Monthly environmental monitoring summary for August 2007

Transcription

Tweed River
Entrance Sand Bypassing Project
Letitia Spit to Kirra
Monthly Environmental Monitoring
Summary
AUGUST 2007
TWEED RIVER ENTRANCE SAND BYPASSING PROJECT
LETITIA SPIT TO KIRRA
MONTHLY ENVIRONMENTAL MONITORING SUMMARY AUGUST 2007
TABLE OF CONTENTS
1.
EXECUTIVE SUMMARY ......................................................................................................... 1
2.
INTRODUCTION ..................................................................................................................... 2
3.
PUMPING AND DREDGING ACTIVITIES ............................................................................... 2
4.
TWEED RIVER ENTRANCE CONDITIONS ............................................................................ 3
5.
SURF SUMMARY.................................................................................................................... 7
6.
MEDIA COVERAGE AND COMMUNITY FEEDBACK .......................................................... 10
7.
INDICATIVE LONGSHORE SAND TRANSPORT ................................................................. 11
8.
ARGUS COASTAL IMAGING SYSTEM................................................................................ 12
9.
CONTACT DETAILS ............................................................................................................. 14
1. EXECUTIVE SUMMARY
This report provides a summary of pumping and dredging activities, as well as surf, beach,
river, entrance and weather conditions for the southern Gold Coast Beaches, Duranbah, the
Tweed River Entrance and Letitia Spit.
•
The number of vessels that passed through the entrance in August was higher than
on average.
•
Surf quality in August was generally average, with reports of excellent surf conditions
at the end of the month with the ocean storm occurring from 20th to 27th of August.
•
The amount of sand moving north towards the Tweed River Entrance was more than
the August average.
1
2. INTRODUCTION
This document provides a summary of sand quantities delivered by the
system, as well as surf, beach, river, entrance and weather conditions
for the southern Gold Coast Beaches, Duranbah, the Tweed River
Entrance and Letitia Spit for ongoing monitoring purposes.
Information has been sourced from TRESBP monitoring programs,
GCCC coastal reports, media coverage, Surfing NSW and Surfing
Queensland and the following World Wide Websites:
•
www.burleighcam.com.au
•
www.bom.gov.au
•
www.coastalwatch.com.au
•
www.surfingaustralia.com.au
•
www.swellnet.com.au
•
www.tracksmag.com
3. PUMPING AND DREDGING ACTIVITIES
Sand Delivery for AUGUST 2007
PUMPED
DREDGED
AUGUST
2007
TOTAL
DELIVERY
0
83,698
PUMPED
DREDGED
2007
TOTAL
DELIVERY
431,180
0
431,180
Location
Snapper Rocks East
Amount
3
(m )
83,698
Total Sand Delivery This Year (January to August 2007)
Amount
3
(m )
Total Sand Delivery to Date by the Stage 2 Permanent Sand Bypassing System
(May 2000 to August 2007)
Amount
3
(m )
PUMPED
DREDGED
TOTAL
DELIVERY
STAGE 2
4,289,021
1,862,793
6,151,814
2
4. TWEED RIVER ENTRANCE CONDITIONS
VOLUNTEER VIDEO MONITORING LOG
The following Entrance Condition observations for August 2007 were recorded by volunteers Mr Brian
Mason and Mr Robert Ford:
Date
Observations
3 August
Late Morning
Fine weather. Fair crossing conditions. No break outside the entrance.
10 August
Afternoon
Fine weather. Calm crossing conditions.
24 August
Morning
Storm conditions. Dangerous crossing conditions.
31 August
Morning
Cloudy. Calm crossing conditions. No break outside the entrance.
3
TWEED RIVER ENTRANCE CONDITIONS CONTINUED
VOLUNTEER MARINE RESCUE REPORTS
Volunteer Marine Rescue Pt Danger (VMR) has been monitoring daily entrance conditions on behalf
of the TRESBP since 20 January 2002. Monitoring results for August 2007 are presented below.
The navigation ratings from 1–5 are as follows:
1 – Impassable
2 – Difficulty encountered
4 – Relatively good crossing
5 – Good conditions
3 – Some difficulty encountered
– Weekends and public holidays
Date
Navigation Rating
Impassable-----------Good
Entrance Conditions
1
2
3
4
5
Number
of Boats
1
Moderate
46
2
Moderate
43
3
Rough
60
4
Moderate/ Rough
81
5
Moderate
230
6
Moderate
83
7
Moderate
88
8
Moderate
68
9
Moderate
80
10
Moderate
123
11
Moderate
235
12
Slight
271
13
Slight
129
14
Moderate
43
15
Moderate
76
16
Rough
60
17
Rough
50
18
Moderate
64
19
Moderate
31
20
Rough
0
21
Rough
6
22
Rough
8
23
Rough
20
24
Rough
16
25
Rough
2
26
Rough
2
27
Rough
10
28
Rough
28
29
Moderate
62
30
Moderate
115
31
Moderate
207
4
Daily Number of Vessels Passing Through Tweed River
Entrance and Navigation Conditions, August 2007
5
Navigation rating
Boats Passing
300
NB.
1. Peaks in number of vessels passing
frequently coincide with weekends.
2. Forecast conditions may influence
number of vessels passing.
250
Rating from 1 to 5 (1 being impassable, 5
being good navigational conditions)
Daily Number of Vessels Passing Through
Entrance
4
200
3
150
100
2
50
1
0
01
02
Wed Thu
03
Fri
04 05 06 07 08
09
Sat Sun Mon Tue Wed Thu
10
Fri
11 12 13 14 15 16
17
Fri
18 19 20 21 22 23
24
Fri
25
26 27 28 29
30
31
Fri
Date
Siginficant Wave Height (m) measured at the Tweed Waverider Buoy
Daily Number of Vessels Passing through
Tweed River Entrance and Significant Wave Heights
August 2007
75% Wave Height Exceedance for Winter, ~0.9m (1995-2001)
Vessels Passing
4.00
300
250
3.00
Significant Wave Height (m)
Daily Number of Vessels Passing
Through Entrance
Days logged in August:31
Total Crossings recorded:2337
Average Crossings per day:75
200
2.00
150
100
1.00
50
0.00
01
02
Wed Thu
0
03
Fri
04
05
06
07 08
09
10
Fri
11 12
13
14 15
16
(NB:Rough sea conditions recorded for 3-4/8, 16-17/8 & 20-28/8)
Date
17
Fri
18 19 20 21 22
23
5
24
Fri
25 26 27
28 29
30
31
Fri
4,000
3,500
6.0
2006/07
Average crossings
per month 2,500
5.5
3,000
5.0
2,500
4.5
2,000
4.0
1,500
3.5
1,000
3.0
500
1994/95
Average crossings
per month 1,000
2.5
0
2.0
-500
1.5
-1,000
1.0
-1,500
0.5
-2,000
September October November December January
Number of
vessels
passing
through the
entrance per
month
(2006/07)
February
March
April
Month
6
May
June
July
0.0
August
Number of
vessels
passing
through the
entrance per
month
(1994/95)
Ave. Monthly Significant Wave Height (m)
Monthly No. Vessels passing through entrance
Comparison of the Number of Vessels Passing Through the Entrance per month
(2006/07 compared to 1994/95 prior to entrance improvements) and
the Average Monthly Significant Wave Heights (2006/07 compared to Average 2002- 2006)
Average
monthly
wave height
(Hsig)
Average
monthly
wave
height(Hsig)
(Ave. 20022006)
5. SURF SUMMARY
Over the first three weeks of August calm waves of between 0.5 – 1.5m from the SE were
th
predominant on the Southern Gold Coast. After 20 August, swells rose significantly to between 1.3 –
4m. Winds varied over the month with the most predominant wind conditions being SE and SW at 1050 Knots.
Readings from the Tweed Waverider Buoy showed a minimum significant wave height of 0.45m on 10
August and a maximum significant wave height of 4m on 21 August. There were 22 recorded days
when waves dropped below 1.0m and 8 days when waves were above 2.0m.
Source: Tweed and Brisbane Waverider Buoy, RealSurf, Swellnet, Burleighcam, Coastalwatch, BoM.
August 2007
Hsig (m.)
4.5
4
3.5
Hsig (m.)
3
2.5
2
1.5
1
0.5
0
01
02 03 Fri 04
Wed Thu
Sat
05
Sun
06
Mon
07
08
09 10 Fri 11
Tue Wed Thu
Sat
12
13
Sun Mon
14
15
16 17 Fri 18
Tue Wed Thu
Sat
19
Sun
20
Mon
21
22
23 24 Fri 25
Tue Wed Thu
Sat
26
27
Sun Mon
28
29
30 31 Fri
Tue Wed Thu
Date
A link to data recorded continuously at the Tweed Waverider Buoy is available at:
www.epa.qld.gov.au/sandbypass/
SURF & SURF LIFE SAVING EVENTS
Events in August 2007
25 August – Malibu Teams Challenge (Kirra Point)
Upcoming events in September 2007
22-23 September – Billabong Girls Queensland Surf Series
Source: Surfing Australia, Surf Life Saving Australia & Surf Life Saving Queensland
7
SURF SUMMARY CONTINUED
VOLUNTEER SURF QUALITY OBSERVATIONS
The following observations for August 2007 were made by volunteers Mr Brian Mason and Mr Robert
Ford on behalf of the TRESBP.
Date
Duranbah
Frog’s Beach / Snapper
Rocks
Kirra Point
3 August
Late Morning
1 – 1.5m NE swell, plunging
waves. 14 surfers present.
Unpleasant conditions with
strong wind.
3 surfers present. Small
longshore transport
occurring. No offshore bar
apparent.
1 – 1.5m spilling waves. 3
surfers present. No
longshore transport
occurring.
10 August
Afternoon
1 – 1.5m NE swell, plunging
and spilling waves. 6 surfers
present. Flat surfing
conditions.
20 surfers present. No
longshore transport
apparent.
<1m spilling waves. 1 surfer
present. No longshore
transport occurring.
Offshore bar present. [Gold
Coast City] Council
[undertaking dune works
along Central Kirra using
sand from the beach face
drawing back beach
alignment.]
24 August
Morning
>>2.5m NE swell. 0 surfers
present. Erosion on
Duranbah beach.
longshore transport
apparent.
1.5 – 2m and >>2m plunging
waves. 8 surfers present. No
longshore transport
occurring. Beaches are
holding up well.
31 August
Morning
1 – 1.5m ENE spilling swell.
37 surfers present. 2m
scarp[ing] [contained within]
Duranbah beach [sand
store. No dune erosion]
longshore transport
apparent.
1 – 1.5m spilling waves. 3
surfers present. No
longshore transport
apparent. Seems the
offshore bar has come
[on]shore south from the
Miles St groyne to
Greenmount. There is an
area of deep water just
offshore 4 – 5m in width
from north [of] Mile St
groyne to the stormwater
outlet.
NB – [ ] Bracketed comments added for clarity.
8
SURF SUMMARY CONTINUED
PHOTOGRAPHS OF SURF CONDITIONS
Kirra, 24 August 2007
Malibu Teams Challenge, Kirra, 25 August 2007
Source: Surfing Australia
Source: Courier Mail
Snapper Rock, 22 August 2007
Snapper Rock, 29 August 2007
Source: SwellNet
Coolangatta, 22 August 2007
Rainbow Bay, 27 August 2007
Source: SwellNet
9
6. MEDIA COVERAGE AND COMMUNITY FEEDBACK
MEDIA COVERAGE
2 August, Gold Coast Bulletin, “Kirra’s shore thing” (also appears on 17 August, Gold Coast Bulletin, “A sea
change, for sure”
“The work will include reducing the width of the beach while retaining sand to protect against storm
erosion, increasing turfed parklands to cater for population growth, extra parklands at Kirra and sand
pumping off North Kirra to improve surfing conditions.”
16 August, Tweed Border Mail, “Pumping options eyed to aid Kirra”
“Gold Coast City Council are pushing the Queensland government to review sand dredging at Kirra to
improve the break’s once-legendary waves.”
16 August, Tweed Border Mail, “Saving surf break could take years”
“Surfers have welcomed news that Gold Coast City Council is pressing the Queensland government to
review sand pumping to Kirra beach, but believe it would take years for the beach to regain its former
glory.”
22 August, Daily News, “Gun surfers making the most of wacky weather”
“While the wild weather might have forced most of the Tweed indoors yesterday, the surfing fraternity
made the most of the large swell, with some of the sport’s biggest names taking to the waves at
Snapper Rocks.”
23 August, Daily News, “Americans amazed by ferocious surf”
“Although it was a “blast from the past” to actually see some rideable surf at Kirra, the waves were
nothing like Kirra’s old time ”kegs””
24 August, Gold Coast Bulletin, “It’s a big-surf surfeit”
“The winds are going to back off a bit and turn southerly and that’s better for the Queensland points
between Snapper and Kirra”
25 August, Daily News, “Mick cuts it at the groyne”
“Mere mortal surfers could only watch in awe… The swell will be large, but by tomorrow morning
lighter southerly winds could create good conditions for wave hounds.”
26 August, Surfing Australia, “Malibu Teams Challenge”
“It was great to be back surfing Kirra… The waves have been pumping all week on the Superbank, so
it was great to able to combine both of them today”
27 August, Gold Coast Bulletin, “Doctors operate on surf victim”
“A 21 year old bodyboarder received serious spinal injuries when he was dumped in monster surf at
Kirra on Saturday.”
30 August, Daily News, “D-bah falling apart”
“The whopper seas have gouged and pushed the Duranbah Beach shoreline inland, up to five metres
or more in places.”
31 August, Courier Mail, “Delighted with what’s left”
“The Gold Coast’s Superbank from Snapper to Kirra turned on spectacular tubes for a week, with the
end section from Coolangatta to Big Groyne showing the best form.”
10
7. INDICATIVE LONGSHORE SAND TRANSPORT
The longshore sand transport information presented in the graph below is based on a simplified
sediment transport model and should only be used as an indicator of the actual sand transport
quantities for the month.
It is estimated that during August 2007, 68,000m³ of sand was moved north towards the Tweed River
entrance by natural processes. This is more than the average modelled sand transport quantity for the
month of August.
LETITIA SPIT INDICATIVE LONGSHORE TRANSPORT ASSESSMENT
Cumulative Monthly Net Transport
100,000
20
75,000
15
50,000
Wave Heights (m.)
Sediment Transport (cu m), northward positive
Net Daily
25,000
10
0
5
-25,000
-50,000
Avg August
Trans 19891995 (WBM
Model)
01
02 03 Fri 04
Wed Thu
Sat
05
06
07
08
09 10 Fri 11
Sun Mon Tue Wed Thu
Sat
12
13
14
15
16 17 Fri 18
Sun Mon Tue Wed Thu
Sat
August 2007
11
19
20
21
22
23 24 Fri 25
Sun Mon Tue Wed Thu
Sat
26
27
28
29
30 31 Fri
Sun Mon Tue Wed Thu
0
Avg August
Trans 19952007 (Lands
Tweed
Model)
Wave
Heights
8. ARGUS COASTAL IMAGING SYSTEM
The University of New South Wales is monitoring Letitia Spit to North Kirra for the project using an
ARGUS coastal imaging system. Images are available on the internet at the following address:
http://www.wrl.unsw.edu.au/coastalimaging/public/tweed/index.html
These images are updated hourly and all past photos can be accessed in the archives.
Merged and rectified images taken at mid tide for each of the locations are shown below. Refer to
Appendix A for beach width and shoreline analysis for each of the beaches.
DURANBAH BEACH
30 July 2007
31 August 2007
RAINBOW BAY
31 July 2007
31 August 2007
12
ARGUS COASTAL IMAGING SYSTEM CONTINUED
COOLANGATTA - GREENMOUNT
31 July 2007
31 August 2007
NORTH KIRRA - KIRRA
30 July 2007
30 August 2007
13
9. CONTACT DETAILS
This report was completed by Becky Wong.
For more information regarding the Tweed River Entrance Sand Bypassing Project please refer to
the following web addresses:
www.tweedsandbypass.nsw.gov.au
www.epa.qld.gov.au/sandbypass/
www.wrl.unsw.edu.au/coastalimaging/public/tweed/index.html
For all enquires regarding this report, please contact Becky at any of the addresses below:
Becky Wong
Environmental Engineer
Tweed River Entrance Sand Bypassing Project
NSW Department of Lands
[email protected]
Level 12, 10 Valentine Avenue
Parramatta NSW 2124
Ph: (02) 8836 – 5325
Fax: (02) 8836 – 5364
14

Monthly environmental monitoring summary for August 2007

Transcription

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