Coastal and Estuarine Dynamics in the Arafura Timor Seas

David WilliamsCoastal Oceanography

Australian Institute of Marine ScienceArafura Timor Research Facility

Darwin

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6

4

49

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Once upon a time …….. a long time ago …………

coastal

estuarine

Short term projects

NTC

Site Length of record

Centre Island 1973 - 1987

Melville Bay (Gove) 1964 – 2006

Aurari Bay 1979 - 1986

Snake Bay 1980 - 1986

Darwin Harbour 1959 – 2012*

Port Keats 1980 – 1986

Milner Bay (Groote-BOM) 1993 -2012*

Coastal Tide gauge network operated by NT Government

Several other sites with a few years of record

Dept Nat Resources, The Arts & Sport HYPLOT V133 Output 27/04/2011

Period 3 Year 00:00_01/01/1975 to 00:00_01/01/1978 1975-78

G9070122 Centre Island Tide G100.00 2 Day Max & Min Level (m)

G9070122 Centre Island Tide G100.00 1 Month Mean Level (m)

1

2

3

4

5

1975 1976 1977

Dept Nat Resources, The Arts & Sport HYPLOT V133 Output 28/04/2011

Period 3 Year 00:00_01/01/1995 to 00:00_01/01/1998 1995-98

G8260215 Melville Bay Tide Ga120.00 2 Day Max & Min Tide Level (m)

G8260215 Melville Bay Tide Ga120.00 1 Month Mean Tide Level (m)

0

1

2

3

4

5

1995 1996 1997

Dept Nat Resources, The Arts & Sport HYPLOT V133 Output 28/04/2011

Period 3 Year 00:00_01/01/1982 to 00:00_01/01/1985 1982-85

G8160007 Snake Bay Tide Gauge100.00 2 Day Max & Min Level (m)

G8160007 Snake Bay Tide Gauge100.00 1 Month Mean Level (m)

1

2

3

4

5

1982 1983 1984

Dept Nat Resources, The Arts & Sport HYPLOT V133 Output 28/04/2011

Period 3 Year 00:00_01/01/1974 to 00:00_01/01/1977 1974-77

G8150029 Darwin Harbour Tide120.00 2 Day Max & Min Tide Level (m)

G8150029 Darwin Harbour Tide120.00 1 Month Mean Tide Level (m)

-0.2

1.8

3.8

5.8

7.8

9.8

1974 1975 1976

Dept Nat Resources, The Arts & Sport HYPLOT V133 Output 28/04/2011

Period 3 Year 00:00_01/01/1981 to 00:00_01/01/1984 1981-84

G8130003 Port Keats Tide Gaug100.00 2 Day Max & Min Level (m)

G8130003 Port Keats Tide Gaug100.00 1 Month Mean Level (m)

-0.1

1.9

3.9

5.9

7.9

9.9

1981 1982 1983

Tide gauges

coastal

estuarine

Short term projects

NTC / AIMS

South Alligator River – Van Diemens Gulf

5 m tide range ~ 100 km inland from mouth (6 m range at mouth)

Dept Nat Resources, The Arts & Sport HYPLOT V132 Output 28/04/2010

Period 1 Year Plot Start00:00_01/02/2007 2007/08Interval12 Hour Plot End 00:00_01/02/2008

G8200041 South Alligator R. 100.00 Max & MinLevel (m)

-5

-0

5

10

Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan

Study Location

Location of tidal bores

What we hope to achieve

• No previous field studies on tidal bores.• Role of tidal bore on sediment transport not

understood.• Sediment transport / estuarine ecology unknown.• Environmental flow requirements.• Develop sediment transport /water quality models and

contribute to catchment management.

The Daly River

Level and ADCP

level & S4level & ADCP

level

Tide levels in the lower estuary. Green line: ocean tide levels, Blue line: inside the mouth near Palmerston Island, Pink line: 10km upstream. Due to the shoals the tidal amplitude reduces with distance upstream and the tides become more asymmetric

0

1

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8

00:0006:00

12:0018:00

00:0006:00

12:0018:00

00:00

time (hrs)

tid

e l

eve

l (m

)

ocean

inside mouth

10km inside

Flood dominance

Tide dominance

We found that recent flood did not take sediment out to sea

1.8

2.3

2.8

3.3

3.8

4.3

4.8

5 6 7

Flood tide asymmetry

Qin = Qout therefore Vin > Vout

Field trip August 2003 Focus on tidal bore

1 day tidal bore experiment: July – August 2003And 1 month long estuarine study (August 2003)

1 site for bore

Safety awards

4 m/s

Passage of bore

Undular bore dynamics

Speed

Water level

SSC nephelometers

Turbulent eddies form after the passage of the bore

Up and down welling

Horizontal shear Backscatter in shear zone

Downstream of shoal

100

7

Downwelling occurs on the edge of shears and eddies. Upwelling toward the centre.

Is important for the re suspension of sediment and nutrient.

boat track 2003 on 1980 map

Boat track on latest satellite image

1885 chart

surveyed by Lt Carrington

HMS Palmerston

Historical evidence for siltation at the mouth.

Compare bathymetric surveys of Carrington (1885) with our surveys in 2004at the RAN tide gauge station

Distance

Depth (m)

634000 635000 636000 637000 638000 639000 640000 641000 642000

8518000

8519000

8520000

8521000

8522000

8523000

8524000

8525000

8526000

8527000

8528000

8529000

1885 D aly M outh Survey

637000 638000 639000 640000 641000 642000 643000

8519000

8520000

8521000

8522000

8523000

8524000

8525000

8526000

8527000

8528000

8529000

D aly M outh 2004 Survey

637000 638000 639000 640000 641000 642000 643000

8519000

8520000

8521000

8522000

8523000

8524000

8525000

8526000

8527000

8528000

8529000

D aly R iver EstuarySurvey M arch 2006

Comparison of bathymetric surveys 1885 - 2004 - 2007

Year Volume (m3)

Planar Area(m2)

Volume/Area~mean depth (m)

1885 111,465,813 17,153,758 6.50

2004 95,041,625 23,779,795 4.00

2006 93,030,645 21,731,400 4.28

Dodgy calculations

Need to know LAT derived in 1885

Need to recalculate using a bit more care.

cage

Area 1050 km2

Darwin Harbour

Charles Pt

Lee Pt

Gunn Pt

Area: 620 km2

50 km

Transects

Moorings

Location of measurement sites

-1

0

1

2

3

4

5

6

7

8

9

0:00 6:00 12:00 18:00 0:00

nth Abuoy

Darwin

Wickham

StormPt

Prawn

Rocks

Darwin Harbour Tide Levels

Outer boundary to upstream Middle Arm

3.85

3.90

3.95

4.00

4.05

4.10

4.15

4.20

1958 1968 1978 1988 1998 2008

Darwin Harbour

mean Annual

Linear (mean Annual)

1.7 mm / year

R² = 0.1547

y = 0.0051x + 4.0135R² = 0.2143

3.7

3.8

3.9

4

4.1

4.2

4.3

4.4

-40 -30 -20 -10 0 10 20 30 40

MM

SL

SOI

SOI v MMSL

Predicted versus recorded 1974

Effect of cyclonic winds on Christmas eve 1974 reaching >=220 km/hr

3.85

3.90

3.95

4.00

4.05

4.10

4.15

4.20

1958 1968 1978 1988 1998 2008

Darwin Harbour

mean Annual

Linear (mean Annual)

1.7 mm / year

R² = 0.1547

Measurements with ADCP

120,000 m3/s

Darwin Harbour

Model network

Darwin Harbour

Circulation around headlands and embayments

Darwin Harbour

Currents near islands

Sediment Plumes

Distinctive particle traces

Darwin Harbourdredging disposal proposal

Sediment concentration (mg/L)

Darwin Harbourdredging disposal proposal

Sediment concentration (mg/L)

0 1020

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40

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60

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80

90

100

110

120

130

140

150

160170180190

200

210

220

230

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290

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320

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340350

0%

4%

8%

12%

16%

<=0.2

>0.2 - 0 .4

>0.4 - 0 .6

>0.6 - 0 .8

>0.8 - 1

>1 - 1 .2

>1.2 - 1 .4

>1.4

D arw in N R S Septem ber 2009

Sediment import – 34t / m / month

0 1020

30

40

50

60

70

80

90

100

110

120

130

140

150

160170180190

200

210

220

230

240

250

260

270

280

290

300

310

320

330

340350

0% 4% 8% 12% 16%

>0 - 0 .2

>0.2 - 0 .4

>0.4 - 0 .6

>0.6 - 0 .8

>0.8

East A rm near B laydin P t

Sediment import – 9t / m / month

0 1020

30

40

50

60

70

80

90

100

110

120

130

140

150

160170180190

200

210

220

230

240

250

260

270

280

290

300

310

320

330

340350

0% 2% 4% 6% 8% 10%

>0 - 0 .2

>0.2 - 0 .4

>0.4 - 0 .6

>0.6 - 0 .8

>0.8 - 1

>1 - 1 .2

>1.2 - 1 .4

>1.4

H udson C k deploym ent 1

Sediment export– 17t / m /month

Year 2009 day 200 hour 0.0002000.

0.20

East Arm

Residual currents – 1 lunar tide cycle

Understanding Flushing Characteristics

69

IXSURVEY Darwin Projects

New Technology First Darwin Port Corporation Surveys using modern

multi-beam technology Requires a tightly integrated survey system

comprising: Multibeam Echosounder Motion and Heading Reference Unit GPS 1 PPS timing

70

IXSURVEY Darwin Projects

Changes in shallow sounding technology Leadline

2 soundings / minute Single Beam

20 soundings / second Multibeam

2000 soundings + / second

71

IXSURVEY Darwin Projects

Jan 2010 First Darwin Survey Charles Point Patches LNG Terminal East Arm

Charles Point Patches

72

IXSURVEY Darwin Projects

Jan 2012 Check Survey on

Charles Point Patches

required due to changes

Charles Point Patches

73

IXSURVEY Darwin Projects

Combined Master Surface

Included 3rd party data

Deconfliction Most recent Least depth

74

IXSURVEY Darwin Projects

Hydrographic Survey Products High resolution bathymetry

Navigation safety Object / wreck detection Modelling for large vessel movements Modelling currents and water movement Modelling sediment movement

Sonar Backscatter Sediment classification Benthic Habitat Mapping

75IXSURVEY Darwin Projects

High Resolution Bathymetry

USS Peary

76IXSURVEY Darwin Projects

Entrance to Middle Arm – Looking South

77IXSURVEY Darwin Projects

Sonar Backscatter

Elizabeth River

Northern Australian Observation System

Conclusion

There are a few basic requirements

•Tides

•Bathymetry

•Currents

•River flows

•Sediment properties

•Other physical, chemical and biological parameters