COASTAL COMPARTMENTS, SEDIMENT CELLS AND

VULNERABILITY ASSESSMENT: A Progress Report

Presentation to

WALIS MARINE GROUP

MATT ELIOT AND IAN ELIOTDamara Pty Ltd, Innaloo , WA

19 July 2011

BASIC CONCEPTS

• The project develops a hierarchy of planning units, based on the geologic framework of the coast.

• At the broadest planning levels the planning units comprise a set of discrete coastal compartments determined by geologic boundaries, structures, landforms and coastal aspect together with the landforms they contain.

• At the most detailed planning levels the planning units are identified as sediment cells in which sediments sources, transport pathways and sinks can be clearly defined.

• Together, coastal compartments and sediment cells provide a framework for a variety of applications including:

(a) planning and management of natural resources within the nearshore marine and coastal environment; and

(b) assessment of vulnerability to coastal hazards, climate change and rise in sea level.

Zones: Broad sectors of the Australian continent based on climate

Divisions: Provides an overview of the whole state suitable for maps at scales of about 1:5,000,000

Provinces: Areas defined on geomorphologic or geological criteria suitable for regional perspectives at scales of about 1:1,000,000

Regions: Areas with recurring patterns of landform and geology suitable for regional mapping at scales of approximately 1:250,000

Land Systems: Areas of characteristic landform patterns suitable for mapping at regional scales of 1:50,000 to 1:100,000

Compartments: A local unit based on one or more definite landforms suitable for mapping at scales of about 1:25,000 to 1:50,000

Landforms: A local unit based on one or more landforms suitable for mapping at scales of about 1:5,000 to 1:15,000

Sediment Cells: A local unit based on several linked landforms suitable for mapping at scales of about 1:5,000 to 1:25,000

PRIMARY COMPARTMENTS AND SEDIMENT CELLS

POTENTIAL APPLICATIONS

COMPARTMENTS

Landforms (Framework) & Processes (Drivers)

PLANNING PURPOSES

Marine & coastal

planning

Habitat descriptio

n

Marine & coastal

risk assessme

ntMarine

conservationEBFM

Major Landform Assemblages(After: Searle & Semeniuk 1985)

•Nearshore MorphologyIslandsLinear reefs and submarine ridgesPavementsSand banks Sand flats and seagrass meadows

•Landforms of the Shore Shoreline shapes (straight, irregular, arcuate and zeta-form)Rocky coasts (cliffs, ramps and platforms)Beaches (sheltered and exposed forms)

•Onshore LandformsLimestone plateaux and outcropsForedunes Frontal dunes (blowouts and parabolic dunes)Barriers EstuariesDeltasCoastal lagoons and wetlands

An extreme event or events may change the type or location of a land system.

eg. Avulsion (channel switching) and delta shift

Gradual landform change associated with land surface instability ultimately results in structural change.

eg. Barrier evolution

STABILITY SUSCEPTIBILITY

Likelihood of erosional change to landforms related to current land surface condition

Likelihood of structural breakdown leading to a change in the land system

Likelihood of landform and/or land system change

VULNERABILITY

= +

SUSCEPTIBILITY Long-term Structural

Change

Cliff & talus slope

Climbing dunes

Ashburton River Delta 1963

Open river mouthActive spit

Spit

Perched barrier and climbing dunes

No barrier. Perched beach and old dunes

Ashburton River Delta 2009

Open river mouthActive chenier

STABILITYShort-term Landform

ChangeMouth

Mouth

The susceptibility of rocky coast refers to the intrinsic propensity of a coastal land system or landform structure to alter in response to projected change in metocean conditions over a long period, commonly extending to millennia.

Variation in structure may occur spatially, due to differences in rock type; or temporally as a result in the differences in the strength of the same rock type and exposure to disparate processes.

Rank 1: High cliff (>10m) plunging to subtidal level

Rank 2: Moderate to high cliff (>10m) with an intertidal platform

Rank 4: Rock pavement or intertidal platform and low bluff (<5m high)

Rank 3: Cliff (5 - 10m high) and wide intertidal platform

Rank 5: Gently sloping rocky shore

ROCKY COAST SUSCEPTIBILITYThe sequence illustrated here loosely follows that described by

Sunamara (1992).

SANDY (BARRIER) COAST SUSCEPTIBILITY

The sequence illustrated here follows that described by Roy (1994).

The susceptibility of a sandy barrier refers to the intrinsic propensity of the structure comprising the barrier system to alter in response to projected change in metocean conditions, particularly sea level rise over.

Barrier formation occurs over a long period, commonly millennia, although structural change from one type to another may occur within tens to hundreds of years.

Rank 1: Episodic Transgressive BarrierNested blowouts and parabolic dunes.

Rank 2: Prograded BarrierLow, foredune ridge plain

Rank 3: Stationary BarrierLow or narrow ridge of blowout

Rank 4: Receded BarrierLow narrow dune ridge & old shoreline

Rank 5: Mainland BeachNarrow duns & beach abutting bedrock.

STABILITY ON MIXED SANDY AND ROCKY COAST

The sequence illustrated here follows that described by da Silva

(2010).

Estimates of beach instability are based on the exposure of the beach to metocean processes.

The variability of sandy beaches in different settings has been described by Nordstrom (1992) and Short (2005).

The stability of sandy beaches perched on rocky substrates is not as well known, although such beaches are common features of the Australian coast. The sequence shows beaches subject to increasing exposure to wave and sea level variation.

Rank 1: No beach OR a foredune is located on a high rock platform (>HAT)

Rank 2: Perched beach is located on a supratidal rock platform

Rank 3: Perched beach adjoining a low bluff

Rank 4: Perched beach on an intertidal platform or beachrock ramp

Rank 5: Perched beach on shallow inshore pavement

Rank 1: Undisturbed dune sequence OR Fully vegetated (>75% cover on barrier).

Rank 2: 50 to 75% vegetation cover on barrier OR <25% active dunes or bare sand

Rank 3: 25-50% vegetation cover on barrier OR 25-50% mobile dune

Rank 4: <50% vegetation cover on barrier OR 50-75% active dunes or bare sand

Rank 5: Mobile sand sheets OR <25% vegetation cover on barrier.

STABILITY ON SANDY COASTThe sequence illustrated here follows that described by Short (1988).

Estimates of instability are based on the land surface condition and the proportion of area in a compartment or cell that is currently bare sand or subject to erosion.

Destabilisation of dunes occurs with destruction of a foredune, scarping of the frontal dunes or removal of the vegetation cover.

Changes to vegetation cover take place in a short period, commonly sub-decadally.

SUSCEPTIBILITY STABILITY

1 NEARSHORE MORPHOLOGY (Depth <25m)

INSHORE SUBSTRATE (Depth <5m)

2 SHOREFACE STRUCTURE

BEACHFACE MORPHOLOGY & PROFILE

3 SHORELINE SHAPE AND ORIENTATION

FRONTAL DUNE COMPLEX &TIDAL FLAT MARGINS

4

BARRIERS, PERCHED BEACHES & DELTAS

VEGETATION COVER :BARRIERS & TIDAL FLATS (

SUSCEPTIBILITY

(Potential for structural impacts)

INSTABILITY

(Current changes to land surface)

BARRIER; PERCHED BEACHES AND RIVER

DELTAS

RankVEGETATION COVER: BARRIERS AND TIDAL

FLATS

Rank

(a) Episodic, Transgressive Barrier OR

(b) Dunes on supratidal rock surface OR

(c) WD Delta: Mainly closed river mouth

1

No barrier OR

Undisturbed dune sequence OR

Fully vegetated (>75% cover on barrier) OR

Wide Halophytic zone and narrow salt flats

1

(a) Prograded Barrier OR

(b) Perched beaches on intertidal rock OR

(c) WD Delta: Intermittently open mouth f

2

50 to 75% vegetation cover on barrier OR <25%

active dunes or bare sand: OR

Narrow Halophytic zone, broad salt flats, few tidal

creeks

2

(a) Stationary Barrier; OR No Barrier OR

(b) Tombolo OR

(c) WD Delta: Permanently open river mouth

3

25-50% vegetation cover on barrier

25-50% mobile dunes; OR

Narrow Halophytic zone, broad salt flats, common

tidal creeks

3

(a) Receded Barrier OR

(b) Salient & Cuspate foreland OR

(c)) RD Delta: Inherited deltaic features

4

<50% vegetation cover on barrier; OR

50-75% active dunes or bare sand; OR

Broad bare salt flats with Halophytic patches,

palaeochannels and tidal creeks

4

(a) Mainland beach OR

(b) Narrow spit or chenier OR

(c) RD Delta: Active delta & stream channels

5

Mobile sand sheets OR

<25% vegetation cover on barrier OR

Broad bare salt flats with residual mounds,

palaeochannels and tidal creeks

5

Land system and landform description andRanking for susceptibility and instability

AREAS OF LANDFORM

DESCRIPTIONInshoreShoreline and beachfaceBarrier

Cell

South

North

INSHORESHORELINE

AND BEACHFACEBARRIER

24

Seven Mile Beach

NINE MILE BEACH

Between Seven Mile Beach and Bobs Hole at Nine Mile Beach the 20m isobath is approximately 7km offshore. The ridge of limestone reef, which includes Nine Mile Break, trends NNW and parallel to the coast. It becomes more irregular with distance north but continues to enclose a lagoon. Multiple ridges of shallow limestone reef, platforms and stacks shelter the coast and close with the shore at Bobs Hole.

The shoreline has a shallowly-indented arcuate form and is zeta-shaped to the south. In the south, the beach abuts a 2km long, high platform. The northern section of the coast faces WSW with the nearly continuous beach sheltered by reef close to shore. The exposed, reflective beach is rhythmic with shallowly indented embayments between shoreline salients associated with inshore reef outcrops close to shore.

An episodic transgressive barrier comprised of nested parabolic and blowout dunes overlie a limestone basement of unknown depth and distribution. Its vegetation cover is between 25 and 75%. The frontal dune is partly scarped or steeply faced to seaward, and its 25 to 75% vegetation cover disturbed by numerous access tracks. The foredune is absent from much of the coast, particularly south of Getaway Beach.

SEDIMENT CELL DESCRIPTION

CellSouthern Boundary

of Cell

Inshore

Shoreline Plan

Aspect

Barrier

Susceptibility Score

Susceptibility Rating

Inshore

Substrate

Beach Profile

Barrier Vegetation

Frontal Dune

Instability Score

Instability Rating

MATRIX SCORE

Vulnerabilit

y

34 CAPE BURNEY SOUTH 4 4 5 1 14 M 4 5 4 3 16 H 4

33 West Bank 4 2 3 1 10 M 3 4 4 4 15 H 4 M-H

32 Phillips Road Coast 4 2 3 1 10 M 4 4 4 3 15 H 4 M-H

31 Lucys 4 2 3 1 10 M 4 4 4 4 16 H 4 M-H

30 Duncans Pool 4 2 3 1 10 M 4 4 4 4 16 H 4 M-H

29 Flat Rocks 4 2 3 1 10 M 3 3 4 3 13 M 3 M

28 Headbutts 1 3 3 1 8 L 3 3 4 3 13 M 2 L-M

27 Shire Boundary 2 3 3 1 9 L 3 5 4 3 15 H 3 M

26 Bookara South 3 1 3 1 8 L 3 5 4 3 15 H 3 M

25 NINE MILE BEACH 4 3 3 1 11 M 4 4 4 5 17 H 4 M-H

24 Seven Mile Beach 1 2 3 2 8 L 3 3 3 2 11 M 2 L-M

23 Harleys Hole 1 2 3 2 8 L 3 3 2 2 10 M 2 L-M

22 Dongara North 1 2 3 2 8 L 3 3 2 2 10 M 2 L-M

21 LEANDER POINT 3 2 3 1 9 L 2 3 3 3 11 M 2 M-H

20 South Leander Point 3 3 4 1 11 M 5 5 4 3 17 H 4 M-H

19 White Point 3 3 4 1 11 M 5 5 4 3 17 H 4 M-H

18 CLIFF HEAD 3 2 5 1 11 M 4 4 4 3 15 H 4 M-H

M-H

SUSCEPTIBILITY (STRUCTURAL INTEGRITY)

Susceptibility

Scores

Indicative

SusceptibilityProjected Site Implications

4 - 9 Low Structurally sound geologic or geomorphic feature.

Determination of susceptibility may require resolution of metocean processes

10 – 14 Moderate Some structural features are unsound.

Detailed assessment of coastal hazards and risks is advised.

15 - 20 High Structural features are extensively unsound.

Development is not recommended.

LANDFORM INSTABILITY

Instability

Scores

Indicative

InstabilityPresent Actions on Similar Sites

4 - 9 Low Resilient natural system occasionally requiring minimal maintenance

(eg. Alfred Cove, Milyu Reserve & Scarborough).

10 - 14 Moderate

Management responses are required to accommodate a range of occasional

major events, regular

moderate events or frequent minor events. (eg. Broun Bay).

15 - 20 High

Current management responses require ongoing installation or repair of major

stabilisation works

(eg. Esperance, Port Geographe).

CONSEQUENCES FOR COASTAL MANAGEMENT

INSTABILITY (CONDITION)

(Existing morphologic change to land surface)

Low (Stable) Moderate High (Unstable)

Example

SUSCEPTIBILITY

(STRUCTURE)

(Potent

ial

change

to

geologi

cal

structu

re

Low

Barrier perched on

extensive tracts of

coastal limestone

(1) Vegetated

swales in parabolic

dunes landwards of

a vegetated frontal

dune ridge

overlying coastal

limestone above

HWL

(2) Vegetated

dunes landwards of

a vegetated frontal

dune ridge and

perched on coastal

limestone at HWL

(3) High foredune

ridge and/or

vegetated foredune

plain overlying

coastal limestone

below HWL

Moder

ate

Weakly lithified

barrier with

intermittent

limestone outcrops

(2) Mainly

vegetated swales in

parabolic dunes

landwards of a

mainly vegetated

frontal dune ridge

(3) Vegetated

dunes landwards of

a mainly vegetated

frontal dune ridge

(50 to 75% cover)

and overlying

coastal limestone

(4) Cliffed or

discontinuous

foredune fronting

moderate numbers

of mobile blowouts

and sand sheets

(<50% of the

alongshore reach)

High

Barrier comprised

wholly of sand.

No bedrock

apparent along

shore or in dunes

(3) Swales in

parabolic dunes

landwards of a

partly vegetated

frontal dune ridge

(4) Mainly

vegetated dunes

landwards of a

partly vegetated

frontal dune ridge

with 25 to 50%

cover

(5) No foredune.

Eroded frontal dune

with numerous

mobile blowouts

and sand sheets

(>50% of the

alongshore reach)

KEY Combined estimate of vulnerability Low Low-to-moderate Moderate Moderate-to-high High

INDICATIVE VULNERABILITY MATRIX

MIXED SANDY AND ROCKY COAST

Cell Southern Boundary of CellSusceptibility

Rating

Instability

Rating

Vulnerability

Rating

34 CAPE BURNEY SOUTH M H M-H

33 West Bank M H M-H

32 Phillips Road Coast M H M-H

31 Lucys M H M-H

30 Duncans Pool M H M-H

29 Flat Rocks M M M

28 Headbutts L M L-M

27 Shire Boundary L H M

26 Bookara South L H M

25 NINE MILE BEACH M H M-H

24 Seven Mile Beach L M L-M

23 Harleys Hole L M L-M

22 Dongara North L M L-M

21 LEANDER POINT L M L-M

20 South Leander Point M H M-H

19 White Point M H M-H

18 CLIFF HEAD M H M-H

Key Vulnerability Implications for Development

Low Coastal risk is unlikely to be a constraint to

development

Low-to-moderate Coastal risk may present a low constraint to

development

Moderate Coastal risk may present a moderate constraint to

development

Moderate-to-high Coastal risk is likely to be a significant constraint to

development

High Coastal risk is a highly significant constraint to

development

Key Vulnerability Implications for Development

Low Coastal risk is unlikely to be a constraint to

development

Low-to-moderate Coastal risk may present a low constraint to

development

Moderate Coastal risk may present a moderate constraint to

development

Moderate-to-high Coastal risk is likely to be a significant constraint to

development

High Coastal risk is a highly significant constraint to

development

VULNERABILITY ESTIMATESCOMPARTMENTS AND CELLS

KEY Ranked estimate

Low

Low to Moderate

Moderate

Moderate to high

High

INDICATIVE VULNERABILITY MATRIX BASED ON LARGE LAND SYSTEMSVULNERABILITY = SUSCEPTIBILITY +

INSTABILITY

 INSTABILITY

(Existing Landform Change)SUSCEPTIBILT

Y(Potential Change to structure)

Low(Apparently accreting)

Medium(Apparently unchanging)

High(Actively eroding)

Rocky Coast

LowHard rock (granite)cliffs and rocky shores

Soft rock (sandstone) cliffs and rocky shores

Weakly lithified rock (calcarenite) cliffs & rocky shores

Sandy Coast

Medium

Shoreline advance greater than 1.0 m/yrPrograded & episodic transgressive barrierVegetation cover >75% on barrier

Shoreline change from -1.0 to + 1.0 m/yrStationary barrierBetween 25% and 50% vegetation cover on barrier. Foredune present

Shoreline retreat greater than 1.0 m/yrRetreating barrier& cuspate foreland. Vegetation cover <50% on barrier.Cliffed frontal dunes

Deltaic

Coast High

Less frequently than 10 yearly inundation ofRiverine floodplains, Mudflats & salt marshes, Spits

Five to 10 yearly inundation of: Riverine floodplains, Mudflats & salt marshes, Spits

Annual to 5 yearly inundation of:Riverine floodplains, Mudflats & salt marshes, Spits

VULNERABILITY ESTIMATESPRIMARY COMPARTMENTS

POTENTIAL APPLICATIONS

COMPARTMENTS

Landforms (Framework) & Processes (Drivers)

PLANNING PURPOSES

Marine & coastal

planning

Habitat descriptio

n

Marine & coastal

risk assessme

ntMarine

conservationEBFM

ISO 31000 Methodology

applied to NCCOE (2004) vulnerability

assessment

Improve understanding of the biophysical environment

Determine gaps in available information and assess further needs

Implement strategy based on current available information

Identify areas requiring new work or replacement of infrastructure

Estimate current environmental, social and economic costs

Acquisition of new information and data as the cycle is repeated

Determine a strategy for hazard management and risk avoidance

Monitor and assess actions implemented under the strategy

STARTDETERMINE THE SCOPE 0F PROJECTED CHANGE & RESPONSE URGENCY

Agree on environmental, social and economic values for risk mitigation

Identify projected hazards and risks to people & property

Community Involvement through information exchange and workshops

Community Involvement through information exchange and workshops

Community Involvement through information gathering and workshops

(1) Initial strategy is based on available information.(2) Review strategy at 5 year intervals

PLANNING CYCLE FOR COASTAL RISK ASSESSMENT

Project in cycle Community participation Planning for hazard & risk mitigation© Ian Eliot 2009

AS NZS (2009) ISO 31000Risk Assessment Framework Adapted to Coastal Management

From: Rollason et al. (2010) and Rollason & Haines (2011)

Commonwealth Climate Change

AssessmentsNCVA LAPP ANUGA PNP

State Government Coastal

Assessments

SPP2.6 Review

Coastal Process Studies

Coastal Planning Studies

Coastal Hazard

AssessmentsPilbara

Cities

Cities Project

Regional Strategie

s

Local Government Coastal

AssessmentsDIVERSE!!

Thanks for your attention