prepared  for 

Townsville City Council 

 

 

 

June  2011 

SAUNDERS  BEACH

 

ASSESSMENT  OF  COASTAL  EROSION  MITIGATION  

OPTIONS 

Saunders 

Docum

Docum

First Is

Documen

Revision

code

A

B

Beach ‐ Ass

Project :

ment Title :

Client :

ent Code :

ssue Date :

nt Status Re

Date

Revised

08Jun11

14Jun11

Coastal Eng2

tel :

email : p.rie

essment of 

Saunders

ecord

Cha

Initial Rele

Final Repo

ineering Solut25 Wirilda Way

Fish Creek VIC 3959 Australia

+ 61 3 5683 2

edel@coasten

Coastal Ero

Beach - A

apter/section/

plus any re

ease

ort addressing

tions Pty Ltd y

2495

ngsol.com.au

sion Mitigat

Assessmen

pages revised

emarks.

g TCC comme

Coa

ema

tion Options

Coast

nt of Coas

d,

ents

astal EngineerP.O.

59 HulcoSamford

Autel : + 61fax : + 61

ail : p.obrien@

s

tal Erosion

tal Erosion

T

Author

POB

POB

ring Solutions Box 677

ombe Road d QLD 4520 ustralia 1 7 3289 70111 7 3289 7022

@coastengsol.

n Mitigation

n Mitigation

Townsville C

11-649q

08th J

Authority

R

Pty Ltd

2 com.au 

 

    

n Options

n Options

ity Council

qld-pobrpB

June 2011

Reviewed

HPR

HPR

 

Saunders 

Table o 

SUMMAR

1  INTR

1.1  G

1.2  R

1.3  L

1.4  L

2  LOCA

2.1  B

2.2  O

2.2.1

2.2.2

2.2.3

2.3  S

3  ERO

3.1  C

3.2  D

3.3  G

4  ASSE

4.1  T

4.2  S

4.2.1

4.3  C

4.3.1

4.3.2

4.3.3

4.3.4

4.3.5

4.4  N

4.4.1

Beach ‐ Ass

of Conten

RY ................

RODUCTIO

General .......

Regional Set

Local Setting

Local Foresh

AL COAST

Background .

Overview of 

1  Longsh

2  Cross-s

3  Vulnera

Summary of 

OSION MITI

Coastal Defe

Design Storm

Generic Eros

ESSMENT

The Saunder

Southern Pre

  Recom

Central Prec

  Possib

2  Beach

3  Seawa

4  Seawa

5  Recom

Northern Pre

  Recom

essment of 

nts

....................

N ................

....................

ting .............

g ..................

ore Land Te

TAL PROC

....................

Sand Transp

hore transpo

shore trans

ability of Sa

Coastal Proc

IGATION O

ence Line .....

m Conditions

sion Mitigatio

OF EROS

rs Beach Coa

ecinct ..........

mmended St

inct .............

le Erosion M

Nourishme

all .................

all with Beac

mmended In

ecinct ..........

mmended St

Coastal Ero

....................

....................

....................

....................

....................

nure ............

CESSES ......

....................

port Processe

ort ...............

sport ............

aunders Bea

cesses ..........

OPTIONS ...

....................

s ...................

on Options ..

SION MITIG

stal Reach ...

....................

trategy ........

....................

Mitigation S

ent ................

....................

ch Nourishm

terim Strate

....................

trategy ........

sion Mitigat

....................

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es ................

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ach foresho

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GATION O

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Strategies ...

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ment ............

egy ..............

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tion Options

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ore to storm

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m events ......

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....... 1 

....... 1 

....... 1 

....... 2 

....... 3 

....... 8 

....... 8 

....... 9 

....... 9 

..... 10 

..... 11 

..... 12 

..... 14 

..... 14 

..... 14 

..... 15 

..... 18 

..... 18 

..... 18 

..... 19 

..... 19 

..... 19 

..... 20 

..... 22 

..... 23 

..... 24 

..... 24 

..... 25 

 

Saunders 

5  REC

5.1  B

5.2  B

5.3  B

6  REFE

Appendix

Appendix

Appendix

Table o

Figure 1 :Figure 2 :Figure 3 :Figure 4 :Figure 5 :Figure 6 :Figure 7 :Figure 8 :

Beach ‐ Ass

OMMENDE

Between the

Between Sou

Between Sau

ERENCES .

x A - Resu

x B - Refe

x C - Gene

of Figure

: Location o: Saunders : Foreshore: Foreshore: Foreshore: Indicative : Evidence o: Typical init

essment of 

ED EROSIO

e Black River 

uthern End o

unders Beach

....................

ults of Bea

rence Docu

eric Erosion

es

of SaundersBeach coas

e Propertiese Propertiese Propertiesbuffer widthof overwashtial beach n

Coastal Ero

ON MITIGA

and Southe

of Cay Street

h Road and A

....................

ch Transec

ument .........

n Mitigation

s Beach in astal reach ... & Survey T - central se - southern

hs - Cay Strh during TCnourishment

sion Mitigat

ATION STR

rn End of Ca

 and Saunde

Althaus Cree

....................

ct Surveys

....................

n Options..

a regional co....................Transects -ection of Sasection of S

reet, SaundC Yasi .........t profile ......

tion Options

RATEGY ....

y Street .......

ers Beach Ro

ek ..................

....................

....................

....................

....................

ontext .............................northern Sa

aunders BeaSaunders Bers Beach .........................................

s

....................

....................

ad ...............

....................

....................

....................

....................

....................

....................

....................aunders Beach .............

Beach ......................................................................

...................

...................

...................

...................

...................

...................

...................

...................

...................

...................each ...........................................................................................................

 

    

..... 26 

..... 26 

..... 26 

..... 27 

..... 28 

....... 1 

....... 1 

....... 1 

....... 2 

....... 3 

....... 4 

....... 5 

....... 6 

....... 7 

..... 12 

..... 21 

 

Saunders 

SUMMA

Backgrou

• SaundTowncoastafronta

• Recenthreatearly then fSaund

• In resof Coapotencoasta

• The nconsidbetweUnallo

• The walong itself, along

Prevailin

• ThereSaund

• The pratherepisod

• The sflush swith thto swe

• Conseongoibufferin per

Beach ‐ Ass

ARY

und

ders Beachsville’s CBDal reach be

age to the se

nt erosion et of erosion.2009 and afollowed by ders Beach

ponse to thastal Erosiotially viableal communi

nature of landeration wheen private ocated Stat

width of buffthe Saundeas well as tthe norther

g Coastal

e is a net traders Beach

primary sourr than a steadic and hea

upply of sasediments ohe need to eep sand no

equently theng averagers naturally riods of eros

essment of 

is a coastaD. An approtween the Bettlement.

events have. Very high

again in earlTC Yasi in foreshore.

hese conceron Mitigatione mitigation ity. This rep

nd tenure frohen assessiproperty boe Land (US

fer betweeners Beach fthe castellarn section).

Processe

ansport of a each year.

rce of sand ady annual

avily reliant

nd to the cooff the catchhave stormorthwards o

ere are ineve north-westrecharged sion on Sau

Coastal Ero

al communitoximately 1Black River

e heightened tides accoly 2010 cauFebruary 2

rns, Townsvn Options fostrategies tport presen

onting the tong appropr

oundaries aSL) for which

n the beach foreshore -

ated planfor

es

pproximate.

supply to Srate, the suon process

oast from thhment and s or sustain

off the subm

vitably perioterly sand trprior to the

unders Beac

sion Mitigat

ty located a.4km long fentrance a

d concerns mpanied by

used foresho2011 - which

ville City Coor Saundershat can be

nts the findin

ownship Saiate erosionnd the beach Council is

and privatedue to the sm of the se

ely 10,000m

Saunders Beupply of thises affecting

he Black Rivthrough the

ned periodsmerged delta

ods where aransport of onset of adch. Howeve

tion Options

approximateforeshore nend Althaus

by the locay moderatelore erosionh caused co

ouncil has cs Beach. Tconsidered

ngs of those

aunders Bean mitigation ch consists s the trustee

e property bslight crescaward prop

m3 to 14,000

each is the s sand to Sag the sand d

ver relies one lower reac of strong sa onto Saun

actual sand 10,000m3 to

dverse norther these ero

s 

ely 25kms wear the nortCreek form

al community rough sea. These ero

onsiderable

ommissioneThe objectiv

for the foree investigat

ach is an imoptions. Tof an Espla

e for manag

boundaries ient shape o

perty bounda

m3 of sand

nearby Blaaunders Bedelta at the

n infrequentches of the south-eastenders Beac

supply doeo 14,000m3

herly sea coosion phase

west-north-wthern end o

ms the ocean

ty regardinga conditionsosion event damage to

ed an Asseve is to identeshore frontions.

mportant he foreshoranade on gement purp

is not constof the shorearies (partic

northwards

ack River. Heach is some

river entran

t major floodriver, in conrly wave coh.

es not match3 each year,onditions – res are typic

 

Page | i  

west of of the n

g the s in ts were

o the

ssment tify ting the

re

poses.

tant eline cularly

s along

However ewhat nce.

ds to njunction onditions

h the , nor are resulting ally

Saunders 

followmore

• Whilsprevawith sstrongyear t

• The reoverwgreat dunessubstathe intlocatio

• Whenvulnerthis foto thewash simult

• Howedama

• Duringover itquick procethat othat o

• The hincrea

Recomm

• WhendefineIn othSaundas a sprotec(ie. wi

Beach ‐ Ass

wed by perioenergetic s

t there are tiled whereb

sand at a long cycles of eto year arou

elatively lowwash. This p

that waves s - ocean wantially subtertidal beaon.

n considerinrability of thoreshore, th damage thover the be

taneous wa

ever in termsging as less

g less sevet), thereby csuccessionsses can acccur on Sauccurred in e

high rates ofased ocean

mended Ero

n considerine a “Coastaer words, itders Beachseawall. Prcted, whereithin the ero

essment of 

ods of beachsouth-easter

these cycleby the shoreng-term rateerosion andund the ave

w foreshore phenomenono longer d

ater levels amerged. Och slope m

ng erosion mhe Saundershe local comhat can be ineach duringave action c

s of shorelins severe bu

re events, wcausing recn, their accuct to restoreunders Beaearly 2009 a

f shoreline rwater level

osion Mitig

ng foreshorel Defence Lt forms the l shoreline, roperty and

eas foreshorosion buffer

Coastal Ero

h recovery wrly wave ac

es of beach eline betweee that matcd accretion rage shorel

along Saunon occurs wdissipate thare such th

Once the stoay not have

mitigation ms Beach for

mmunity andnflicted by t severe cycan cause ex

ne recessiout more freq

waves can dcession of thumulating efe beach proach. The eleand early 20

recession inls and wave

gation Stra

e protectionLine” which landward boor alternativ

d infrastructure areas sers).

sion Mitigat

when greatctivity.

erosion anden the Blaches the sanmean that tline position

nders Beacwhen the stoeir energy dat the wave

orm causinge retreated

measures, it reshore to sd foreshore the elevatedclone occurrxtensive da

on, such sevquent storm

directly attahe beach faffect can be

ofiles as parevated tides010 were in

n recent yeae activity.

ategy

measures represents oundary of vely the aligure landwaraward of th

tion Options

er sand sup

d accretion,ck River andnd moved othere are apn.

ch makes it orm tide buidirectly on tes wash oveg overwash inland much

is importanstorm events

infrastructud ocean warences. Su

amage.

vere eventsevents.

ack the beacace. If suche considerabrt of the typis and simul

ndicative of

ars have co

on any shothe landwaany erosiongnment of ard of the Coe line lie wi

s 

pply is initia

, over time ad Althaus Cff the shoreppreciable f

particularly lds during a

the beach ser the beachabates, theh further tha

nt to apprecs. Because

ure are partter levels a

uch storm tid

on their ow

ch itself (rat events occble before nical erosionltaneous rosuch pheno

oincided with

oreline, it is ard limit of an buffers to any protectiooastal Defenthin the act

ated during y

a steady-stareek is supp

eline. Howevfluctuations

susceptiblea cyclone toslope or on th slope sinc

e actual posan its pre-st

iate the spee of the low icularly susnd waves thde inundatio

wn are not a

ther than wacur in relativnatural beac / accretionugh sea coomena.

h a period o

necessary tacceptable e

protect the on structurence Line remtive beach s

 

Page | ii  

years of

ate has plied ver from

e to o be so the ce it is sition of torm

ecific level of ceptible hat can on and

as

ash vely ch cycles nditions

of

to erosion.

e such main system

Saunders 

• WhenSaundRiver three

o Somo

o Ceis ais a

o Noen

• This sare insince partitiintegr

• The rerequirforesh

Southern

• No dir

• Givennortheforeshshould

• The fobe es

Central P

• Two vstakehoption

Option

o inishto

o onto

Beach ‐ Ass

n considerinders Beachand Althaucoastal pre

outhern Precost end of C

entral Precinalmost the eapproximat

orthern Prectrance of A

separation i any way cothe processoning lends

rate well ove

ecommenderes considehore.

Precinct : B

rect interven

n the episoderly storm ehore and frod occur on

oreshore shtablished at

Precinct : Be

viable optionholders for ns being:

n 1 : Beach

itial placemhoreline that

4 consecut

n-going plackeep the re

essment of 

ng appropria it is necesss Creek. In

ecincts, nam

cinct : from Cay Street.

nct : from tentire oceately 1.4kms

cinct : fromlthaus Cree

nto coastal ompartmenses affectins itself to theer the entire

ed erosion ration of dif

Between the

ntion, since

dic nature ofevents, thereont dune. It the foresho

hould be mot regular int

etween Sou

ns are availthe long-ter

h Nourishme

ent of approt existed in tive years;

cement of aeinstated bu

Coastal Ero

ate erosion sary to consn doing so it

mely:

the entrancIt is approx

he southernn frontage oin length.

approximaek. It is app

precincts dtalised. Th

ng each have developme Saunders

mitigation sfferent strate

e Black Riv

e this Southe

f sand suppe will invariais therefore

ore along th

onitored by tervals alon

uthern End o

lable for conrm protectio

ent only

oximately 11941. This

an average ouffer charge

sion Mitigat

mitigation osider the ent is evident

ce of the Blximately 4.2

n end of Caof the deve

ately Saundeproximately

does not impey are not i

ve significanment of viabl

Beach coa

strategy for egies for th

ver and the S

ern Precinc

ply; and thatably be per

e also recomis Southern

regular survg this south

of Cay Stree

nsideration on of this 14

20,000 m3 s initial sand

of between ed with sand

tion Options

options alonntire coastathat the sho

ack River to2kms in leng

ay Street to loped comm

ers Beach R400 metres

ply that the isolated or dnt influencesle erosion m

astal reach.

the Saundee three prec

Southern E

ct is currentl

t it does notriods of shommended thn Precinct.

veys. Apprhern precinc

et and Saun

by Townsv400 metre lo

of sand to rd placemen

5,000m3 and.

s 

ng the subul reach betworeline can

o approximagth.

Saunders Bmunity of Sa

Road northws in length.

coastal prodiscrete secs on the oth

managemen

ers Beach ccincts along

End of Cay S

ly in a phas

t necessarilrt-term eroshat no future

ropriate tranct.

nders Beac

ville City Coong Central

reinstate thet could be u

nd 10,000m

P

rban foreshween the Blbe conside

ately the so

Beach Roadaunders Be

wards to the

ocesses withctions of shhers. Howent strategies

coastal reacg the entire

Street

se of accreti

ly coincide wsion of the e developm

nsect lines n

h Road

uncil and otl Precinct. T

e position oundertaken

m3 of sand p

 

Page | iii  

hore of ack

ered as

outhern-

d, which ach. It

e ocean

hin each oreline,

ever this s that

ch

on.

with

ment

need to

ther These

of the over 3

per year

Saunders 

Option 2

o se

o coeswge

o plimupshtim

o onto

Recom

o Eiapit imestrintup

• Irrespregula

Northern

• No dir

• Howebe peno int

• Continlines.

 

 

Beach ‐ Ass

: Seawall an

elect an alig

omplete a dstimated to

within the sizeotextile co

acing an inmproved beapon the chohould be at mes to serv

n-going plackeep the b

mmended in

ther of thesppropriatelyis recommeechanicallyrategy, mecto the deplepper beach

pective of thar surveys o

Precinct : B

rect interven

ever given thriods of shoensification

nue to mon

essment of 

nd Beach N

gnment for t

detailed strurequire the

ze range of ntainers.

itial volumeach and fore

osen alignmleast a sane as a buffe

cement of auffer in fron

nterim strat

se long-termy designed aended that ty redistributichanical plaeted foredunarea.

e option adon previous

Between Sa

ntion, since

he dynamicort-term eron of develop

itor the fore

Coastal Ero

Nourishmen

the seawall

uctural desige placement1 tonne to 5

e of sand in eshore ame

ment of the Cd volume oer in front of

an average ont of the sea

tegy

m measuresand for the nthe strategyng sand on

ant and equne area - th

dopted, the fsly establish

aunders Bea

e this Northe

c nature of thosion of this pment shoul

eshore throu

sion Mitigat

nt

(ie. a Coas

gn of a buriet of either ap5 tonne, or

the existingenity. The vCoastal Deff 35m3 / mef the seawa

of between awall charge

s will invarianecessary a

y recently imn the beach ipment are

hereby haste

foreshore shed beach tr

ach Road a

ern Precinct

he Althaus foreshore.

ld occur in f

ugh annual

tion Options

stal Defence

ed seawall;pproximatelalternativel

g buffer in frvolume of afence Line; etre length oall.

5,000m3 aned with san

ably be expeapprovals to

mplementedprofile shouused to moening the na

should contiransect line

nd Althaus

t is currently

Creek entra It is therefo

future on th

surveys of

s 

e Line).

which at thly 15,000m3

y constructe

ront of the sany importedhowever asof foreshore

nd 10,000md.

ensive and o be obtaine

d by Townsvuld be conti

ove sand upatural rehab

nue to be mes.

Creek

y in a phase

ance area, tore also recis northern

established

his stage is 3 of armoured of sand-

seawall to pd sand will s a guide the available a

m3 of sand p

require timeed. In the iville City Coinued. Undp the beach bilitation of

monitored th

e of accretio

there will incommendedforeshore p

d beach tran

 

Page | iv  

r rocks -filled

provide depend ere at all

per year

e to be nterim,

ouncil of der this

slope the

hrough

on.

variably d that precinct.

nsect

Saunders

1 INTR

1.1 Ge

SaundersTownsvillcoastal reto the set

In recent been thre

TownsvillMitigationstrategiespresents

This repo

• This Sthe Sa

• Sectioforesh

• Then

• This isSaund

• Sectio

• Techn

• Appen

 

1.2 Re

As shownBay is a wfaces appGreat Bar

The gradiflat, provid

 Beach ‐ Ass

RODUCT

eneral

s Beach is ae’s CBD. A

each betweettlement.

years this featening priv

e City Counn Options fos that can bthe findings

ort has been

Section 1, waunders Be

on 2 providehore and ne

in Section 3

s followed iders Beach

on 5 then su

nical referen

ndices to su

gional Se

n on Figure wide cresceproximately rrier Reef.

ient of the sding some

sessment of 

TION

a coastal coAn approximen the Blac

foreshore havate and pu

ncil has theor Saunderse considere

s of those a

n structured

which consiseach foresho

es a broad oearshore reg

3, a numbe

n Section 4 coastal rea

ummarises

nces are lis

upport the te

etting

1, Saunderent-shaped e

north-east

seabed appnatural prot

Coastal Ero

ommunity lomately 1.4kmck River Ent

as been expublic assets

refore comms Beach. Thed for the fossessments

as follows:

sts of an intore.

overview ofgions of the

r of generic

4 by an asseach.

the recomm

ted in Secti

echnical co

rs Beach is embaymenonto the br

roaches ontection due

osion Mitigat

ocated approm long forestrance and A

periencing v.

missioned ahe objectiveoreshore fros.

troduction a

f the coastae Saunders

c strategies

essment of

mended ero

on 6.

ontent of the

located on t between Coad open w

nto the localto the atten

tion Options

oximately 2shore nearAlthaus Cre

variable rat

an Assessme is to identionting the co

and provides

al processesBeach coas

to mitigate

specific stra

osion mitiga

e assessme

the southerCape Pallarwaters betw

foreshoresnuating effe

s

25kms west-the norther

eek forms th

es of erosio

ment of Coaify potentialoastal comm

s some bac

s that are shstal reach.

erosion are

ategies in th

tion strateg

ent are then

rn shores orenda and Leen the ma

s of Saundect on incom

-north-westn end of the

he ocean fro

on which ha

astal Erosionlly viable mimunity. Thi

ckground re

haping the

e offered.

he context o

y.

included. 

f Halifax BaLucinda Poiainland and

ers Beach aming wave e

 

 Page | 1  

t of e ontage

ave

n itigation is report

garding

of the

ay. The nt. It the

re quite energy.

Saunders

NevertheBarrier Refetches thforeshore

 

1.3 Lo

Figure 2 snumber othis repor

• the de

• the enSaund

• Althau

• an unBeach

Througholong ocea There havrecent yeThe locat

 Beach ‐ Ass

less, the feteef system hat the largee.

Figu

cal Settin

shows the sof features ert. The mos

eveloped ar

ntrance andders Beach

us Creek, w

-named creh suburb.

out this repoan frontage

ve been intears; and thetions of thes

sessment of 

tches to thebeing some

est waves c

re 1 : Loca

ng

setting of Saevident in thst relevant o

rea that con

d delta of the coastal rea

which forms

eek that disc

ort the term of the deve

ermittent bee results of se transect

SAUNDERS  BE

LUC

Coastal Ero

e north-easte 75kms offcan propaga

ation of Sau

aunders Behis figure whof these bei

nstitutes the

e Black Rivach;

the norther

charges acr

Saunders Beloped subu

each transethese survelines and th

EACH 

HALIFAX BAY 

CINDA  POINT 

osion Mitigat

t of Halifax Bfshore. It isate across H

unders Bea

each within ahich are refeng:

e community

ver, which fo

rn boundary

ross the for

Beach is usurban comm

ect surveys eys have behe survey re

TOWNSVILL

CAPE 

PALM  ISLAND 

tion Options

Bay are quis from acrosHalifax Bay

ach in a reg

a more locaerred to in l

y of Saunde

orms the so

y of the reac

eshore to th

sed to definemunity of Sa

undertakeneen made aesults are s

LE

MAGNETIC  ISLAN

 PALLARENDA

s

ite long, witss these opeand onto th

gional cont

al context. Tater discus

ers Beach;

uthern bou

ch; and

he south of

e the approaunders Bea

n along Sauavailable forummarised

CAPE  CLEVELAND

GREAT BARRIER REEF 

ND 

h the main en north-eahe Saunder

text

There are asions throu

ndary of the

the Saunde

oximately 1.ach.

nders Beacr this asses in Appendi

 

 Page | 2  

Great ast rs Beach

a ghout

e

ers

4km

ch in sment. ix A.

Saunders

The survesomewhahighest - crest also South of tRL+3.5m been a di

1.4 Lo

The naturwhen assFigure 5, Esplanadpurposesphotograp

The widththe Saundcastellatesection).

 Beach ‐ Ass

ey results (sat variable. with levels

o tends to be

the sealed pto RL+5.0mstinct fored

cal Fores

re of land tesessing appthe foreshoe on Unallo. These figphs taken in

h of buffer bders Beach

ed planform

sessment of 

Figur

supplementThe foredugenerally ae around th

pavement om AHD. Aloune in rece

shore Lan

enure alongpropriate eroore betweenocated Stategures have bn late 2009.

between theh foreshore -

of the seaw

dev

Coastal Ero

e 2 : Saund

ted by on-siune along thround RL+5

his level.

of the Esplaong the souent years wit

nd Tenure

g the foreshoosion mitigan private proe Land (USbeen provid.

e beach and- due to theward proper

veloped  foresSaunders  Be

osion Mitigat

ders Beach

ite observathe northern 5m AHD. T

anade, the fouthern-mostth a crest a

e

ore of Saunation optionsoperty bounL) for which

ded by Town

d private proe slight cresrty boundar

shore  of  each 

tion Options

h coastal re

tions) indicapart of Sau

The foresho

oreshore tet end of Cayround RL+4

nders Beachs. As evidendaries andh Council isnsville City

operty bouncent shape

ries (particu

s

each

ate that the unders Beacre immedia

ends to be loy Street, the4.0m to RL4

h is an impoent in Figure the beach the trusteeCouncil and

ndaries is no of the foreslarly along t

foreshore lch is typical

ately behind

ower, beingere has typi4.5m AHD.

ortant consie 3, Figure 4consists of

e for managd use aeria

ot constant shore and tthe northern

 

 Page | 3  

evel is lly the this

g around cally

deration 4 and an ement l

along the n

Black River

Entrance

Saunders

Property widths folsea cond25m metrdiminishe2010; and

In recent has beenFigure 6).overlays w

These recthreat of sdamage t

 

Figu

 Beach ‐ Ass

boundarieslowing signitions in theres existed ed since thad as a cons

years an in undertaken. The resulwere prepa

cent erosionshoreline reto the foresh

ure 3 : Fore

sessment of 

overlain onnificant erose period of Jalong most

at time due tequence of

nformal survn by Integrats indicate tred, foresho

n events haecession. Thore.

eshore Prop(supe

Coastal Ero

n the aerial sion earlier tJanuary to Mt of the foresto additionaf TC Yasi in

vey of the poated Sustainthat since 2ore buffers

ave heightenTC Yasi in e

perties & Serimposed on

osion Mitigat

photographthat year whMarch. Minshore. The

al high tidesn February 2

osition of a nability Serv2009 when thave been

ned concernearly Februa

Survey Trann a 2009 aer

   

tion Options

hs of 2009 shich was ca

nimum buffeese buffer w and advers

2011.

section of tvices of Towthe aerial phfurther redu

ns by the loary 2011 als

nsects - norial photogra

s

show the reaused by higer widths of widths have se sea cond

the beach ownsville Cityhotographsuced by som

ocal commuso caused c

orthern Sauaph) 

esidual buffegh tides andaround 14mbeen furtheditions in Ja

opposite Cay Council (r for the prome 5m to 6

unity regardconsiderable

unders Bea

 

 Page | 4  

er d rough m to er anuary

y Street refer to perty m.

ing the e

ach  

Saunders

 

 Beach ‐ Ass

Figure 4

sessment of 

: Foreshor(supe

Coastal Ero

re Propertieerimposed on

osion Mitigat

           

es - centran a 2009 aer

         

tion Options

al section orial photogra

s

of Saundersaph) 

s Beach

 

 Page | 5  

 

Saunders

 

 Beach ‐ Ass

Figure 5 :

sessment of 

Foreshore(supe

 

Coastal Ero

e Propertieerimposed on

osion Mitigat

            

s - southern a 2009 aer

tion Options

rn section rial photogra

s

of Saundeaph) 

rs Beach

 

 Page | 6  

 

Saunders

 

 Beach ‐ Ass

Figure (provide

sessment of 

6 : Indicated by Integra

Coastal Ero

tive buffer wated Sustain

osion Mitigat

widths - Canability Servi

tion Options

ay Street, Sices of Town

s

Saunders Bnsville City Co

Beach ouncil) 

 

 Page | 7  

 

Saunders

2 LOC

2.1 Ba

The coastowards tprocessesEntrance coast via waves ansandy de

Previous history of utilised m1941) to isound tecstrategy fdirect releAppendix

ParticularappreciatJanuary 2subseque

• ThereSaund

• The srapidlyconsisnorm”

• Never

o sigof

o the20

o thehase

• Althouaverabeen

 Beach ‐ Ass

CAL COA

ckground

tal processhe north-wes shaping thimmediatelthe extensi

nd currents oltas indicati

detailed anerosion an

mathematicaidentify andchnical basifor this foresevance to thx B.

rly relevant te that these2010 and thent severe e

e is a net traders Beach

horeline cay during higstently show”.

rtheless sin

gnificant accSaunders B

e foreshore009) since 1

e foreshoreas accreted easonal time

ugh some sge trend ovone of sma

sessment of 

ASTAL

d

es in Halifaest along thhe beach aly to the souive shoals wonto local bng their sup

nalysis of shd accretion

al modelling measure his to supporshore. Givehis assessm

findings of e findings whe devastatievents do n

ansport of a each year.

n be very dgh-energy wwn either un

ce 1941 the

cretion of thBeach;

south-east941;

north-east since 1941

eframes.

sections of Sver the entirall net accre

Coastal Ero

PROCES

x Bay resulhe foreshorere strongly uth-east. Twithin the enbeaches. Opply of sedi

horeline pos cycles sinc, surveys a

historical reart the determen the impoment of eros

that earlier were determing effects oot alter the

pproximate.

dynamic. Siwave eventsniform on-go

ere have be

he shoreline

t of Saunde

of Saunder, but is part

Saunders Bre coastal petion.

osion Mitigat

SSES

lt in the trane of Saundeinfluenced

This river sysntrance delt

Other smallements to th

sition of Sauce at least 1nd historicaalignments mination of ortance of thsion mitigati

study are smined prior tof TC Yasi iconclusion

ely 10,000m

ignificant chs. There is oing erosio

een some n

e to the sou

ers Beach R

rs Beach Roticularly dyn

Beach have recinct from

tion Options

nsport of saers Beach. by the presstem has prta - which h

er local creee coast.

unders Beac1941. That al aerial phoof the localan appropr

hat earlier wion options,

summarisedo the adverin Februarys or overall

m3 to 14,000

hanges in thno particulan or accreti

et changes

th of the de

Road has rec

oad (to the namic with s

clearly retrem the Black

s

nd from theConsequenence of therovided sed

have then beeks and stre

ch (Smithercomprehen

otographs (d shoreline. iate erosion

work by Dr. it is include

d below. It irse sea andy 2011. How

findings of

m3 of sand

he shorelinear location ton - “fluctua

to the shor

eveloped su

ceded by u

entrance ofsignificant f

eated in recRiver up to

e south-eastntly natural e Black Rivediments to theen worked

eams also h

rs, 2009) rensive earlierdating back It provides

n mitigation Smithers aned herein a

is importantd tide conditwever thesethat study.

northwards

e position octhat has ations are th

reline, name

uburban com

p to 15m (a

f Althaus Cluctuations

cent decadeo Althaus Cr

 

 Page | 8  

t

er he d by have

veals a r study

k to a

nd its s

t to tions of e

s along

ccur

he

ely

mmunity

as at

reek) over

es, the reek has

Saunders

• In recattribuThe eupper

• It is pohave high t

2.2 Ov

Waves mtransport.intensity a

2.2.1 Lo

Longshorthat contrdetermineunderstanerosion m

Waves aralongsho

The anglebe the waaccount fo

On most cproducinglocation, tduring oththere is nthe case.

Typically annual lowhere theboth longaverage n

Whilst thesand is besame ratebe no netSaundersinto Halifa

 Beach ‐ Ass

cent years, tuted to highelevated ocer beach area

ostulated thbeen part oides will not

verview of

ove sand in. Both procand directio

ongshore t

re transport rol beach mes in large pnding of lon

managemen

rriving with tre current w

e at which taves themseor notable v

coasts, wavg day-to-daytransport mher times ofo net chang

longshore mngshore moe net transpshore direcnet north-we

ere may be eing lost ane as it is bet change to s Beach is tax Bay furth

sessment of 

the increaseher than norean water lea.

hat since theof the 18.6 yt be as high

f Sand Tr

n two fundacesses can on in respon

transport

is the movemorphology,

part whethengshore sannt practices.

their crests which initiate

he incomingelves), nevevolumes of

ves arrive ay and seaso

may be to thef the year. ge in the be

movement iovement. Cport rate is tctions througesterly rate

a net longsnd thereforeing transpothe beach ohe nearby B

her to the so

Coastal Ero

ed erosion ermal tides oevels during

e higher anyear tidal eph or as frequ

ransport

mental wayoccur simul

nse to preva

ement of salongshore s

er shorelinesnd transport

at an anglees and main

g waves acertheless thsand to be

at the beachonal reversae left (lookinIf the volum

each positio

is greater inCertainly thiowards the ghout a typiof 10,000m

shore transpe the beach rted along tover annuaBlack Riverouth contrib

osion Mitigat

experiencedccurring in g such even

d more freqpoch, in comuent.

Processe

ys - by longsltaneously, ailing wave

and along thsand transps erode, act is essentia

e to the planntains sand

ct on the beaheir continuamoved ann

h from a numals in transpng seaward

mes of transn over annu

n one directs is the casnorth-west

ical year. Em3 to 14,000

port along Sis eroding.

the shore atl timeframe. Certainly

bute sand to

tion Options

d on Saundconjunction

nts resulted

quent tides tming years a

es

shore transbut both vaconditions.

he beach. Oport is probacrete or rem

al for the det

n alignmentd transport a

ach face maal and relennually on loc

mber of diffeport directio

d) during paport are equal timefram

tion than these for the Sat despite theEarlier inves0m3 each ye

Saunders Be So long ast any partic

es. The primother rivers

o Saunders

s

ders Beach n with rough

in substant

that occurreas the cycle

port and byary significa

Of all the vaably the momain stable.termination

t of the shoralong the be

ay only be vntless actioncal shoreline

erent offshoon. At a parrt of the yeaual in each

mes. Howe

e other – whaunders Beere being sastigations esear.

each, this ds sand is beular location

mary sources and creekBeach, but

is more direh sea condittial erosion

ed in recente wanes ext

y cross-shorntly in their

arious proceost influentia. Conseque of success

reline createeach.

very small (n is sufficienes.  

ore directionrticular beacar and to thdirection thver this is n

hich resultsach shoreliand movemstimated an

does not meeing supplien, then there of sand suks that discht it is the Bla

 

 Page | 9  

ectly tions. of the

t years treme

re

esses al. It ently an sful

e an

as may nt to

ns - ch e right

hen not often

in a net ne,

ment in n

ean that ed at the re will upply to harge ack

Saunders

River whicoastal re

However episodic aThe suppsedimentsneed to hsand nort

Consequeongoing ain periodsfollowed bmore ene

Whilst theprevailed sand at areflected only a minsince 194

In other wa long-tertransport

It is pertinregion thaCungulla that sandsteadily eerosion a

2.2.2 Cr

Cross-shoonshore/ooccurs dustorms or

Strong waerosion oprofile. Tseaward eonto the bbeach co

 Beach ‐ Ass

ch overwheeach of Sau

rather thanand heavily

ply of sand ts off the cat

have stormsthwards off

ently there aaverage nors of erosionby periods o

ergetic south

ere are theswhereby th long-term rin the findinnor change41.

words, whilsrm balance was match

nent to noteat are experand Bushla is now bein

eroding. Howt Saunders

ross-shore

ore transpooffshore mouring ambier cyclones th

ave action af the beach

The eroded sedge of thebeach, whendition. 

sessment of 

elmingly prounders Beac

n a steady ay reliant on pto the coasttchment an

s or sustainethe submer

are inevitabrth-westerly on Saundeof beach reh-easterly w

se cycles ofhe shorelinerate that mangs of Dr. S to the net v

st there werein these proed by the lo

e that this is riencing eroands Beachng suppliedwever this dBeach.

e transport

ort is the moovement. Wnt conditionhat it becom

and elevateh as sand is sand is mov

e surf zone. re waves a

Coastal Ero

ovides the gch.

annual rate, processes at by the Blacd through thed periods orged delta o

bly periods wy sand transers Beach. covery whe

wave activity

f beach erose between tatches the s

Smither’s eavolume of s

e cycles of ocesses beong-term ne

quite a diffosion probleh, the longshd to these fodiminished l

t

ovement of sWhilst this wns (ie. the nmes most ev

ed ocean waremoved fr

ved offshor Subsequend onshore

osion Mitigat

greater volu

the supply affecting theck River relhe lower reof strong soonto Saunde

where actuasport of 10,0However th

en greater sy.

sion and ache Black Risand movedarlier study, sand on the

local erosioecause the ret supply of

ferent scenaems. For exhore sand troreshores. longshore s

sand perpewashing of s

ormal day-tvident and m

ater levels drom the dune during thent milder w

e winds then

tion Options

me of sand

of sand to Se sand deltaies on infreaches of th

outh-easterlers Beach.

al sand sup000m3 to 14hese erosioand supply

ccretion, oveiver and Altd off the showhich concdowndrift S

on and accrrate of northsand from

ario to otherxample at Rransport ratConsequen

supply of sa

ndicular to and up andto-day condmost critica

during such ne system ae storm to cave condition re-work it

s

to the imm

Saunders Ba at the Blacquent majoe river, in cy wave con

pply does no4,000m3 eacn phases ais initiated

er time a stethaus Creekoreline. Thcluded that tSaunders B

retion, thereh-westerly lothe south-e

r foreshoresRowes Bay,tes are greantly these beand is not th

the beach –d down the bditions), it isal.

events canand upper recreate a sanons can retuto establish

 P

mediate dow

Beach is somck River Enr floods to fonjunction w

nditions to s

ot match thech year – rere typically during year

eady-state k is suppliedis behaviouthere has beach coasta

e was neverongshore s

east.

s in the Tow Nelly Bay,

ater than theeaches hav

he primary c

– in other wbeach profi

s during sev

n cause sevegions of thnd bank neaurn this sanh the pre-sto

 

Page | 10  

wndrift

mewhat ntrance. flush with the weep

e esulting

rs of

has d with ur is een al reach

rtheless and

wnsville

e rate ve been cause of

words, le

vere

vere he ar the nd back orm

Saunders

During paoccur in omay take

There is astorms orphenomelonger disare such

Once ovecurtailed. slope andareas sincan wash

Nevertheoverwashabates, thfurther thaearly partbreak dire

Nevertheof the prothe upper

2.2.3 Vu

The relatioverwashresponse

More thanconseque(Hopley, shoreline greater wmore receexpected

The imagoff the beThe uppesuch natu

 Beach ‐ Ass

articularly seonly one or many year

another pror cyclones, tenon occursssipate theirthat the wa

erwash com Instead of

d carried insce the fores

h over the d

less since wh, the beachhe actual poan its pre-stt of the stormectly on the

less when oofile. Naturar beach prof

ulnerability

ively low forh. Recent c of the Sau

n 10 metresence of TC A1974). Howrecession a

wave energyent event refollowing s

es presenteeach face aner beach proural features

sessment of 

evere stormtwo hours;

rs.

cesses affethere can b

s when the sr energy dirves wash o

mmences, fuf being movshore. The shore is notunes and p

waves are nh itself doesosition of thtorm locatiom prior to o beach) wh

overwash oal features sfile are wipe

y of Saund

reshore alocyclone evenders Beac

s erosion ofAlthea whe

wever in Fealong the C

y. It is evideesulted in shuch a seve

ed in Figurend depositeofile is seens being flatt

Coastal Ero

ms, very signwhereas re

ecting crosse considerastorm tide brectly on theover the bea

urther recesved offshore

consequent only inundenetrate inl

not actively s not retreate intertidal on. It is the overwash (wich has a g

ccurs, it flatsuch as a loed out by th

ders Beach

ng Saundernts offer tes

ch to overwa

f Saunders n it crossedbruary 2011

Cay Street oent that ovehoreline recre event.

e 7 show theed inshore bn to be devotened by ov

osion Mitigat

nificant erosecovery of th

s-shore sandable “overwbuilds duringe beach sloach slope si

sion of the e, sand in thnces of overated by stoland.

attacking tht significantlbeach slopeseverity an

when oceanreater effec

ttens the beow foredunehe overtopp

foreshore

rs Beach mstimony to tash events.

Beach is red the coast 1 the more

ocean frontaerwash of thcession bein

e extensiveby waves asoid of any foverwash.

tion Options

sion of sandhe beach by

d transport.wash” of somg a cyclone pe or on theince it is sub

foreshore she upper berwash can brm surge, b

he submergly. Once the may not h

nd nature of levels are s

ct on shoreli

each slope -e, scarp anding water le

to storm e

makes it partthis vulnera

eported to hnear Balgalsevere TC

age despite he Saundersng much les

e amount of s they washoredune, be

s

d from the uy onshore tr

During pame foreshor

to be so gre dunes - obstantially s

still occurs bach is swepbe devastatbut destruct

ged beach she storm cauhave retreatf the conditisuch that wine recessio

- particularlyd/or berm thevels and w

events

ticularly susbility and ill

ave occurrel Beach in DYasi causethe higher

s Beach forss than mig

beach sandhed over theerm or erosi

 P

upper beachransport pro

articularly sees. This reat that wacean water submerged.

but is signifipt up over tting to foresive cyclonic

slope duringusing overwted inland mons during

waves actuaon.

y in the upphat are typic

wave action.

sceptible to ustrate the

ed as a December 1d much lesstorm tide aeshore duriht intuitively

d that was se crest of thon scarp du

 

Page | 11  

h can ocesses

evere

aves no levels

.

cantly he

shore c waves

g wash much the

ally

per part cal of

1971 s and ing this y be

swept he beach. ue to

Saunders

When convulnerabiforeshoredamage tthe beach

Such storparticularforeshore

However damagingcan directbeach fac

If such evconsideratypical eroperceivedGiven theevents, thintensity oconditions

2.3 Su

The impoSaunders

• ThereSaund

SAND  SW

 Beach ‐ Ass

nsidering erlity of the S

e, the local cthat can be h during sev

rm tide inunrly to foreshe occurred d

in terms of g as less setly attack thce.

vents occur able before osion / accrd by local ree particular vhis increaseof such eves that occur

mmary o

ortant aspecs Beach can

e is a net traders Beach

WEPT  INSHORE  O

sessment of 

rosion mitigaunders Becommunity inflicted by

vere cyclon

ndation and ore vegetat

during TC Y

Figure 7

shoreline revere but mohe beach its

in relativelynatural bea

retion cyclesesidents andvulnerability

ed erosion hents in recenrred in early

of Coastal

cts of the locn be summa

ansport of a each year.

FF  BEACH 

Coastal Ero

gation measeach foreshand foreshothe elevatee occurrenc

simultaneotion. Indeed

Yasi as a res

: Evidence

ecession, sore frequen

self (rather t

y quick succach processs that occurd Council toy of the Sauhas been dunt years. Thy 2009 and

l Process

cal coastal arised as fo

pproximate.

osion Mitigat

sures, it is imore to stormore infrastrued ocean waces.

ous wave acd considerasult of overw

e of overwa

such severent storm evethan wash o

cession, theses can act r on Saundeo have beenunders Beaue primarily he elevatedearly 2010

ses

processes tollows:

ely 10,000m

tion Options

mportant to m events. Bucture are pater levels a

ction can caable damagwash.

ash during

e events on ents. Duringover it), ther

eir accumulto restore bers Beach. n increasingch foreshorto the incre

d tides and swere indica

that are sha

m3 to 14,000

s

appreciate Because of particularly sand waves

ause extense to the Sau

TC Yasi

their own ag less severeby causin

ating effect beach profil The erosio

g somewhatre to erosioneased occusimultaneouative of such

aping the sh

m3 of sand

SAND  SWEP

 P

the specificthe low levesusceptible that can wa

sive damageunders Bea

are not as re events, wg recession

can be es as part o

on threat is t in recent yn by moderrrence and us rough seh phenome

horeline of

northwards

PT  INSHORE  OFF

 

Page | 12  

c el of this to the

ash over

e - ach

waves n of the

of the

years. ate

ea na.

s along

F  BEACH

Saunders

• The pratherepisodEntran

The sflush swith thto swe

• Conseongoibufferin perfollowmore

• Whilsprevawith sstrongyear t

• The reoverwgreat dunessubstathe intlocatio

• Whenvulnerthis foto thewash simult

• Howedama

• Duringover itquick procethat othat o

• The hincrea

 Beach ‐ Ass

primary sourr than a steadic and heance.

upply of sasediments ohe need to eep sand no

equently theng averagers naturally riods of eros

wed by perioenergetic s

t there are tiled whereb

sand at a long cycles of eto year arou

elatively lowwash. This p

that waves s - ocean wantially subtertidal beaon.

n considerinrability of thoreshore, th damage thover the be

taneous wa

ever in termsging as less

g less sevet), thereby csuccessionsses can acccur on Sauccurred in e

high rates ofased ocean

sessment of 

rce of sand ady annual

avily reliant

nd to the cooff the catchhave stormorthwards o

ere are ineve north-westrecharged sion on Sauods of beachsouth-easter

these cycleby the shoreng-term rateerosion andund the ave

w foreshore phenomenono longer d

ater levels amerged. Och slope m

ng erosion mhe Saundershe local comhat can be ineach duringave action c

s of shorelins severe bu

re events, wcausing recn, their accuct to restoreunders Beaearly 2009 a

f shoreline rwater level

Coastal Ero

supply to Srate, the suon process

oast from thhment and s or sustain

off the subm

vitably perioterly sand trprior to the

unders Beach recovery wrly wave ac

es of beach eline betweee that matcd accretion rage shorel

along Saunon occurs wdissipate thare such th

Once the stoay not have

mitigation ms Beach for

mmunity andnflicted by t severe cycan cause ex

ne recessiout more freq

waves can dcession of thumulating efe beach proach. The eleand early 20

recession inls and wave

osion Mitigat

Saunders Beupply of thisses affecting

he Black Rivthrough the

ned periodsmerged delta

ods where aransport of onset of adch. Howevewhen great

ctivity.

erosion anden the Blaches the sanmean that tline position

nders Beacwhen the stoeir energy dat the wave

orm causinge retreated

measures, it reshore to sd foreshore the elevatedclone occurrxtensive da

on, such sevquent storm

directly attahe beach faffect can be

ofiles as parevated tides010 were in

n recent yeae activity.

tion Options

each is the s sand to Sag the sand d

ver relies one lower reacs of strong sa onto Saun

actual sand 10,000m3 to

dverse norther these eroer sand sup

d accretion,ck River andnd moved othere are apn.

ch makes it orm tide buidirectly on tes wash oveg overwash inland much

is importanstorm events

infrastructud ocean warences. Su

amage.

vere eventsevents.

ack the beacace. If suche considerabrt of the typis and simul

ndicative of

ars have co

s

nearby Blaaunders Bedelta at the

n infrequentches of the south-eastenders Beac

supply doeo 14,000m3

herly sea coosion phasepply is initia

, over time ad Althaus Cff the shoreppreciable f

particularly lds during a

the beach ser the beachabates, theh further tha

nt to apprecs. Because

ure are partter levels a

uch storm tid

on their ow

ch itself (rat events occble before nical erosionltaneous rosuch pheno

oincided with

 P

ack River. Heach is some

Black Rive

t major floodriver, in conrly wave coh.

es not match3 each year,onditions – res are typic

ated during y

a steady-stareek is supp

eline. Howevfluctuations

susceptiblea cyclone toslope or on th slope sinc

e actual posan its pre-st

iate the spee of the low icularly susnd waves thde inundatio

wn are not a

ther than wacur in relativnatural beac / accretionugh sea coomena.

h a period o

 

Page | 13  

However ewhat r

ds to njunction onditions

h the , nor are resulting ally years of

ate has plied ver from

e to o be so the ce it is sition of torm

ecific level of ceptible hat can on and

as

ash vely ch cycles nditions

of

Saunders

3 ERO

3.1 Co

When con“Coastal Dwords, it fshoreline

Property aforeshorebuffers).

Defining tto what asBeach for

• an aligbound

• an alig

• an aligon thetime).

3.2 De

When conCoastal Drequired. extreme s

However storm tideBeach sumitigationmore sev

This represtrategy -determinascope of tmitigatingstages of

 Beach ‐ Ass

OSION M

oastal Def

nsidering foDefence Linforms the la, or alternat

and infrastre areas seaw

the positionssets are toreshore incl

gnment alodaries of pri

gnment alo

gnment note central se

sign Stor

nsidering foDefence Lin

The Queenstorm event

whilst the ces and wavech an even

n. As discusvere followin

esents a sig- but particuations of crithis assess

g erosion caimplementa

sessment of 

MITIGATI

fence Lin

oreshore prone” which reandward botively the al

ructure landward of the

n of the Coao be defendlude:

ng the landivate proper

ng the seaw

tionally seawction of Sau

rm Condi

oreshore proe it is also nnsland Coat for such pu

characteristes (typically

nt may not bssed in the ng successi

gnificant tecularly for onetical combinment of ero

an still be evation.

Coastal Ero

ION OPT

e

otection meepresents thundary of aignment of

dward of theline lie with

astal Defencded. Option

ward boundrties); or

ward bound

ward of the unders Bea

itions

otection menecessary t

astal Plan nourposes

ics of such y by applyinbe the most

preceding Sve storms o

chnical chale that incornations of mosion mitigavaluated, w

osion Mitigat

TIONS

easures on ahe landward

any erosion any protect

e Coastal Dhin the activ

ce Line therns for a Coa

dary of the

dary of the U

existing forach (where t

easures on ato define a Dominates th

an event cang numerica

critical fromSection 2.2of moderate

lenge to anporates bea

moderate, yation optionsith their det

tion Options

any shorelind limit of acbuffers to p

tion structur

efence Lineve beach sy

refore entailastal Defenc

USL and Es

USL and Co

reshore - sathe shorelin

any shorelinDesign Evehe 100-year

an be deteral modellingm the viewp.3, shorelin

e severity ra

ny detailed dach nourishet more freqs. Neverthetailed design

s

ne, it is neccceptable erprotect the Sre such as a

e remains pystem (ie. w

ls considerace Line alon

splanade (ie

ouncil Espla

ay along thene has retre

ne, as well aent for whichr average re

mined by a g techniquesoint of prove recession

ather than a

design of anhment as anquent eventeless broadn being def

 P

essary to drosion. In oSaunders Ba seawall.

protected, wwithin the ero

ation by Coung the Saun

e. on the se

anade; or

e 1941 aligneated since

as defining h immunity ecurrence in

detailed stus), for Saunviding erosion is likely to a single maj

n erosion mn element. Sts are beyo strategies

ferred to late

 

Page | 14  

efine a other Beach

whereas osion

uncil as nders

eaward

nment that

a is nterval

udy of nders on be or event.

mitigation Such nd the for er

Saunders

3.3 Ge

In essenc“hard” str

Soft (or n

• Do noresult

• Avoidundev

• Plannfrom t

• Beachbeach

• Beachsand fthereb

• Channshore

Hard (or s

• Seaw

• Seawwhilst

• Groynthereb

• Groynmaintcause

In many loand “hard

A more deAppendixBeach copresentedsolutions)

 

 Beach ‐ Ass

eneric Ero

ce, erosion uctural solu

on-structura

othing - allowing losses;

ing developveloped are

ned retreat -the vulnerab

h nourishmeh, thereby p

h scrappingfrom the intby improvin

nel relocatioline erosion

structural) s

walls - which

walls with bet sand is inte

nes / offshoby retaining

nes / offshoaining sand

ed by the gr

ocations thed” solutions.

etailed descx C. To assoastal reachd overleaf in).

sessment of 

osion Miti

mitigation outions.

al) solutions

wing coasta

pment - by ieas;

- removing tble area;

ent - rehabiproviding an

g - by using ter-tidal zong erosion b

on - relocatn so that the

solutions tha

h act as phy

each nourishermittently p

re breakwag sand on th

re breakwad on the bearoyne’s inter

e optimum .

cription of eist in evalua

h, a summarn Table 3.1

Coastal Ero

igation O

options can

s would typ

al processe

mplementin

the erosion

litate erodinn adequate e

earthmovinne or nearshbuffers on th

e dynamic rey have a le

at can be ut

ysical barrie

hment - wheplaced in fro

ters - used he eroding f

ters with beach, and berruption to l

manageme

each generiating these ry of the adv(for non-str

osion Mitigat

Options

be conside

ically includ

s to take th

ng regulator

threat by re

ng foreshoreerosion buf

ng plant andhore sandbahe beach;

river or creeesser impac

tilised to mi

rs to preven

ere the seawont of the w

to inhibit thforeshore fo

each nouriseach nourishongshore s

ent strategy

c erosion mvarious optvantages aructural opt

tion Options

ered as “soft

de:

eir natural c

ry controls w

elocating ex

es by directffer;

d equipmenanks into th

ek entrancect.

tigate the th

nt shoreline

wall defineswall for impr

he natural loor longer pe

hment - whhment redusand supply

may includ

managementions in the nd disadvanions) and in

s

t” non-struc

course while

with regard

xisting deve

t placement

t to mechanhe upper be

es that may

hreat of ero

e recession;

s the inlandroved beach

ongshore meriods;

ere the struces the dow

y.

e a combin

nt option is pcontext of tntages of en Table 3.2

 P

ctural solutio

e accepting

to building

elopment aw

t of sand on

nically relocach or dune

be contribu

sion include

extent of eh amenity;

ovement of

ucture assiswndrift eros

ation of bot

provided in the Saundeach type ar(for structu

 

Page | 15  

ons, or

g the

in

way

nto the

cate e,

uting to

e:

erosion,

f sand,

sts in ion

th “soft”

ers re ral

Saunders

 Beach ‐ Asssessment of 

Table 3.1  

Coastal Ero

:  Non‐struc

osion Mitigat

ctural Erosio

tion Options

n Mitigation

s

n Options 

 P

 

Page | 16  

Saunders

 

 

 Beach ‐ Asssessment of 

Table 3.

Coastal Ero

.2  :  Structu

osion Mitigat

ral Erosion M

tion Options

Mitigation O

s

Options 

 P

 

Page | 17  

Saunders

4 ASS

4.1 The

When conSaundersand Althacoastal pr

• Southmost

• Centralmos

• Northentran

This sepaare in anysince the partitioninintegrate

4.2 So

The Soutshoreline of Saundeexperiencdecades. the Saund

This accrebanks thaRiver durthe lower

Any matethrough Hfloods arenear the rforeshoreun-named

 Beach ‐ Ass

SESSME

e Saunde

nsidering aps Beach it isaus Creek. recincts, na

hern Precincend of Cay

al Precinct st the entire

ern Precincnce of Altha

aration into y way compprocesses

ng lends itsewell over th

uthern P

hern Precinnorth of the

ers Beach ccing short-te Compariso

ders Beach

etion is predat form the ding major floreaches of

erial finer thaHalifax Bay e depositedriver mouth

es. Similar pd creek that

sessment of 

NT OF

ers Beach

ppropriate es necessaryIn doing so

amely:

ct : from theStreet.

: from the se ocean fron

ct : from apaus Creek.

coastal prepartmentalisaffecting eaelf to the dehe entire Sa

recinct

nct of the Sae Black Rivecomprises aerm episodions with ae

h township h

dominantly delta of the ood events f the river.

an sand tenand beyond closer to th. Waves thprocesses dt enters Hal

Coastal Ero

EROSIO

h Coastal

erosion mitigy to consideo it is eviden

e entrance o

southern enntage of the

pproximately

cincts doessed. They aach have sievelopment aunders Bea

aunders Beer Entrancea broad ridgic erosion, t

erial photogrhas prograd

due to the Black Rivewhen subs

nds to be did. Whereashe Black Rivhen work thedeliver smalifax Bay so

osion Mitigat

ON MITIG

l Reach

gation optioer the entire nt that the s

of the Black

nd of Cay Sdeveloped

y Saunders

s not imply tare not isolagnificant infof viable er

ach coastal

ach coastae. The foresge with a vethis area haraphy of 194ded variably

onshore trar. Sand is d

stantial flow

stributed wis the coarsever entrancese sand de

aller volumeome 450 me

tion Options

GATION

ons along thcoastal reahoreline ca

k River to ap

Street to Saucommunity

Beach Roa

that the coaated or discfluences onrosion mana reach.

l reach is thshore imme

egetated primas accreted 41 suggest

y by 50m to

ansport of sdelivered ins flush the a

idely as theer sand frac

ce - resultingeposits ontos of sand o

etres south

s

OPTION

he suburbanach betweenn be consid

pproximatel

unders Beay of Saunde

ad northwar

astal procescrete sectionn the othersagement st

he 4.2kms loediately alonmary dune.substantialthat the for80m since

and from thnto Halifax Baccumulate

e flood watections that ag in substano and alongnto Saundeof Cay Stre

 P

NS

n foreshore n the Black dered as thr

y the south

ach Road, wers Beach.

rds to the oc

sses within ens of shorel. However rategies tha

ong sectionngside the s Whilst ly in recent reshore southat time.

he shoals anBay by the Bed deposits

ers disperseare swept ountial sand shg adjacent ers Beach freet.

 

Page | 18  

of River

ree

ern-

which is

cean

each ine, this

at

n of the suburb

uth of

nd sand Black from

ed ut by hoals

rom the

Saunders

These naHowever south-eas

4.2.1 Re

Given thisPrecinct, foreshore

However with northforeshoreoccur on

The foresestablishe

4.3 Ce

The Centconstituteextends fIt is the sethe foresh

The greatfrom acroof sand towave eve- which m(which typ

As discusthe presenortherly processescertainty tof a conti

4.3.1 Po

Possible e

• Beachforeshthe bu

• Seawreces

 Beach ‐ Ass

atural processignificant s

st - typically

ecommend

s on-going tthere appea

e in the futur

given the eherly storm e and front dthe foresho

shore shoulded at regula

ntral Prec

tral Precinctes almost thfrom the souection of forhore Esplan

test threat ooss the openo this precinents (typicalmay not matcpically occu

ssed earlierent time it is wave energs causing into this premnuing erosi

ossible Ero

erosion mit

h Nourishmhore. This wuffer.

wall - a propesion. Shou

sessment of 

sses will cosupply rates

y during nor

ded Strateg

trend of sanars little neere. A strate

episodic natevents, thedune. It is thore along th

d be monitoar intervals a

cinct

t is the apprhe entire oceuthern-mosreshore thanade, with p

of erosion ton fetches tonct from thely during thch the dem

ur during the

, this foreshin an erosi

gy both beinncreased er

mise. Any eon trend on

osion Mitig

igation strat

ent - to estawill require

erly designeuld the seaw

Coastal Ero

ontinue to sus will be therth Queensl

gy

nd supply aed to implem

egy of Do N

ture of sandre will invar

herefore alsis Southern

ored by regualong this s

roximately 1ean frontagt end of Ca

at is most atprivate prop

o this foresho the north-ee south, thise dry seasoand on locae wet seaso

hore therefoon phase, png greater trosion may

erosion mitign this foresh

gation Strat

tegies for th

ablish a widon-going be

ed structurawall be locat

osion Mitigat

upply sand e result of eand’s dry se

nd general ment any eothing is th

d supply; anriably be peso recommen Precinct.

ular surveyssouthern pre

1400 metre ge of the Saay Street not risk of eroserty bounda

hore is recueast. Whils supply is p

on) moving al foreshoreon).

ore experienprimarily as than normaldiminish so

gation stratehore.

tegies

he Central P

de natural beach re-nou

al seawall toted within th

tion Options

to the Saunepisodic higheason.

accretionarrosion proteerefore app

nd that it doeeriods of shoended that n

s. Appropriecinct.

long sectiounders Bea

orthward to asion. The saries within

urring periodst there appprovided by sand from t

e buffers du

nces cyclesa result of

l. Whilst it iomewhat in egy needs t

Precinct inc

uffer of sanurishment o

o provide a he zone of n

s

nders Beachh-energy w

ry trend on tection measpropriate.

es not neceort-term erono future de

iate transec

on of the forach suburbaaround Sau

shoreline hametres of t

ds of adversears to be ahigh energythe Black Rring north-e

of erosion high tides ais possible tcoming yea

to accommo

clude:

nd in front oon an annua

physical banatural beac

 P

h coastal reaves from t

the Southersures along

essarily coinosion of the evelopment

ct lines need

reshore whian commununders Beacas encroachthe shorelin

se sea condan adequatey south-eas

River Entraneasterly eve

and accretiand coexistithat these cars, there isodate the lik

f the erodedal basis to m

arrier to shoch fluctuatio

 

Page | 19  

each. the

rn g this

ncide

should

d to be

ch nity. It ch Road.

hed into ne.

ditions e supply sterly nce area ents

ion. At ing cyclic s no real kelihood

d maintain

oreline ons

Saunders

(remeresult transp

• Seawdesignsand ambiemaint

The overacosts, wilwill be the

As discusinundatioand accesthe erosio- not the ehazard anfloor leve

During paSaundersachieved peak of thmitigation

Some comto suppor

4.3.2 Be

This strat

• Initial sand erosio

• On-goerosioadditio

The detersubsequefuture clim

 

 Beach ‐ Ass

embering thin the remo

port process

wall with beaned seawalto form a na

ent conditioain the bea

all and relatl be very me cost of im

ssed, the San and the pssing propeon mitigatioeffects of ovnd one that ls and the s

articularly ses Beach forethrough the

he storm tidn options.

mment on tert the recom

each Nouri

tegy basical

Nourishmebuffer in fro

on caused b

oing Renouon, it will beonal sand.

rmination ofent determinmate scena

sessment of 

at this foresoval of sandses. In othe

ach nourishmll would be arrow beacns. Neverthch.

tive effectivuch dependplementatio

aunders Bepossible simerty and infrn strategiesverwash durequires dif

structural de

evere cycloeshore. Hoe provision e, and this

echnical asmmendations

ishment

lly consists

ent - throughont of the seby the nomi

rishment - g necessary

f the paramnations of forios) is beyo

Coastal Ero

shore experd from the foer words, no

ment - undeavailable duh in front ofheless, freq

eness of eadent upon thon that will i

ach foreshomultaneous drastructure cs discusseduring severefferent mitigesign of nea

nes, little caowever somof a wider fconsiderati

spects of eas presented

of:

h the placemelected Coanated Desig

given that thto recharge

meters assocoreshore reond the sco

osion Mitigat

riences erosoreshore ino sandy bea

er this scenuring severef the seawaquent sand

ach of thesehe location invariably d

ore is quite damaging eclose to the

d below relae cyclone evgation measarshore pro

an be done me mitigationforeshore buon can be a

ach of the thd in followin

ment of a suastal Defencgn Event. F

he nourishee these ero

ciated with asponse and

ope of this a

tion Options

sion and ac front of theach would f

ario the strue events. Hll offers the re-nourishm

e three optioof the prefeetermine th

low - makineffects of wae shore. It iste to the mivents. Thatsures whichperties.

to prevent n of overtopuffer to atteapplied to th

hree possiblng sections

ufficient voluce Line that Figure 8 illu

ed foreshoresion buffers

a nominated buffer reqassessment

s

ccretion cyce structure bform in fron

uctural beneHowever the

amenity of ment would

ons, as wellerred Coasthe preferred

ng it suscepaves washins important itigation of st is quite a dh relate prim

storm tide ipping wavesenuate overwhe assessm

le strategiesof this repo

ume of sancan accomstrates the

e will experis by periodi

d Design Evuirements (t of erosion

 P

les) then thby natural st of the sea

efits of a proe placemenf a beach dube required

l as their indtal Defence d option.

ptible to storng over the to apprecia

shoreline redifferent coa

marily to hab

inundation os could be wash during

ment of eros

s is offered ort.

d to establismmodate the

concept.

ience cyclesc placemen

vent and th(for current mitigation o

 

Page | 20  

is will sand awall.

operly nt of uring d to

dividual Line. It

rm tide beach

ate that ecession astal bitable

of the

g the sion

below

sh a e

s of nt of

e and options.

Saunders

 

Initial No

It is evidesignificanerosion blocation - Clearly thimported

In the absand otherthe Centr

The volumbetween 2009); alomeasured

Approximbetween treinstate

Given thissince it issources asupplied o

As discusexpected nourishmprotection

 Beach ‐ Ass

ourishment

ent by referent bearing onuffer. A mosince sand

he position ofrom extern

sence of a dr stakeholderal Precinct

me of requir1941 and 2ong with thed by Towns

mately 120,0the southerthe shorelin

s significant likely to ex

are to maintover a wide

ssed previoto continueent throughn that it affo

EXISTINGPR

COASTAL DEFENCE LINE 

sessment of 

Figure 8 : T

t

ence to Figun the volumore seawardd already onof the Coasnal sources

determinatioers, an initiato that whic

red sand ha2007 that wae subsequeville City Co

000 m3 of sarn-most endne to its 194

t volume of xceed most tain sand suer timeframe

ously, the epe into the fuh sand placeords.

G  SHORELINE ROFILE 

EROSION  BUFFERBY  BEACH  NOU

Coastal Ero

Typical init

ure 8 that thme of sand td location wn the foreshtal Defenceto create o

on of the Coal nourishmch existed in

as been estas derived fnt change touncil (refer

and would nd of Cay Str41 position.

sand, it is ucommercia

upplies to ote of say 3 to

pisodic erosture. This mement will g

R  ENHANCED URISHMENT 

osion Mitigat

tial beach

he location ohat needs t

will require more can be

e Line deterr suppleme

oastal Defeent to reinsn 1941 is of

imated on tfrom geo-reto the shorer to Figure 6

need to be ireet northwa

unlikely thatal sand suppther stakeho 4 consecu

sion procesmeans that gradually be

tion Options

nourishme

of the Coasto be initiallymore importconsidered

rmines just hent this buffe

nce Line bystate the posffered as a

the basis of ectified aeriaeline opposi6).

mported anards to Sau

t it could beply allocatioolders. The

utive years.

ses affectinthe erosion

e depleted -

RENOURISHPRO

s

ent profile

stal Defencey placed to ted sand thad as being phow much ser requirem

y Council, thsition of eropoint of refe

f the net shoal photograpite Cay Stre

nd placed alnders Beac

e supplied inons - particue 120,000m

ng the Centrn buffer crea- thereby dim

ED  SHORELINE OFILE 

 P

e Line will hform the rean a landwapart of the bsand needsent.

he local comoded sectionerence.

oreline chanphy (Smitheeet that has

long the forch Road in o

n any singleularly if thosm3 could inst

ral Precinctated by the minishing th

 

Page | 21  

 

have a quired ard uffer.

s to be

mmunity ns of

nge ers, been

reshore order to

e year, e tead be

t are initial

he

Saunders

On-goingshould nocompone

On-going

It is difficuare closeThe problthe Blacka predeteundertakecampaign

Given thelikelihoodsurveys aonset of e

For budge10,000m3

In summarequire th

• initial shoreconse

• on-gokeep

4.3.3 Se

A seawalconstructeit was locbe a veryduring se

However foreshoreprocessesWaves waany sand all) tides, strategy o

ConsequeBeach.

 Beach ‐ Ass

renourishmot be constrnt of succes

g Renouris

ult to determly matchinglem of short

k River deltaermined annen through n should buf

e requireme of any cyc

at least twiceeach cyclon

eting purpo3 of sand to

ary, a beachhe following

placement line that ex

ecutive year

oing placemthe reinstat

eawall

l appropriated along th

cated such t robust struvere events

more impoe fluctuations - with the ashing direfrom in fronwaves may

on its own w

ently a seaw

sessment of 

ment will therued as a “fassful beach

shment

mine the reng the rates ot-term buffe

a) is one thanual re-nourregular beaffer volume

ent to also elone erosioe yearly - a

ne season.

ses it is sugbe placed a

h nourishme:

of approximisted in 194rs;

ent of an avted buffer ch

tely designee alignmen

that it was eucture to accs, and the e

rtantly, suchns. It would

erosion proctly againstnt of the stry wash agawill inevitabl

wall option

Coastal Ero

erefore be railure” of be

h nourishme

nourishmenof longshoreer depletion at needs berishment ratach transects fall to criti

ensure that tn, it is recomnd that any

ggested thaas annual r

ent strategy

mately 120,041. This init

verage of bharged with

ed to accomt of a nomin

exposed regcommodate

expected sc

h a structurtherefore h

oblem simpt the seawaucture, loweinst the sealy lead to th

cannot be c

osion Mitigat

equired to reach nourisent strategie

nt requiremee transport o(due to onltter understte, regular mt surveys thically low le

the erosion mmended t

y renourishm

at an allowarenourishme

y for the Ce

000 m3 of stial sand pla

etween 5,0h sand.

mmodate senated Coasgularly to the the local wcour at the to

re would be have significly being trall during amering the beawall - leavihe degradat

considered

tion Options

recharge thhment, as it

es througho

ent, since naout of the bly sporadic tanding. Asmonitoring o

hat trigger a evels.

buffer is futhat the forement should

nce be madent along th

ntral Precin

and to reinsacement co

00m3 and 1

vere stormstal Defencee effects of

wave climatoe.

built withincantly advernsferred to

mbient and seach to the ng no beacion of the b

a viable mit

s

e buffer witt is typically

out the world

atural sand uffers over supply froms an alternaof buffer cosand re-no

lly rechargeeshore shoud be comple

de for betwehe Saunders

nct of Saund

state the poould be unde

10,000m3 of

s and cycloe Line on Saf wave actioe, the signif

the dynamrse effects othe downdr

storm condiextent that

ch at all in freach.

tigation stra

 P

h sand. Thy an integrad.

supply prolong timefra

m the reservative to nomndition cou

ourishment

ed prior to thuld be monieted prior to

een 5,000ms Beach for

ders Beach

osition of theertaken ove

f sand per y

nes can be aunders Be

on, it would ficant overto

mic zone of non local bearift foreshoritions will reduring som

ront of it. A

ategy for Sa

 

Page | 22  

his l

cesses ames. ves of

minating ld be

he tored by

o the

m3 and reshore.

would

e er 3 to 4

year to

each. If need to opping

natural ach re. emove me (or

seawall

aunders

Saunders

4.3.4 Se

To countecould be than that

Alternativburied weforeshoreerosion b

The purpofront of thstorm reqdirectly exby the negenerated

It is suggenecessaryDefence Lsuch a scas sacrific

Furthermoplacemen

The seawarmouringEngineerifundamentwo layersrocks with10,000m2

Alternativbe used t

In summaPrecinct o

• select

• compto req1tonn

• placinimproupon be at as a b

 Beach ‐ Ass

eawall with

er the adverundertakenrequired fo

vely the seleell back frome between thuffer - or co

ose of any she buried sequired of a fxposed to wt northerly ld by waves

ested that ay in front ofLine, some

cenario, the cial and like

ore this initint of betwee

wall would ng material oing designsntal modes s of interlochin the size 2 of heavy g

vely sand fillto construct

ary, a strateof Saunders

ting an align

lete a detaiquire the plae to 5 tonne

ng an initial ved beach the chosenleast a san

buffer in fron

sessment of 

h Beach No

rse effect ofn to create ar a full beac

ection of a Cm the existinhe buried seould be enh

smaller scaeawall to acull beach no

waves (eitheongshore tragainst the

a sand buffef the seawaor all of thisforeshore i

ely to be sig

ial buffer cren 5,000m3

need to be donto a foress need to incof seawall f

cking rock arange of 1t

geotextile as

led geotextit the cut-off

egy of a seas Beach wo

nment for th

led structuracement of ee, or alterna

volume of sand foresho alignment d volume ofnt of the sea

Coastal Ero

ourishment

f an exposea sand buffech nourishm

Coastal Defng shorelineeawall alignanced throu

ale beach noccommodateourishment er by a severansport) the seawall fa

er of some 3ll. Dependis might be ain front of th

gnificantly da

eation wouland 10,000

designed aphore does ncorporate stfailure. It is

armour overtonne to 5 ts the underl

ile containeseawall bu

awall and beould entail th

he seawall (

ral design ofeither approatively cons

sand in the ore amenityof the Coasf 35m3 / meawall.

osion Mitigat

t

ed seawall oer in front ofment strateg

fence Line ce (say alongnment and tugh the plac

ourishment e moderate option. Ho

ere storm sehen the turbace will very

35m3 / metring upon theavailable inhe seawall aamaged or

ld need to b0m3 to recha

ppropriatelynot constitutructural ele

s estimated rlying geotexonne wouldlying filter.

ers (such asried at the b

each nourishe following

(ie. a Coast

f a buried soximately 1structed of s

existing bufy. The volustal Defenceetre length o

tion Options

on foreshorf the seawa

gy.

could be mag the seawathe existing cement of a

would be tostorm even

owever shoueason or byulence and

y rapidly rem

re length of e selected l the exiting alignment wremoved du

be supplemarge the bu

. Simply duute a viable ements andthat the 1.4xtile fabric.

d be require

s the Elcoroback of the

hment for thg:

tal Defence

eawall; whi5,000m3 of

sand-filled g

ffer in front me of any ie Line; howof foreshore

s

e amenity, all - albeit wi

ade such thard propertyshoreline c

additional sa

o place onlynts - not theuld the seawy the gradua reflected w

move any re

foreshore wlocation of tforeshore r

would need uring a maj

ented with affer.

mping rockseawall stru

d details tha4km long se Approxima

ed, along wit

ck proprietabeach.

he 1.4km lo

Line).

ch at this stf rocks with

geotextile co

of the seawmported sa

wever as a ge available a

 P

sand nourisith a width l

at the seawy boundariecould serve and.

y sufficient se 100 year Awall becomal removal o

wave energyemaining sa

would be the Coastal reserve. Unto be consior storm ev

an average

ks or other sucture. t mitigate a

eawall will reately 15,000th approxim

ary system)

ong Central

tage is estimin the size rontainers.

wall to proviand will depeguide there at all times t

 

Page | 23  

shment ess

wall was es). The

as the

sand in ARI e of sand y and.

nder dered

vent.

annual

such

ll of the equire 0m3 of mately

could

mated range of

de end should to serve

Saunders

• on-gokeep

4.3.5 Re

Considerathe most seawall. appropria

In the inteCouncil othis stratethe deple

This optimaccommoarea.

Followingthe deposThis bermerosion eback into with this nmany yea

The currein effect h

4.4 No

The Northforeshoreentrance propertiesblock) imm

An analysand 2007of the beanatural pr

Since 200January tare typicathan has inland tha

 Beach ‐ Ass

oing placemthe buffer in

ecommend

ation of the technically Both of the

ately design

erim it is recof mechanicegy, mechated foredun

mises the avodate mode

g erosion evsition of san

m establishmvent. Substhe upper b

natural rehaars.

ent practice hastening th

orthern Pr

hern Precine which exteof Althaus Cs in Reef Stmediately a

sis of geo-re7 this foreshach was higrocesses th

07 the foresto March 20al of the natoccurred in

an it is at pr

sessment of 

ent of an avn front of th

ded Interim

above discviable is eitse measureed and for t

commendedcally redistribnical plant a

ne area.

vailable sanerate storm e

vents, naturnd to createment occurssequent onsbeach profilabilitation of

of mechanhis natural r

recinct

ct is the apends northwCreek. It fotreet, as we

adjacent to t

ectified aerihore had expghly variableat occur at

shore has e009, Januartural variabin recent timeesent.

Coastal Ero

verage of be seawall c

m Strategy

cussions regther beach es will invarthe necessa

d that the stbuting sandand equipm

nd resourceevents and

al recovery e a low berms relatively rshore windsle and the fof the upper

ically movinrebuilding p

proximatelywards from aorms the ocell as public the creek en

ial photograperienced ne over shortthe entranc

xperiencedry 2010 andlity that affees. Althoug

osion Mitigat

etween 5,0charged with

garding eronourishmenriably be exary approva

trategy reced on the bea

ment are use

es on the bereduce som

of the uppem in front of rapidly - typs and high tioredune arebeach and

ng sand fromrocess.

y 400 metreapproximateean frontagopen space

ntrance.

aphy (Smithnet accretiot timeframece to Althau

a number od TC Yasi inects this pregh in 1961 t

tion Options

00m3 and 1h sand.

sion mitigatnt alone, or pensive andals to be obt

ently implemach profile sed to move

each to enhmewhat the

er beach arany erosion

pically withinides graduaea. Howevforedune re

m the berm

e long sectioely Saunde

ge to the eige (with picn

hers, 2009) n. Howeves and is sig

us Creek.

of high enen February 2ecinct, albeithe shorelin

s

10,000m3 of

tion strategiin conjunctd require timtained.

mented by Tshould be csand up the

ance its cap damage to

ea typicallyn scarp cut n two to foually work saer the timesegion are qu

into the up

on of the Sars Beach R

ght northernnic facilities

indicated ther it was notgnificantly af

rgy erosion2011. Thest somewhate was some

 P

f sand per y

ies indicatetion with a bme to be

Townsville Continued. Ue beach slo

pacity to o the upper

y occurs throinto the forr weeks of tnd from thisscales assouite long - ty

per beach a

aunders BeaRoad to the n-most privaand an ame

hat betweented that the ffected by t

events - inse erosion et more advee 30 metres

 

Page | 24  

year to

s that buried

City Under ope into

beach

ough reshore. the s berm ociated ypically

area is

ach

ate enities

n 1941 position he

events ersely s further

Saunders

4.4.1 Re

Given thisimplemenDo Nothin

However periods ointensificaPrecinct.

The foresestablishe

 

 Beach ‐ Ass

ecommend

s general acnt any erosiong is therefo

given the df short-termation of dev

shore shoulded for this p

sessment of 

ded Strateg

ccretionary on protectioore appropr

dynamic natm erosion ofvelopment s

d continue tpurpose.

Coastal Ero

gy

trend on thon measureriate.

ture of the Af this foreshshould occu

to be monit

osion Mitigat

he Northern es along this

Althaus Creore. It is ther in future o

ored by reg

tion Options

Precinct, ths foreshore

ek entranceerefore alsoon the fores

gular survey

s

here appearin the futur

e area, thero recommenhore along

ys of transec

 P

rs little needre. A strate

re will invarinded that nothis Northe

ct lines alre

 

Page | 25  

d to gy of

ably be o

ern

eady

Saunders

5 REC

The recomconsideraoutlined b

5.1 Be

• No dir

• No int

• Estab

5.2 Be

• Two vstakehThese

Option

o inishto

o onto

Option

o se

o coeswge

o plimupshtim

o onto

 Beach ‐ Ass

COMMEN

mmended eation of diffebelow.

tween the

rect interven

tensification

blish new tra

tween So

viable optionholders for e options be

n 1 : Beach

itial placemhoreline that

4 consecut

n-going plackeep the re

n 2 : Seawa

elect an alig

omplete a dstimated to

within the sizeotextile co

acing an inmproved beapon the chohould be at mes to serv

n-going plackeep the b

sessment of 

NDED ER

erosion mitigerent strateg

e Black R

ntion.

n of develop

ansect lines

outhern E

ns are availthe long-ter

eing:

h Nourishme

ent of approt existed in tive years;

cement of aeinstated bu

all and Beac

gnment for t

detailed strurequire the

ze range of ntainers.

itial volumeach and fore

osen alignmleast a sane as a buffe

cement of auffer in fron

Coastal Ero

ROSION

gation stratgies for the

River and

pment shou

s to be surve

End of Ca

lable for conrm protectio

ent only

oximately 11941. This

an average ouffer charge

ch Nourishm

the seawall

uctural desige placement1 tonne to 5

e of sand in eshore ame

ment of the Cd volume oer in front of

an average ont of the sea

osion Mitigat

MITIGA

egy for the three preci

Southern

ld occur in f

eyed on a r

ay Street a

nsideration on of this 14

20,000 m3 s initial sand

of between ed with sand

ment

(ie. a Coas

gn of a buriet of either ap5 tonne, or

the existingenity. The vCoastal Deff 35m3 / mef the seawa

of between awall charge

tion Options

ATION S

Saunders Bncts along t

n End of

future.

regular basi

and Saun

by Townsv400 metre lo

of sand to rd placemen

5,000m3 and.

stal Defence

ed seawall;pproximatelalternativel

g buffer in frvolume of afence Line; etre length oall.

5,000m3 aned with san

s

TRATEG

Beach coasthe foresho

Cay Stre

s.

nders Bea

ville City Coong section

reinstate thet could be u

nd 10,000m

e Line).

which at thly 15,000m3

y constructe

ront of the sany importedhowever asof foreshore

nd 10,000md.

 P

GY

stal reach reore. These

et

ach Road

uncil and ot of foreshor

e position oundertaken

m3 of sand p

his stage is 3 of armoured of sand-

seawall to pd sand will s a guide the available a

m3 of sand p

 

Page | 26  

equires are

d

ther re.

of the over 3

per year

r rocks -filled

provide depend ere at all

per year

Saunders

Recom

o Eiapis mestrintup

• Irrespannua

5.3 Be

• No dir

• No int

• Monitlines.

 Beach ‐ Ass

mmended in

ther of thesppropriatelyrecommendechanicallyrategy, mecto the deplepper beach

pective of thal surveys o

tween Sa

rect interven

tensification

or this fores

sessment of 

nterim strat

se long-termy designed aded that the

y redistributichanical plaeted foredunarea.

e option adon previousl

aunders B

ntion.

n of develop

shore throu

Coastal Ero

tegy

m measuresand for the ne strategy reng sand on

ant and equne area - th

dopted, the fly establish

Beach Ro

pment shou

gh annual s

osion Mitigat

s will invarianecessary aecently imp

n the beach ipment are

hereby haste

foreshore sed beach tr

oad and A

ld occur in f

surveys of p

tion Options

ably be expeapprovals to

plemented bprofile shouused to moening the na

should contiransect line

Althaus C

future.

previously e

s

ensive and o be obtaine

by Townsvilluld be conti

ove sand upatural rehab

nue to be ms.

Creek

established

 P

require timeed. In the ile City Couninued. Undp the beach bilitation of

monitored th

beach trans

 

Page | 27  

e to be nterim it ncil of

der this slope the

hrough

sect

Saunders

6 REF

Hopely, DDecembe

Smither, Earth andTownsvill

 Beach ‐ Ass

FERENC

D. 1974. Cer 1971. Aus

S.G. 2009d Environmee City Coun

sessment of 

ES

oastal chanstralian Geo

9. Coastal Eental Sciencncil.

Coastal Ero

nges producographer, 1

Erosion at Sces, James

osion Mitigat

ced by Trop2(5): 445-4

aunders Bes Cook Univ

tion Options

pical Cyclon456.

each - Backversity, Tow

s

ne Althea in

kground Briewnsville. 200

 P

Queenslan

efing. Schoo09. Prepared

 

Page | 28  

nd;

ol of d for

Saund

 

 

 

 

 

 

ers Beach ‐ A

Location

Assessment

Appe

n of the Bea

 

SAUNDERS  1 

SA

t of Coastal E

endix A

ch Transect 

AUNDERS  2 

SAUND

Erosion Miti

- Resu

Survey Lines

DERS  3 

SAUNDERS  4

SA

igation Opti

lts of B

s plotted ove

4 

AUNDERS  5 

ions

Beach Tr

erleaf in App

SAUNDERS  6 

S

ransect

pendix A 

SAUNDERS  7 

 Page |A ‐ 1

Surveys

 

1  

s

 

SAUNDERS 1  POST 458353 7882156 

6.22m AHD Brg 40 

Chainage  April 09  Chainage  March 10 ‐0.4  5.37  ‐0.4  5.37 0.1  5.38  0  5.38 4.2  5.33  4.7  5.3 9.5  5.14  9.9  5.13 11.7  4.9  13.1  4.56 13.1  4.51  15  3.04 14.2  4.3  21.5  2.75 14.9  4.25  27.4  2.28 15.6  3.24  43.7  0.78 18.8  3.03  53.7  0.54 24.2  2.8  62.8  0.38 26.9  2.55  85.8  ‐0.03 28.2  2.27 31.3  1.8 34.8  1.45 41.8  1.16 52.5  0.71 65  0.32 72  0.25 87.4  ‐0.06 

 ‐1

0

1

2

3

4

5

6

‐20 0 20 40 60 80 100

Saunders 1

April 09

March 10

SAUNDERS 2  POST 458567 7881942 

5.99m AHD Brg 40 

Chainage  April 09  Chainage  March 10 ‐10.9  4.64  ‐10.9  4.64 ‐8.1  4.78  ‐8.1  4.78 ‐4.1  4.99  ‐4.1  4.99 ‐0.3  5.07  ‐0.3  5.07 0.2  5.04  0  5.09 2.7  5.05  3.7  5.04 6.4  5.09  7.1  5.02 12.5  4.65  25.1  3.93 20.9  4.23  28.8  3.03 24.5  4.01  39  2.62 26.2  3.88  49.1  1.33 26.9  3.33  56.2  0.83 33.2  3  78.6  0.28 38  2.7  102.6  ‐0.22 39.5  2.53 40.6  2.3 42.6  1.97 45.8  1.52 47.9  1.33 52.6  1.16 58.5  0.96 65  0.69 81  0.34 96  0 

 

‐1

0

1

2

3

4

5

6

‐20 0 20 40 60 80 100 120

Saunders 2

April 09

March 10

SAUNDERS 3  POST 458737 7881806 

5.60m AHD Brg 40 

Chainage  April 09  Chainage  March 10 ‐2.9  4.79  ‐2.9  4.79 ‐0.3  4.64  ‐0.3  4.64 0.2  4.66  0  4.66 2.9  4.58  5.4  4.48 5.2  4.56  9.5  4.28 13.3  3.92  13  3.89 14  3.36  16  2.88 16.4  3.18  22.5  2.75 21.7  2.94  26.6  2.38 25.9  2.57  39.4  0.96 28.5  2.04  43.3  0.74 31.1  1.62  70  0.26 35.8  1.25 46.6  0.89 59.5  0.6 70.6  0.3 

 

0

1

2

3

4

5

6

‐10 0 10 20 30 40 50 60 70 80

Saunders 3

April 09

March 10

SAUNDERS 4  POST 458898 7881663 5.76mAHD Brg 40 

Chainage  April 09  Chainage  March 10 ‐17.2  5  ‐17.2  5 ‐14.9  4.83  ‐14.9  4.83 ‐10.8  4.83  ‐10.8  4.83 ‐3.5  5.15  ‐3.5  5.15 ‐0.2  4.88  0  4.88 0.2  4.87  7.6  4.17 7  4.19  11.9  3.97 8.7  4.14  16.6  2.89 11.1  4.03  25.9  2.53 12.9  3.99  37.6  1.19 13.5  3.48  43.5  0.74 16.8  3.26  62  0.45 21.5  3.1  98  ‐0.5 26.4  2.56 27.9  2.2 30.7  1.74 36.7  1.26 45  0.99 61.3  0.46 78.5  0.12 98.6  ‐0.48 

 ‐1

0

1

2

3

4

5

6

‐40 ‐20 0 20 40 60 80 100 120

Saunders 4

April 09

March 10

SAUNDERS 5  POST 459092 7881498 5.20mAHD Brg 40 

Chainage  April 09  Chainage  March 10 ‐15.5  4.82  ‐15.5  4.82 ‐12.6  4.78  ‐12.6  4.78 ‐9.6  4.71  ‐9.6  4.71 ‐4.2  4.28  ‐4.2  4.28 ‐2.2  4.19  ‐2.2  4.19 ‐0.3  4.27  0  4.31 0.4  4.27  12.6  3.56 1.8  4.2  13.9  2.91 3.5  4.01  17  2.51 6.3  3.82  25.4  2.44 13.3  3.63  35.2  1.23 13.7  3.44  43  0.7 14.2  3.01  54.8  0.35 16.6  3.11  67  0.25 18.5  3.15  81  0 22.4  2.62 23.8  2.28 25  2.11 28  1.67 32  1.35 37.3  1.15 42.2  1.01 53  0.67 66.7  0.31 80.7  0.02 97  ‐0.5 

 ‐1

0

1

2

3

4

5

6

‐40 ‐20 0 20 40 60 80 100 120

Saunders 5

April 09

March 10

SAUNDERS 6  POST 459400 7881244 4.63mAHD Brg 40 

Chainage  April 09  Chainage  March 10 ‐5.8  3.7  ‐5.8  3.7 ‐3  3.61  ‐3  3.61 ‐0.2  3.69  ‐0.2  3.69 0.2  3.72  0  3.76 2.6  3.82  9.8  4.19 4.6  3.83  12.4  2.99 10.2  4.25  16.7  2.54 11.3  3.41  24.9  2.48 12.5  3.22  36.1  1.22 17.8  2.9  36.4  1.2 21.6  2.51  43.7  0.8 23.1  2.26  75  0.05 25.2  1.98 27.5  1.65 31  1.39 36  1.18 44  1.04 57.3  0.63 76  0.06 

 

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

‐20 0 20 40 60 80 100

Saunders 6

April 09

March 10

SAUNDERS 7  POST 459636 7881064 4.66mAHD Brg 40 

Chainage  April 09  Chainage  March 10 ‐13.8  3.56  ‐13.8  3.56 ‐7.5  3.45  ‐7.5  3.45 ‐3.4  3.53  ‐3.4  3.53 ‐0.1  3.65  0  3.68 0.2  3.66  3.2  3.52 3.2  3.62  7.4  4.04 5.2  3.83  9  3.07 7.1  4.09  14.8  2.18 8  4.17  24.1  2.42 9.1  3.21  41.9  0.76 12.2  2.87  75  0 15.7  2.58 16.9  2.52 22.4  2.27 25.8  2.08 31.5  1.44 42.4  1.06 47.5  0.87 58.3  0.6 74  0.03 84  ‐0.21 

 ‐0.5

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

‐20 0 20 40 60 80 100

Saunders 7

April 09

March 10

Saunders

COA

 Beach ‐ Ass

ASTAL E

sessment of 

EROSION

Coastal Ero

AT SAUN

S

osion Mitigat

Appen

NDERS BE

School of

tion Options

dix B -

EACH - B

f Earth And

s

Referen

BACKGRO

Dr

d Environ

James

 Pa

nce Docu

OUND BR

r. Scott Sm

nmental Sc

Cook Uni

 

age |B ‐ 1  

ument

RIEFING

by

mithers

ciences

iversity

COASTAL EROSION AT SAUNDERS BEACH BACKGROUND BRIEFING Dr Scott Smithers School of Earth and Environmental Sciences James Cook University

Introduction Saunders Beach is an approximately 2.4 km long beach segment located to the north of Black River at the southern end of Halifax Bay (Figure 1). Saunders Beach is characterised by a broad (>80 m wide) low-tide bench composed of fine sand that extends seaward from a relatively narrow (10-20 m) and steep upper beach composed of coarser sediments. A sharp break in slope typically separates the upper beach and the low tide terrace at a level between Mean Low Water Spring (MLWS) tide and Mean Sea Level (MSL) position. The settlement at Saunders Beach is developed over a narrow beach ridge plain composed of successive ridges and relatively low-lying swales; however at the eastern end of Saunders Beach this is reduced to just a single narrow ridge. Erosion of the upper foreshore opposite houses at the southern and central end of the settlement has reduced the distance between the upper beach and property boundaries. Recent recession of the shoreline and loss of established trees has increased concerns about possible future shifts in the shoreline and the possibility that coastal assets and environments may be damaged by any such shifts. Coastal processes and shoreline behaviour have been investigated at Saunders Beach as part of a broader coastal erosion study of the Northern Beaches. Information from this study provides important background data within which to consider the driving variables and significance of recent shoreline changes. Recent changes in shoreline position at Saunders Beach must be viewed within the context of broader patterns of sediment supply and redistribution within Halifax Bay, and natural variability in the processes that deliver sediment to the coast and onto and off the beaches.

Physical Setting and Processes The shoreline in Halifax Bay is predominately sandy, and is largely composed of coastal landforms such as beach ridges, dunes, tidal inlets, estuaries, and salt flats formed within the last 6000 years by coastal processes. These landforms typically form a narrow (up to 1.5 km wide but generally narrower) fringe of geologically recent sediment deposits and landforms at the coast (Figure 2). Because coastal processes built the landforms, their elevation is closely constrained by sea-level history since around 6000 years ago; only rocky outcrops extend more than six or so metres above the Highest Astronomical Tide (HAT) mark. Sea level was 130 m lower than now at the peak of the ice age 18000 years ago, exposing the entire continental shelf. As the ice subsequently melted, sea level rose to around 1-1.5 m above present by around 6000 years ago, before falling to its current level (Figure 3). The shoreline began to build out after sea level reached this higher level around 6000 years ago and as it fell to present. The mineralogy and sedimentology of coastal sands in Halifax Bay indicates they are mostly weathered from local rocks and delivered to the coast by local rivers and creeks. The extent to which the shoreline built out in Halifax Bay varies according to factors such as the sediment supply, exposure to waves and currents, and coastal alignment. Generally,

however, the shore prograded as an upper sandy beach ridge unit built out and over a lower unit of finer intertidal and subtidal sands (like those on the broad lower intertidal flats today). Where inlets and estuaries were sufficiently sheltered from high-energy waves, muddier deposits dominated by mangrove materials developed. These deposits are now exposed on the foreshore at several locations within Halifax Bay, indicating localised retreat of the shoreline since they were emplaced. In some locations this shoreline retreat has opened a corridor where wave action can entrain and suspend fine sediments but sedimentation is relatively low, allowing nearshore reefs, such as Paluma Shoals to establish and thrive. Larcombe et al. (2001) presented a schematic model that depicts these interactions (Figure 4). From the age of the exposed mangrove deposits and inshore reefs we know that this phase of coastal recession may have begun several thousand years ago at some locations within Halifax Bay. Following the ice age sea level rose quickly and flooded the low gradient continental shelf. As inundation progressed the shoreline retreated rapidly westward, and reworked unconsolidated sediments. Residual gravels and coarser deposits (marking earlier channel positions) now form pavements where fine sediments were winnowed away. The general shape of the coastline in Halifax Bay is a legacy of this process. The irregular occurrence of pavements of residual coarse sediments at the shore separate embayments formed where finer sediments were eroded, and define the broader scale changes in coastal alignment within Halifax Bay. Net littoral drift is to the north and sediments are exchanged between the embayments described above. A series of small to moderate size streams traverse the coastal plain to discharge at the coast, with the larger rivers (The Bohle and Black Rivers, and Bluewater Creek) occurring toward the south of the study area (Figures 1 & 5). Most of these coastal streams flow only seasonally following wet season rains, when extreme flows associated with cyclonic and monsoonal deluges can cause major flooding, significant erosion and reconfiguration of coastal morphology. Some streams have developed sandy deltas indicative of sediment delivery to the coast, where prevailing longshore currents tend to move materials progressively north. The delta at the mouth of the Black River is the most conspicuous of these features. During the dry season, or when wet season flows are not competent, coastal processes (waves and currents) may significantly modify coastal morphology at stream and inlet mouths. The shoreline can be very dynamic, with substantial changes in shoreline position and character known to occur quickly during episodic high-energy events. For example, more than 10 m of beach retreat occurred at both Saunders Beach and at the Black River settlement when Tropical Cyclone Althea (category 3: estimated central pressure 952 mb) crossed the coast near Balgal Beach in December 1971 (Hopley, 1974). Longer-term changes associated with prevailing wind and wave conditions also affect this coast; complex and truncated beach ridge sequences have been interpreted as evidence of ‘natural’ changes in coastal configuration along the northern beaches (Hopley and Murtha, 1975).

Historical and Recent Change at Saunders Beach The general pattern of shoreline change at Saunders Beach can be established through the analysis of geo-rectified aerial photographs that have been taken at the appropriate scale at an irregular interval since 1941 (1941, 1961, 1974, 1983, 1987. 1991, 1996, 2000, 2004, 2005) together with shoreline positions accurately mapped with GPS (Figure 6). These analyses indicate that:

1. Sections of Saunders Beach have shown net accretion and others have shown net erosion since 1941 – there is no universal erosion or accretion trend. This is the case along the entire Halifax Bay shoreline. These variations appear to result from variations in alongshore sediment transport, with eroded beach segments commonly updrift of sites of significant accretion. It is important to note that erosion and accretion zones on the beach can change through time (both seasonally, inter-annually, and at longer (decadal and millennial) timescales).

2. Fluctuations in shoreline position at a site – phases of accretion and erosion – are

demonstrated by the fact that changes in shoreline position to both seaward and shoreward are identified at all 18 transects along Saunders Beach from the geo-rectified photos. In summary, at no transect has the shoreline consistently either eroded or built out – fluctuations are the norm.

3. Based on the total data set of shoreline changes for all transects (including those at Bluewater) an average accretion rate for the entire shoreline for the period was calculated at 0.24 m (n = 272). This is in good accord with the longer-term rate of accretion established for this segment of Halifax Bay by looking at the age of onshore coastal sediment deposits (Holmes, 1992). In summary, although some sections of Saunders Beach have clearly retreated in recent decades, the average net trend over the entire beach is has been one of average net accretion, and is very similar to the longer term rate.

4. The shoreline to the immediate south of Saunders Beach settlement significantly

accreted and became vegetated between 1941 and 2007. This area comprises a broad vegetated ridge with a vegetated dune to seaward. The vegetated dune was eroded severely during the high tides and moderate seas of early 2009.

5. The shoreline in front of the settlement from its southern end to a point near

Saunders Beach Road has retreated by as much as 15 m from its 1941 position (transect 18 (near the turning bay at the eastern end of the Esplanade) and transect 22 (opposite 105 Cay Street)). The upper beach along this section is now markedly scarped, and held in sections by mature Casuarina trees, with scalloped embayments between. Many of these trees were lost during the erosion events of early 2009, with further retreat of the upper beach in these areas. Some recovery of the beach has occurred since, with infill of the upper beach below the scarp and progradation of a new berm.

6. Between 1941 and 2007 the beach between Saunders Beach Road and the mouth of

Deep Creek has shown net accretion, but this end of the beach is highly variable over shorter periods (including seasonal), and is significantly affected by processes near the creek mouth.

Observations of recent changes include:

7. The upper beach between the southern end of the settlement and Saunders Beach Road is now (and has been for some time) marked by a conspicuous scarp, in places exceeding 1 m high, which locally retreated several metres during the 2009 January - March high tides. Typically the eroded sediment was redeposited relatively rapidly (within two to three weeks) on the upper shoreline further north along the beach.

8. Erosion in early 2009 coincided with very high tides and moderately rough weather.

It is pertinent to note that the very high tides occurred as part of the broader 18.6 year lunar tidal cycle, which effectively meant that the high tides this year were the highest over this multi-decadal cycle, and that there were a greater number tides high enough for waves to affect the upper beach. The combination of higher tides and rough weather increased the erosion of the upper beach. As this cycle wanes over the next decade the elevation and frequency of very high tides will reduce.

9. The eroded scarp cut into an older vegetated beach ridge dominates the upper beach

long most of the settlement. As indicated above, in places the top of this scarp separates the active beach by more than a metre, and waves at high tide swirl at its base. However, elsewhere on the beach a broad berm of recently deposited sand has been deposited in front of the eroded scarp. At these locations the beach exhibits both erosionary and accretionary traits.

10. New sediment can only be added to the beach ridge on which the settlement is

located when waves swash on to it and deliver sediment from the beach below. The scarp effectively separates the active beach from the beach ridge surface, and impedes the deposition of new material on top of the ridge.

11. The Casuarina trees have been very effective at holding the upper beach position,

and mediating further retreat of the upper beach. Where they have recently failed it is likely that they would have performed better if they were located in thicker plantings and not as a single row. Many fallen trees appear to have been outflanked by erosion concentrated in bare areas.

Other points for consideration:

12. Saunders Beach is a location where coastal erosion during the last major cyclone to affect the region (TC Althea) was accurately measured. During that event the shoreline retreated by 12 m and waves broke over the first beach ridge and onto the road (Hopley 1974). This event generated a storm surge estimated to be 3.66 m at nearby Toolakea, but luckily the peak coincided with the low tide raising water levels to near the high tide level only. On the northern beaches some recovery from this erosion occurred quite rapidly, with as much as 2.5 m accretion noted within 6 months.

13. The Black River is the nearest and most significant sediment source for the Saunders

Beach. Approximately 1 million cubic metres of sand were extracted from this river between 1970 and 2001. Extractive activities have now ceased. Although the impacts of extraction would be expected to only be modest due to other contributions and the redistribution of existing delta sediments (see Figure 5), it is possible that these activities have contributed to the local erosion experienced at Saunders Beach, either directly as a result of disruption to sediment supply, or indirectly as a consequence of reconfiguration of the delta. Given the irregular nature of both events that deliver sediments and redistribute them along the coastline, the significance of these processes is hard to determine. Nonetheless, the termination of extraction removes the possibility of any ongoing negative effects.

14. Both modelling and measurement confirm the transport of sediment north along the

beach. Estimates of littoral drift indicate that around 10-14 000 m3 of sand is

transported north along this section of shoreline on average each year. Observations of sediments redistributed during high-energy events indicate that sediments can be quickly redistributed on this shoreline. The implications are that any discontinuities in alongshore sediment supply might be expected to manifest relatively quickly, and that sediment introduced to the upper beach may be redistributed relatively rapidly. Where sediments are temporarily stored in the system, such as the ridge to the south of the settlement a deficit may develop updrift and contribute to shoreline retreat. However, recent erosion on Saunders Beach can be more directly attributed to higher water levels and wave energy conditions acting on an already destabilised and upper beach.

Conclusions The shoreline at Saunders Beach is dynamic, with all sections of the beach showing phases of erosion and accretion since 1941. When the entire data set for the entire beach is examined an average rate of accretion of 0.24 m per year is calculated. The pattern of shoreline change between 1941 and 2007 is, however, spatially variable along the beach. The differences can be summarised as:

• Significant accretion to the immediate south of the settlement (where the broad vegetated ridge and dune have developed).

• Retreat of as much as 15 m and significant scarping of the upper beach in front of the settlement from Saunders Beach Road south.

• Highly variable but net accretion between Saunders Beach Road and Deep Creek.

The entire shoreline was affected by the combination of moderate seas and very high tides on several occasions in early 2009, during which the upper beach was significantly eroded (reports of several metres retreat in just a few days). The high tides that focused the wave action on the vulnerable upper beach were associated with the peak of the 18.6-year tidal cycle that is now on the wane. Although sediment extraction from the Black River may have disrupted sediment supply to Saunders Beach it is more likely that variations in sediment deposition and transfer together with wave erosion during the higher tides have been responsible for shoreline retreat along the shoreline at both decadal and event timescales. Sediment is actively transported north alongshore on this beach as indicated by modelling, measurement and observations of sediment redistribution following erosive events. If renourishment is considered as a treatment option the mobility of ‘natural’ sediments on this shoreline will need to be considered and strategies to mediate this be included in the renourishment plan (sediment size, positioning, time of emplacement and augmentative stabilisation). Casuarinas can effectively hold the shoreline position against erosion events, and more contiguous and wider plantings should be considered.

References Holmes, K.H., 1992. Townsville-Rollingstone coastal sector. MA50/2, Department of

Environment and Heritage, Brisbane.

Hopley, D., 1974. Coastal changes produced by Tropical Cyclone Althea in Queensland; December 1971. Australian Geographer, 12(5): 445-456.

Hopley, D. and Murtha, G.G., 1975. The Quaternary Deposits of the Townsville Coastal Plain. Monograph Series, 8. Department of Geography, James Cook University of North Queensland, Townsville, 30 pp.

Hopley, D., Smithers, S.G. and Parnell, K.E., 2007. Geomorphology of the Great Barrier Reef: evolution, diversity and change. Cambridge University Press, Cambridge.

Larcombe, P., Costen, A. and Woolfe, K.J., 2001. The hydrodynamic and sedimentary setting of nearshore coral reefs, central Great Barrier Reef shelf, Australia: Paluma Shoals, a case study. Sedimentology, 48(4): 811-835.

Lewis, S.E., Wust, R.A.J., Webster, J.M. and Shields, G.A., 2008. Mid-late holocene sea-level variability in eastern Australia. Terra Nova, 20: 74-81.

Figure 1 Satellite image showing coastal zone features and major settlements Halifax Bay (Google,

2008).

Figure 2 Map of surface deposits and landforms within the study area (redrawn from Hopley and Murtha, 1975).

Figure 3 a) Global postglacial sea-level history from reef records (Hopley et al., 2007); b) data and various interpretations of sea level fall since around 6000 years ago on inshore Great Barrier Reef (from Lewis et al., 2008).

Figure 4 Coastal sediment transport and development in depositional shoreline settings such as Cleveland Bay (left) and in erosional shoreline settings such as Halifax Bay (right). (Larcombe et al., 2001).

Figure 5 Coastal sediment budget for southern end of Halifax Bay estimated from several sources including Boral 1998, DallaPozza 2005 and Holmes 1992.

Formatted:Formatted:Formatted:Formatted: Top: 2.75 cm

Figure 6 Net shoreline change between 1941 and 2007 derived from geo-rectified aerial photography along Saunders Beach

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