 1.1 I

I 1. INTRODUCTION The Tomaga River IS located on the far south coast of NSW, approximately 260 kms I south of Sydney and 20 kms south of (see Figure 1.2) The Central Mappmg Authonty's Topographic (I 250000) reference IS Mogo (Figure 1.1)

I The Tomaga River has a catchment area of 98 km2 and a waterway area of 1 6 km2 The estuary IS approximately 11 km long and IS well mixed The entrance, located at , Mossy Pomt, IS open and untramed The nver extends to Mogo, a small settlement on the Pnncess Highway It IS tidal mto approximately 11 km upstream of the entrance leremadra Creek, the major tnbutary, Joms the nver some 75 km upstream of the entrance The waterway IS generally shallow and extensively mfilled I With manne and flUVial sediments

The study area concentrates on the Tomakm Spit approximately 400 m north of the - nver entrance This Spit forms part of the Tomakm Beach dunal system and acts as a • barner between the Tomaga River and Broulee Bay I ErOSIOn of the Tomakm Spit IS perpetual Presently there IS concern by Eurobodalla Council and local reSidents that the Tomaga River may break through the SPit mto Broulee Bay at Tomakm Beach Such an event would create two ocean entrances of I complex hydraulics Under these circumstances It IS likely that the eXlstmg entrance at Mossy pomt would begm to shoal due to the presence of a second entrance and loss of aVllllable ebb tidal energy Over time the second (new) entrance IS likely to I naturally close off due to sediment bemg transported mto the entrance area from higher energy wave conditIOns m Broulee Bay

I The break through would cause the loss of Telecom commumcatlOn services and would have a detnmental affect on navigation, the eXlstmg boat ramp faCIlities and a permissive occupancies along the waterfront at Mossy Pomt It IS unlikely that a break through would ever be allowed to happen, and If It were ever likely, then corrective actIOn would most likely be taken to protect the SPit

The study assesses past historIcal trends of rIver bank erOSIOn, and Identifies pOSSible management optIOns to protect the SPit from further erosIOn The followmg sectIOns I outline the study mvestlgatlOn undertaken, under the headmg of D Photogrammetnc AnalYSIS, I D Sediment DynamiCs, and I D Management Options

I I I

I 2. PHOTOGRAMMETRIC ANALYSIS I 2.1 Methodology Photogrammetnc analysIs of the Tomaga RIver was conducted USIng I Commonwealth and State Government mappIng agencIes photography taken over a 31 year penod from 1962 to 1993 The penod was dIVIded Into approxImately 10 year Intervals and the photography used was of a hIgh qualIty I and gave good coverage of the study area The detaIls of the photography are I lIsted In Table 2.1 Table 2.1 I Summary of Photogrammetric Data DATE FILM No. TITLE FLYING FOCAL SCALE COLOUR HEIGHT LENGTH CONDITION I (ft) (mm) 27-0ct-62 NSW 4121 Currowant Mogo 11,000 210 16,000 B&W TImber Good I InterpretatIOn Study 04-Jun-72 NSW2016 NSW Coasthne 20,000 153 40,000 B&W Good I 14-May-80 AAM 1450 Broulee 4,000 153 8,000 Colour C Excellent 15-Apr-93 NSW 4121 PW Coastal 6,000 153 12,000 Colour I SurveIllance Excellent

I Photogrammetnc dIgItI SIng allows the photography to be transformed to a computer dISC In X, y, z co-ordInates ThIS allows the photography to be plotted In 2 forms, plan and profile In thIS process, a stereo paIr of consecutIve frames I from the aenal photography for each year studIed, are placed Into the WIld ACI AnalytIcal Stereo plotter The operator now can vIew 60% of the aenal photography In 3-dlmenslOns The resolutIOn of thIS Instrument as speCIfied by I the manufacturer IS one mIcron, at the scale of the photography

To dlgltlse and compare any detaIl from the photography beIng analysed, I control POInts are establIshed and cross checked WIth ground survey InformatIOn The Central MappIng Authonty Integrated Survey Gnd (lSG) was used and landforms such as bUIldIngs were Identified to confIrm the accuracy I of the dlgltISIng process

General landforms In the study area, IncludIng the hIgh water mark, shoals, I scarp top and toe, bUIldIngs, roads, tracks and vegetatIon were recorded on the computer Figures 2.1 to 2.4 show the landforms dIgItised from the aenal I photographs and plotted USIng the CAD package Intergraph To assess scarp movement, SpIt profiles needed to be set up as close to I perpendIcular to the scarp as pOSSIble Ten profIles at 50m mtervals were used I 2 I

I to calculate erosIon rates and volume losses at each profile Figures 2.5 to 2.8 show the profIle observatIOns I The accuracy of the photogrammetnc analysIs depends on the followmg factors

I CJ quality of aerIal photography, CJ quality of ground control, CJ mstrument used and ItS resolutIon, I CJ method of aenal trIangulatIOn, and CJ accuracy of the operator and the plottmg machme

I The accuracy of the vertIcal and hOrIzontal measurement for each year of photography IS shown m Table 2.2 Note the fIgures quoted are upper lImIts, I therefore all the data observed are wlthm these ranges Table 2.2 Photogrammetric Accuracy (m) I , 'DATE HORIZONTAL VERTICAL 'PHOTOGRAPHY ACCURACY ACCURACY < COMMENT I I 27110/62 ±O5 ±O3 Good

I 04/06172 ±O5 ±O4 Good I 14/05/80 ±O3 ±O2 Excellent 15/04/93 ±O4 ±O2 Excellent I 2.2 River Scarp Analysis

I Figures 2.1 to 2.4 show the scarp locatIOn, dIgItised from the aerIal photography, from 1962 to 1993 Figure 2.5 overlays each scarp locatlon and provIdes a good summary of the erosion behaVIOur The relatIve scarp I movement was measured agamst the 1962 scarp locatIOn for each profile

The erodmg scarp extends from the northern boat ramp to the outer most curve I of the SPit Ten profiles at 50 m mtervals cover the erodmg sIte and extend from the beach seaward of the dune across the rIver onto the opposite shoal I The profIle observatIOns are Illustrated on Figures 2.6 to 2.8 respectIvely The rates of erosIon were calculated by averagmg the lInear movement of the scarp at the profile for each date of aerIal photography The scarp pOSItIOn I relative to the 1962 locatIOn IS shown m Table 2.3 Table 2.4 and 2.5 shows the scarp movements and the associated rate of eroSIOn at each profIle locatIOn I Figure 2.9 Illustrates the graphs of the scarp movements and eroSIOn rates I I 3 I I Table 2.3 I Shoreline Position Relative To 1962 YEAR ' , PROFILE • ,:f,= . . , , , :r~ 'f/;-~ ~ , " ,

·1.:: ... i';;ll;2,?l ~ ,)+:3 ~.£ !i2;'4 v 5 . ,;- ~ " '; 7,~; 8 9 )10 I , " , , . ~:"";~l~ . , 1!'~~'i:':O~ oc/~t " · I 1962 00 00 00 00 00 00 00 00 00 00 1972 46 8 1 7 1 83 57 47 45 40 50 25 I 1980 11 8 159 150 139 12 1 120 145 150 144 43 I 1993 164 199 190 187 160 189 204 220 178 64

Table 2.4 I Shoreline Movement (m)

" • c. PERIOD OF PROFILE .. ; •.. ,(~1{'~~.,d1:; A' .~."l.~& ~',' ,.,.~~,,. '" ~' ~, . ,,' .. . I ,.:.;. 'j ;","'" .~{:~,~; " " , , " · , }~~: " ,

ANALYSIS 1 " i" 3', ,- 5. 6 ;7 . .' 8 ·9 10 '~/~. , ' I ~ '" " .. , 7y .;; '-!" I~~~,' ~_::."" . , -, " I 1962-72 46 8 I 7 1 83 57 47 45 40 50 25 I 1972-80 72 78 79 56 64 73 100 II 0 94 1 8 1980-93 46 40 40 48 39 69 59 70 34 2 I

I TOTAL 164 199 190 187 160 189 204 220 178 64 I Table 2.5 I Erosion Rate (metres/year) PERIOD OF PROFILE 4/ , , , " -IV J ~ ',' t :t ; , " "" ' i - ' ' " , 'h 4 9, I ANALYSIS l' ;:s p2" 3 , , r~ 5 6 ' 7: ' 8 '110 . . , , . , I 1962-72 046 081 071 083 057 047 045 040 050 025 1972-80 090 098 099 070 080 091 125 I 38 1 18 023

I 1980-93 035 031 031 037 030 053 045 054 026 016 I 1962-1993 057 070 067 063 056 064 072 077 065 021 I Note: All positives values represent erosIOn since 1962 I 4 I I 2.3 Discussion of Results Profiles 1 and 10 represent the outer most pomts of the study area The boat I ramp (Profile 10) and the outer most curve on the SPit (Profile 1) are the extre1ll1tles to the erosIOn site (Figure 2.5) I The boat ramp appears to be actmg as a type of groyne arrestmg the erosIOn to the north Over time natural nver migratIOn has formed the general onentatlOn of the bend found today This bend contmually changes due to tidal and flood I currents transportmg the sediments causmg the erosIOn It should be noted that, the shoals further around the SPit upstream towards the I entrance at profile 1 have undergone steady accretIOn smce 1962 (see Figure 2.5) This also IS attnbuted to nver migratIOn Some of the sediments may have been transported from the erosIOn site, however the sediment dynamiCs of I thiS sectIOn of the nver IS complex and out of the range of thiS study

The outside of the nver bend (Profiles 1 to 10) experIences higher velOCities I than the mSlde, which mcreases the potential to transport sediment both laterally and longltudmally The erosIOn process between profiles 1 to 10 IS I typical of natural nver migratIOn. The strong curvature of the nver near the erosIOn site causes a concentratIOn of flow agamst the outSide of the bend, resultmg In Increased velOCities ThiS In I tum leads to Increased sediment carryIng capacity caUSIng erosIOn of the outSide bend Sediment can be moved both up and downstream or across fiver onto the shoals on the outSide bend ThiS IS an ongomg process and IS I attnbutable to natural fiver migratIOn Figure 3 2 shows the conceptual sediment flowpaths wlthm the study area.

I AnalYSIS of the results show that between profiles 1 to 10 erosIOn has been steady SInce 1962 Between 1962-72 the scarp eroded some 4 0 to 8 3m at a rate of 04 to 0 8m1year Similar behaVIOur occurred between 1972-80 With I another 5 6 to 11m at a rate of 0 7 to 1 38m1year, and agam between 1980-90 showmg another 3 4 to 6 9m at a rate of 0 26 to 0 5m1year

I It appears that the bulk of the erosIOn occurred dunng the 1972-80 peflod, between profiles 5 to 10 ThiS may have been Influenced by higher storm and flood events The erosIOn behaVIOur SInce 1980 appears to have decreased I becomIng more umform - around 0 25 to 0 7m1year

Based on trends over the past 30 years It IS anticipated that the SPit has some I 30 years of life before the potential for "break out" becomes a cntIcal Issue When the SPit reaches thiS state then urgent corrective actIOn would be needed I to stop the "break out" from occurrmg I I I 5 I 3. SEDIMENT DYNAMICS I 3.1 Sediment Sampling On the 14th July 1993 a sedIment samplIng exerCIse was carned out wlthm the study area mcludmg the SPIt entrance and upstream shoals. Sample locatIons I are shown on Figure 3.1

The posItIOn of the samples was selected usmg the 1993 aenal photography and I the surroundmg land features Table 3.1 IdentIfIes the sItes of extractIOn All samples were collected by shovel, labelled and placed m plastic bags Each sample was mspected and notes made descnbmg the colour, smell and general I consIstency I 3.2 Sediment Classification ApproxImately two-thIrds of the samples were clean, well sorted quartzose marme sands, whIte m colour These samples were taken from the beach and I the entrance shoal The remammg samples contamed organIcs glvmg them a dark grey colour These were taken from the shoal opposIte the erosIOn SIte, adjacent to the mangroves A healthy communIty of mud crabs was found m I these locatIOns

EIght samples, representatIve of a partIcular target area were tested m the I laboratory for gram sIze dlstnbutlOn ThIS mvolves droppmg the samples through a settlIng tube to determme gram sIze and velocIty dlstnbutlOn The analysIs showed all samples to be fine gramed and well sorted The mean gram I sIze of the clean sands was 0 26 mm, whIle those samples contammg organICS had gram sIzes rangmg from 0 19 to 0 26 mm

I Coarser gramed sedIments were generally located on the outsIde bend as the current IS stronger and there IS greater potentIal for the fmer sedIment to be transported away from the bank The fmer sedIments were located m areas of I depOSItion, bemg the adjacent mner shoals

Figure 3.2 schematIcally shows the maJonty of sedIment movement behaVIOur I m the study area The natural headlands and stable alIgnment of Tomakm Beach means that there IS very lIttle sedIment mfeed outsIde the entrance shoals However the shoals wlthm the estuary are constantly under gomg I change dependmg on the preVaIlIng condlt!ons ThIS relIes heaVIly on the tIde, flood, storm and dry weather condItIOns The channel bed sedIments move up I and down the estuary governed by typIcal tidal flows Figure 2.5 shows the southern end of the entrance SpIt under gomg steady I accretIOn smce 1962 ThIS IS a contnbutmg factor to the behaVIOur of natural fiver mIgration I I I 6 I

I Table 3.1 Summary of Samples Tested

I FIELD IDENTIFICATION COMMENT I LABORATORY IDENTIFICATION

I A3 Centre of entrance shoal Clean golden beach sand I 50997 Mean gram sIze = 0 26mm C2 Centre face of scarp Well sorted clean golden beach sand

I 50998 Mean gram sIze =0 29mm

C5 Shoal opposIte scarp at waters edge Well sorted grey In colour I beach sand Shght trace of organIcs 51000 I Mean gram sIze = 0 22mm C6 Shoal opposIte scarp Moderately sorted grey In colour I 51001 Mean gram sIze = 0 26mm DI Base of scarp at water lIne Well sorted clean hght m colour beach sand I 51002 Mean gram sIze =0 25mm

I EI Shoal opposIte scarp profile I Dark grey In colour Trace of organIc and pungent odour 51003 I Mean gram sIze = 0 19mm

FI Shoal opposIte boat ramp profIle 10, 30m from mangroves Well I sorted, grey In colour beach sand 51004 I Mean gram sIze =0 27mm Note: Samples A3, C5, C6, EI and FI are representative of possible sHes for nounshmg the scarp I I I I I 7 I I 3.3 Scarp Nourishment Sources Ideally, the source of sand for nourIshment should match, as closely as I possible, the eXlstmg gram size of the scarp If this IS not possible, then as coarse a gram size as possible should be selected to mmlmlse losses I Sediments from the scarp ranged from a mean gram size of 0 25mm to o 29mm While sediments from the opposite shoal ranged from a mean gram size of 0 19mm to 027mm ThiS IS a close match makmg these sands I compatible With those of the scarp and therefore sUitable for nourIshment Sand for nourIshment could be taken from the opposite shoal, startmg at the I edge of the mSlde channel When proceedmg With thiS, consideratIOn should be given to mamtammg an adequate channel and mmlmlsmg velocities on the 'I outside bend I I I I I I I I I I I I I 8 I

I 4. MANAGEMENT OPTIONS

I Photogrammetnc analysIs was used to quantify bank erosIOn rates and Spit volume losses These were applied to develop management optIOns to protect I the Spit Management optIOns to protect the Spit could mcIude • Do nothmg; I • Sand nounshment, • Rock np rap, • Reno mattress and gablOns, I • Sheet pilmg, • Timber revetment, • Rock/timber groynes, I • Spur wall I From these, three management options have been exammed, which are Option A : Do Nothing - no capital cost and accept contmued bank eroSIOn, relocatIOn of Telecom services and future threat of break I through of the SPit Option B : Nourishment - placement of 30,000 m3 of sand along the I erodmg scarp and plantmg of native coastal species Option C : Placed Rock - constructIOn of a rock revetment wall some 500m I 10 length compnsmg of approximately 4,250 tonnes of rock

The above optIOns are discussed 10 the follow 109 sectIOns A summary of the estimated construction costs and the ments of each optIOn are presented 10 I Table 4.1

Other optIOns such as, reno mattresses, sheet pilmg, timber revetment, groynes I and spur walls were not considered further based on the grounds of aesthetics, ability to successfully combat the erosIOn process and the practicality of I construction, mamtenance and cost

I 4.1 Option A : Do Nothing "Do Nothmg" Implies that no work be carned out to control bank I erosIOn ErOSIOn would contmue at current trend rates ThiS option mvolves no capital costs but would mcur costs associated With the I relocatIOn of Telecom's phone cables Unabated erosIOn will eventually result 10 the nver breakmg through I the narrow sectIOn of the Spit I I 9 4.2 Stabilisation Works 4.2.1 Option B : Nourishment Nounshment would mvolve the artificIal placement of sand on the erodmg nver bank to replemsh the scarp This solutlOn would not stop the erOSlOn process at the scarp however, It would provide a buffer to any further loss The extent of nounshment would detenmne the amount of buffer I The followmg factors need to be considered when nounshmg an erodmg bank, I o the amount of eroslOn and the state of the bank, o slope of the scarp, I o gram size dlstnbutlon, o the 10catlOn of matenal used to nounsh the bank, and I o volume of matenal to be used The height of the scarp face IS around 6m AHD and IS denuded of I vegetation The sand dune has a slope of approximately 1 3 bemg at the natural angle of repose I The mean sand gram size found on the scarp ranged from 0 25 to o 29mm bemg a fine to medIUm classlficatlOn Gram size has a direct relatlOnshlp With the slope m that, the coarser the materIal the steeper I the grade The mean sand gram size found on adjacent shoals ranged from 0 19 to 0 26mm bemg a fme to medIUm classlficatlOn I The sediment on the adjacent shoal IS considered to be sUitable for use as nounshment matenal of the scarp Its accessibilIty and abundance make It an attractIve optlOn from both an economic and environmental I vlewpomt Dredgmg the shoal would enable the channel to be reshaped to reduce the potential for bank erOSlOn ApproXimately 30,OOOm3 of sand would be required to restore the scarp to the 1962 I profile

Plantmg of appropnate coastal natIve species would asSiSt m I stabllIsmg the dune and help the nourIshment works blend mto the surroundmg enVIronment Some appropnate native species are, spmlfex, tee-tree, coastal banksla and wattle The eXlstmg bltou bush I should be eradicated

One mam disadvantage With Sand Nounshment IS that It does not stop I the eroslOn process from occurnng However It buys time by creatmg a buffer The sHe Will need to be topped up With more sand as required AddltlOnal funds would be needed to cover mamtenance m I the future I I 10 I

I 4.2.3 Option C : Placed Rock Imtlally, thIs optIon would Involve excavatIOn and tnmmIng of the eXIstIng bank profile to below low water wIth a slope of 1(V) 1 5(H) I A sUItable geotextIle fabnc would then be laId on the tnmmed slope to stop fIne sedIment partIcles escapIng through the rock layer Some 4,250 tonnes of rock would be placed on top of the fabnc to a I thIckness of approxImately 0 8m I The rock should be placed so that It extends down to a level eqUIvalent to the eXIstIng thalweg depth or preferable the depth of scour An addItIOnal quantIty of rock should be placed at the toe to ensure I contInued protectIOn of the bank should undercuttIng occur ThIs IS consIdered necessaI) as the presence of armounng Itself may cause scounng of the bed locally The armounng should be able to adjust to I localIsed changes The mam advantage of the "Placed Rock OptIOn" IS that It would I arrest the erosIOn of the scarp as long as the wall stays In tact The constructIOn method IS relatIVely easy and the maIntenance of the rock arrnounng can be achIeved by sImply toppmg up when and where I requIred

The dIsadvantages are the unnatural appearance of the rock compared I to the natural envIronment and the hIgh capItal cost AddItIOnal funds would be needed to cover maIntenance m the future I 4.3 Cost estimate I To facIlItate costIng, all of the Items assocIated WIth each optIon were converted Into a standard UnIt such as m3 or m2 and costed on a rate per UnIt I QuantItIes for the rock revetment were based on the typIcal cross sectIon In Figure 4.1 Volumes for the nounshment were based on approxImatIng the 1962 profile and a typIcal cross sectIon shOWIng the nounshed area IS gIven In I Figure 4.1 Appendix C detaIls the estImated costs Table C.1 shows the development of I UnIt rates used In each optIon, and Tables C.2 and C.3 gIve the cost breakdown for each optIon A summary of costs and the ments of each optIon IS presented I m followmg table I I I I 11 I

Table 4.1 I Summary Of Management Options

I " ,.4:;~:rtMAT~I:l~~.j,.I~:::::;f;t=!!j'~l~S;;; CONSTRUCTION I COST A '" No capital outlay Do Nothing '" Bank will continue to erode I $0 '" Relocation of Telecom services '" Possible break through of SPit I B '" Abundant sand supply readily available Nourishment $275,000 '" Blends Into the natural environment I '" Creates at least a 30 year buffer '" Improved channel navigatIOn '" May require topping up of sand I C '" Reduced aesthetics from rock revetment Placed Rock '" May have Increased environmental Impacts from $200,000 constructIOn I '" ReqUIres maintenance '" Arrests scarp movement I I I I I I I I I I I 12 I I 5. RECOMMENDATIONS Based on hlstoflcal bank movements It IS estImated that It wIll take up to I approxImately 30 years before the Tomaga RIver breaks through the SPIt In vIew of thIs eStimated time It IS suggested that Eurobodalla CouncIl adopt the "do nothmg" optIOn at thIs time and regularly mOnItor the erosIOn of the SPIt However, the fmal I decIsIon rests wIth CouncIl and needs to be based on socIal (fisk), economIc and envIronmental factors.

I In the short term It IS recommended that councIl undertake remedIal works to reduce the fisk of a breakthrough m the foredune at ItS narrowest and most vulnerable pomt (FIgure 2.5, profile No 6 ) ThIS would mclude fencmg and slgnpostmg of the I degraded area to dIscourage pedestnan traffIc usmg It as a thoroughfare The mmor "blowout" could be topped up WIth fill sand and stabIlIsed WIth appropnate vegetatIOn to reduce the potentIal for the nver to breakthrough MInImal dIsturbance I to the eXlstmg vegetatIOn should be ensured dunng construction of these works

I If protectIOn of the sand SpIt IS the preferred management optIOn, then sand I nounshment IS recommended as the best option I I I I I I I I I I I 13 I

I 6. REFERENCES JANSEN, P P, et aI, "Principals of River engineering", Pitman 1979

I GOVERNMENT, "Coastline Management manual" September 1990

I PUBLIC WORKS DEPARTMENT, NSW, " Estuary Inventory of New south Wales" 1992

I NEW SOUTH WALES GOVERNMENT, "Draft Estuary Management manual" October 1992

I CAROLlN, R & CLARKE, P, " Beach Plants of South Eastern AustrallQ ", Sanity & Associates 1991

I SWART, D H , "Beach Nourishment and Particle Size Effects", Coastal Engmeenng 16,61-81,1991 I I I I I I I I I I I I I 14 I I 7. ACKNOWLEDGMENTS This report was prepared by the Estuanes and Environment Pohcy Branch, Estuary I Management SectIOn The report was wntten and compiled by Mr J Howleson and edited by Mrs A Montefiore-Kmg Mr R Clout undertook the photogrammetnc analysIs whIch was presented by Mr S Phonesouk The sediment samphng exercise I was carned out by personnel from the Branch and the samples tested at Manly HydraulIcs Laboratory Techmcal assistance was provided by Mr R Latimer, Mr A I Woolley and Mr I Creighton I I I I I I I I I I I I I I I 15 I I I I I I I I I FIGURES I I I I I I I I I I I I \ I NSW I \ I I I I ...... -"'- Melville Pomt I .;L ...... -"-- ...... -"- I - ...... L...... ------seaen ...... -"'-

I -""- -"'- I ...i..-

Co ~ ~ I E. $. (j# I 0

~~ I (J I fJ..'if I ~ Cij~ I

0 100 200 300 400 500 m I ! SCALE TOMAGA RIVER I BANK EROSION STUDY LOCALITY MAP I Figure 1 2 I

I N I KEY BuildIngs "liB t I Road p SUNPATCH -::::== ==::::- w w Track o o o o o o U> I Vegetation Line N .... N oL0o N +I033000N +I033000N HIgh Water Mark I ----- .., Shoal " -- - Rock ...... -... _.. _--- ...... I Scarp Top

I ...... oo ...... I I /;;~ G ~ _/--- tt 0 /// / / / I / / w / o / o U') 1 U') 1 I N \ N 1 +I032500N +,' I I I \ \ /-, \ / I \ I I I \ I I \ I I \ I I \ I I ~I _/ I I I --- , I ... I I ------I I ~ \ / 1 \ 1 \ / \ / tlI;}. PUBLIC J ESTUARIES AND I \ // [ ~ WORKS ENVIRONMENT BRANCH " ...... _-"" / TOMAGA RIVER BANK EROSION STUDY ~.~.c~10~0~====~2~O~0 ______3~O=O======4=q.0 _____ 5_0_? m I 'L..... I I I SCALE I: 5000 LANDFORM DETAIL 1962 I ' DATE: AUG. 1993 Figure: 2.1 I I I N

I KEY t I Buildings ~le Road p SUNPATCH l.IJ =::::::::::::::::= 0 l.IJ Track 0 o I 0 o \D o Vegetation Line N .... O~O N N +I033000N +I033000N I High Water Mark ------:-" Shoal " -- I Rock .. ------.. _- Scarp Top - I I I I

",-

l.IJ o / " o / I III III / N N I +I032500N + ! I I ,I ",'" --I I I I I --_/ / I Mossy PoInt \ ,'. (". I ...... -, / __ , ,/ ,...... t I I "_..... \ : .. ~ I '// ~ : / I , •••••••••• ..-..... i I \ , I I ;' I ,I" \ I II _------__ / ,/ ;" .. ' " ~: I .", ..--;;. ... ____ '\ ...... : \ /,," ',...... -_ .. _------' : / .. ' ..... __ .... 1 PUBUC ESTUARIES AND \ /," , ~ J I \ b ' \ [ ~ WORKS ENVIRONMENT BRANCH 4 '" ~ ' , \ " .... ,. --: ...... _-1 .. ' : TOMAGA RIVER BANK EROSION STUDY I ':.. ; ...... 100 200 390 400 50? m \ ..... I . I LANDFORM DETAIL SCALE I: 5000 1972 I MOSSY POINT DA TE: AUG. 1993 Figure 2.2 I I I N I KEY t I Buildings uQ11III Road p w ==:::::::::::::: 0 w Track 0 o 0 o I o Vegetation LIne '" r­ O~O '" N +'033000N ~+'033000N I HIJh Water Mark Shoal /------~'\--- ~ I Rock ------...... - / Scarp Top '_ \, \J I --....' -,----- I ". I -- (: / ",

I , , , w , o o !, ...... '-...... '; U) I U) , N ., , N , +'032500N I " ,, I ,: I I ,, ( I , I I /" ...,/ /--- -' . \, I .... '., / , .. -- I ... \ · I · \ ·· I I " ·.. I Point\' I : I ! \ · I ... ·! \ ... ·! ,. -- .. -- .. ~ ...... \ --f-'.... ' .. '...... '----: .... ·: \ / ...... - .. -- · ~ PUBUC] ESTUARIES AND \ / ,-,,--...,' · I \ · [ W WORKS ENVIRONMENT BRANCH \ ., / :''" · \ " ;' .. ' \ ...... ' \ ... TOMAGA RIVER BANK .... , EROSION STUDY ,· I , · o 100 200 300 400 500 m .. · " ...-=~~ ___~======...... ~! ======.1 ...... I ...... -~ LANDFORM DETAIL " SCALE I : 5000 .. ---_ .. _-_ ...... 1980 I ------_ .... " MOSSY POINT .. , ...... -...... DATE: AUG. 1993 Figure 2.3 I 'I I N I KEY t Bulldlngs I SUNPATCH Road

w w Track o o o o I o ,....o Vegetation LIne 0 ~ 0 '"N N N N +'033000N High Water Mark ~'"'- +'033000N I /------:,." Shoal -- I Rock ~- .... ------.. -.. - Scarp Top ----- I ('---' t _____ .. ,,_,- / ,/ I · ·~""-",,,,,,,,,'-"': ... " ·· I ,,'" " ·. "",,-" G ~ .." .... ' /' ~~ (' · I / 0 f\ (' · / ct / .·· w I // . o /\ ,. I I . o t ... ----.. ~ .. - .. - ...... ' .... I III III \ I " I N I I I N .'. +'032500N J + /' I I I ...... \. I \ \ I I I I ·: I · I ·"--- / I I I \ I I \ \ \ \ ~ PUBUC 1 ESTUARIES AND \ [ I \ ~ WORKS ENVIRONMENT BRANCH \ \ TOMAGA RIVER BANK I " EROSION STUDY 100 200, 300 400, 50? m ...... ! I LANDFORM DETAIL SCALE I: 5000 1993 I MOSSY POINT DATE: AUG. 1993 Figure: 2.4 I I 1 / I I N I I I KEY I 1 I Buildings I ~ ,,1111 \ (!) \ \... t Road p \ +- \ ~ ==::::::::::::= I Track \ ~ \ 0 SUNPATCH High Water 1 ° Mark \ w w ------") 0 \ o I Shoal 0 \ o '" 0 o ---- U) \ l"­ _...... N N Rock --_ _- ...... N I +I033000N I --:::::::=:::~~~.. +I033000N I Scarp Top I Profiles I \\\\\ I LEGEND I YEAR SCARP AT TOP OF BANK 1993 1980 I 1972 1962 .- .­ '" I / '" / ct° / / w I 1/ o ,\ ,. I / I o If) If) \ I " I N N I I I +I032500N J + ;'" I I I I \ \ I I I I I I I 1 I I \ I I \ \ \ \ ~PUBUC ESTUARIES AND I \ WWORKS ENVIRONMENT BRANCH \ \ \ TOMAGA RIVER BANK I '- EROSION STUDY o... 300, 400, 500, m SCARP COMPARISON I SCALE I. 5000 1962 to 1993 MOSSY POINT DATE: AUG. 1993 Figure: 2.5 I I I I I o 50 100 200 I PROFILE 4 CHAINAGE(M) I

c~ :i I < z o I ~«-'W~ _02~~~~~~~~~~~~~~~~~~::::~::::~~~-=-=-=-=C ------=:-=-=-=-~~~-=-=------=~~~=:::=-~::~~-:~-=-=-=-==-=-=-=-=-~-=-=-=-=-=-=-==-=-~------o 50 100 150 200 250 300 350 I PROFILE 3 CHAINAGE(M)

I 'i c :i « I z 2 0 ------I­« >w I ~ -24------~------,_------,_------,------,------.------~ o 50 100 150 CHAINAGE(M) 200 250 300 350 I PROFILE 2

I ~ ci ~ « z I 2 0 I­ « >w I ~ -2. ~------_,------,_------,_------_,------,,-______,-______o 50 100 150 CHAINAGE(M) 200 250 300 350 PROFILE I KEY ~ PU8UC J ESTUARIES AND I [ W WORKS ENVIRONMENT AL BRANCH NOTES: ----1993 TOMAGA RIVER BANK ---1980 EROSION STUDY I " Top of Scarp as observed by Photogrammetrist. 1972 I 2 Refer to figure 2.5. 1962 PROFILES DATE: AUG. 1993 Figure 2 6 I • I

I 6 ~ ci 4 :i I

I -3+------,r------,------.------~------~ o 50 100 150 200 250 I PROFILE 7 CHAINAGE(M) I 6

~ I ci 4 :i

6 I ~ 4 :io I ~ -:,e===::;~~~~~~==~~~=== o 50 100 150 200 250 I CHAINAGE(M) PROFILE 5 I KEY ~PUBLIC ESTUARIES AND ~WORKS ENVIRONMENT AL BRANCH NOTES ---1993 TOMAGA RIVER BANK ---1980 I Top of Scarp as observed by Photogrammetrlst. EROSION STUDY ---1972 I 2 Refer to figure 2.5. ---1962 PROFILES DATE: AUG. 1993 Figure: 2.7 I I

I 6

~ ci 4 I :x: .,( z o i= I « Gj 0 ~ ------...J ------~~ I W -3,~------r_------_,------_,------,------~------~ o 50 100 150 200 250 300 I PROFILE 10 CHAINAGE(M) I 6

~ I :x:~ 4 .,( z o i= « I Gj 0 ______I til ~~~::;~ -3,T------,------,------,------r------,------~ o 50 100 150 200 250 300 I CHAINAGE(M) PROFILE 9 I 6 ~ I q 4 :J: .,( oZ i= I « > I ~O~~~~~~

-3,T------r_------_,------r------,------,------~ ,I o 50 100 150 200 250 300 PROFILE 8 CHAINAGE(M) KEY ~ PUBUC] ESTUARIES AND I [~ WORKS ENVIRONMENTAL BRANCH NOTES: ---1993 TOMAGA RIVER BANK ---1980 EROSION STUDY I Top of Scarp as observed by Photogrammetrlst. ---1972 I 2 Refer to figure 2.5. ---1962 PROFILES DATE: AUG. 1993 Figure: 2.8 I I I SHORELINE POSITION I Relative to 1962 _25 .------, ! I ~20 E ~ 15

I ; 10 I ~ 5 91 O+-~--~--+_~--_r--r__+--;_--r__+~ o 1 2 S 4 5 6 7 8 9 W I PROFILE 1-1972 - 1980 -1993 I I I I

RATES OF RECESSION I Metres / Year I I I I o 1 2 3 4 5 6 7 8 9 10 PROFILE

I 1-1962-72-1972-80-1980-93-1962-931 I TOMAGA RIVER BANK EROSION STUDY I SCARP EROSION STUDY I Figure 2.9 I I / / I I N I I I I 1 KEY 1'6 I I II) I \.­ t Buildings I ~ I C Road I 7 I I 0 SUNPATCH Track 1° I w a I Vegetation Line a I oL0o a I

w a I a III III N N I +I032500N / / ~ DI + I I I \ \ I I I I I '" Mossy.. PoInt / '/--_..... / I / \: / " -- , / / i';' '\ I ~", I ...... _ / / .. /' , .. ,., .... ,' ,,' , / ...... , .. I A I ..- : II A2 /Q /" ,/ : I ~ ./ " \ \ A3,Q,/ ------.. ,' I '-' ...... ,...... : A4~ I .",.,' •••• " .... ,.,." : ~ I ,/., ,r ...... : ~PUBLIC ESTUARIES AND \ -- ...... / / /" ~ ~WORKS ENVIRONMENT BRANCH I \ ;I' ,t \ \ " ( \ \ ,/ ~ , TOMAGA RIVER BANK " ,...... ~ ! EROSION STUDY I .! .' o }0.o 200 300 400 500 m l .... " SEDIMENT SAMPLING •---=~~~~======~!------I======~I------..I ! SCALE I: 5000 .. ----- ...... : LOCATIONS " .. " I MOSSY POINT DATE: AUG. 1993 Figure: 3.1 I I I \ I ~

I Bed sechments In this portion of the channel are mobile I under typical flow little or no I I Melville Point I Predominantly I ebb ------=...... =---.f- I TP-- Bank erosion caused by I natural river mitigation Stable beach I ------alignment I Scour of entrance PenmsslVe Occupancy channel dUring ebb I (Wharves)

Primary path of sediment I MOSSY POINT Infeed on flood tide I NOTE ArrfNfS Indicate dlrectlOl'l only. not volume of sediment movement I I o 100 200 300 400 500m I TOMAGA RIVER BANK EROSION STUDY CONCEPTUAL SEDIMENT FLOW PATHS I Figure 3.2 I,

This will boy 30 years of bank I. 20m :.1 I erosIOn based on historical rates Suggested species. Coastal Wattle Coastal Rosemary EXisting Brtou Bush I APPROX 6-7m AHD Coastal Tea-Tree I Splnlfex I TOMAGA RIVER PACIFIC OCEAN MSL I OmAHD

I TYPICAL CROSS SECTION - OPTION B I Sand Nouris~ment I I I I APPROX 6-7m AHO I TOMAGA RIVER PACIFIC OCEAN I, +1m AHO MWL MSL .:.:.o:.:..m:..:AHO:...... ¥------'%!l:Q~ SUitable Geotextlle FabriC OmAHO I _-----""\IC&~f_-- 1QO-5OOmm Quarry Run

-3m AHO I Below MInimum Scour I TYPICAL CROSS SECTION - OPTION C Placed Rock I

TOMAGA RIVER I BANK EROSION STUDY MANAGEMENT OPTIONS BAND C I Figure 4.1 I I I I I I I I

I PLATES I I I I I I I I 'I I I I N.S.W. P.W.D. REPORT No. Coast & Rivers TOMAGA RIVER BANK EROSION STUDY 93031 I Branch I I I I I I I I I I I I I I I I I SCALE AERIAL PHOTOGRAPHY OF STUDY AREA - 1962 PLATE No.1 I 1 :16,000 I NSW Public Works REPORT No. Estuaries & Environment TOMAGA RIVER BANK EROSION STUDY 93031 I Polic Branch I I I I I I I I I I I I I I I I

I SCALE AERIAL PHOTOGRAPHY OF STUDY AREA -1972 PLATE No. 2 1:40,000 I I N.S.W. P.W.D. REPORT No. Coast & Rivers TOMAGA RIVER BANK EROSION STUDY 93031 I Branch I I I I I I I I I I I I I I I I I SCALE AERIAL PHOTOGRAPHY OF STUDY AREA -1980 PLATE No. 3 I 1:8,000 I N.S.W. P.W.D. REPORT No. Coast & Rivers TOMAGA RIVER BANK EROSION STUDY 93031 I Branch I I I I I I I I I I I I I I I I I SCALE AERIAL PHOTOGRAPHY OF STUDY AREA ·1993 PLATE No.4 I 1 :12,000 I I I I I I I I

I APPENDIX A I Correspondence I I I I I I I I I I I GCJH liTRE Contact: i\1r G Clarke I (042) 268527

I Secretary Tomalan ResIdents & Ratepayers AsSOCIatIOn I 14 Kingston Place TOMAKIN NSW 2537 I Attention: Mary Handley ~''1 '/ I 1 8 I~ \,; 100"._;;.L I

I Dear Madam, I Tomaga River Erosion I Reference IS made to your letter of 13 October 1992 regarding the above The Department met With Eurobodalla ShIre CouncIl on the 24 September 1992 I to dISCUSS the barIk erOSIon problems of the Tomaga RIver Councu reiterated ItS adVIce that It has a fully cOmmItted works program over the next few years and that no CouncI! funds are currently aVaIlable to consIder works at I Tomakm I Counct1 though, did indicate It does recogruse the problems of the Tomaga RIver and suggested It would consIder plaCIng bank protectIon proJect(s) on ItS future works I program as other work pnonties perrrut NotWIthstandIng the above, should your ASSOCIatiOn WIsh to pursue the matter of protectIon further, then the AsSOCIatiOn could contact the Department of ConservatIon I and Land Management, Nowra, who may be able to asSISt With dune care works Works could include dune shaping/profiling, fenCIng and vegetatIng Such works however would not be guaranteed to be fully effectIve or remrun in place Without substantIal dune toe I protectIon to prevent scour at the base of the bank I Yours faIthfully I

I for M V Monaghan Manager I South Coast Region ~ omakin Residents & Ratepayers I /'Association Incorporated.

• - • '0' • • • • • I' ...... 0·......

,. 14 K~ngston 21. I ~ .~ " Tomaklrl ~ N.S.W. 2537 I 13/10/92

I Garry Clarke )l~c Works Dept: SlLth Coast Reg~on ~.Box 546 LLONGONG EAST NSW 2520

I TOMAGO RIVER EROSION. TOMAKIN ular S~r - rther to your letters sent to us dated 18 Feb and a copy of letter - ~t to Eurobodalla Counc~l dated 7 Apr.92. I the above Assoc~at~on have heard from Counc~l (letter copy attached) at~ng that they have no money to help w~th the Eros~on of the Tomak~n Iver Bank.

wondered ~f you could adv~se us and help as the R~ver ~s gett~ng rse, ~s there some other Department you could name that m~ght be ~n I e pos~t~on to help w~th our R~ver Bank. lank you I lJu~s faithfully I . 1/ /1 i. -I{11-c J :1

I RY HANDLEY(MRS) PI."BLlC WORKS DE:>T n Secretary RECEIVED I 15 OCT 1992

SQ I.r, Co ;3t Region,,! I Office I \&ut: ~UU.1U.. U.

I ALL COMMUNICATIONS TO E ADDRESSED TO COUNCIL CHAMBERS THE SHI CLERK MORUYA 2537 P 0 \10RUY.o. 2537 aox. IN RE::IL Y PL:ASE PHONE 0'.7"000 OUOTE ~E=ERENCE NO 80/0272-1500 I TELEX .0..0.61278 FAX 044 ;4123.1 r "NOUIRIES OX "873 I l PHONE (0") 25 August 1992 I Tho: Secretary Tomak~n Res~dents and I Ratepayers Assoc~at~on 14 K~ngston Place I TO~JlliIN NSW 2537 I Dear Madam RIVER B~ EROSION, TOMAKIN

I Further to your letter of 10 August 1992, ~t ~s adv~sed that Counc~l does not have funds allocato:d for any stab~lJ..satJ..on I works along the bank of the Tomaga R~ver. It J..S Counc~l' s intentJ..on to contact the PublJ..c Works Department to seek advJ.ce on desJ.gn of su~table protectJ..on of I the bank and possible methods of funaJ..ng. Thank you for your ~nterest in the welfare of the area.

I .~y further enquJ..rJ.es regarding thJ.s matter should be directed to G Anderson on telephone number 741398 . .1 Yours faJ..thfully

I -- I Per:. I I I I I I I 'Qrbr QtounriI of tur suire of QEurobobaIIa

ALL COMMUNICATIONS TO 9E AOORESSE:J TO COUNCIL CHAMBERS I TriE SHIRE CLE"lK MORUYA 2537 PO 30X 99 MORUYA 2537 IN REPLY cLEASE ?~CNE 0447.,000 QUOTE RE==~ENCE No TELEX AA61278 FAX 044 741234 I r ENOUIRIES G Anaerson OX 4873 L 1 PHONE. (044) I J 15 June 1992

I The Manager Soutn Coast D~v~sion Publ~c Works Deparc~ent I PO Box 546 WOLLONGONG EAST NSW 2520

I Attent~on: Mr G Clarke I Dear S~r A I TOMAqO RIVER BANK EROSION TOMAKIN Further to your letter of 9 June 1992, the following is advised:

I 1 Counc~l views the ongoing eros~on to the oanks of t~e Tomago River with some concern, particularly ~n the area of the townsh~p.

I 2 No formal or ~nformal documentat~on of the erosion has been carr~ed out. I 3 Council is not considering any action either in the way of stud~es or physical works at this stage.

Thabk'you. for your. enqu~ry. I .~. I Yours faithfully A W RATCLIFFE I Shire Clerk I I I I I I GC.JH 6TCMAGO Contact: Mr G Clarke I (042) 268527

ShIre Clerk I Eurobodalla ShIre CouncIl PO Box 99 I MORUYA NSW 2537

il a I I .. ; ~"I"'\ I .... - \J t.,. ''"I .::'";j~1 I Dear Sir, A I Bank Tomagn, River Erosion. Tomakin Further to our correspondence of ,the 2 AprIl 1992 regarding the I above, the Tomakm ResIdents & Ratepayers AssocIation Incorporated has sought the Departtnent's advice on whether CounCIl IS considermg any future action to initlate the arrest of the erOSIon problem(s).

I The Departtnent would appreciate CouncIl advIsing accordingly. I Yours faIthfully I I ..

for. M V Monaghan . : . I .... Manager South Coast Reglon I I I I I I I iii omakln Residents & Ratepayers I Association Incorporated. - "... I:' :. '.. : :.:. '.' : .; .. :: "; ::.:.:": ::: .:.: .' . 0" • :.

~ 14 ~ ~ KIngston Place Tomakin N.S.W. 2537

11/5/92 I

PUbl~C Works Department I P.O. Box 546 WOLLONGONG EAST NSW 2520 I

I Dear Mr Clarke,

Re your letter to the Eurobodalla Sh~re Counc~l,re our concern of I R~ver Bank at Tomak~n, dated 7/4/92.

Our members and Comm~ttee at our mett~ng today,would l~ke to know l ~f anyth~ng has come from the Counc~l re the R~ver Bank and ~f they are go~ng to anyth~ng about the proble~. As yet we have had reply from the Counc~l. ..

...... ,. I Your! fa~thfully . j'/! /1 I/Vl1!J~ M ~ANDLEY ( RS) I Hon Secret C

~f~U~8L~1-C-~-'-O-R-KS--D-E-?-T-.'~ I R:C:;PJED I South Coast Regional I Office I I G::.SJ 3Ta-1. QIV Contact: Mr G Clarke I (042) 268527

I The ShU"e Clerk Eurobodalla Sh1re CounC1l POBox 99 I MORUYA NSW 2537 I I Dear SU",

I Tomaga River Bank Erosion. Tomakin

Correspondence has been recently rece1ved from the Tomakm Res1dents I and Ratepayers Assoc1atlOn (dated 3 February 1992 and attached) expressmg concern over Tomaga R1ver bank erOSlOn.

In response to the letter a Departmental officer, Mr G Clarke, met I wIth representatlVes of the ASSOC1atlOn to Inspect areas of bank erOSIon, namely the narrow neck behmd the beach and along the edge of Jack Buckley Park as shown 10 Figure 1. Bank erOS1on of the sand SP1t is severe I and undenmnmg of the toe has resulted in loss of sand and exposure of a Telecom servIce cable. It 1S eV1dent Telecom has attempted to stab1lise the sect10n of cable affected. Res1dents were adv1sed in general terms of the I need for careful assessment of the extent of the problem and the various types of bank protectlon measures that could be cons1dered. Funding of any - investlgatlOn and/or works was advIsed as bemg subject to pnontles of both I Eurobodalla ShU"e Counc1l and the State Government. Should Councll be mterested in addressmg bank erosion of the nver, the Department would be w1lling to attend a me.etlpg with representatives I from Counc1l as well as other partles such:... ~s the Department of Conservatlon and Land Management and Telecom to 'dlscuss relevant ISSUes. I Yours faIthfully, I

I for: M V Monaghan Manager I South Coast Region I I I ti~ omakin Residents & Ratepayers I Association Incorporated. [8j ..... '.' . . . .. " ...... '., . • , 0' ,-. : ••• ' o· '; • ", ::...... : : . : : : : : : : : ' : .. :' . :.::!.:':. :':.: :::.: :: : . I l~ Kingston Pl~ct Tomakln ","S.W. 2537

I 3-2-92

I Dept: of Public Workq 3 North Street I !AT£~ANS BAY NSW ZS1R I Dear Sir, I I RE TOMAGO RIVER BANK I am requested by th~ above Assoclacion, to put ~n a letter to your dGparcment concerning the R~vcr Bank at I Tomak1n, 1£ poss~ble we would llke an Eng~nccr from your department to come down and inspect the River Bank, and tell us what c~n be done to save S31d Bank, which is fall~ng I into thp River v~ry quickly. The R~ver ~s verv popular with Holiday makers and residents al~kc for walks ~nd f~sh~ng, and 1:: concerns us all to s~·· : .. ~. I it deteriorate like ~t 1s.

I Hnpl"g you can help us 1n this matter. I I Yours falthfully I M!!af!Hon Secretary. I I I I I I I I I I I

I APPENDIXB I Sediment Sampling Exercise, 14th July 1993 I I I I I I I I I I I I

PU1lLIC WORKS DEPARTMENT OF N. S. W, MANLY HYDRAULICS LABORATORY I 110B KING STREET, MANLY VALE N S.W. 2093, . TEL 02-949-0200 I SAND SAMPLE ANALYSIS SITE TOMAGA RIVER CLIENT P W.D COAST AND ESTUARIES BRANCH I FIELD ID A3 SAMPLE SAND50997 I ANALYSED 27-JUL-93 13.40

I HISTOGRAM EXCEEDENCE

CLASS INTERVAL WEIGHT SPHERE SIZE CUMULATIVE I (phl.) % (phl.) (mm) % -1 25 -1 00 o 0 -1 00 2 00 o 0 -1 00 -0 75 o 0 -0.75 1 68 0.0 I -0 75 -0.50 o 0 -0 50 1 41 o 0 -0 50 -0.25 o 0 -0.25 1 19 o 0 -0 25 o 00 o 0 o 00 1.00 0.0 o 00 0.25 0.0 o 25 0.84 o 0 I o 25 o 50 o 0 0.50 o 71 o 0 o 50 o 75 o 0 o 75 o 59 o 0 o 75 1.00 o 0 1 00 0.50 o 0 1 00 1 25 1 3 1 25 0.42 1 3 I 1 25 1 50 4 5 1.50 o 35 5 8 1 50 1 75 15 3 1 75 o 30 21 1 1 75 2 00 34 9 2 00 o 25 56 0 2 00 2 25 27 8 2 25 o 21 83.8 I 2 25 2 50 10 8 2 50 0.18 94.6 2.50 2 75 3 6 2 75 o 15 98 2 2.75 3 00 1 2 3 00 o 13 99 3 3 00 3 25 o 7 3 25 011 100 0 I 3 25 3 50 o 0 3 50 o 09 100.0 3 50 3.75 0.0 3 75 0.07 100.0 3 75 4 00 o 0 4.00 o 06 100 0 I 4 00 4.25 o 0 4 25 o 05 100 0 I MOMENT MEASURE STATISTICS FOLK STATISTICS MEAN = 1 97 (phl.) MEAN = 1.93 (phl.) MEAN = o 26 (mm) MEAN = o 26 (mm) DEVIATION = o 30 (ph1.) DEVIATION = 0.27 (phi) I SKEWNESS = o 07 SKEWNESS = -0.04 KURTOSIS = 0.52 KURTOSIS = 1.17 I OTHER STATISTICS MEDIAN = 1 96 (phi) ~ Coarser than 2 00 o 00 MEDIAN = o 26 (mm) % Fl.ner than 0 063 1.33 I r. Shell content N/A I I I I

PUBLIC IIORKS DEPARTMENT OF N S II., MANLY HYDRAULICS LABORATORY I 110B KING STREET, MANLY VALE N S II 2093, AUSTRALIA TEL 02-949-0200 I SAND SAMPLE ANALYSIS

SITE TOMAGA RIVER CLIENT P II D COAST AND ESTUARIES BRANCH I FIELD ID C2 SAMPLE SAND50998 I ANALYSED 27-JUL-93 13 53

I HISTOGRAM EXCEEDENCE

CLASS INTERVAL \/EIGHT SPHERE SIZE CUMULATIVE I (phl.) % (phl.) (mm) ~ -1 25 -1 00 o 0 -1 00 2.00 o 0 -1 00 -0 75 o 0 -0 75 1.68 o 0 I -0 75 -0 50 o 0 -0 50 1 41 0.0 -0 50 -0 25 o 0 -0 25 1 19 o 0 -0 25 o 00 o 0 o 00 1 00 o 0 o 00 o 25 o 0 o 25 o 84 o 0 I o 25 o 50 o 0 o 50 071 o 0 o 50 o 75 o 0 o 75 o 59 o 0 o 75 1 00 o 4 1 00 0.50 o 4 1 00 1 25 2 1 1 25 0.42 2 5 I 1 25 1 50 9 7 1 50 o 35 12 3 1 50 1 75 27 1 1 75 o 30 39.4 1 75 2 00 35 3 2 00 o 25 74.7 2 00 2 25 19 1 2 25 o 21 93 9 I 2 25 2 50 5 3 2 50 o 18 99 2 2 50 2 75 o 6 2 75 o 15 99 8 2 75 3 00 o 2 3 00 o 13 100 0 3 00 3 25 o 0 3 25 0.11 100 0 I 3.25 3 50 o 0 3 50 o 09 100.0 3 50 3 75 o 0 3.75 0.07 100.0 3.75 4 00 o 0 4 00 o 06 100.0 I 4 00 4 25 0.0 4.25 0.05 100.0 I MOMENT MEASURE STATISTICS FOLK STATISTICS MEAN = 1.82 (phl.) MEAN = 1.79 (phl.) MEAN = o 28 (mm) MEAN = o 29 (mm) DEVIATION = o 27 (phl.) DEVIATION = 0.25 (phl.) I SKEIINESS = -0 06 SKEIINESS = -0 09 KURTOSIS = -0 25 KURTOSIS = 1 05 I OTHER STATISTICS MEDIAN = 1 83 (phl.) ~ Coarser than 2 00 0.00 MEDIAN = o 28 (mm) % Fl.ner than 0.063 o 14 I ~ Shell content N/A I I I I

PUBLIC WORKS DEPARTMENT OF N S W, MANLY HYDRAULICS LABORATORY I 110B KING STREET, MANLY VALE N S W 2093, AUSTRALIA TEL' 02-949-0200 I SAND SAMPLE ANALYSIS SITE TOMAGA RIVER CLIENT P W D COAST AND ESTUARIES BRANCH I FIELD ID C4 SAMPLE SAND50999 ANALYSED 27-JUL-93 14 06

I' PARTICLES > 2 0 MM WERE SHELLS

I HISTOGRAM EXCEEDENCE CLASS INTERVAL WEIGHT SPHERE SIZE CUMULATIVE I (phl.) % (phl.) (mm) % -1 25 -1 00 o 0 -1 00 2 00 o 0 -1 00 -0 75 - o 0 -0 75 1 68 o 0 I -0 75 -0 50 o 0 -0 50 1 41 o 0 -0 50 -0 25 o 0 -0 25 1.19 0.0 -0 25 o 00 o 0 o 00 1 00 0.0 0.00 o 25 o 0 o 25 0.84 o 0 I o 25 o 50 o 0 o 50 o 71 o 0 o 50 o 75 o 0 o 75 o 59 o 0 o 75 1 00 o 0 1 00 o 50 o 0 1.00 1.25 1.3 1 25 o 42 1.3 I 1 25 1 50 4 6 1 50 o 35 5 9 1 50 1 75 12 8 1 75 o 30 18 7 1 75 2 00 34 4 2 00 o 25 53.1 2.00 2 25 32 3 2 25 0.21 85 4 I 2.25 2 50 11.9 2 50 o 18 97 4 2.50 2 75 2 4 2 75 0.15 99.8 2 75 3.00 o 2 3.00 o 13 100.0 3.00 3 25 o 0 3 25 o 11 100.0 3 25 3 50 o 0 3 50 o 09 100 0 3 50 3 75 o 0 3 75 o 07 100 0 3.75 4 00 o 0 4 00 o 06 100.0 4 00 4 25 o 0 4 25 o 05 100 0

MOMENT MEASURE STATISTICS FOLK STATISTICS

MEAN = 1 97 (phJ.) MEAN = 1.95 (phl.) MEAN = o 26 (mm) MEAN = o 26 (mm) DEVIATION = o 28 (phl.) DEVIATION = o 26 (phl.) SKEWNESS = -0 16 SKEWNESS = -0 15 KURTOSIS = 0.35 KURTOSIS = 1.16

OTHER STATISTICS

MEDIAN = 1 98 (phl.) % Coarser than 2 00 0.08 MEDIAN = o 25 (mm) %Fl.ner than 0 063 1.31 I % Shell content N/A I I I I

PUBLIC WORKS DEPARTMENT OF N. S. W. MANLY HYDRAULICS LAB ORA TORY I 110B KING STREET. MANLY VALE N.S W. 2093. AUSTRALIA. TEL: 02-949-0200 I SAND SAMPLE ANALYSIS SITE TOMAGA RIVER CLIENT P W.D COAST AND ESTUARIES BRANCH I FIELD ID C5 SAMPLE : SAND51000 I ANALYSED 27-JUL-93 14 22 I HISTOGRAM EXCEEDENCE

CLASS INTERVAL WEIGHT SPHERE SIZE CUMULATIVE I (phl.) 1. (phl.) (nun) % -1.25 -1 00 o 0 -1 00 2 00 0.0 -1 00 -0 75 o 0 -0 75 1.68 o 0 I -0 75 -0 50 o 0 -0 50 1 41 o 0 -0.50 -0 25 o 0 -0 25 1.19 o 0 -0 25 o 00 o 0 o 00 1 00 o 0 o 00 o 25 o 0 o 25 o 84 o 0 I 0.25 o 50 o 0 o 50 o 71 0.0 o 50 o 75 o 0 o 75 o 59 o 0 o 75 1 00 o 3 1 00 o 50 o 3 1 00 1 25 1 0 1 25 o 42 1 3 I 1 25 1 50 4 6 1 50 o 35 5 9 1.50 1 75 11 5 1. 75 o 30 17 4 1 75 2 00 31 2 2 00 o 25 48 7 ,I 2 00 2 25 31 5 2 25 o 21 80.1 2 25 2 50 12 1 2 50 o 18 92 2 2.50 2 75 4 1 2 75 o 15 96 3 2.75 3 00 1 8 3 00 o 13 98 1 3 00 3 25 1 5 3 25 o 11 99 6 3 25 3 50 o 4 3 50 o 09 100 0 3 50 3 75 o 0 3.75 o 07 100.0 3.75 4 00 o 0 4 00 o 06 100.0 4.00 4 25 o 0 4 25 o 05 100 0

MOMENT MEASURE STATISTICS FOLK STATISTICS

MEAN = 2.02 (phl.) MEAN = 1.98 (phl.) MEAN = o 25 (mm) MEAN = o 25 (nun) OEVIATION = o 34 (phl.) DEVIATION = o 29 (phl.) SKEWNESS = o 23 SKEWNESS = -0 06 KURTOSIS = 1 22 KURTOSIS = 1 33 OTHER STATISTICS MEDIAN = 2.01 (phl.) % Coarser than 2 00 o 00 MEDIAN = o 25 (nun) 1. Fl.ner than 0 063 1.88 I 1. Shell content N/A I I I ,I

PUBLIC WORKS DEPARTMENT OF N S W, MANLY HYDRAULICS LABORATORY I 110B KING STREET, MANLY VALE N S W. 2093, AUSTRALIA TEL 02-949-0200 I SAND SAMPLE ANALYSIS

SITE TOMAGA RIVER CLIENT P W.D COAST AND ESTUARIES BRANCH I FIELD ID C6 SAMPLE SAND51001 I ANALYSED 27-JUL-93 14 35 I HISTOGRAM EXCEEDENCE

CLASS INTERVAL WEIGHT SPHERE SIZE CUMULATIVE I (ph1) % (ph1) (mm) % -1 25 -1 00 o 0 -1 00 2 00 o 0 -1 00 -0 75 o 0 -0 75 1.68 o 0 I -0.75 -0 50 o 0 -0.50 1 41 0.0 -0 50 -0 25 o 0 -0 25 1 19 o 0 -0 25 o 00 o 0 o 00 1 00 o 0 o 00 o 25 o 0 o 25 o 84 o 0 I o 25 o 50 o 0 o 50 o 71 o 0 o 50 o 75 o 0 0 75 o 59 o 0 o 75 1 00 o 0 1 00 o 50 o 0 1 00 1 25 o 3 1 25 o 42 o 3 I 1 25 1 50 o 9 1 50 o 35 1 2 1 50 1 75 3 6 1 75 o 30 4.8 1 75 2 00 12 0 2 00 o 25 16 8 2 00 2.25 38 6 2 25 o 21 55 3 » 2 25 2 50 30 1 2 50 o 18 85 4 2.50 2 75 10 7 2 75 o 15 96.1 2.75 3 00 2 5 3 00 0.13 98.6 3 00 3 25 1.2 3 25 o 11 99 8 I 3 25 3.50 o 2 3.50 o 09 100 0 3.50 3 75 o 0 3 75 o 07 100 0 3 75 4 00 o 0 4 00 o 06 100 0 I, 4 00 4.25 o 0 4 25 o 05 100 0 I MOMENT MEASURE STATISTICS FOLK STATISTICS MEAN = 2 24 (ph1) MEAN = 2 20 (ph1) MEAN = o 21 (mm) MEAN = o 22 (mm) DEVIATION = o 27 (ph1) DEVIATION = o 24 (ph1) I SKEWNESS = o 19 SKEWNESS = -0 06 KURTOSIS = o 79 KURTOSIS = 1 23 ,I OTHER STATISTICS MEDIAN = 2 22 (ph1) % Coarser than 2 00 o 00 MEDIAN = o 22 (mm) % F1ner than 0 063 1.80 I % Shell content N/A I I I I

PUBLIC WORKS DEPARTMENT OF N S W. MANLY HYDRAULICS LABORATORY I 110B KING STREET. MANLY VALE N S W. 2093. AUSTRALIA TEL 02-949-0200

" SAND SAMPLE ANALYSIS

SITE TOMAGA RIVER CLIENT P W D COAST AND ESTUARIES BRANCH I FIELD ID : Dl SAMPLE SAND51002 , ANALYSED 21-JUL-93 14 48 a PARTICLES> 2 0 WERE SHELLS. HISTOGRAM EXCEEDENCE

CLASS INTERVAL WEIGHT SPHERE SIZE CUMULATIVE I, (phl.) % (phl.) (nun) % -1 25 -1 00 o 0 -1 00 2.00 o 0 -1.00 -0 75 o 0 -0 15 1 68 o 0 I -0 15 -0 50 o 0 -0 50 1 41 o 0 -0 50 -0 25 o 0 -0.25 1.19 o 0 -0.25 o 00 o 0 o 00 1.00 0.0 , o 00 o 25 o 0 o 25 o 84 0.0 0.25 o 50 o 0 o 50 o 71 o 0 0.50 o 75 o 0 o 15 0.59 o 0 o 15 1 00 o 3 1 00 o 50 o 3 1 00 1 25 1 8 1 25 o 42 2 1 I 1 25 1.50 4 6 1.50 0.35 6 1 1 50 1 15 13 4 1 15 0.30 20.2 1 15 2.00 38.8 2 00 o 25 59.0 2 00 2 25 29 1 2.25 0.21 88 1 I 2 25 2 50 8 4 2 50 0.18 91 1 2 50 2 15 1 8 2 15 o 15 98 9 2 15 3 00 o 4 3 00 o 13 99 3 I, 3 00 3 25 o 1 3 25 0.11 100 0 3 25 3 50 o 0 3 50 0.09 100 0 3 50 3 15 o 0 3.15 0.01 100 0 3 15 4 00 o 0 4 00 o 06 100 0 I 4 00 4 25 o 0 4.25 o 05 100 0 I MOMENT MEASURE STATISTICS FOLK STATISTICS MEAN = 1 93 (phl.) MEAN = 1.92 (phl.) MEAN = o 26 (nun) MEAN = 0.26 (mm) DEVIATION = o 21 (phl.) DEVIATION = 0.25 (phl.) I SKEWNESS = -0 18 SKEWNESS = -0 14 KURTOSIS = 0.10 KURTOSIS = 1.28 I OTHER STATISTICS MEDIAN = 1 94 (phl.) % Coarser than 2.00 0.46 MEDIAN = 0.26 (mm) %Fl.ner than 0.063 1.43 'I % Shell content NIA J I I I

PUBLIC WORKS DEPARTMENT OF N.S W • MANLY HYDRAULICS LABORATORY I 110B KING STREET, MANLY VALE N S W 2093, AUSTRALIA TEL 02-949-0200 I SAND SAMPLE ANALYSIS SITE TOMAGA RIVER CLIENT : P W D COAST AND ESTUARIES BRANCH I FIELD ID El SAMPLE SAND51003 II ANALYSED 27-JUL-93 15 06 PARTICLES > 2 o MM WERE SHELLS I HISTOGRAM EXCEEDENCE

CLASS INTERVAL WEIGHT SPHERE SIZE CUMULATIVE I (ph~) % (ph~) (mm) % -1.25 -1.00 o 0 -1 00 2 00 0.0 --1.00 -0 75 o 0 -0 75 1 68 o 0 'I -0 75 -0 50 o 0 -0 50 1 41 o 0 -0 50 -0.25 o 0 -0 25 1 19 o 0 -0 25 0.00 o 0 o 00 1 00 o 0 o 00 o 25 o 0 o 25 o 84 o 0 I 0.25 o 50 o 0 o 50 o 71 o 0 o 50 o 75 o 0 o 75 o 59 o 0 o 75 1 00 o 3 1 00 o 50 o 3 1 00 1 25 o 5 1 25 o 42 o 8 I 1 25 1 50 1 2 1 50 o 35 2 0 1 50 1 75 2 9 1 75 o 30 4.9 1 75 2 00 6 6 2 00 o 25 11.5 I, 2 00 2.25 18 2 2 25 o 21 29 6 2 25 2 50 32 6 2.50 o 18 62 2 2.50 2 75 18 9 2 75 o 15 81.1 2 75 3 00 12 4 3 00 o 13 93 5 3 00 3 25 5 0 3 25 o 11 98.5 I 3 25 3.50 1 5 3 50 o 09 100 0 3 50 3 75 o 0 3 75 o 07 100 0 3 75 4 00 o 0 4 00 o 06 100 0 I, 4 00 4 25 o 0 4 25 o 05 100.0 I MOMENT MEASURE STATISTICS FOLK STATISTICS. MEAN = 2 43 (ph~) MEAN = 2 39 (ph~) MEAN = o 19 (mm) MEAN = o 19 (mm) DEVIATION = 0.37 (ph~) DEVIATION = 0.34 (ph~) 'I SKEWNESS = -0.02 SKEWNESS = -0.05 KURTOSIS = o 26 KURTOSIS = 1.21 I OTHER STATISTICS MEDIAN = 2 41 (ph~) % Coarser than 2 00 o 04 MEDIAN = 0.19 (mm) % F~ner than 0 063 4 55 I % Shell content N/A I I I I

PUBLIC 1l0RKS DEPARTMENT OF N S. II . , MANLY HYDRAULICS LAHORA TORY I 110B KING STREET, MANLY VALE N S II 2093, AUSTRALIA TEL. 02-949-0200 I' SAND SAMPLE ANALYSIS SITE TOMAGA RIVER CLIENT P II D COAST AND ESTUARIES BRANCH I FIELD ID Fl SAMPLE SAND51004 'I ANALYSED 27-JUL-93 15 18 PARTICLES> 2 00 MM IlERE SHELLS. I HISTOGRAM EXCEEDENCE

CLASS INTERVAL IlEIGHT SPHERE SIZE CUMULATIVE I (ph1) r. (ph1) (nun) r. -1 25 -1 00 o 0 -1 00 2 00 o 0 -1 00 -0 75 o 0 - -0 75 1 68 o 0 I -0 75 -0 50 o 0 -0 50 1 41 o 0 -0 50 -0 25 o 0 -0 25 1 19 o 0 -0 25 o 00 o 0 o 00 1 00 o 0 o 00 o 25 o 0 o 25 o 84 o 0 I, o 25 o 50 o 0 o 50 o 71 o 0 o 50 o 75 o 4 o 75 o 59 o 4 o 75 1 00 o 9 1 00 o 50 1 4 1 00 1 25 2 8 1 25 o 42 4.2 I 1 25 1 50 6 7 1 50 o 35 10 8 1 50 1 75 15 1 1 75 o 30 25 9 1 75 2 00 30 8 2 00 o 25 56 8 2 00 2 25 26 3 2 25 o 21 83.0 I 2 25 2 50 10 8 2 50 o 18 93 9 2 50 2 75 3 7 2 75 o 15 97.5 2 75 3 00 1 4 3 00 o 13 98 9 3 00 3 25 1 1 3 25 0.11 100.0 I 3.25 3 50 o 0 3 50 o 09 100 0 3 50 3.75 o 0 3 75 o 07 100.0 3 75 4 00 0.0 4 00 0.06 100.0 I 4.00 4 25 o 0 4 25 o 05 100 0 I MOMENT MEASURE STATISTICS FOLK STATISTICS MEAN = 1 96 (ph1) MEAN = 1 90 (phi) MEAN = o 26 (nun) MEAN = 0.27 (nun) DEVIATION = o 36 (ph1) DEVIATION = o 33 (ph1) I SKEIlNESS = o 14 SKEIlNESS = -0 15 KURTOSIS = o 78 KURTOSIS = 1 25 I OTHER STATISTICS MEDIAN = 1 9S (ph1) 1 Coarser than 2.00 0.23 MEDIAN = o 26 (nun) r. F1ner than 0 063 2.05 I r. Shell content N/A I I I

Publl.c Works NSW • ..".. Manly Hycirauhcs TOMAGA RIVER BANK EROSION STUDY Report No. 93031 I ~01 Laboratory I SITE: TOMAGA RIVER

o SAMPLE: 50997 I o o o I M o o o I '" o o o I

o o o I r--

o I o o ID

II o o dP o Ll'l ~ o o o I "" o o o I' M

o o I o N

o I o o I M

o o 00 .50 1 00 1 50 2.00 2.50 3 00 3.50 4.00 I SIZE (phi) I I GRAIN SIZE DISTRIBUTION Figure Bl I I

. Pubhc Works NSW I .-. Manly Hydrauhcs TOMAGA RIVER BANK EROSION STUDY Report No. 93031 I ®(I Laboratory I SITE: TOMAGA RIVER

o SAMPLE: 50998 I o o o I M o o o I '" o o o I a)

o o I o "

o I o o \D

I o o aP o I: '" o o I o.... o o I ...,o

o o I o N

o I o o 'I M

o o 00 50 1 00 1.50 2.00 2 50 3 00 3.50 4.00 I SIZE (phi) I ,I GRAIN SIZE DISTRIBUTION Figure B2 I I

I Pubhc works NSW I • ..".. Manly Hydrauhcs TOMAGA RIVER BANK EROSION STUDY Report No. 93031 I Wo Laboratory

I SITE: TOMAGA RIVER

a SAMPLE: 50999 a I a a .-i

I a a a I '" a a a I ex>

a I a

a I a a '" I a a dP~ I lfl a a I ....a a a a I ""

a I a a N

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a 0.00 50 1 00 1 50 2 00 2.50 3 00 3 50 I SIZE (phi) I I GRAIN SIZE DISTRIBUTION Figure B3 I I

I Publl.c Works NSW I .e.. Manly Hydraul1cs I TOMAGA RIVER BANK EROSION STUDY Report No. 93031 I ~o Laboratory I SITE: TOMAGA RIVER

o SAMPLE: 51000 I o o o I .-i o o o I '" o o o I 0)

o o I o r--

o I o o '" I o o I ""0tn o o I ....o o o o I M

o o I o N

o I o o ,I .-i

o o 00 .50 1.00 1 50 2.00 2 50 3 00 3.50 4.00 I SIZE (phi) I I G~IN SIZE DISTRIBUTION Figure B4 I I

Publl.c works NSW I ...... Manly Hydraulics TOMAGA RIVER BANK EROSION STUDY Report No. 93031 I ~o Laboratory I SITE: TOMAGA RIVER

o SAMPLE: 51001 I o o o I .-i o o o I en o o o I co

o o o I r--

o I o c::. '" I o o clP o I Ll1 o o I ....o o o I ...,o

o o I o N

o I o o I .-i

50 1 00 1.50 2 00 2 50 3 00 3 50 4.00 I SIZE (phl) I I GRAIN SIZE DISTRIBUTION Figure B5 I I

Pubhc Works NSW I I • ..".. Manly Hydrauhcs TOMAGA RIVER BANK EROSION STUDY Report No. 93031 I ~o Laboratory

I SITE: TOMAGA RIVER

a SAMPLE: 51002 I a

I a a 0- I 0'1 a a ~- I CD

a a o­ I r--

a I a 0- \0 I I a a I 0-.... --

a a 0- - I C""l

a I a o­ N

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· Pubhc Works NSW I • ..".. Manly Hydrauhcs I TOMAGA RIVER BANK EROSION STUDY Report No. 93031 I WQ Laboratory I SITE: TOMAGA RIVER

a SAMPLE: 51003 I a a a I .-i a a a I en a a a CD

a a I a r-

a I a a '"

I a a dP o I ltl a a a I "" a a a I M

a a I a '"

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a 0.00 .50 1 00 1 50 2.00 2 50 3 00 3 50 4.00 I SIZE (phi) I I GRAIN SIZE DISTRIBUTION Figure B7 I I

Publl.c Works NSW .-. Manly Hydrauhcs TOMAGA RIVER BANK EROSION STUDY Report No. 93031 I ~o Laboratory

I SITE: TOMAGA RIVER

o SAMPLE: 51004 o I o o .-i

I o o o I '" o o o I

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o I a 00 50 1.00 1 50 2 00 2.50 3.00 3.50 SIZE (phi) I I GRAIN SIZE DISTRIBUTION Figure B8 I I

Publl.c works NSW • ..,... Manly Hydrauhcs TOMAGA RIVER BANK EROSION STUDY Report No. 93031 I ~Q Laboratory

I SITE: TOMAGA RIVER

a SAMPLE: 50997 a I a a ~

I a a a I '" a a a I co

a a a I r-

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a I a a I ~ a a~-----r-----.-----'-----.------r-----. a I o 00 1 00 2.00 3.00 4 00 5 00 6.00 VELOCITY cm/s I I FALL VELOCITY DISTRIBUTION Figure B9 I I

/fOl'\ Pubhc Works NSW I (;:::'"":':::.!) Manly Hydrauhcs TOMAGA RIVER BANK EROSION STUDY Report No. 93031 I ~ Laboratory

I SITE: TOMAGA RIVER

o SAMPLE: 50998 o I o o....

I o o o I '" o o o I co

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o I o o '" I o o I o.... o 04------r----~----~----~------r_----._--__. o I o 00 1 00 2 00 3 00 4 00 5 00 6 00 7 00 VELOCITY cm/s I 'I FALL VELOCITY DISTRIBUTION Figure B10 I I

Q Publl.c Works NSW I .-. Manly Hydrauhcs TOMAGA RIVER BANK EROSION STUDY Report No. 93031 I ~II Laboratory I

I SITE: TOMAGA RIVER

o SAMPLE: 50999 o I o ....o

o I o o I '" o o o I CO o o o I r-

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a I a a I .... o 04-____~----~----_.----_.------r_--__. a I a 00 1.00 2 00 3.00 4 00 5.00 6 00 VELOCITY cm/s I I FALL VELOCITY DISTRIBUTION Figure Bll I I

o P'ubll.c Works NSW I .-. Manly Hydrauhcs TOMAGA RIVER BANK EROSION STUDY Report No. 93031 I ~Q Laboratory

I SITE: TOMAGA RIVER

o SAMPLE: 51000 o I o o M

I o o o I '" o o o I CO

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o I o o I M o 04------r----~----~----_.------,_--__. o I o 00 1. 00 2.00 3 00 4.00 5 00 6 00 VELOCITY crn/s I I FALL VELOCITY DISTRIBUTION Figure B12 I I

Publl.c Works NSW I ...... Manly Hydrauhcs TOMAGA RIVER BANK EROSION STUDY Report No. 93031 I ~o Laboratory

I SITE: TOMAGA RIVER

o SAMPLE: 51001 I, o o .....o

o I o o I 0\ o o o I cc o o o I r--

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o I o o I ..... o o~ ____-' ____ -r ____ -. ____ -. ____ -. o I 0.00 1.00 2.00 3 00 4 00 5.00 VELOCITY cm/s I I FALL VELOCITY DISTRIBUTION Figure B13 I I ' Publl.C works NSW I • ..".. Manly Hydrauhcs TOMAGA RIVER BANK EROSION STUDY Report No. 93031 I 9o Laboratory

I SITE: TOMAGA RIVER

o SAMPLE: 51002 o I o o .-<

o I o o I 0'\ o o o I CO o o o I r--

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o I o o I .-< 01-o ____-, ____ -. ____ -. ____ -. ______.- ____,- __--. o I 0.00 1 00 2.00 3.00 4.00 5.00 6.00 7 00 VELOCITY crn/s I I FALL VELOCITY DISTRIBUTION Figure B14 I I

Publl.c Works NSW I ,.."., Manly Hydrauhcs TOMAGA RIVER BANK EROSION STUDY Report No. 93031 I ~o Laboratory

I SITE: TOMAGA RIVER

o SAMPLE: 51003 o I o ....o

o I o o I a\ o o o I CO o o o I t-

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1 PubllC Works NSW I • ..".. Manly Hydrauhcs TOMAGA RIVER BANK EROSION STUDY Report No. 93031 I 9o Laboratory I SITE: TOMAGA RIVER

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I 0 0 0 0.00 1.00 2.00 3.00 4.00 5 00 6.00 7.00 8 00 I VELOCITY crn/s I I FALL VELOCITY DISTRIBUTION Figure B16 I I I I I I I I I I APPENDIX C I Cost Estimates of Management Option I I I I I I I I I I I I Table C.1 Development of Unit Rate OPTION ITEM DESCRIPTION RATE UNIT BASIS ($I I ROCK ARMOUR ProJect Duranon - - EstImated 4 week operanon Supply & place granote rip rap 4250 m3 PWD Bodalla Quarry 40km to Tomaga (0 1 m to 0 5m dIameter) Assume density of 1 711m3 when placed Two excavators 1350 m3 $4,150/wk each IncludIng overnme I Two dump trucks 1350 m3 $4,1501wk each IncludIng overnme Geotextlle fabric 300 m3 ($2 251m2) x (3,310 m2) = $7,4SO (($7 ,450)/(2,500m3) = $3 00/m3 I Supervoslon by foreman 215 m3 x 2,SOO m3 = $S,375

TOTAL 7465 m3 x 2,SOO m3 = $186,625 I NOURISHMENT ProJect DuratIon -- Crrtlcal path based on workIng rate of dozer Volume of nourishment = 30,000 m3 Assume density of 1 711m3 when placed Assume dozer operanon of 400 t/hr assume 8 hr/day I (400 t/hr) I (1 711m3) x (8 hr/day) = 1,682 m3/day (30,000 m3) x (1 711m3) I (400 t/hr) I (8 hr/day) = 16 days Assume 3 weeks I Cutter SuctIon Dredge 615 m3 South Coast RegIon, Scott RenWIck (042) 268551 $20,000 establishment ($5 00/m3) x (30,000 m3) = $150,000 $15,000 dIsestablishment I ($150,000 + $20,000 + $15,000) 130,000 m3 = $6 151m3 Dozer 07 050 m3 Rates $110/hr up to 8 hrs ($110/hr) x (8 hrs/day) = $B80/day $BOO/day 11882 m3/day = $0 471m3 I Use $0 501m3 Supervoslon by Foreman 015 m3 Assume salary of $SO,OOOlyr = $33/hr Assume 8 hr/day ($33/hr) x (8 hr/day) x (16 days) I (30,000 m3) = $0 141m3 I Use $0 151m3 TOTAL 680 m3 x 30,000 m3 = $204,000

LANDSCAPING Supply Dune Vegetenon 225 m2 Bexley Garden Centre, I 15 MImosa Street, Bexley I Telephone 507445 - coastel wattle - coastel rosemary M,n,mum of one plant required for every 2 m2 - coastel tea-tree Plants (6' pots) = $4 50 each - splnofex I NOURISHMENT (12,600 m2) I (2 m2/plant) = 6,300 plants (6,300 plants) ($4 50/plant) = $28,000 I ROCK ARMOUR (4,SOO m2) /2 m2/plant) = 2,250 plants (2,250 plants) x ($4 SO/plant) = $10,125 Labour wrth Planting 036 m2 Assume plannng of 350 plants Ilabourerl day I Assume $250 I labourer I day

ROCK ARMOUR (2,250 plants) I (350 plants/day) x ($250/labourer/day) = $1,610 I $1,610/4,500 m2 = $0 361m2 NOURISHMENT (6,300 plants) I (350 plants/day) x ($2SO/labourer/day) = $4,500 I $4,500 112,600 m2 = $0 361m2 TOTAL 261 m2 ROCK ARMOUR x 4,500 m2 = $1 I ,745 I NOURISHMENT x 12,600 m2 = $32,886 I I I

I Table C.2 Cost Estimate OPTION A - Rock Armour

ITEM DESCRIPTION RATE ($) UNIT QUANTITY AMOUNT ($)

I 1 Supply & place granite np rap 7500 m3 2,500 187,500 (0 1m to 0 5m dlemeter) I 2 Geotextlle fabnc 225 m2 3,310 7,448 3 Supervision by foreman 215 m3 2,500 5,375 I 4 Dune vegetalion 225 m2 4,500 10,125 5 Planting 036 m2 4,500 1,620

SUB-TOTAL 212,068 I + 15% contingency 31,810 TOTAL $243,878 I SAY $245,000 I

I Table C.3 Cost Estimate OPTION B - Nourishment

ITEM DESCRIPTION RATE ($) UNIT QUANTITY AMOUNT ($)

I 1 Site establishment - Unit - 20,000 2 Cutter suction dredge 500 m3 30,000 150,000 I 3 Disestablishment (Dredge) - Unit - 15,000 4 DozerD7 050 m3 30,000 15,000 I 5 Supervision by foreman 035 m2 12,600 4,410 6 Dune vegetation 225 m2 12,600 28,350 I 7 Planting 036 m2 12,600 4,536 SUB-TOTAL 237,296 I + 15% conlmgency 35,594 TOTAL $272,890 I SAY $275,000 I Note These costs are only preliminary The 15% contingency takes Into account I pOSSible changes In deSign and vanabon In quanbtles and pnces I I I