Appendix 7-Marine and coastal environment

694 Pages·2006·39.44 MB·English

Yannarie Salt Project

Marine and coastal environment
of the eastern Exmouth Gulf

Volume I: Report

Straits Salt Pty Ltd

391/3 February 2006

p:\straits\391_solarsalt\reports\ermp\technical reports\marine environment report (mer)\marine environment report mcb_sjs 23_2_06 for
draft ermp.doc

Yannarie Salt Project

Marine and coastal environment
of eastern Exmouth Gulf

Prepared for:

Straits Salt Pty Ltd

Prepared by:

Oceanica Consulting Pty Ltd

October 2005

Report No. 391/3
Client: Straits Salt Pty Ltd

Revisions history

DISTRIBUTION REVIEW
Author
Version Recipients No. Copies & Format Date Reviewer Date

1 M. Bailey Biota/Straits 2 hard copies 25/8/05 TN and GH 12/9/05
2 M. Bailey Parsons Digital 15/9/05 G Bott
Brinkerhoff
3 M. Bailey Oceanica Hard copy 15/9/05 K Hillman 27/10/05
4 M Bailey Parsons Digital 27/10/05
Brinkerhoff/
Straits
5 M Bailey/S Parsons 2 bound and CD 24/2/06
(revised Shute Brinkerhoff/
to include Straits
additional
survey in
Dec 05)

Status
This report is “Draft” until the author and director have signed it off for final release. A “Draft” report should not
be used for any purpose other than to be reviewed with the intention of generating a “Final” version.

Approved for final release:
Author Director Date: 24/2/06

Disclaimer
This report has been prepared on behalf of and for the exclusive use of Straits Salt Pty Ltd, and is subject to and
issued in accordance with the agreed terms and scope between Straits Salt Pty Ltd and Oceanica Consulting Pty
Ltd. Oceanica Consulting Pty Ltd accepts no liability or responsibility whatsoever for it in respect of any use of
or reliance upon this report by any party.

Cover
Main image: Humpback whale and calf Exmouth Gulf (Oceanica);
Minor images: Hope Point (Oceanica); Flood tide at Hope Creek (Oceanica)

Copying this report without the permission of Straits Salt Pty Ltd and Oceanica Consulting Pty Ltd is not
permitted.

© Copyright 2006 Oceanica Consulting Pty Ltd
Contents
1. Introduction.......................................................................................................1
1.1 Objectives...........................................................................................................................1
2. Management of Exmouth Gulf.........................................................................3
2.1 Relevant Marine Policies...................................................................................................3
2.1.1 Overview.................................................................................................................3
2.1.2 EPA Guidance Statement No. 1 (Tropical Arid Zone Mangroves)..........................3
2.1.3 EPA Guidance Statement No. 29 (Benthic Primary Producer Habitat
Protection)...............................................................................................................4
2.1.4 Pilbara Coastal Waters...........................................................................................5
2.2 Consideration of Application for World Heritage Listing..............................................7
2.3 Marine Reserves Report....................................................................................................9
2.4 Relevant Commonwealth and State Acts and Agreements........................................12
2.4.1 Commonwealth Legislation..................................................................................12
2.4.2 State Legislation...................................................................................................15
2.4.3 International Agreements and Conventions.........................................................16
2.5 Pastoral and mining leases............................................................................................17
2.6 Fisheries..........................................................................................................................18
2.7 Marine Bioregionalisation..............................................................................................20
2.8 Defence Training Area....................................................................................................21
3. Physical Environment.....................................................................................23
3.1 Overview..........................................................................................................................23
3.2 Geomorphology and landforms....................................................................................24
3.3 Bathymetry and coastal topography............................................................................25
3.3.1 Gulf Scale.............................................................................................................25
3.3.2 Local Scale...........................................................................................................26
3.3.3 Supratidal flats.....................................................................................................28
3.4 Climate.............................................................................................................................31
3.4.1 Local winds: east coast of the Gulf......................................................................35
3.4.2 Cyclones...............................................................................................................37
3.5 Freshwater inflows.........................................................................................................39
3.5.1 Hinterland flows....................................................................................................39
3.5.2 Influence of rainfall: local......................................................................................41
3.5.3 Groundwater........................................................................................................41
3.6 Oceanography.................................................................................................................42
3.6.1 Regional Context (Leeuwin Current)....................................................................42
3.6.2 Wave Climate.......................................................................................................45
3.7 Water levels.....................................................................................................................46
3.7.1 Astronomic tides...................................................................................................46
3.7.2 Barometric effects................................................................................................50
3.7.3 Wind effects.........................................................................................................51
3.7.4 Storm surge..........................................................................................................52
3.7.5 Long-term sea level rise.......................................................................................54
3.7.6 Tsunami................................................................................................................56
3.7.7 Summary of factors affecting water levels and their likely significance...............57
3.8 Circulation and currents................................................................................................59
3.8.1 Gulf-scale Circulation: Massel et al. (1997).........................................................59
3.8.2 Gulf-scale Circulation: APASA (2005a & b)........................................................61
3.9 Tidal Creeks.....................................................................................................................67
3.9.1 Summary of key processes and features.............................................................67
3.9.2 Tidal creeks on the east coast of Exmouth Gulf..................................................68
Oceanica: Straits Salt: Marine and coastal environment of eastern Exmouth Gulf i
3.10 Inundation of the intertidal and supratidal areas........................................................71
3.10.1 Model set-up........................................................................................................71
3.10.2 Extent of inundation due to astronomic tides.......................................................72
3.10.3 Position of the High Water Mark..........................................................................77
4. Marine Environment........................................................................................79
4.1 Overview..........................................................................................................................79
4.2 Review of Key Studies....................................................................................................79
4.2.1 Sediments: Brunskill et al. (2001)........................................................................79
4.2.2 Water quality: McKinnon and Ayukai (1996) and Ayukai and Miller (1998).........85
4.2.3 WA Museum Survey............................................................................................87
4.2.4 Benthic Habitat Studies........................................................................................88
4.3 Yannarie Salt Project: Marine Surveys........................................................................95
4.3.1 Overview..............................................................................................................95
4.3.2 Methods................................................................................................................98
4.4 Marine Surveys: Water Quality Results......................................................................101
4.4.1 Physical..............................................................................................................101
4.4.2 Seawater analysis..............................................................................................103
4.4.3 Nutrients.............................................................................................................104
4.5 Marine Surveys: Sediment Quality Results................................................................107
4.5.1 Results...............................................................................................................107
4.6 Marine Surveys: Benthic Habitat.................................................................................115
4.6.1 Transects............................................................................................................116
4.6.2 Spot surveys......................................................................................................122
4.6.3 Mapping..............................................................................................................139
5. Marine Fauna.................................................................................................143
5.1 Protected/Listed Species.............................................................................................143
5.2 Whales............................................................................................................................145
5.2.1 Review of existing information...........................................................................145
5.2.2 Surveys..............................................................................................................148
5.3 Dugongs.........................................................................................................................151
5.4 Sea turtles......................................................................................................................155
5.4.1 Natural History of Marine Turtles of the Region.................................................155
5.4.2 General...............................................................................................................158
5.5 Sharks and rays............................................................................................................159
5.6 Sea snakes.....................................................................................................................160
5.7 Fish.................................................................................................................................160
5.8 Prawns...........................................................................................................................161
6. Social, Cultural and Economic (non-fishing) Features..............................163
6.1 Recreation and tourism................................................................................................163
6.1.1 Recreational Boating..........................................................................................163
6.1.2 Tourism..............................................................................................................163
6.2 European History..........................................................................................................164
6.3 Shipwrecks....................................................................................................................165
7. Conclusions...................................................................................................167
7.1 Summary of key processes.........................................................................................167
7.1.1 Gulf Scale...........................................................................................................167
7.1.2 Creek scale........................................................................................................171
7.1.3 Importance of the east coast mangrove and nearshore system........................174
7.2 Anthropogenic Pressures............................................................................................175
7.3 Appropriate Environmental Management Unit..........................................................176
ii Oceanica: Straits Salt: Marine and coastal environment of eastern Exmouth Gulf
8. References.....................................................................................................181

List of Tables

Table 2.1 EPA cumulative loss thresholds for BPPH .............................................4
Table 3.1 Tidal and Survey Levels at Exmouth and Hope Point, datum is CD
at Exmouth (source: (1) National Tidal Facility Australia; (2)
Worley Parsons 2005...........................................................................47
Table 3.2 Significance of inundation on ecosystem processes in the intertidal
and supratidal areas.............................................................................58
Table 4.1 Percent of sites with <10%, 10-29% or >30% of seagrass in three
regions sampled in 2000, 2001 and 2003 in Exmouth Gulf (source:
Department of Fisheries)......................................................................95
Table 4.2 Site visits to Exmouth Gulf for sediment and water quality
sampling...............................................................................................96
Table 4.3 Analytical methods and reporting limits..............................................100
Table 4.4 Summary of salinity data from east coast of Exmouth Gulf................102
Table 4.5 Summary of sediment nutrient results (mg/kg)...................................108
Table 4.6 Summary concentrations of nutrients and carbon derived from
Brunskill et al. (2001) (all concentrations mg/kg)................................109
Table 4.7 Summary of metal concentrations recorded in Exmouth Gulf
Sediments (all values are mg/kg).......................................................109
Table 4.8 Summary statistics on metals and trace elements derived from
Brunskill et al. (2001)..........................................................................110
Table 4.9 Summary particle size distribution statistics.......................................111
Table 4.10 Sediment core descriptions and photographs ....................................113
Table 4.11 Acid sulphate soils laboratory results.................................................115
Table 4.12 Start/end points for video transects 9/9/2004 (Map datum:
WGS84)..............................................................................................116
Table 4.13 Oceanica survey of Department of Fisheries monitoring sites,
January 2005......................................................................................126
Table 4.14 Oceanica habitat spot survey results, December 2005......................128
Table 5.1 Listed Marine Species for the Exmouth Gulf Region (excludes
birds)..................................................................................................143
Table 5.2 Results of Exmouth Gulf dugong surveys (Oceanwise 2005).............153
Table 6.1 Shipping lost in Exmouth Gulf region (Source: WA Museum
database) ...........................................................................................165
Table 7.1 Marine management units for the eastern Exmouth Gulf...................177

Oceanica: Straits Salt: Marine and coastal environment of eastern Exmouth Gulf iii
List of Figures

Figure 1.1 Eastern Exmouth Gulf Region................................................................2
Figure 2.1 Notional environmental quality areas for Exmouth Gulf (DoE,
2004a)....................................................................................................6
Figure 2.2 WA Government Proposed World Heritage Boundary (Feb. 2006)........9
Figure 2.3 Detail of marine reserve boundaries and nominal boundary for
eastern Exmouth Gulf...........................................................................11
Figure 2.4 Jurisdictional boundaries (source: National Oceans Office
http://www.oceans.gov.au/atlas/noo-mpa.htm).....................................14
Figure 2.5 Exmouth Gulf mining and pastoral tenement Information as of
March 2005 (source Straits Ltd)...........................................................18
Figure 2.6 Boundaries of the Exmouth Gulf Prawn Fishery (source:
Department of Fisheries)......................................................................19
Figure 2.7 Defence training area (source: Australian Government National
Oceans Office http://www.oceans.gov.au/atlas/noo-mpa.htm).............21
Figure 3.1 Landsat image of Exmouth Gulf and salt flats (20 Jan 2004,
source DOLA).......................................................................................23
Figure 3.2 Eastern Exmouth Gulf geomorphic and stratigraphic relationships
(source: Parsons Brinckerhoff 2005b)..................................................24
Figure 3.3 Northwest Cape and Exmouth Gulf bathymetry (source: APASA
2005)....................................................................................................25
Figure 3.4 Rendered view of Exmouth Gulf bathymetry (Source: Centre for
Whale Research 2004a).......................................................................26
Figure 3.5 Sources of height data additional to charts and remotely captured
data used to generate bathymetry and topography on the east
coast.....................................................................................................27
Figure 3.6 Bathymetry of eastern coast of Exmouth Gulf......................................28
Figure 3.7 Survey transects across the supratidal flats on east of Exmouth
Gulf (source Parsons Brinkerhoff)........................................................30
Figure 3.8 Ponding and salt scalds from past ponding at rear of Deans Creek.....31
Figure 3.9 Annual 9:00 AM and 3:00 PM wind roses for Learmonth (source:
Bureau of Meteorology)........................................................................33
Figure 3.10 Monthly average temperatures Learmonth (source: Bureau of
Meteorology) ........................................................................................34
Figure 3.11 Monthly average rainfall: Learmonth (source: Bureau of
Meteorology) ........................................................................................34
Figure 3.12 Monthly wind roses for Learmonth, based on 10 years of
measurement (source APASA 2005 a).................................................36
Figure 3.13 Average annual frequency of tropical cyclones in the Australian
region (source: Bureau of Meteorology)...............................................37
Figure 3.14 Satellite image at 10:30 am 22 March 1999 showing the eye of
cyclone Vance in Exmouth Gulf (Bureau of Meteorology 2000)...........38
Figure 3.15 Conceptual hydrogeological model (source: Parsons Brinckerhoff
2005b)..................................................................................................42
Figure 3.16 Sea Surface Temperatures 13 March 2005 (source: CSIRO 2005).....43
iv Oceanica: Straits Salt: Marine and coastal environment of eastern Exmouth Gulf
Figure 3.17 Leeuwin Current in the North West Cape/Ningaloo region: (A) Sea
surface temperatures (B) Generalised summer flow patterns
(source: Woo and Pattiaratchi 2003)....................................................44
Figure 3.18 Sea Surface Temperatures 13 July 2002 showing colder waters
fringing the Pilbara Coast and in Exmouth Gulf (source CSIRO
2005)....................................................................................................44
Figure 3.19 Exmouth Gulf Wave Climate: wind waves increase in size with
distance downwind...............................................................................46
Figure 3.20 Example of tidal signature at Exmouth Marina (source:
Department of Planning and Infrastructure)..........................................47
Figure 3.21 Tidal range in the Shark Bay to Exmouth Gulf region (source:
National Tidal Facility, Flinders University)...........................................48
Figure 3.22 Comparison of the phase and amplitude of the major tidal
constituents along the study area as predicted by the HYDROMAP
model. Inset shows the location of the output stations (source:
APASA 2005).......................................................................................49
Figure 3.23 Example of tidal residual data for Exmouth, January 2000 (source:
Department of Planning and Infrastructure)..........................................50
Figure 3.24 Example of wind set-up effects on water elevations at Hope Point,
the plot shows difference between tidal levels and tide plus wind
(mm).....................................................................................................51
Figure 3.25 Astronomical tide data with and without wind set-up effects at
Hope Point (19 Dec. 2004 to 30 April 2005).........................................52
Figure 3.26 Storm surge associated with Cyclone Vance (source: Department
of Planning and Infrastructure).............................................................53
Figure 3.27 Modelled peak water levels and wave heights for 1:50 ARI storm
conditions (source: Cardno Lawson Treloar 2005)...............................54
Figure 3.28 Global average sea level rise (1990–2100) from IPCC (2001).............55
Figure 3.29 Tsunami-generated events off Western Australia are colour-coded
to match run-up observations. Mw is a logarithmic measure of
earthquake size, similar to the Richter scale. VEI is the Volcanic
Explosivity Index; Krakatoa with a score of six is one of the largest
in recorded history. There are no recorded observations in
Australia of the tsunami events of 1833 and 1861. Important areas
of oil and gas production along the Northwest Shelf are shown
(source: Geoscience Australia) ............................................................57
Figure 3.30 Particle tracking results from Massel et al. (1997) (a, b and c) and
Landsat image showing frontal formation along east coast (d).............60
Figure 3.31 Location of tide gauges and current meters used in model
validation studies..................................................................................62
Figure 3.32 Tidal currents in the Gulf: Peak ebb + 3 hours after peak ebb..............63
Figure 3.33 Tidal currents in the Gulf: Peak flood + 3 hours after peak flood..........63
Figure 3.34 Comparison of the sea-level variations and current vectors
measured at Whalebone Island and predicted by HYDROMAP for
the location and depth of the instrument. The lower two figures
show the direction the current was flowing toward (source APASA
2005b)..................................................................................................66
Oceanica: Straits Salt: Marine and coastal environment of eastern Exmouth Gulf v
Figure 3.35 Time-series showing the predicted flushing of particles from
Exmouth Gulf under wind and tide-driven circulation (source
APASA 2005b).....................................................................................67
Figure 3.36 Deans Creek, view east........................................................................69
Figure 3.37 South Creek, view west........................................................................69
Figure 3.38 Upper reaches of Hope Creek at low tide, looking south east..............70
Figure 3.39 Davidson Creek looking north (Burnside Island is in the upper left
of the frame).........................................................................................70
Figure 3.40 Examples of wetting and drying model output (a) bathymetry (b)
low tide (c) flooding (d) peak spring tide (source: Worley Parsons
2005a)..................................................................................................72
Figure 3.41 Tidal inundation curve for Hope Point (source: Worley Parsons
2005a)..................................................................................................72
Figure 3.42 Average (± std error) algal mat and mangrove boundary heights
along the east coast of the Exmouth Gulf and number of survey
readings available for each boundary (source: APASA 2005)..............73
Figure 3.43 Percentage of time that water depths are greater than 0.5 m in
Deans Creek ........................................................................................74
Figure 3.44 Hope Creek, view west towards Hope Point. An incoming tide has
just reached the seaward boundary of the algal mat (dark surface)
area behind mangroves (Photograph1: 19 May 2004, 10:44 am) ........75
Figure 3.45 View south of region due east of Giralia Bay taken at the peak of
flood tide, showing that the water has not reached across the full
extent of the algal mat areas. (Photograph 2: 19 May 2004, 11:30
am).......................................................................................................75
Figure 3.46 19 May 2004: Measured tides at Exmouth Marina (source:
Department of Planning and Infrastructure) and modelled and
measured tides at Exmouth and Hope Point........................................76
Figure 3.47 Modelled inundation at 19 May 2004, 11:30 am...................................76
Figure 3.48 Proposed modified and existing marine reserve nominal
boundaries............................................................................................78
Figure 4.1 Locations sampled by Brunskill et al. (2001) showing water depth
contours (m), sediment grab station locations, and locations of
sediment cores.....................................................................................80
Figure 4.2 Relative distribution of particle size fractions within the bulk
sediment samples: (a) clay-like particles (512 µm), (b) silt (12-62
µm) and (c) sand (62-2000 µm) fractions (from Brunskill et al.
(2001))..................................................................................................81
Figure 4.3 Results of surface grab sampling program (a) Surface Carbonate
Carbon concentrations (b) surface Organic Carbon concentrations
(source: Brunskill et al. 2001)...............................................................81
Figure 4.4 Nutrient elements measured in Exmouth Gulf marine surface
sediments by Brunskill et al (2001). (a) Isopleths of nitrogen (b)
nitrogen/phosphorus ratios (c) Isopleths of sulphur..............................82
Figure 4.5 Results of surface grab sampling program (a) Iron concentrations
(b) Manganese concentrations (source: Brunskill et al. 2001)..............83
Figure 4.6 Concentrations of trace elements throughout the Gulf.........................83
vi Oceanica: Straits Salt: Marine and coastal environment of eastern Exmouth Gulf