1

ASSESSING THE UTILITY OF GEOMORPHIC SENSITIVITY MAPPING ON

THE ILLAWARRA COAST

Pamela Abuodha1, Christina Baker2, Chris Sharples3, Darren Skene2

and Colin Woodroffe1

1 Geoquest Research Centre, University of Wollongong2 National Coastal Vulnerability Assessment, Geoscience Australia

3 School of Geography and Environmental Studies, University of Tasmania

17th NSW Coastal Conference, Wollongong 4-7 November 2008

Outline

� Aim and objectives

� Components of vulnerability

� National Coastal Vulnerability Assessment� Smartline mapping

� Polygon mapping

� ‘Smartline’ mapping of the Illawarra coast� Landform types

� Sensitivity rankings and maps

� Evaluation of sensitivity

� ConclusionStanwell Park beach

North Wollongong beach Flagstaff Point

Aims and Objectives

� Map landforms that are sensitive to coastal hazards and the

potential impacts of sea-level rise.

� Describe landform types of the Illawarra and derive sensitivity

rankings.

� Evaluate Smartline and polygon mapping.

Exposure Sensitivity

Potential

impact

Adaptive

Capacity

VulnerabilityAllen Consulting Group, 2005

‘Vulnerability’ is a combination of the physical sensitivity, the assets at risk and the

ability of society to cope with these risks (Harvey and Woodroffe, 2007)

Large swell at Flagstaff Point

Seawall at Warilla

Eroded beach dunes at Corrimal beach

What is ‘coastal vulnerability’?

The National Coastal Vulnerability Assessment

� Department of Climate Change - ‘first pass’ assessment of coastal

vulnerability to the impacts of climate change.

� Identify coastal ecosystems and infrastructure most at risk.

� Rely on geomorphic mapping.

� 2 phases,

1. ‘Smartline’ mapping (UTas)

2. Polygon mapping (GA)

Lake Illawarra and Perkins beach

� Available through the OzCoasts website (www.ozcoasts.org.au)

Smartline Maps(University of Tasmania)

� Geomorphic line map of Australia’s

coastal zone using existing geomorphic and geology data.

� Polyline segmented into various

attributes related to the landform type, exposure, geology etc of the coast.

� Identify shores that are potentially

susceptible (sensitive) to physical instability (erosion, slumping etc).

Broad tidally-defined and shore-parallel zones

Backshore(bedrock slope with soil)

Backshore(dune)

2

Coastal geomorphology polygon mapping

� Procure existing digital polygon datasets � State/local government and private consultancies

� Geology, geomorphology and habitat data

� Develop and apply a consistent coastal geomorphology classification scheme.

� Amalgamate datasets and realign with detailed coastline position.

+1:250K Geology

WA Dept. of Industry and Resources

1:100K Geo-habitat Types

Geoscience Australia

Classification Scheme

Level 1

Level 3

Level 2

Level 4

Level 2a

Level 3a

Coastal depositional environment, i.e. alluvial plain, estuarine plain, coastal barrier/backbarrier, shelf, bedrock feature, anthropogenic feature.

Coastal geomorphic feature, i.e. beach, channel, dune, delta… This is the primary field (1:100K – 1:25K).

Coastal geomorphic feature detail, i.e. dune type. Will be mapped if additional information is available (1:25K – 1:10K).

Sediment texture and lithology, i.e. mud/sand/gravel, carbonate, plutonic… (1:250K – 1:100K).

Rock Type, lithology description i.e. basalt, sandstone, conglomerate… Mapped where data is available (1:100K – 1:25K).

Level 5

Biota, i.e. mangrove, salt marsh, coral, seagrass… Mapped where data is available (1:100K – 1:25K).

Substrate type – CONSOLIDATED or UNCONSOLIDATED

Case Study: The Comprehensive Coastal Assessment ToolkitNSW Dept. of Planning

Lake Illawarra to Seven Mile beach

Reclassification – Level 1 Coastal Depositional Environment Reclassification – Level 2 Coastal Geomorphic Feature

3

Reclassification – Level 4 Biota Type Level 5 – identification of consolidated (hard) and unconsolidated (soft)

sediments.

Line vs. Polygon

� Polylines� Store many attributes for a single spatial location (i.e. backshore, near

shore, exposure described in one line segment).

� Allow simple GIS queries.

� Polygons� Map the spatial extent that vulnerable landform units occupy, allows for

modelling of coastal processes.

Lake Illawarra, NSW, geo-habitats Hardy Inlet, WA, intertidal landform type

Illawarra coast� 80 km S. of Sydney

� 167 km long

� Narrow coastal plain

� Wave-dominated

� Over 300,000 people

Stanwell

Park

Seven

Mile

Pacific Ocean

Lake Illawarra

Rocky shore

01

Coarse grained sand

06

Fine –medium grained sand

07

Cliffs & rocky shore

Sediment plains

Dunes & dune ridges

Artificial shoreline

Plains

(0o – 6o)

Gentle slopes

(6o – 20o)

Steep slopes

(>20o)

High cliffs

(> 50 m)

‘Smartline’ segmentation

Intertidal

Backshore

Profile

01 02 03 11

1 2 3 4

Coastline1 432 5 6 7 8

Landform types - intertidal

Coarse grained

06

Rocky shore

01

Fine – grained

07

4

Landform types - backshore

Dunes & dune ridges03

Rocky shore & cliffs 01

Artificial structures 11

Sediment plains

02

Landform types - profile

High cliffed coast 4

Sediment Plains (0o - 6o)1

Moderate slopes ((6o - 20o) 2

Steep slopes (> 20o

3

GIS queries - sandy sensitivity

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±

200 m

Intertidal 07 (fine sand)Backshore 03 (dunes)

Profile 1 (low plains)

Intertidal 07 (fine sand)Backshore 11 (artificial)

Profile 1 (low plains)

Intertidal 07 (fine sand)Backshore 01 (bedrock)

Profile 1 (low plains)

07 + 03 = 23 Sandy shores backed by dunes

07 + 11 = 27

Sandy shores backed by artificial

structures

07 + 01 = 25

Sandy shores backed by bedrock

GIS queries - sandy sensitivity

Intertidal = 07Fine sand

Backshore = 01Bedrock

07 + 01 = 25

Backshore = 02

Profile = 1

Intertidal = 07

07 + 02 + 1 = 20

Backshore = 11Artificial

Intertidal = 07Fine sand

07 + 11 = 27

Intertidal = 07Fine sand

Backshore = 03Dunes

07 + 03 = 23

Illawarra sandy sensitivity

Intertidal

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Sensitivity

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23

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30

37

40

=

00

20

23

25

27

30

37

40

45.5

0.2

54.3

0.0 10.0 20.0 30.0 40.0 50.0 60.0

Rocky shore (01)

Coarse-grained sandy

shore (06)

Fine-medium grained

sandy shore (07)

Inte

rtid

al la

nd

form

typ

es

Percentage of shoreline

47.1

23.1

18.3

11.5

0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0 45.0 50.0

Rocky shore or cliffs (01)

Sediment plains (02)

Dunes and dune ridges

(03)

Artificial structures (11)

Backsh

ore

lan

dfo

rm t

yp

es

Percentage of shoreline

5

47.3

17.8

34.9

0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0 45.0 50.0

Exposed (1)

Semi-exposed (2)

Sheltered (3)

Sh

ore

lin

e s

eg

men

t exp

osu

re

Percentage of shoreline

70.8

22.5

6.7

0.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0

Low plains (1)

Gentle to moderate

slopes (2)

Steep slopes (3)

High cliffs (4)

Backsh

ore

in

lan

d s

lop

e

Percentage of shoreline

Sandy sensitivity for the Illawarra

37.4

7.6

18.3

5.5

4.4

15.4

3.3

8.1

0 5 10 15 20 25 30 35 40

Not a sandy shore (00)

Open sandy shores backed by plains (20)

Open sandy shore backed by dunes (23)

Open sandy shore backed by bedrock (25)

Open sandy shore backed by artificial

structures (27)

Re-entrant sandy shore backed by plains (30)

Re-entrant sandy shore backed by structures

(37)

Sheltered re-entrant but not a sandy shore

(40)

Sa

nd

y s

en

sit

ivit

y

Percentage of shoreline

Low

Moderate

High

Conclusions

� Geomorphology plays an important role in the identification of coastal areas that are vulnerable to the potential impacts of sea-level rise.

� Coastal geomorphology maps are currently being developed for Australia and these will provide fundamental data layers for assessing the impacts of sea-level rise.

� Illawarra coast:

- high sensitivity 25.9 %

- moderate sensitivity 15.4%

- low sensitivity 21.3 %

- non-sandy shores 37.4 %

� Future study:

Investigate historic rates of shoreline movement

Bellambi/Woonona beach

Questions?