I I. COASTAL STORMS IN N.s.w. .: AUGUST & NOVEMBER 1986 .1 and Their Effect on the Coast I 'I I 1'1

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, . < May 198,8 , 'I " I I : COASTAL STORMS· IN N.s.w. I AUGUST & NOVEMBER 1986 I and Their Effect on the Coast I I I I I

1: 1 I I I I

I M.N. CLARKE M.G. GEARY I Chief Engineer Principal Engineer

I Prepared by : University of N.S.W. Water Research Laboratory I bID IPTIID311IIcr: ~Th'¥@~ , I May 1988 ------..! Coaat a Rivera Branch I I I I CONTENTS LIST OF FIGURES ( ii ) I LIST OF TABLES (iv)

1. INTRODUCTION

I 2. SUMMARY 2

3. ENVIRONMENTAL CONDITIONS 5 I 3.1 METEOROLOGICAL DATA 5 3.2 TIDE LEVELS 7 3.3 WAVE HEIGHTS AND PERIODS 10 I 3.4 STORM mSTORY - AUGUST 1985 TO AUGUST 1986 13

4. WAVE RUN-UP 15 I 4.1 MANLY WARRINGAH BEACHES 15 4.2 BATEMANS BAY BEACHES 15 I 4.3 THEORETICAL ASSESSMENT 16 4.4 COMPARISON OF MEASURED AND THEORETICAL RUN-UP LEVELS 23

5. BEACH SURVEYS 25 ·1 5.1 GOSFORD BEACHES 25 5.2 MANLY W ARRINGAH BEACHES 28 I 5.3 BATEMANS BAY BEACHES 29 6. OFFSHORE SURVEYS . 30 6.1 SURVEY METHODS 30 I 6.2 GOSFORD BEACHES 30 6.3 WARRINGAH BEACHES 31 I 6.4 ASSESSMENT OF ACCURACY OF OFFSHORE SURVEYS 32 7. OFFSHORE SEDIMENT SAMPLES - GOSFORD BEACHES 34 7.1 SAMPLE COLLECTION 34 I 7.2 SAMPLE CLASSIFICATION 34 , 7.3 SAMPLE DESCRIPTIONS 34 I 7.4 COMPARISON OF 1983/84 AND POST STORM OFFSHORE DATA 36 8. REFERENCES 38 9_ ACKNOWLEDGEMENTS 40 I APPENDIX A. List of Stonn Data 41 I I

I - i - I I I I LIST OF FIGURES

I 1. Location Map, Central NSW, Gosford to Batemans Bay 2. Meteorological Conditions, Sydney Airport, August and November 1986 I 3. Meteorological Conditions, Moruya Heads, August and November 1986 4. Synoptic Charts August 1986 5. Synoptic Charts November 1986 I 6. Tide Levels at Fort Denison, August 1986 7. Tide Levels at Fort Denison, November 1986 8. Return Period of Recorded Water Levels at Fort Denison for period 1883 to 1975. I 9. Tide Levels at Batemans Bay Zwarts Gauge, August 1986 10. Tide Levels at Batemans Bay Zwarts Gauge, November 1986 11. Comparison of Tides, Batemans Bay Zwarts and Floatwell Gauges, November 1986 I 12. Wave Height and Period a. Offshore Botany Bay, August, 1986 I b. Offshore Botany Bay, November, 1986 c. Offshore Batemans Bay, August, 1986 d. Offshore Batemans Bay, November, 1986 I 13. a-d Wave run-up, Manly Warringah Beaches, August, 1986 14. a-c Wave run-up, Batemans Bay Beaches, August and November, 1986 15. Beach Changes, Forresters Beach I 16. Beach Changes, Wamberal and Terrigal Beaches 17. Beach Changes, Avoca Beach 18. Beach Changes, Copacabana and MacMasters Beaches I 19. a-e Beach Profiles, Wamberal and Terrigal Beaches. 20. a-e Change in beach volume versus time, Wamberal and Terrigal beaches. I 21. Beach Changes, Narrabeen Beach 22. Beach Changes, Collaroy and South Narrabeen Beaches 23. Location of offshore profiles and samples, Gosford, 1984 and 1986. I 24. a-b Offshore profile and sample locations, Gosford Line 5, 1984 and 1986. Two scales. 25. a-b Offshore profile and sample locations, Gosford Line 9, 1984 and 1986. Two scales. 26. a-b Offshore profile and sample locations, Gosford Line 12, 1984 and 1986. Two scales. I 27. a-b Offshore profile and sample locations, Gosford Line 13, 1984 and 1986. Two scales. 28. Location of offshore profiles, Collaroy-Narrabeen 1979/83 and 1986. I 29. Offshore profile, Collaroy-Narrabeen, Line 1, 1986. 30. Offshore profile, Collaroy-Narrabeen, Line 2, 1986. 31. Offshore profile, Collaroy-Narrabeen, Line 3, 1986. I 32. Offshore profile, Collaroy-Narrabeen, Line 4, 1986. 33. Offshore profile, Collaroy-Narrabeen, Line 5, 1986. 34. Offshore profile, Collaroy-Narrabeen, Line 6, 1986. I 35. Offshore profile, Collaroy-Narrabeen, Line 7, 1986. 36. Offshore profile, Collaroy-Narrabeen, Line 8, 1986. 37. Offshore profile, Collaroy-Narrabeen, Line 10, 1986. I 38. Offshore profile, Collaroy-Narrabeen, Line 17, 1979.

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39. Offshore profile. Collaroy-Narrabeen. Line 18. 1979. I 40. Offshore profile. Collaroy-Narrabeen. Line 19. 1979. 41. Offshore profile. Collaroy-Narrabeen. Line 141. 1983. 42. Offshore profile. Collaroy-Narrabeen. Line 142. 1983. I 43. Offshore profile. Collaroy-Narrabeen. Line 151. 1983. 44. Offshore profile. Collaroy-Narrabeen. Line 254. 1983. I 45. Offshore profile. Collaroy-Narrabeen. Line 255. 1983. I I I I I I I I I I I I I

I - iii - I I I I I LIST OF TABLES 1. Maximum Wind Speeds for August and November 1986 Storms 5 2. Maximum Tide Levels for August and November 1986 Storms 8 'I 3. Maximum Wave Heights for August and November 1986 Storms 11 4. Recurrence Interval of Wave Heights for August and November 1986 Storms 13 I 5. Recorded Storm Events, October 1985 to August 1986 14 6. Estimated Wave Set-up for Various Wave Conditions 19 I 7. Estimated Components of Run-up for August and November 1986 Storms 23 8. Change in Beach Volume, Wamberal and Tenigal Beaches, August 1986 Storm 27 I 9. Details of Offshore Samples, Gosford Area, 1983/84 and 1986 Surveys 35 I I ,I I I I I I I I I

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I - I - I 1. INTRODUCTION I During the stonns of August and November 1986, significant beach erosion and stonn wave run­ up occurred along the coast of New South Wales. Various data on these aspects were obtained by the Public Works Department of NSW (PWD) either during or immediately after the stonns I and are presented in this report together with relevant infonnation collected before the stonns.

I Wave and tide data were recorded by the Department's Manly Hydraulics Laboratory and by the Maritime Services Board (MSB), at various locations along the NSW coast. The wind, atmospheric pressure and rainfall data were monitored by the Bureau of Meteorology. This stonn I data has been collated in this report. Run-up levels at selected locations on some Sydney and Batem~ Bay beaches were measured by the Department and the Eurobodalla Shire Council. Measured run-ups for the Sydney Beaches are compared with those predicted with simple theory I and the differences are discussed. The prediction of stonn wave run-up levels for Batemans Bay is the subject of a separate study.

I In addition, land surveys, aerial photography, offshore profiling, sand sampling data and video records of stonn erosion damage are available for some areas. Where this type of data was I available both before and after the stonns, an assessment was made' of the beach erosion or accretion and offshore profile change.

I The Department has arranged that thisinfonnation be collated into a readily accessible fonn and limited analysis carried out, so that it can be used to provide reliable and substantiated advice on coastal hazards in the future. The Water Research Laboratory (acting through Unisearch Ltd) was I commissioned to carry out this work. The data collected and the analysis and interpretation of it, I are detailed in the following sections. I I I I I I I I 2. SUMMARY

I Two severe stonns occurred in the second half of 1986, the first in August and the second in November. This report brings together the data that describe the weather and the sea during the stonns and then documents the investigations carried out to detennine the effect of the stonns on 1 the beaches in the Gosford, Sydney and Batemans Bay areas.

I THE AUGUST STORM - 4TH TO 9TH AUGUST 1986

A low pressure system moving across NSW deepened into an intense coastal low off CoITs ·1 Harbour and brought gale force winds and heavy rainfalls to the NSW Central Coast between 4th and 9th August.

·1 Atmospheric pressure fell to 1002mb, 16mb below nonnal August pressure for Sydney; winds gusted to 54 knots and heavy rain fell on the Georges River catchment causing severe flooding in I the Liverpool area. The maximum wave height of l3.2m was recorded off Botany Bay on the 5th with a second I maximum of 12.6m on the 8th. Maximum significant wave height of 7.5m was recorded on the 6th and again on the 8th and the significant wave height exceeded 4.0m for four days. A maximum wave period of 15.1 seconds was recorded on the,8th and wave periods stayed in the I range of 11 to 13.5 seconds from the 6th to the 15th August.

The stonn coincided with spring tides, a gauge height of 1.77 m being predicted at Fort Denison I on the 6th and 7th. The measured tide was 1.99 m, 0.22 m higher than predicted and it stayed I 0.1 m or more above predicted for four days. THE NOVEMBER STORM - 17TH TO 23RD NOVEMBER 1986

I An intense low developed over southern NSW bringing gale force winds to the Central and Southern NSW coast.

I Atmospheric pressure fell to 993mb, 21 mb below the nonnal November pressure for Sydney; winds ~sted to 48 knots. Heavy rainfall was recorded in the Batemans Bay region and light I rainfall in the Gosford and Sydney regions. Maximum wave height of 12.2 m was recorded off Botany Bay on the 20th. Maximum I significant wave height of 6.9 m was recorded on the same day and the significant wave height exceeded 4.0m for two days. Maximum wave period of 13.5 seconds was recorded several times I between 19th and 22nd and the wave period stayed above 10 seconds between 18th and 23rd. The stonn coincided with spring tides, gauge heights between 1.71 and 1.67m being predicted at Fort Denison between 18th and 20th. The measured maximum tide was 1.95 m on the 20th, I 0.28 m above the predicted and it stayed 0.1 m or more above the predicted for two days. I I I

I - 3 - I I RECURRENCE INTERVALS OF THE AUGUST AND NOVEMBER STORMS Following the classification of storm severity adopted in the PWD Elevated Ocean Levels reports (PWD 1985b and 1986a) both the August and November storms fall into the extreme category I (category "X"), that is, storms where the significant wave height exceeds 6.0m. These storms occur, on the average, every 3.5 years. More precise recurrence intervals can be calculated on the basis of published wave height exceedance statistics as discussed in Section 3.3.4, but the I published data give widely differing results and at present only ranges of recurrence interval can be stated. Thus the August storm had a recurrence interval between 6.5 and 3.0 years and the I November storm between 3.5 and 1.5 years. I ELEVATED OCEAN LEVELS Ocean level rises along a coastline during a storm due to the coincidence of high tide, storm surge, wave set-up and wave run-up. Tide gauges record the tide plus the storm surge, including I the atmospheric set-up and wind set-up. Wave set-up in the surf zone is not at present being monitored except on an experimental research basis put the final wave run-up levels, which include all the set-up components, can be measured during the storm or immediately after the I storm from debris lines. I Run-up levels can also be estimated from theory knowing the predicted tides and the wind field and wave statistics of the storm.

I Measurements of wave run-up taken in August and November are compared with the theoretical estimates and reasonable agreement is found on exposed beaches where wave refraction effects are minimal. In the August storm measured run-up levels of 4 to 6mAHD on Narrabeen/Collaroy I Beach compare well with the theoretical estimate of 6.1 m AHD. In the Batemans Bay area, on the exposed beach of Malua Bay, the measured run-up level of 5.5 m AHD compares well with I the theoretical estimate of 5.2 m AHD. In the November storm. run-up levels were measured only in the Batemans Bay area and the I observed run-up level of 5.5 m AHD at Malua Bay compares reasonably well with the theoretical estimate of 4.9 m AHD.

I COASTAL EROSION

Beach erosion occurs during storms where high energy waves cut the beach berm, moving the I sand into an off-shore storm bar. Build-up of the bar causes the storm waves to break further off-shore thus reducing the wave energy reaching the beach until an equilibrium storm beach I profile, comprising an erosion scarp and an off-shore storm bar, develops. Low energy wave climate slowly moves the sand stored in the off-shore bar back into the beach berm.

·1 Beach erosion in the Gosford area was monitored by photogrammetric means for the August storm and by beach surveys carried out by the Soil Conservation Service for both August and' '~.A;. I " I I

I - 4- I I November storms. Maximum beach berm erosion of 200 m3 1m of beach length was recorded on Forresters Beach. On the other beaches the berm erosion maxima reached to between 100 and 150m3/m. In a I previous study (PWD 1985a) the PWD had determined design storm erosion volumes for Wamberal, Terrigal and Avoca beaches varying between 50 and 250m31m. The berm erosion in I the August 1986 storm on these beaches was significantly smaller. The beach surveys carried out by the Soil Conservation Service indicated similar berm erosion volumes but also showed that while severe erosion took place in the August storm, the less I intense and shorter November storm seems to have caused no further erosion, but possibly slowed I down the beach recovery. The state of some of the Gosford and Sydney area beaches following the August 1986 storm was recorded on video cassette by the Public Works Department of NSW, Coastal Branch. Details of I these are given in Appendix A.

Offshore surveys carried out in the Gosford area in 1983/84 were compared with surveys done I after 1986 storms. Only four survey lines were available for comparison and these showed that between 100 and 3OOm31m of sand had been stored in the offshore storm bar. No changes in the I offshore profile could be reliably detected below RL-16mAHD.

In Warringah, beach erosion from the August storm was monitored by photogrammetric means. I Maximum beach berm erosion of 180m31m was recorded on South Narrabeen Beach. Narrabeen Beach showed less than 1oom3/m erosion on average and on Collaroy Beach the erosion varied between 100 and 150m3/m. In general the erosion observed during the August 1986 storm was I significantly less than the erosion that occurred in the 1974 storms.

Offshore surveys were carried out on Collaroy and Narrabeen Beaches in 1979 and 1983 and after I the 1986 storms. The location and profile data of the survey lines is assembled in this report but detailed analysis of the survey records is required before any pre and post storm comparisons can I be carried out I I I I I I I

I - 5 - I I 3. ENVmONMENTAL CONDITIONS 3.1 METEOROLOGICAL DATA

The following ~nformation is compiled primarily from the Bureau of Meteorology Monthly I Summaries for August and November 1986 (Bureau of Meteorology, 1986a and 1986b). It has been supplemented with data from their hourly data sheets, 9 am and 3 pm weather bulletins, and I chan records from various instruments. The location of the weather stations is given in Figure 1. The one hour mean wind speed used here is the average wind speed over an hour, and has been estimated from the chan records. ,.The 10 minute mean wind speed obtained from the Bureau of I Meteorology is the average wind speed over a 10 minute period. The one hour figures have been used where possible because they are more relevant to wave generation and wind set-up.

I 3.1.1 August 1986 Storm Description

On the 4th of August a low near Adelaide moved to the NSW coastal area and over the next few I days deepened into an intense coastal low near Coffs Harbour. Upper air influences deepened the low to below 990mb, and for the period from the 4th to the 8th the NSW Central Coast was buffeted by strong to gale force winds and intense rainfall. Strong winds were reported in coastal I waters throughout NSW from the 4th to the 9th and coastal gales from the 5th to the 8th. I Oceanic gales were reponed from the 5th to the 12th. At Sydney Airpon (Mascot) wind gusts reached a maximum of 54 knots (28 mls) early on the 6th August and one hour mean wind speeds were up to 28 knots (l4m/s) on that day (Table 1 and I Figure 2). Wind direction was generally from the ESE and SE (Figure 2). At Moruya Heads (appro)C 22km south of Batemans Bay) 10 minute mean wind speed is recorded twice daily and reached a maximum of 24 knots (12m/s) on the 6th. (Table 1 and Figure 3). Wind directions I were generally from the south and SSE but turned to the SSW on the afternoon of the 6th (Figure 3).

TABLE 1. Maximum Wind Speeds For August and November 1986 Storms

August November Location Mean Gust Mean Gust I Sydney Airpon 14 28 14 25 Moruya Heads 12 26

I Wind Speeds in metres/sec.

I These strong winds generated very rough seas and heavy swell which created serious problems for shipping off the illawarra Coast. In the Metropolitan area, the gales downed high tension wires in a south-western suburb, causing the death of two people. Much minor damage to propeny and I trees was· also sustained. I I ------I

I -6- I Record rainfall for August was received in the Metropolitan and adjacent Tableland regions during I the August 1986 stonn. Daily rainfall at Sydney Airport was 111 mm in the 24 hours to 9 am on the 5th, and 207 mm in the following 24 hours (Figure 2). This was the highest daily rainfall for several years. As a consequence major flooding occurred on the 5th to 8th in the Georges River I and Nepean-Hawkesbury Rivers and minor flooding on the Shoalhaven River on the 6th. Widespread and severe local flooding also occurred on the 5th and 6th, mainly in the metropolitan district. The flooding was responsible for the loss of several lives and the damage bill to homes, I properties, and vehicles by water was estimated at hundreds of millions of dollars. Rainfall at Moruya Heads was much less severe, with 35 mm recorded in the 24 hours to 9 am on the I 4th August (Figure 3). Daily synoptic charts for the 3rd to the 9th August are shown in Figure 4. Atmospheric pressure I at Sydney airport is plotted as a time series in Figure 2 and indicates that a low of 1002mb occurred at about midnight on the 5th August. Nonnal August atmospheric pressure for Sydney is 1018 mb (Bureau of Meteorology, 1986a). Atmospheric pressure at Moruya Heads, recorded I seven times each day by the Bureau of Meteorology, is plotted as a time series in Figure 3 and indicates that a low of 1010mb occurred at about 5:00pm on the 5th August. Nonnal August atmospheric pressure for Moruya Heads is 1017mb (average of the 9:00am and 3:00pm values I obtained from the Bureau of.Meteorology, Melbourne). I The one hour mean wind speed and direction for Sydney Airport, at hourly intervals has been extracted from Bureau of Meteorology charts and time series plots are given in Figure 2. Daily rainfall data is also shown. The 10 minute mean wind speed and direction at Moruya Heads are I measured twice daily by the Bureau. This data was obtained from the Bureau and is plotted in Figure 3 together with the daily rainfall.

I The stonn coincided with predicted spring tides. I 3.1.2 November 1986 Stonn Description Strong winds were reported in coastal waters from the 17th to 23rd November and strong to gale force wind over much of the state on the 18th and in the eastern half on the 19th. These were in I association with an intense low which developed over the southern NSW coast on the 18th November. Gale force winds were reported in ocean waters on the 18th and 19th, in coastal . waters over southeastern parts of the state on the 20th and near the NSWNictorian border on the I 21st.

I Winds gusts at Sydney Airport reached 48 knots (25 mls) at about midday on th~ 20th, and one hour mean wind speeds were generally 20 to 27 knots (10 to 14m/s) for most of the afternoon. Wind direction was from the west to south west on the 19th and south west to south on the 20th I and 21st (Figure 2). At Moruya Heads the 10 minute mean wind reached 26 knots (13m/s) from the SSW on the afternoon of the 19th. No damage was reported, but heavy swell arising from I gale force winds at sea caused some difficulties. I I I

I - 7- I Rainfall for the month was generally average to above average, with very much above average I falls noted in some coastal areas and adjacent highlands, particularly lllawarra, and in parts of the Riverina and SW slopes. The highest daily rainfall at Sydney Airport was 47 mm in the 24 hours to 9:00 am on the 14th, about 4 days before the storm occurred. During the storm perio<,l, the I rainfall in Sydney was generally low with a maximum of 25 mm in the 24 hours before 9:00 am on the 19th (Figure 2). No major flooding was reported. At Moruya Heads the rainfall was more I severe with 115 mm recorded in the 24 hours to 9 am on the 19th November (Figure 3). Daily synoptic charts for the 11th to the 23rd November are shown in Figure 4. Atmospheric pressure at Sydney airport is plotted as a time series in Figure 2 and indicates that a low of I 993mb occurred at about 5:00pm on the 18th. Normal November atmospheric pressure for Sydney is 1014mb (Bureau of Meteorology, 1986b). Atmospheric pressure at Moruya Heads is I plotted as a time series in Figure 3 and indicates that a low of 992 m b occurred at about 2:00 am on the 19th. Normal November atmospheric pressure for Moruya Heads is 1014 mb (average of I the 9:00am and 3:00pm values obtained from the Bureau of Meteorology, Melbourne). One hour mean wind speed and direction for Sydney Airport, at hourly intervals has been extracted from Bureau of Meteorology charts and time series plots are given in Figure 2. Daily I rainfall data is also shown. The 10 minute mean wind speed and direction for Moruya Heads are measured twice daily by the Bureau. This data was obtained from the Bureau and is plotted in I Figure 3 ,together with the daily rainfall. I The storm coincided with predicted spring tides. 3.2 TIDE LEVELS

I 3.2.1 Fort Denison Tide levels are recorded by the MSB at Fort Denison in Sydney Harbour. The location is well I inside the harbo)Jr and is very protected from ocean waves. Water levels recorded would include barometric and wind set-up al! well as astronomical tides, but would not include wave set-up since I~ it is in a very sheltered location and is not within the breaker wne. The gauge uses a Harrison recorder that was installed in 1908. '

. The present gauge datum is 0.925 m below AHD and is referred to as "the zero of the Fort I Denison Tide Gauge". It has been used for all tide levels in this report, unless otherwise specified. This datum is approximately ISL W (Indian Spring Low Water) and is often referred to I by that name. This has been done in this report. However, ISL W is now treated as a variable not a datum. Eastern Standard Time is used throughout the year and has been used in this report.

I The tides recorded during both the August and November 1986 storms have been replotted from high and low times and heights obtained from the MSB, and are reproduced in Figures 6 and 7. These plots also show the predicted tides at Fort Denison and the residuals between measured and I predicted tides. I I I

I - 8 - I It should be noted that the predicted tides are calculated using haanonic constituents and mean I sea level derived in an earlier year, and that these can c.hange from year to year. It is common for measured and predicted tides to differ even in the absence of SlOans. Variations of up to ±O.2 m have been observed and variations of ±O.l m are. typical. Care should therefore be taken I in interpreting tidal residuals, since they are only partly due to the SlOans.

The maximum level recorded during the August SlOan was 1.99m above tide gauge zero (1.06m I above AHD), and occurred at approximately 9:05 pm on the 6th. The level was 0.22 m above the predicted height of 1.77 m (0.85 m AHD) for that time. The tidal residual exceeded 0.2m for about 1.5 days and exceeded 0.1 m for almost 4 days (Figure 6). Tide predictions for Fort I Denison are supplied to the MSB by the Tidal Laboratory, Flinders Institute for Atmospheric and Marine Sciences, Flinders University of South Australia. About 8% of predicted high tides I exceed 1.77m (Easton, 1970). An analysis of recorded extreme water levels at Fort Denison for the period'1883 to 1975 (LePlastrier, et al. 1976) indicates that a level of 1.99m is likely to I occur on average once or twice per year (Figure 8). The maximum level recorded during the November stoan was 1.95 m above tide gauge zero (1.02m above AHD) , and occurred at approximately 1O:ooam on the 20th. This was 0.28 m I above the predicted height of 1.67 m (0.75 m AHD) for that time. The tidal residual exceeded 0.2m for one high and two low tides and exceeded 0.1 m for 2 days. About 16% of predicted I high tides exceed 1.67m (Easton, 1970). Recorded water levels at Fort Denison indicate that a level of 1.95 m is likely to occur on average two or three times per year.

I The tide predictions indicate spring tides of height 1.77 m above Fort Denison Zero on the 6th and 7th August and 1.71 m on the 18th November.

I The predicted and measured maximum tide levels for the two storms are summarised in Table 2. The maximum recorded tide levels for the two storms only differ by 0.04 m and are not abnormally high. The highest recorded tide level at Fort Denison is 2.37 m (1.45 m AHD), and I occurred during stoans in May 1974 (PWD, 1985b).

I TABLE 2. Maximum Tille Levels For August and November 1986 Stoans

Tide August November I Predicted Fort Denison 0.85 0.75 Recorded Fort Denison 1.06 1.02 Recorded Batemans Bay Zwarts 0.86 1.00 I Recorded Batemans Bay Floatwell NA 1.02 I . Heights in metres above AHD. I An assessment of the possible components of the tidal residuals is given in Section 4.3. I I I

I - 9- I 3.2.2 . Batemans Bay I Tide levels are recorded by the PWD at two locations in Batemans Bay. A Zwarts gauge consisting of a Zwarts pole acoustic water level recorder with a Datataker logging system is located approximately 250 m north of Snapper Island (AMG Coordinates 247791.5 E, I 6043097.3 N). The location is shown in Figure 14a. The location has a mean water depth of about 6 m and is exposed to wave action. The gauge was operating during both the August 1986 I and November 1986 storms. It records water levels at one second intervals and the data is analysed to give wave data as well as tidal data. The water levels are based on Batemans Bay I Hydro Datum (BBHD) which is 0.889 m below AHD. A Aoatwell recorder consisting of a float gauge with an optically read pulley wheel and a solid state recorder, is located at the Clyde Princess Jetty near the entrance to the Clyde River, adjacent I to the Batemans Bay town centre (AMG Coordinates 244570E, 6044985N). The location is shown in Figure 14a. This part of the bay is protected from most wave action. The gauge was I operating during the. November but not the August storm. It records water levels at one minute intervals. The water 1evels are based on AHD.

I Eastern Standard Time is used throughout the year and has been used in this report.

The data from both recorders is numerically filtered and water levels at 15 minute intervals are I stored in the PWD database at Manly Vale. This data was used to reproduce the tide records in Figures 9, 10 and 11. These plOts also show the predicted tides at Fort Denison. A value of 0.036 m has been subtracted from the predicted heights to convert from Fort Denison Datum to I BBHD. I Tide levels recorded at the Zwarts gauge during the August and November storms are plotted in Figures 9 and 10 together with the predicted highs and lows for Fort Denison. The maximum level recorded at the Zwarts gauge during the August storm was 1.75mBBHD (0.86m AHD), and I occurred at approximately 9:15 pm on the 6th August. The level was approximately equal to the predicted height of l.77m (0.85m AHD) at Fort Denison for that time. The maximum level recorded during the November storm was 1.89m BBHD (l.OOm AHD), and occurred at I approximately 9: 15 am on the 19th November. The level was 0.25 m above the predicted height of 1.67 m (0.75 m AHD) at Fort Denison for that time. The gauge failed for about 3 days I between 15th and 18th, just before the November storm. Comparisons of predicted high and low tides at Fort Denison with measured tides at the Batemans I Bay Zwarts gauge are given in Figures 9 (August) and 10 (November). The low tide residuals are generally larger than the high tide residuals.

I The Aoatwell gauge was not operating during the August storm. Tide levels recorded at the Aoatwell gauge during the November storm are plotted in Figure 11 together with the envelope of tide levels from the Zwarts gauge. The maximum level recorded during the November stonn I was 1.91 m BBHD (1.02m AHD), and occurred at approximately 9:30am on the 19th. The level I i ••••",\, I I

I - 10- I was 0.19m above the predicted height of 1.76m (0.83m AHD) at Fort Denison for that time. I The predicted and measured maximum tide levels for the two storms are summarised in Table 2. Comparison of measured tides at the Zwarts gauge with those at the Aoatwell gauge is also given in Figure 11. The differences are generally less than 0.1 m, but exceed 0.2 m on a number of I occasions.

Batemans Bay is about 230km south of Sydney bu~ the tides are generally fairly similar in both I time and height. There are no tidal predictions for Batemans Bay, but an analysis of the tidal constituents at the Zwarts gauge (PWD, 1987) indicated the same mean sea level as Fort Denison. I Tide level statistics are not available but are likely to be similar to those for Fort Denison (see Section 3.2.1).

I An assessment of the possible components of the tidal residuals is given in Section 4.3. I 3.2.3 Other Tidal Data Tidal data is available from the PWD for a number of other locations on the coast but these have not been considered here. These include, North Coast, Ettalong, Camp Cove, Balgowlah, Botany I Bay, Port Keni.bla and Eden. I 3.3 WAVE HEIGHTS AND PERIODS 3.3.1 Offshore Botany Bay I Wave height and period data for both the August 1986 and November 1986 storms, were recorded offshore of Botany Bay. The instrument is a Datawell Waverider buoy operated by the MSB and is located in approximately 75 m, of water about 3 km east of Cape Solander, (Latitude I 34°02'34"S, Longitude 151° 15' 08" E). ,The location is shoWl) in Figure 1. Wave data from this location has been collected almost continuously since April 1971 and long term wave statistics are available. The instrument measures water surface elevation as a time series and cannot measure I wave direction. The data is transmitted to shore and is recorded and analysed by the MSB. Recently the PWD Manly Hydraulics Laboratory has arranged to access this data. Data used for I this report was obtained from the PWD.

The water level is recorded every half second for 34 minutes in each hour and both time series' I and spectral analysis are carried out Details of the analysis are given in Reference PWD, 1986b. The commonly used parameters are the significant and maximum wave heights, which are determined with the time series analysis, and the spectral peak period, which is determined from I the spectral analysis. The significant wave height is the average height of the one-third highest waves in the wave group. The maximum wave height is the highest wave for the same group. I The spectral peak period is the wave period corresponding to the maximum of the energy spectrum. Eastern Standard Time is used throughout the year and has been used in this report. )\ I The wave heights measured at the-offshore Botany Bay Waverider buoy are generally considered to be deep-water values. However, since the instrument is in approximately 75 m of water the I .(...... l-., I I

I - 11 - I

longer period waves have already been affected by shoaling and refraction. Small amplitude wave I theory predicts that a 10 second wave travelling from deep water to a depth of 75 m will have its wave height reduced by about 1% by shoaling. A 12 second wave will have been reduced by about 4% and a 14 second wave by about 7%. Small amplitude wave theory also predicts that I wave refraction offshore from the waverider buoy would be small for 10 second and shorter wave periods, but could be significant for the longer period waves, particularly those with wavefronts at I large angles to the contours. In the August 1986 storm the wave heights reached a maximum during the night of the 5th, I dropped during the 6th and 7th, then reache~ a second maximum on the mOrning of the 8th (Figure 12a). The maximum wave height recorded was 13.2m at 7:00pm on the 5th and the maximum significant wave height was 7.5m at 2:00am on the 6th and 9:00am on the 8th. In the I November 1986 storm the maximum and Significant wave heights were 12.2m and 6.9m respectively, both at 7:00am on the 20th (Figure 12b). The significant wave height exceeded 4m for approximately 4 days during the August storm but for only approximately 2 days during the I November storm. These times have been used to indicate the storm durations. The maximum and maximum significant wave heights recorded for the two storms are summarised in Table 3.

I TABLE 3. Maximum Wave Heights For August and November 1986 Storms

August November I Location Hs Hmax Hs Hmax Offshore Botany Bay 7.5 13.2 6.9 12.2 I Offshore Batemans Bay 5.6 11.2 6.0 10.3 I Significant Wave Height (Hs) and Maximum Wave Height (Hmax) in metres.

Immediately prior to the two storms the spectral peak wave period dropped to a low of about 6 I seconds. It then increased and was generally between 9 and 13 seconds during the August storm and between 11 and 13.5 seconds during the November storm (Figures 12 a and 12 b). The maximum periods recorded were 15.1 seconds at 9:00am on the 8th August and 13.5 seconds at I numerous times between the 19th and 21st of November. These figures indicate that in the offshore Botany Bay region the August storm had slightly larger wave heights, slightly shorter I wave periods and was of a significantly longer duration than the November storm. Plots of significant wave height, maximum wave height and spectral peak period versus time for I the 1st to 14th August and the 15th to 28th November are shown in Figures 12 a and 12 b. I 3.3.2 Offshore Batemans Bay Wave data for both the August and November 1986 storms, were recorded offshore from Batemans Bay. The instrument is a Datawell Waverider buoy operated by the PWD and is I located in approximately 75 m of water approximately 7 Ian offshore, Latitude 35 0 42' 30" S, Longitude 1.500 21'24"E (AMG Coordinates 6045000N, 260 640 E). The location is shown in .',,,,,- I . '. I I

I - 12- I I Figure 1. Wave data from this location has been collected almost continuously since 27th May 1986. The data is transmitted to shore and is recorded and analysed by the PWD Manly Hydraulics I Laboratory. Eastern Standard Time is used throughout the year and has been used in this report. Analysis is identical to that for Botany Bay. The buoy is in a similar depth of water to the Botany Bay Waverider buoy, so wave shoaling and refraction offshore from the buoy would be I similar.

In the August storm the maximum wave height recorded was l1.2m at 8:00am on the 6th and I the maximum significant wave height was 5.6m at 7:00am and 9:00am on the 6th (Figure 12c). In the November storm the maximum wave height was 1O.3m at 3:00am on the 19th and the I maximum significant wave height was 6.0m at lO:ooam and 2:00pm on the 20th (Figure 12d). The significant wave height exceeded 4 m for approximately 3 days during both the August storm I and the November storm. The maximum wave heights are summarised in Table 3. Immediately prior to the two storms the spectral peak wave' period dropped to a low of about 6 seconds. It then increased and was generally between 10 and 13 seconds during both storms. I The maximum wave periQd,'recorded was 13.5 seconds in both storms (Figures 12c and 12 d). In the Batemans Bay region, the August and November storms had similar wave heights, wave I periods and durations. The wave heights were lower than those recorded at offshore Botany Bay. 3.3.3 Other Wave Data I Offshore wave data for Byron Bay, Coffs Harbour, Crowdy Head,_ Port Kembla and Eden is available, from PWD, Manly Hydraulics Laboratory, and data from Newcastle is available from the I MSB, but these have not been included here. Inshore wave data from Coffs Harbour is also available from PWD.

I 3.3.4 Recurrence Intervals Following the terminology adopted in the Elevated Ocean Levels Reports (pWD 1985b and I 1985a) where storms with significant wave height greater than 6m are classified as extreme (X), the August and November 1986 storms belong to the "X" category.

A rough estimate of recurrence interval can be based on the occurrence of "X" storms. In the 30 I , ' years 1956 to 1985, 14 "X" storms occurred, however, on several occasions two "X" storms were recorded in the same year and on an annual basis "X" storms occurred only in 9 years. This I gives an approximate recurrence interval of 3.5 years for "X" category storms over this period.

More detailed analyses were carried out by McMonagle & Fidge (1981) and Youll (1981) who I calculated recurrence intervals for wave height data from the offshore Botany Bay waverider. Both authors analysed approximately9 years of data from the period May 1971 to April 1981. McMonagle & Fidge presented their results as a recurrence interval versus significant wave height (Hs) and Youll plotted Hs against the number of storms per year during which that wave height I I I

I - 13 - I was recorded. Recurrence intervals for the August and November stonns based on these two I approaches are given in Table 4.

TABLE 4. Recurrence Interval of Offshore Botany Bay Wave Heights I for August and November Stonns I Stonn Hs Recurrence Interval (years) Date (m) ~c~onagle F1dge Youll August 1986 7.5 6.5 3.0 I November 1986 6.9 3.5 1.5

Different methodology was used in the two papers to calculate the significant wave height versus I recurrence interval relationship. The above recurrence intervals are given as a guide only and it is outside the scope of this repoI1 to determine which method is more appropriate for quantifying the I severity of coastal storms.

3.4 STO~ HISTORY - AUGUST 1985 TO AUGUST 1986 I Wave data from the offshore Botany Bay and Port Kembla waverider buoys has been used to assess the stonn history for the year prior to the August and November 1986 stonns. All stonns I with a significant wave height above 2.5m are summarised in Table 5. This data can be used to gauge the erosion or accretion state of the beaches at the time of the various surveys.

I The offshore Botany Bay records show that the previous severe stonn was nearly ten months before the August 1986 stonn. The offshore Port Kembla records are similar but indicate that a I stonn in April 1986 was more intense in that area than in the offshore Botany Bay area. I I I I I I I I I

I - 14 - I I TABLE 5. Recorded Stonn Events. August 1985 to August 1986 Botany Bay Port Kembla

I Stonn Date Category Description Stonn Date Category Description

26 Oct 85 X Severe I 19-23 Nov 85 B Moderate 19 Nov 85 B Moderate 1 Dec 85 C Low 26-30 Nov 85 C Low 3 Jan 85 C Low I 18-24 Jan 86 B Moderate 18-24 Jan 86 B Moderate 23 Feb 86 C Low 3-10 Feb 86 C Low 8-14 Mar 86 B Moderate 8-13 Mar 86 C Low I 6 Apr 86 B Moderate 7 Apr 86 A High 17 Apr 86 C Low 17 Apr 86 C Low 30 Apr 86 C Low 30 Apr 86 C Low I 21 May 86 B Moderate 21 May 86 B Moderate 31 May 86 C Low 1 Jun 86 C Low 11-17 Jun 86 C Low 18 Jun 86 C Low 29 Jun 86 C Low 30 Jun 86 C Low I 26 Ju1 86 B Moderate I 5-6 Aug 86 X Severe 5-6 Aug 86 X Severe Note: Description Category Significant Wave Height I Severe X > 6.0m High A 5.0-6.0m Moderate B 3.5-5.0m I Low C 2.5-3.5m I I I I I I I I I

I - 15 - I I 4. WAVE RUN-UP 4.1 MANLY W ARRINGAH BEACHES I Maximum wave run up levels occurring along the Manly Warringah coast during the August 1986 stonn, have been estimated by PWD, Coastal Branch (PWD, 1987). The positions of maximum run-up, as indicated by the stonn debris line, were obselVed at 38 locations during the peak of the I stonn and on 11th and 12th August 1986. For each of these locations, the beach profile down to about the water's edge was determined photogrammetrically, from aerial photography taken on 18th August (See section 5.2.1) and the elevation of maximum run-up detennined. The run-up I and profile data is held by PWD (Reference 17).

The locations and run-up levels are shown in Figures 13 a-d. Wave run-up levels recorded in I August varied from 3.0m AHD on Long Reef Beach to 7.2m AHD on Narrabeen Beach. These were between 2.1 m and 6.3m above the predicted maximum tide level of 0.9m AHD at Fort I Denison. Typical values were 5 m to 7 m at exposed locations, and less in the more sheltered areas. Values above 6 m AHD were obselVed at near vertical erosion scalps or at rock walls· I (PWD 1987). An assessment of these run-up levels is given in Section 4.3.

I Run-up was not recorded after the November storm. I 4.2 BA TEMANS BAY BEACHES Maximum run-up levels were recorded at six locations in the Batemans Bay region soon after the August 1986 storms. On each occasion the location and elevation of the maximum run-up were I detennined or pegged for later measurement This was repeated but with 24 locations soon after the November 19.86 stonn. The locations were revisited and the beach profiles sUlVeyed in I December 1986. The profile data is held by PWD (Reference 18). The locations and run-up levels for both stonns are given in Figures 14 a-c. Run-up levels shown I in parenthesis on these drawings correspond to the November stonn.

In the Batemans Bay area the August levels varied from 1.9m AHD in Chain Bay to 5.5m AHD I in Malua Bay. These are between LOrn and 4.6m above the predicted maximum tide level of 0.9m AHD at Fort Denison. In November they varied from l.4m AHD at Surfside Beach to 3.7m AHD in Chain Bay. These are between O.4m and 2.7m above the predicted maximum tide I level of 1.0 m AHD at Fort Denison. However, since only a limited number of measurements were taken, the actual range of run-up levels that occurred is likely to be greater. The I significantly different values for Chain Bay for the two stonns are probably partly due to different offshore wave directions.

I An assessment of these run-up levels is given in Section 4.3. I I I

I - 16- I 4.3 THEORETICAL ASSESSMENT \ I Wave run-up is the result of wave momenturh being dissipated on the beach or other shoreline. The· level reached depends on the water level near the shore, the wave characteristics and the beach characteristics. These are all very· site specific and time dependent, so variations in run-up I levels can be large. For predictions of wave run-up, the water level used must include tide, wave set-up, wind set-up and barometric set-up. These are all additive, and it is usually sufficient to I consider only the maximum water level· for the storm. However, the maxima of the various components do not always coincide.

I The run-up process isa very complex phenomenon governed by the morphodynamic interaction of the beach with the wave climate. Both the wave set-up and wave run-up are driven by surfbeat and sub-harmonic oscillations in the surf zone (Short & Wright, 1984). Theoretical deSCriptions, I however, are based on the simpler approach of radiation stress for wave set-up, and wave run-up I predictions are based on empirical observations. Theoretical prediction of wave run-up for a particular location requires the calculation of the local breaking wave height. This presumes that bathymetric surveys are available to calculate wave I refraction. These calculations must then be carried out for each locality of interest.

In this study only generalised run-up predictions are made, assuming no wave refraction and a I few typical beach slopes. I An estimate of the separate components of total run-up is made in the following sections. 4.3.1 Tide Prediction

I Tides on the east coast of Australia generally have a range of between 1 m and 2 m, and are the largest cause of water level variation. Tidal predictions are based on the analysis of tides in I earlier years and there are a number of limitations involved. First, the tide recorders record changes in water level from whatever cause. This will generally I include barometric set-up and wind set-up. These are often grouped together and called storm surge or meteorological tides. The gauges are normally located in an area which is not subject to breaking waves, so wave set-up is not included. If the gauge is located in an estuary, the water I level can also be influenced by freshwater flows.

The recorded tide is digitised, normally at one hour intervals, and about one year's data (usually I 369 days) is analysed to determine harmonic constituents and the mean tide level. The period of the constituents obtained generally varies from 1 year to about 3 hours (2 hours if shallow water I constituents are included). Some non-tidal effects may be included in the constituents if they have a harmonic form. For instance seasonal effects can be included in the 1 year (SA) component. However, it is normally assumed that non-tidal effects such as wind and barometric I set-up are not included and that the analysis represents normal or average conditions. I I - 17 - I If one year tidal analyses are carried out for a given location for a number of consecutive years, I there' will be some variation of the constituents. There are a number of reasons for this, including annual variations in climate, mean sea level, etc and astronomical causes having periods greater I than a year. Tidal predictions based on these one year analyses cannot include the effects of longer term variations, and are rarely assumed to be accurate to better than 0.1 m. Care must therefore be I taken in inteIpreting differences between measured tides and predictions based on analysis of a different year's tides.

I 4.3.2 Wave Set-up When waves break on the shore, there is a decrease in mean water level or set-down relative to I that just prior to breaking, with the maximum set-down close to the breaking point. From the breaking point the mean water surface slopes upward to the point of intersection with the shore. Wave set-up is defined as the super-elevation of the mean water level caused by wave action I alone, and is related to the conversion of the kinetic energy of the wave motion to potential energy. It depends on a train of waves arriving at the shore over a sufficient period of time to I establish an equilibrium water level. A duration of an hour is considered a minimum for the full set-up to be established. The larger waves in the spectrum are generally too infrequent to contribute to the wave set-up and the significant wave height is normally used. The wave set-up I can be calculated. from the breaking wave height which in tum is calculated from the offshore wave height, wave period, and the beach slope. Normally the equivalent un-refracted offshore wave height and the spectral peak period are used. Wave refraction can have a significant I influence on breaking wave height, and therefore wave set-up, but it is site specific and has not to' I been fully considered here. Various methods are available for estimating the breaker height, one being the empirically derived curves of Goda (CERC, 1984, p2-131). These give a breaker height index (breaking wave height I over equivalent unrefracted offshore wave height) in terms of offshore wave steepness (wave height over wave length) and beach slope. Empirical relationships derived by Weggel (CERC, 1984, p2-l30) can be used to derive the depth of breaking from the breaking wave height, period I and beach slope.

The net wave set-up relative to the normal still water level outside the breaker zone, can be I estimated by calculating the set-down at the breaking zone and the wave set-up between the breaker wne and the shore, USing the theory of Longuet-Higgins and Stewart, (CERC, 1984, p3- I 101).

In a real situation the incident wave height will be non-uniform and there will be gaps in the I breaker line due to uneven topography and rip channels. These will reduce the wave set-up in some areas, so the calculated values would be the maximum. In some areas, however, wave refraction will increase local wave heights and cause the wave to' break in deeper water with a I larger breaking wave height. This would result in higher wave set-ups than the unrefracted I I I

I - 18 - I estimates given here. In other areas the opposite will occur and wave set-ups will be less than I the estimates given here.

Calculations of maximum unrefracted wave set-up for the Batemans Bay and Sydney regions I during the August and November storms (ignoring refraction, etc) have been carried out using the methods outlined above. Beaches in the Sydney area are generally on the open coast and this approach should give a useful prediction of run-up ,levels. '·Batemans Bay beaches are generally I within the relatively shallow bay, and wave refraction would be significant. The unrefracted I estimates will not be applicable to these beaches, but may be appropriate for Malua Bay. The offshore significant wave height has been used in place of the equivalent unrefracted offshore wave height to estimate the breaking conditions. For the August storm the maximum significant I wave height was 7.5m offshore from Botany Bay, and 5.6m offshore from Batemans Bay. For the November storm the maximum significant wave height was 6.9m offshore from Botany Bay, and 6.0m offshore from Batemans Bay. Offshore bed slopes in the region of the wave break are I variable but are generally in the range 0.02 to 0.05.

Calculated breaking wave heights, water depths at breaking point and wave set-up for these two I beach slopes and various wave heights and periods, are given in Table 6. The figures indicate that for conditions occurring during the two storms, the wave set-up is strongly dependent on 1- wave height, and much less dependent on wave period and bed slope. The small differences in wave period between the two storms would have a negligible effect on wave set-up. 1 I I I I I I I I I I

I - 19 - I TABLE 6. Estimated Wave Set-up for Various Wave Conditions

I Wave Wave Bed Slope=0.02 Bed Slope=0.05 Period Height Hb db Set-up Hb db Set-up (s) (m) (m) (m) (m) (m) (m) (m) I 10 4 4.5 5.2 0.57 5.1 5.2 0.56 10 5 5.4 6.3 0.69 6.1 6.3 0.70 10 6 6.3 7.5 0.85 7.0 7.5 0.84 I 10 7 7.1 8.6 0.99 7.9 8.6 0.99

10 8 8.0 9.8 1.14 8.8 9.9 1.16 .' ,

I 12 4 4.9 5.6 0.61 5.6 5.5 0.58 12 5 5.9 6.7 0.74 6.6 6.6. 0.72 12 6 6.7 7.8 0.86 7.6 7.7 0.84 I 12 7 7.6 8.9 0.99 8.5 8.8 0.97 . 12 8 8.5 10.0 1.12 9.5 10.0 1.12

I 14 4 5.3 5.9 0.65 6.1 5.8 0.62 14 5 6.3 7.1 0.78 7.2 6.9 0.74 14 6 7.3 8.3 0.91 8.2 8.1 0.87 I 14 7 8.2 9.4 1.04 9.2 9.2 1.00 14 8 9.0 10.5 1.15 10.2 10.3 1.12

I Notes: 1. Hb = Breaking Wave Height, from Goda, CERC, 1984, p2-131, Figure 2.72 2. db = Depth of Breaking, from Weggel, CERC, 1984, p2-130, Equation 2.92 I 3. Set-up = net wave set-up, from Longuet-Higgins & Stewart, CERC, 1984, pp3-101,102, Equation 3-77 I Using the Botany Bay wave data, the maximum wave set-up in the absence of refraction, assuming beach slopes are typical, is estimated at 1.1 m in August and '1.0 m in November. These I figures should be applicable to, beaches in the Manly Warringah and Gosford area. Using the Batemans Bay wave data, the figures are estimated at 0.8 m in August and 0.85 m in November. I These figures should be applicable to Malua Beach. These values are summarised in Table 7. Most tide recorders are located outside of the breaker zone, so wave set-up does not normally I contribute to the difference between predicted and measured tides.' Batemans Bay Zwarts gauge, is in an area which could be within a breaker zone, in some severe storms where waves break across most of the inner Bay area. However, this does not appear to have been the case during the I August and November storms. I 4.3.3 Wind Set-up Wind set-up is the raising of the mean water level near the shore resulting from wind stress acting on the water surface. It is one of the reasons why predicted and measured tides differ. I The set-up varies with the wind velocity and the fetch available. In the ocean situation it is the I I I

I - 20 - • I comparatively shallow areas of the continental shelf that are affected. It can be estimated using I the theory given by Silvester (1974. p184). This gives the set-up as a function of the fetch length and depth as well as the wind speed.

I In this situation the fetch is that part of the wind field that is acting on continental shelf waters. If the wind field is large in comparison to the width of the shelf. and the winds are directly onshore. the fetch length is generally taken to be equal to the width of the shelf (Silvester. 1974). I This is approximately 40km at Gosford and the northern Sydney beaches. and 30km at Batemans Bay. If the winds are at an angle to the coast. the fetch is increased. but this is limited by the I size of the wind field. The depth at the edge of the shelf is taken as 200m. The depth at the shoreward limit of the fetch. has been taken as 1 m.

I During the August 1986 storm the maximum one hour mean wind speed at Sydney Airport was about 28 knots (14m/s) from the SE direction. These winds were not directly onshore but it is assumed that they would produce a similar set-up to the same wind directly onshore since the I fetch length is increased and the onshore component of the wind decreased. It is assumed that winds in the Manly Warringah and Gosford area would be similar to those at Sydney Airport. I Wind speeds at Moruya Heads were omy slightly lower but were from the SSW to SSE. so the wind set-up is unknown.

I· During the November 1986 storm the maximum one hour mean wind at Sydney Airport was 27 knots (14 m/s) from the west to south direction. Wind speeds at Moruya Heads were similar but were from the SSW direction. It is not known whether the southerly winds would produce set-up 1 or not. but the offshore winds could produce some set-down. A figure of 14 mls has been adopted here to estimate the maximum wind set-up in the Sydney region during the August 1986 storms. Wind directions in the Sydney region during November. and in the Batemans Bay area I during both August and November, were along-shore, or off-shore. The contribution of these I winds to the set-up is not known but is not thought to be large. The values given above indicate a maximum wind set-up of 0.06 m at the Gosford and northern Sydney beaches, during the August storm. Given the uncertainty in the calculations. it is I estimated that the wind set-up in the Sydney and Gosford regions is umikely to have exceeded 0.1 m. For the November storm in the Sydney region, and both' storms in the Batemans Bay I region. the wind set-up is likely to have been less and can probably be ignored. 4.3.4 Barometric Set-up I Barometric set-up is the raising of mean water level caused by a drop in atmospheric pressure. It is one of the reasons why predicted and measured tides differ. An estimate of barometric set-up can be made using simple hydrostatic theory which predicts a set-up of lOmm per millibar (mb) I pressure drop. The average barometric pressure varies from place to place and from month to month. For Sydney it is lO18mb for August and 1014mb for November. For Moruya Heads I near Batemans Bay it is lO17mb for August and lO14mb for November (see Section 3.1). 1 I I

I - 21 - I In the August stonn the pressure dropped to below 990 mb at the centre of the depression, but the I centre was located some distance offshore. The lowest pressure at Sydney Airport was approximately 1002mb and at Moruya Heads was 1010mb. Hence, the Sydney records indicate a maximum pressure drop of 16mb and the Moruya Heads records indicate a maximum pressure I drop of 7mb. These correspond to barometric set-ups of 0.16m and 0.07mb respectively. The variation in atmospheric pressure along the NSW coast from the Gosford area to Batemans 'Bay at the time is not known, but it is unlikely that the barometric set-up in August would have ( I exceeded 0.2 m.

I In the November stonn the Sydney Airport records indicate that the lowest pressure was approximately 993 mb. At Moruya Heads the lowest pressure recorded during the stonn was 992 mb. This indicates maximum pressure drops of 21 mb and 22 mb respectively and I corresponds to barometric set-ups of 0.21 m and 0.22 m. The variation in atmospheric pressure along the NSW coast from Gosford area to Batemans Bay at the time is not known, but it is I unlikely that the barometric set-up in November would have exceeded 0.25 m. 4.3.5 Stonn Sea Level I The sea level outside the breaker zone during a stonn is nonnally estimated by summing the tide height and the wind and barometric set-ups. Inside the breaker zone, the wave set-up must also be included. In predicting the stonn sea level at the peak of a stonn, the worst case is nonnally I considered and it is assumed that the maximum predicted tide, and the maxima of each component of set-up occur simultaneously. This approach has been adopted for his report and I Table 7 gives the recorded wave heights, estimated components of run-up and the stonn sea level and run-up levels'at the peak of both stonns for the Sydney area and Batemans Bay.

I The August stonn occurred during spring tides and was of sufficient duration to ensure that low atmospheric pressure, strong winds and large wave heights occurred at the maximum high tide. The last high tide on the 5th corresponded closely to the first peak in the wave height. The I barometric pressure reached a minimum and the wind speed reached a maximum close to this time. It is therefore valid for the maximum stonn sea level for this stonn to be estimated by I adding the maximum predicted tide to the estimated wave, wind and barometric set-ups. In the Sydney region in August the maximum stonn sea level outside of the breaker zone is I estimated to have been 0.85+0.06+0.16 = 1.07 m AHD. This agrees closely with the maximum recorded tide level of 1.06 m AHD at Fort Denison. The stonn sea level within the breaker zone is estimated to have been the level outside the breaker zone plus 1.1 m wave set-up, ie 2.17 m I AHD.

In the Batemans Bay region in August the maximum stonn sea level outside of the breaker zone I is estimated to have been 0.85+0.00+0.07 =0.92 m AHD. This is 0.06 m higher than the maximum tide level of 0.86 m recorded at Batemans Bay Zwarts gauge. The stonn sea level level I within the breaker zone is estimated to have been the level outside the breaker zone plus 0.8 m wave set-up, ie 1.72 m AHD. I I I I - 22- I

The. Nove.mber storm was of shorte.r duration and the maximum wave heights occurred after the I . largest tides. The barometric pressure reached a minimum before both the maximum tide and the maximum wave height. The maximum storm sea level should therefore be less that obtained by I adding the individual maxima. In the Sydney region for November, the maximum storm sea level outside of the breaker zone, I estimated by summing the tide, wind set-up and barometric set-up, is 0.75+0.00+0.21 =0.96 m AHD. This is 0.06 m lower than the maximum recorded tide level of 1.02 m AHD at Fort Denison. The storm sea level within the breaker zone is estimated to be this plus 1.0 m wave I set-up, ie 1.96m AHD.

In the Batemans Bay region for November, the maximum storm sea level outside the breaker zone I is estimated to have been 0.7S+0.00+0.22 =0.97 m AHD This is slightly lower than the maximum tide level recorded at Batemans Bay Zwarts (1.00 m AHD) and Floatwell (1.02 m AHD) gauges. I The maximum storm sea level within the breaker zone is estimated to be 0.97m AHD plus 0.85 m wave set-up, ie 1.82 m AHD. For the November storm these levels are likely to be over estimates of set-up since the peaks of each component did not coincide. The estimated water I level components are summarised in Table 7. I 4.3.6 Wave Run-up. The elevation of the final run-up of the waves on a beach, is used to assess the possible extent of coastal inundation. This water level is that produced by adding the predicted wave, wind and I barometric set-ups and the wave run-up to the predicted tide level.

In the Manly Warringah area many of the beaches are exposed to ocean storms and simple I estimates of wave breaking and run-up may be useful. In Batemans Bay, however, many of the beaches are partly sheltered from ocean storms and the shallowness of the bay makes wave I refraction more significant. Simple estimates of wave breaking parameters and run-up are therefore probably only applicable in the Malua Bay area.

I The Gosford and Sydney beaches considered here generally show a bar formation during a storm. The slope on the outer face of the bar is typically 0.02 to 0.05 and the top of the bar is 4 to 6 m below AHD (5 to 7 m below high tide level). These parameters would vary with. location and I with the extent and duration of the storm. Inshore of the bar the depth is usually slightly greater than at the bar. The slope of a beach in the run-up region varies with location, elevation and time, and is dependent on factors such as the wave exposure and sand grain size. Typical values I are 0.05 to 0.10. At the very back of a beach the slopes are often much steeper and in some I cases man made structures occur. The data used in this report to estimate wave run-up was derived by Saville, (1958) and is from small scale laboratory tests of monochromatic waves on smooth impermeable slopes (CERe, I 1984, p7-16). I I , I

I - 23- I In the August storm the maximum wave height recorded was 13.2m at offshore Botany Bay and I 11.2 m at offshore Batemans Bay. In the November storm the maximum wave height recorded was 12.2 m at Botany Bay and 10.3 m at Batemans Bay. The wave periods were typically 10 to I 13 seconds. The height of the run-up above still water level, is dependent on the wave steepness which increases with wave height, but decreases with wave period. The maximum run-up therefore does I not necessarily correspond to the maximum wave height. The wave steepness has been calculated for each set of wave data and the maxima have been determined. At Botany Bay the maximum deep water wave steepness was 0.013 in both storms, and at Batemans Bay it was 0.016 in both I storms (calculated from the hourly maximum wave heights and peak periods). Saville's data (CERC, 1984, pp 7-19]) gives wave run-up for these wave steepnesses on a slope of 0.1 as being I about 0.3 times the offshore wave height. The figures for the two locatio~ and two storms are given in Table 7.

I TABLE 7. Estimated Components of Run-up for August and November 1986 Storms " I Sydney Batemans Bay August November Augusi: November Significant Wave Height (Hs) 7.5 . 6.9 5.6 6.0 I Maximum Wave Height (Hmax) 13.2 12.2 11.2 10.3 Maximum Wave Steepness 0.0l3 0.013 0.016 0.016 Predicted High Tide Level 0.85 0.75 0.85 0.75 Estimated Barometric Set-up 0.16 0.21 0.Q7 0.22 I Estimated Wind Set-up 0.06 0.00 0.00 0.00 Estimated Wave Set-up 1.10 1.00 0.80 0.85 Estimated Storm Sea Level 2.17 1.96 1.72 1.82 I Estimated Run-up (O.3xHmax) 3.96 3.66 3.36 3.06 Estimated Run-up Level 6.1 5.6 5.1 4.9

I Heights in metres, Levels in metres above AHD I 4.4 COMPARISON OF MEASURED AND THEORETICAL RUN-UP LEVELS I Wave run-up levels recorded in Manly Warringah in August varied from 3.0m AHD on Long Reef Beach to 7.3m AHD at the south end of Narrabeen Beach (Figures l3a-d). Typical run-up levels were 4 to 6 m AHD with levels above 6 m AHD being recorded on steep erosion scarps I and rock walls. These compare favourably with the estimated value of 6.1 m AHD (Table 7). For more detailed analysis, see PWD (1987).

I The Long Reef Beach site is partially protected by reef and the measured wave run-up in that area is less than the maximum estimated. Narrabeen and Collaroy Beaches is very exposed and could be subject to the maximum wave set-up. The measured run-up levels are higher than the simple estimates made here. It must be remembered that the run-up was measured at a limited I I I

I - 24- I number of locations, and the maximum and minimum values may have exceeded those measured. I In" addition, the estimated wave set-up is for unrefracted waves, and the actual set-up could be higher or lower.

I In the Batemans Bay area the August run-up level of 5.5 m AHD at Malua Bay (Figure 14 c) compares favourably with the estimated value of 5.1 m AHD (Table 7). In November no run-up I measurements were taken at Malua Bay. I I I I I I I I

, I I, I I I I I I I I - 25- I I 5. BEACH SURVEYS I 5.1 GOSFORD BEACHES 5.1.1 Photogrammetric Data Aerial photographs of the Gosford area beaches were taken by Central Mapping AuthOrity (CMA) I at an approximate scale of 1:8000 on the 23rd August 1984 and on the 18th August 1986. In the period prior to the 1984 photography, no severe storms (category "X") had occurred since 1978, I and the beaches were in an accreted state. There were two severe storms between the two dates of photography, one in October 1985 and the other in August 1986 (Table 5). The August 1986 storm occurred shortly before the 1986 photography, and the beaches were generally in an eroded I state.

Photogrammetric analysis was carried out by PWD Coastal Branch, using a WILD AC1 stereo­ I restitution instrument to produce cross-section data at 10m intervals along the main beaches from Forresters Beach to MacMasters Beach. The PWD used this data to calculate beach volumes per I metre of beach length, at each section for both dates. The volumes were those measured per metre of beach length, above Om AHD, between a starting chainage at the top or bottom of the back beach escarpment and the 2 m beach berm contour line for each date. The starting chainages I selected from aerial photographs taken in August 1978 were used throughout. This ensured that beach volumes were calculated in a consistent way and allowed comparisons to be made with I previous work. The differences between the 1984 and 1986 volumes have been determined to assess changes to the beaches during the two year period. It should be noted that these differences do not represent I the true erosion or accretion volumes, since they include material below the new profile and between the new and old 2 m contour lines (see figure below). However, they are still a useful I indication of the beach erosion or accretion. Although two severe storms occurred between the dates of photography, the August 1986 storm appears to be responsible for much of the change. I I I I I I I I

I - 26- I I Shoreward Seaward Boundary Boundary at RL 2m AHD Level ~ Pre-storm

4 I t:Ll Post-storm

I [[] Change R.L. (m) 2 I AHD Pre-storm I Post-storm I Schematic diagram showing areas used to calculate beach volumes. I Plots of change in beach volume versus distance along the beach, (section number), have been prepared for Forresters Beach, Wamberal and Tenigal Beaches, Avoca Beach and Copacabana and I MacMasters Beaches (see Figures 15 to 18). Each plan shows changes in beach volume per metre of beach length, between August 1984 and August 1986.

I· 3 At Forresters Beach the volumes generally indicate slight to severe erosion up to about 200m jm, in the two year period. There is accretion of up to about 70 m3 jm towards the southern end. Warnberal and Tenigal Beaches also show slight to severe erosion up to about 150m3/In, except I at the southern end, which does not appears to have been significantly affected by the storm. Avoca Beach shows erosion to over loo~3 /In, but shows little change at the ends of the beach. I Copacabana and MacMasters Beaches generally show erosion up to about 70 m3jm, but some places show accretion up to about 20m3jm.

I . In 1985 the PWD Coastal Branch carried out a similar photogrammetric analysis on Wamberal, Tenigal and Avoca beaches, using aerial photography dated 1965, 1969, 1973, 1974, 1977 and 1978 (PWD 1985a). For Wamberal, Tenigal and Avoca beaches the design storm erosion I demands taken from that report have been included in Figures 16 and 17 for comparison purposes. In all locations the 1984 to 1986 changes arc less than the design storm erosion I demand. Aerial photographs of the coast from Narrabeen to Budgewoi were also taken by PWD from an I altitude of 762 m on 11th August 1986. Details of these are given in Appendix A. I I I I

I - 27- I 5.1.2 Ground Survey Data I . Wamberal and Terrigal Beaches have been surveyed along five profile lines by the Soil Conservation Service (SCS). The profile lines extended from the back beach area to I approximately RL 2.0m AHD and were surveyed on 7 occasions between 27th June 1986 and 17th December 1986. Profile plots are· presented in Figures 19 a-e. An assessment of stonn erosion volumes has been carried out from these surveys. Beach volumes, defined in a similar I way to the photogrammetric analysis, were calculated for all survey dates. Plots of change in beach volume versus time for all sections are given in Figures 20 a-e.

I These plots indicate that the August 1986 storm caused significant erosion. The pre and post August stonn volumes generally differ by 100 to 120m3 1m on Wamberal Beach and about 70 m31m on Terrigal Beach. The changes are summarised in Table 8. Between the August and I October surveys there was slow but steady recovery at some sections and little change at others. The October and December surveys indicate that the November 1986 storm may have caused a I slowing down of the recovery.

TABLE 8. Change in Beach Volume (m3/m), Wamberal and Terrigal Beaches I August 1986 Storm

Ground Survey Data Photogrammetric Data Location June 86 - August 86 August 84 - August 86 Wamberal Line 4 114 125 Wamberal Line 3 105 77 I Wamberal Line 2 99 40 Wamberal Line 1 104 92 I Terrigal Line 1 71 13

Direct compariso!1 of the ground survey beach volumes with photogrammetric results cannot be I made, since the starting chainages for the volume calculations are different. However, the statting chainages were in a similar part of the beach, and in an area which was not significantly altered by the stonns, so the differences in volumes are comparable (Table 8). For the August stonn, rpe I pre and post stonn survey dates from the photogrammetry are 23rd August 1984 and 18th August 1986, while those for the ground survey data are 27th June 1986 and 13th August 1986. The I June to August 1986 ground survey erosion volumes have been ploued on the photogrammetric plans to allow comparison (Figure 16).

I In addition, video records were made by the Public Works Department of NSW, Coastal Branch to document the state of the beaches immediately after the August 1986 storm. Details of these I are given in Appendix A. I I I I

I - 28- I I 5.2 MANLY WARRINGAH BEACHES 5.2.1 Photogrammetric Data I As part of the Collaroy/Narrabeen Beaches, Hazard Definition Study (PWD, 1987) an assessment of the August 1986 storm erosion on Collaroy and Narrabeen Beaches has been made. A summary of this information is included in this report so that a complete data set of storm I information is available within the one document.

Aerial photographs of Collaroy and Narrabeen beaches were taken by CMA at an approximate I scale of 1:10000 on the 18th August 1986, just after the August 1986 storm. Aerial photographs, taken by CMA between the 7th and 19th April 1985 were also available. As mentioned in Section 5.1.1, there was an earlier severe storm in October 1985 which is also between the dates I of photography. Photogrammetric analysis of the two sets of photographs was carried out by PWD, Coastal Branch as detailed in Section 5.1.1. The differences between the 1985 and 1986 / I beach volumes have been determined to assess the extent of erosion caused by the August 1986 storm. Plots of volume change per metre length of beach are reproduced in Figures 21 and 22.

I The Collaroy Beach volume changes generally indicate erosion of between about 50 and 175 m3/m length of beach. The Narrabeen Beach volume changes vary from accretion of about 50 I m3/m to erosion of about 100 m3/m length of beach. As part of the above mentioned study, an assessment was mad~ of beach changes related to the MaylJune 1974 storms. Beach volumes were determined from 1972 and 1974 aerial photographs. I The changes are shown in Figures 21 and 22 for comparison purposes. The Figures indicate that these two severe storms have affected these beaches to varying degrees along their length and the I estimated 1974 erosion does not represent the maximum recorded erosion at all points on the beach.

I Aerial photographs of the coast from Narrabeen to Budgewoi were also taken by PWD from an altitude of 762m on 11th August 1986. Details of these are given in Appendix A.

I 5.2.2 Ground Survey Data

The Manly Warringah beaches were surveyed on the 11th, 12th and 14th August 1986 at a I number of locations corresponding to wave run-up measurements. The locations are shown in Figures 13 a-d. The surveys generally extended from the back beach area to the water line and I were perpendicular to the beach alignment. In addition, video records were made by the Public Works Department of NSW, Coastal Branch I to document the state of the beaches immediately after the August 1986 storm. Details of these are given in Appendix A. I I I I

I - 29- I I 5.3 BATEMANS BAY BEACHES 5.3.1 Ground Survey Data I The beaches were surveyed in December 1986 at a number of locations corresponding to wave run-up measurements. The locations are shown in Figures 14 a-c. The surveys generally extended I to the water line and were perpendicular to the beach alignment I I I I I I I I I I I I I I I I I I - 30-

I 6. OFFSHORE SURVEYS I 6.1 SURVEY METHODS PWD Coastal Branch has surveyed the ocean bed in a number of locations, including the Gosford and Manly Warringah areas. The surveys are generally carried out from the Department's 5.5 m I "Sea Master" Shark Cat. They involve echo sounding along fixed profile lines with a "Raytheon" echo sounder and position fixing at regular intervals with a Motorola Mini-ranger System. Some lines extend to about 7 kIn offshore but others are much shorter. They generally extend shoreward I to about the wave breaker line.

Before and after the survey the echo sounder is calibrated with a bar check. This consists of I lowering a reflective bar to various fixed depths below the boat and adjusting the recorder to give I the correct depths. The boat generally aims to travel along a straight path directly towards one of several Mini­ Ranger shore stations. Depth is recorded continuously on the echo sounder chart and the position I is fixed at intervals o~ 50m to 200m by recording the distance from two shore stations. The location of the shore stations is known, so each fix is later converted to Australian Mapping Grid (AMG) coordinates. The depth at each fix, and its coordinates are tabulated for plotting purposes. I The recorded tide height from an appropriate gauge is used to correct the depths to a fixed datum. If required the echo sounder data is digitised or a limited number of data points are selected to I define changes in bed slope. These are used to supplement the data obtained at the fixes. If this is done it is assumed that the boat travelled at constant speed and in a straight line between fixes.

I 6.2 GOSFORD BEACHES PWD Coastal Branch surveyed the ocean bed offshore of the Gosford area between Wamberal I Beach and MacMasters Beach, in 1983/84 and again in 1986. Between October 1983 and January 1984,21 lines were surveyed all to approximately 7km offshore. Fourteen lines were surveyed in late August 1986, about three weeks after the storm, and four of these (Lines 5, 9, 12 and 13) I corresponded with lines surveyed in: 1983/84. These four lines have been used to assess changes between 1983/84 and 1986. The locations of the four profile lines is shown in Figure 23.

I The purpose of the 1986 surveys was to monitor changes in the nearshore sea bed profiles as a result of the August storm and most were not surveyed as far seaward as they were in 1983/84. Three of the lines used for comparison extended to 3 or 4 km offshore and one to 7 km offshore, I during the 1986 survey. The plan position of the 1986 survey lines generally corresponded to the earlier surveys, except for Line 12, for which there was a maximum deviation of about 75 m. I Comparison of 1983/84 and 1986 profiles should therefore be done with caution since differences can be caused by positioning errors as well as by profile changes.

I In Figures 24 a to 27 a, the profiles are plotted in section to allow comparison of the 1983/84 and 1986 data. The shoreward part of these profiles have been replotted at a larger scale in Figures I 24 b to 27 b'

I The seaward extent of sediment movement during the August storm has been assessed from this I data together with offshore sediment descriptions and is discussed in Section 7.4. 6.3 WARRINGAH BEACHES

The area offshore of Collaroy and Narrabeen Beaches was surveyed in 1979/83 and again in I August 1986 by PWD, Coastal Branch. Eight profile lines were surveyed in 1979/83 and nine in 1986. They extended to between 0.7 and 2.0km offshore. The location of the lines is shown in I Figure 28. The plan position of the 1986 survey lines correspOnded approximately to the earlier surveys, but some. lines were not very straight and the two surveys were as much as 75 m apart I (see Figure 28). The profiles of the 17 offshore lines have been plotted in Figures 29 to 45: These figures show the cross-sections plotted with straight lines joining the arbitrary fix points. Intermediate points I between fixes do not necessarily lie on these"' straight lines. However, echo sounder charts are available if more detailed data is required (See Appendix A).

I The profile data as assembled at present does not allow pre and post storm comparisons to be made as the lines have been plotted from arbitrary origins. The full survey data is, however, available for analysis as indicated in Appendix A. I I I I

I - 32- I 6.4 ASSESSMENT OF ACCURACY OF OFFSHORE SURVEYS I The Gosford offshore data has been examined in order to estimate the errors in depth sounding, and position fixing, and to assess their impact on results. They can be divided into measurement errors related to the limitations of the equipment and operating technique, and positioning errors related to the difficulty of positioning or re-positioning the boat at the intended locations.

I The accuracy of echo soundings is normally assumed to be ±O.25 to ±O.5 m (PWD estimate) but this depends on the calibration of the instrument and on the method of use. The instrument measures the distance from the transponder to the seabed, by timing the interval between the I transmission of sound waves and the reception of the reflected signal from the seabed. The sources of inaccuracies include the following. The speed of sound in water varies with temperature and salinity and calibration of the instrument involves a correction for these I parameters. This is normally included as part of the bar check (see Section 6.1). It is generally assumed that the instrument is mounted so that the distance measured is the true vertical distance I to the bed, but this cannot always be the case since the boat is tilting with the waves. This is not normally a significant problem with a boat like a "Sea Master" Shark. Cat. The depth of the transponder below the sea surface is corrected for in the bar check, but is not always constant, I particularly if there are significant changes to the weight distributions on the boat or the boat trayels at high speed. Again this is not normally a significant problem with a boat like a "Sea Mtu,ter" Shark. Cat. Depths below sea level are converted to depths below some datum using tide . ) I records from a nearby location. This assumes that the tide level offshore is the same' as that onshore. This is valid in the locations considered here, but may not be in locations on the outer I part of broad continental shelves. The Motorola Mini-Ranger System used to measure distances to the shore stations, uses a pulse I radar, transmitter-receiver system. The manufacturers quote a "probable range error" of ±3 m (Motorola, 1972). If the angle between the measured distances is 90 degrees, the maximum error in positioning a fix can be estimated as 1.4 (the square root of two) times the range error. This ,I assumes that the ranges are large compared to the range error. If the angle is 60 or 120 degrees, the maximum error is twice the range error, and if it is 30 or 150 degrees it is 4 times. It can be significantly more if the angle between the two distance measurements is smaller than 30 or larger 1 than 150 degrees. I When used in conjunction with an echo sounder, an additional error. is introduced if the recording of the position fix is not done at preCisely the same time as the recording of the depth. To these possible errors can be added any horizontal distance between the instrument and the echo sounder. I If the shore station is in a very elevated location, a correction may be required to convert the measured range to its horizontal equivalent. This correction has been included in the surveys described here. The error in positioning or repositioning the shore stations is not known, but is I unlikely to exceed 2m. I The offshore Gosford surveys had the primary shore station at the origin of the line and a sec~ndary station between 0.8 and 1O.Okm along the coast. On the longer lines, a different I ~,"'" I I

I - 33- I secondary station was used on the offshore portions. During the 1983/84 and 1986 surveys, the I smallest angle between ranges was about 30 degrees. The maximum error in positioning the mini-ranger relative to the shore stations would be about 12 m. Since both stations are on the shore, this error is likely to be greatest in the longshore direction. The overall positioning error is I unlikely to exceed 20m.

When offshore profiles are surveyed the boat attempts to travel at constant speed and in a straight I line from a known location towards a shore station. This cannot always be achieved, and it is common for the boat to stray off course. Examination of the profile lines from the offshore I Collaroy and Narrabeen surveys (Figure 28) indicates that the boat tracks are far from Straight, with misalignment often greater than 50m. When re-surveying an offshore profile line it is important to relocate and duplicate the boat track as accurately as possible. If this is not achieved I satisfactorily then the profile comparison may not be valid. Comparison of the boat tracks from the 1979/83 and 1986 offshore Collaroy '!lld Narrabeen surveys (Figure 23) indicates that the two surveys were sometimes as much as 75 m apart. Comparison of the boat tracks from the 1983/84 I and 1986 offshore Gosford surveys (Figure 28) indicates that boat positioning was generally good (10 to 20m) but that occasionally the two surveys were as much as 75 m apart. Profiles are normally ploued as a depth versus distance from the shore station, so positioning errors will result I in depth errors due to the variations in depth perpendicular to the track line. These errors may be I large where the seabed is s~ep, rough or irregular or where there are reefs and channels. Bed slopes 7 km offshore are typically 0.001 to 0.003, so an onshore offshore positioning error of 10m would produce a maximum error of about 0.03 m. Longshore positioning errors should be I much less important since the lines are approximately perpendicular to the contours. These can therefore be ignored except where the bed is rough. Bed slopes 1 to 2 km offshore are typically 0.01 to 0.02 so onshore-offshore positioning errors are much more significant An onshore­ I offshore positioning error of 10m would result in a maximum error in depth of 0.2m. Closer inshore the slopes are steeper still and can exceed 0.04. An onshore-offshore positioning error of I 10 m in this region would result in an error in depth in excess of 0.4 m. I I I I I I I I

I - 34- I I 7. OFFSHORE SEDIMENT SAMPLES - GOSFORD BEACHES 7.1 SAMPLE COLLECTION Bed sediments were collected during the offshore su'rveying \Vorl<:. in 1983/84 and again in late :1 August 1986. The samples. were dredged from the bed using a simple 100mm diameter cylinder. The locations were on or close to the four main offshore profile lines numbered 5, 9, 12 and 13 I described in Section 6.2 and to four subsidiary lines numbered 71, 72, 74 and 76 (see Figure 23) . . Samples on the four main lines are also shown on the profile plots in Figures 24 to 27. The depths and locations were fixed by the same equipment as was used for the offshore profiling (see I Section 6.1). , I 7.2 SAMPLE CLASSIFICATION An offshore sand classification system postulated by Roy (1978) describes the original source of the sediment and various zones of sediment activity. Essentially there are two groups of sand, I classified as nearshore and inner-shelf sands. The nearshore sands fonn the active wedge of the beach profile and consist of inner and outer nearshore sands. The inner nearshore sands are "beach" sands which are readily eroded in stonns and deposited on the nearshore slope over the I outer nearshore sands. Thc··inner nearshore sands (INS) are usually coarser than the outer near shore sands (ONS). This is a fairly reliable trait to enable differentiation of the two groups. Other characteristics such as colour and grain size sorting tend to be less reliable. The inner shelf I sands are less active and are usually only disturbed in severe wave conditions ..These. sands are generally coarser, more poorly sorted and contain more iron-staining which gives a red-brown I colour, than the ONS sands. Often some mud is evident in this region.

The extent of offshore transport can be estimated by combining results from the profile I comparisons and sediment type changes. Areas in which the sand type changes from ONS to INS or the sand is much coarser, and which are associated with deposition on the profile, have been I assumed to indicate the extent of offshore transport for that stonn. The changes observed cannot be directly related to the August storm because the 1983/84 surveys were a considerable time before and do not represent pre-stonn conditions. However, the analysis gives an indication of I- the likely effects of stonns on the offshore profile. I 7.3 SAMPLE DESCRIPTIONS Details of approximate distances from the shore station, depths and sediment classifications of the samples from offshore Terrigal, Wamberal, Avoca, MacMasters and Copacabana are given in I Table 8. I I I

·1 . - I I - 35- I TABLE 9. Details of Offshore Samples, Gosford Area. 1983/84 and 1986 Surveys I Approx Sample No. Distance Depth Sediment Line Location Offshore(m) ISLW(m) Description No. Post Post Post Post I 83/84 83/84 83/84 83/84 Storm Storm Storm Storm Wamberal 13 89 600 12.0 INS/ONS I 174 600 12.2 INS/ONS 88 1400 25.5 INS/ONS 175 1400 25.3 INS/ONS 87 1850 30.5 River Cobbles I 176 1850 30.3 River Gravel Terrigal 12 164 200 1.2 INS ;1 113 400 8.3 ONS 165 450 9.9 INS/ONS 166 1000 18.4 ONS on Reef 112 1050 18.6 ONSonReef I 111 1500 24.0 Reef 167 1600 24.1 Reef Avoca 9 168 275 2.7 INS 56 300 4.4 INS I 169 320 4.8 INS 173 600 11.7 INS 57 1000 18.9 ONS I 63 1600 27.5 ONS 170 1700 28.0 ONS 58 2200 34.3 ONS I 171 2500 37.0 ONS 62 2700 38.4 ONS Avoca 74 184 250 6.0 INS 187 340 8.6 INS 186 380 9.9 INS 173 440 11.7 INS 185 550 12.9 INS 183 740 18.0 INS/ONS 182 1200 23.3 ONS Avoca 76 190 300 6.8 INS I 189 340 8.3 INS 188 690 14.3 INS/ONS 182 1250 23.3 ONS MacMasters 5 33 350 9.1 ONS I 34 850 18.9 ONS 192 1050 23.4 ONS 35 1400 31.3 ONS I Copacabana 71 196 . 150 4.4 INS 197 175 4.5 INS 195 300 6.9 INS 198 300 6.4 INS 194 480 12.0 ONS 193 700 17.0 ONS 192 1000 23.4 ONS 191 1300 29.5 ONS I I J I

I - 36- I I 7.4 COMPARISON OF 1983/84 AND POST STORM OFFSHORE DATA 7.4.1 Wamberal!ferrigal Beaches

The 1983/84 Line 12 samples indicate that the INS/ONS boundary was located in water depths I less than 8m (below ISLW). The post-stonn samples indicate a mixed INS/ONS sample at about 10 m water depth. However, there are no other samples in water depths between 1 m and 18 m to better define the possible deposition of beach sand (INS) in the offshore area. The extent of accumulation evident from the profile plots is relatively small compared to that on other profiles. It would seem that the cut and fill process at this point was not as significant as at other locations and hence it iscmore difficult to obtain INS sand which has not been mixed with ONS sand. The profile plots indicate that it is likely that beach sand has been deposited out to a water depth of about 9m. The volume of sand moved into the bar between 1983/84 and 1986 is estimated at I loom31m (Figure 26b). I The possible accumulation of beach sand in the offshore area is more evident on Line l3, where the volume of sand moved into the bar is estimated at 260m3/m (Figure 27b). However, samples were not taken in water depths less than 12 m in either the 1983/84 or post stonn conditions. It I is likely that deposition of beach sand on this profile was limited to water depths less than 12 m. I 7.4.2 Avoca Beach The 1983/84 Line 9 samples indicate that the INS/ONS boundary was in depths between 4m and 19 m. The post-stonn samples indicate the boundary is in depths between 12 and 28 m. The I large depth range between samples spanning the inferred boundary for both the 1983/84 and post stonn conditions makes it difficult to estimate if any INS' sand has been transported offshore. However, the profile plots indicate that significant quantities of sand accumulated in water depths I between 4 and 12m. The volume of sand moved into, the bar between 1983/84 and 1986 is estimated at 320m3/m (Figure 25b). This sand is assumed to be INS sand cut from the profile I further inshore by wave action and deposited by currents out into these depths of water. Samples from Lines 76 and 74 indicate that the INS/ONS boundary is located in water depths of I about 14 and 18 m respectively. This supports the view that on Line 9 beach sands have been moved into water depths up to about 12 m.

I 7.4.3 MacMasters/Copacabana Beaches For both 1983/84 and post-stonn conditions, the Line 5 samples are all ONS sand. However, I there were no post stonn samples taken from water depths less than 23 m. The post stonn profiles show an accumulation of sand in water depths from about 3 to 10 m. The volume of sand moved into the bar between 1983/84 and 1986 is estimated at 170m3/m (Figure 24b). This I is assumed to be beach sand (INS) cut from the profile further inshore.

The post-stonn samples from Line 71 indicate that the INS/ONS boundary was probably in depths I of water of about 9 m. This supports the assumption that beach sands at the Line 5 profile, were I I I

I - 37- I I moved out to about 10m water depth between the two sUiveys. I I I I I I I I I I I I I I I I I I I - 38- I I 8. .REFERENCES [1] Bureau of Meteorology (1986a). Monthly Weather Review, New South Wales, August, 1986.

I [2] Bureau of Meteorology (1986b), Monthly Weather Review, New South Wales, November, 1986.

I [3] Coastal Engineering Research Center (1984). Shore Protection Manual, Department of the Anny. USA. 4th Edition. 1984. I [4] Easton, A.K. (1970) •. The Tides of the Continent of Australia. Horace Lamb Centre, Flinders University of South Australia, Research Paper No. 37. May 1970. I [5] LePlastrier. B. and Foster, D.N. (1976). Parsley Bay Breakwater Investigation, Water Research Laboratory Technical Report No. 76/9. December 1976. I [6] McMonagle. C.J. and Fidge. B.L. (1981). A Study of Extreme Values of Water Levels and Wave Height at Coifs Harbour. Institution of Engineers. Australia. Australian Conference on Coastal & Ocean Engineering (5th, Perth, 1981), pp 267-271.

I [7] Motorola (1972). Mini-Ranger JI1 Automated Positioning Systems.

[8] Public Works Department (1985a). Wamberal Beach and Avoca Beach - Coastal I Engineering Advice. report prepared by Civil Engineering Division. Public Works Department of NSW Report No. 85040. May 1985. I [9] Public Works Department (1985b). Elevated Ocean Levels. Storms affecting the NSW Coast 1880-1980, report prepared by Blain Bremner & Williams Pty Ltd and Weatherex Meteorological Services Pty Ltd. Public Works Department of NSW Report No. 85041, I December 1985.

[10] Public Works Department (1986a). Elevated Ocean Levels. Storms affecting the NSW Coast I 1980-1985, report prepared by Lawson and TreloarPty Ltd and Weatherex Meteorological Services Pty Ltd. Public Works Department of NSW Report No. 86026. August 1985. I [11] Public Works Department (1986b). New South Wales Wave Climate, Annual Summary 1985/86, report prepared by Manly Hydraulics Laboratory. Public Works Department of I NSW Report No. 465, September 1986. [12] Public Works Department (1987). Collaroy/Narrabeen Beaches, Coastal Process Hazard Definition Study, report prepared by Coastal Branch, Public Works Department of NSW I Report No. 87040. December 1987. [13] Roy. P.S. and Stephens. A.W. (1978). Quaternary Geology and Offshore Sediment Budget I for the Byron Bay Region, Geological Survey of NSW. Department of Mines Geological Survey Report No. GS 1978{276. 1978.

[14] Short. A.D. and Wright. L.D. (1984), Morphodynamics of high energy beaches: an I Australian perspective, Coastal Geomorphology in Australia, Ed. B.G. Thorn. Academic I I I

I - 39- I [15] Silvester. R. (1974). Coastal Engineering. 2. (Developments in Geotechnical Engineering. I Vol 4B). Amsterdam: Elsevier. 1974. [16] Youll. P.H. (1981). Botany Bay Waverider System - Ten Years of record. Institution of I Engineers. Australia. Australian Conference on Coastal & Ocean Engineering (5th, Perth, 1981) pp 245-251. I [17] Public Works Department of NSW. Coastal Branch. file No. 80-036-006. [18] Public Works Department of NSW. Coastal Branch. file No. Rlool/61. I I I I I I I I I I I I I I I I I - 40 - I 9. ACKNOWLEDGEMENTS

The Assistance of the University of NSW Water Research Laboratory, particularly Messrs. K. B. Higgs and R. Nittim, in collating and reporting the information herein is gratefully acknowledged. I As described in the report, a number of other organisations assisted in providing data and information. I I I I I I I I I I I I I I I I I

I - 41 - I . APPENDIX A. List of Storm Data I The Public Works Department of NSW, Coastal Branch holds records of the data used to prepare this report. This data includes the following:-

I 1. Collaroy and Narrab.een Beaches, Photograrnmetric plots and profile comparisons. Drawing No. 86116. I 2. Collaroy and Narrabeen Beaches, Offshore survey data. 20th to 21st August 1986, Collaroy/Narrabeen book No. 87066. 26th July 1979 to 12th May 1983, Collaroy/Narrabeen book No. 82310. I Echo sounding charts contain detailed information on sediment/reef boundaries and seabed morphology between fix points. I 3. Gosford Beaches, Photograrnmetric plots and profile comparisons. Drawing No. 83042. 4. Gosford Beaches, Offshore survey data. Survey date, 25th to 29th August 1986.

I 5. Warringah Beaches, Wave run-up measurements. Survey date, 12th to 14th August 1986.

6. Batemans Bay Beaches, Wave run-up measurements. Survey dates, 6th August and 19-20th I November 1986. 7. Central Mapping Authority Aerial Photography, I Bondi Beach to Wybung Head. Photography date, 18th and 19th August 1986. 8. Public Works Department of NSW Aerial Photography, I Narrabeen to MacMasters Beach, Film No. 70.86.52, Print Nos. 1 to 66 MacMasters Beach to Budgewoi, Film No. 70.86.53, Print Nos. 1 to 77.

I The Public Works Department of NSW, Coastal Branch, also has a video cassette library containing a number of V.H.S. video tapes which record the state of the beaches and erosion damage following the August 1986 storms. The tapes have no sound recorded. Details are as I follows:-

I Cassette No. Subject Picture Quality 22 Narrabeen Beach, 9f)f86 Variable 24 Narrabeen to Lady Robinsons Beach, 8/8/86 Good I 25 Patonga to Lady Robinsons Beach, 9/8/86 Good 26* Gosford Beaches, 9/8/86 and 14/8/86 Good I 28 Long Reef to Cronulla, 18/8/86 Good

* Source:- Gosford City Council. (All others I filmed. by Public Works Department). I I I I I I

TERRI GAL BEACH I AVOCA BEACH flGcHASTERS BEACH I NEW SOUTH I WALES AIRPORT· STATION + OFFSHORE BOTANY BAY I WAVERIDER BUOY I I OFFSHORE PORT KEHBLA I WAVERIDER BUOY I I I I I

OFFSHORE BATEMANS BAY I + WAVERIDER BUOY - 0 10 20 30 40 50 km , I ,. ! I SCALE HORUYA HEADS WEATHER.STATION I I LOCALITY MAP I FIGURE 1 I ------

30 30

., ., .. • It_ ZO It_.. 20 ., ..• ., .... CD C D -C _C X~ ,,~ ..C 10 ..C 10 :It :It•

2 3 4 5 6 7 B 9 10 \I 12 13 14 15 15 16 17 IB 19 ZO 21 22 23 24 25 Z6 27 2B 29 .j AugUlt 1986 NDvellblr 1186

360 360 C C D_ D_ ::~ 270 -z 270 u .....u .. _u ..u ~ . ~ . IBO .. IBO O~.. o ~ -0 ., .. ., ..0 ~.!! 90 "" C" 90 " --" 0 0 I 2 3 4 5 6 7 B 9 10 \I 12 13 14 15 15 16 17 Augult 1986 Noveslr t986

.. 1030 1030 ~ .. ~ ..~ ..~ .. 1020 .. 1020 ~ ...... ~ ~ i 1010 !! i 1010 ..~- ~- J: r... c. .. 1000 1000 D ..D & ..c• ..c 990 I 2 3 4 5 6 7 B 9 10 \I 12 13 14 15 15 16 17 IB 19 20 21 22 23 24 25 AugUlt t9B6 Nove ...... 1986

200 r- 200 ., -.. D -~ c_ c_ : I r- a:- 100 -.. e 100 .. a:-.. . Il -.. H 0 -.. - 0 (J) II 0 0 C I 2 3 4 5 6 7 B 9 10 \I 12 13 14 15 15 16 17 IB 19 20 21 23 24 25 26 ' 27 2B 29 ::0 2~ rn Augult 198a Novellbl'" t986 f\) Meteorological Conditions, Sydney Airport, August and November 1986 Source of Data: Bureau of Meteorology - - - - ,... ------30 T I 30 T I ~ ~ 0 • ~ 20 •~ 20 "'-· "'- ~~• ~~. _c cC _c c %t!; %2£ c \0 c 10 0 0 ·>: ·>:

0 0 2 3 4 5 6 7 B 9 10 II 12 13 14 15 15 16 \7 IB \9 20 21 22 23 24 25 26 27 2B 29 ,I August 19B6 Noveaaber 1986 360 360

c Dc _ D_ -z 270 -z 270 ~ .... ~ ~ u u ·L . 0 IBO ·L .0 IBO -o .L o- .L .. ~ ~ ~ 0 c .~ 90 ,5E 90 --'" '" 0 0 I 2 3 4 5 6 7 B 9 10 \I 12 13 14 15 15 \6 17 IB \9 20 21 22 23 24 25 26 27 2B 29 August 1986 November 1986

1030 1030 ,•L •,L • ·• 1020 Normal August Pressure - 1017 me • 1020 c L Normal November Pressure· SOU ID.b 0-· ------~----~~------. 0------. ~ ~ 1010 u" 1010 c- -c-e • o '"D. 1000 '"D. 1000 D •c ·~• !l...... 990 990 ~ 4 ·14. \6 \7 24 27 2 3 ' 5 6 7 B 9 10 II 12 13 15 15 IB 19 20 21 22 23. 25 26 2B 29 i August 1986 November 1986

200 200

~• -_ E • c_ c_ 100 - a:-• • a:-• .E \00 11 ~ ,. H 0 0 GJ · · 0 0 C 2 4 5 6 7 B 9 10 \I 12 13 14 15 ::IJ 3 t 15 16 17 IB 19 20 21 22 23 24 25 26 27 2B 29 rn August 1986 November 1986 w tvle t e o~r 010 g i cal Cond it ions. Moruya Heads, August and November 1986 Source of Data: Bureau of Me t e or 01-09 Y I I I

I DAILY WEATHER MAPS 1000 K (00 GMT) I 3 - 9 August 1986 Oltes are rinled left·hand corner _of ."ch map. LEGEND I Isobars are drawn .t 4 tlPa intervals . Cold Front . . Warm Front . . Occi~on I }foulh I I I I I I I I I I I I PREPARED BY BUREAU OF METEOROLOGY SYNOPTIC CHARTS I 3 r d to 9 t h AUG US T 1986

I FIGURE 4 I I I

I DAILY WEATHER MAPS 1000 K (00 GMT) I 17 - 23 November 1986 Dates are rinSed left·hand corner of each map.

LEGEND I Isobars are drawn at 4 hPa intervals · . Cold Front · . Warm Front . OCclusion I · Trou&h I I I I I I I I I I I I SYNOPTI ( (HARTS I 17 th to 23 rd NOVEMBER 1986 I FIGURE 5 I I I ~I 2 I

I x E

-W I .c x 01 ...... !x QJ 1 + ::r:: I QJ LJ ...... tI r-- I x x x x x .x X X X X 1 X I X I X X X T, X Predicted Tide. Fort Denison I I Measured Tide. Fort Denison 0 I 2 3 4 5 6 7 B 9 10 11 12 13 14 15 I August 19B6 Datum: Zero of the Fort Denison .Tide Gauge I E .3

r-i .2 I ro :J LJ ...... 1 I ([) QJ IT .0

r-i I ro -.1 August 1986 LJ ...... I r-- -.2 Residual = Measured - Predicted I I Tide Height, Fort Den isDn, Sydney August 1986 I Source of Data: MSB I FIGURE 6 I I ~ . I I 2 I x x x x I x x E x x x X -W x I s= x 01 x ·M QJ I :r: QJ. D ·M x I I- x x x x x x x I x x

x Predicted T i·de, Fort Denison I - Measured Tide, Fort Denison o +---~--~--~----~--~--~--~----~--~--~--~----+---~--~ 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 I November 1986 Datum: Zero of the Fort Denison Tide Gauge I E ,3

rl .2 I m ::J D . 1 'M I UJ QJ IT 19 20 21 22 25 9 rl I m -.1 November 1986 D ·M I I- -.2 Residual = Measured - Predicted I I Tide Height, Fort Denison, Sydney November 1986 I Source of Data: MS8 I FIGURE 7 I ------

E 2'5 UJ \!l «::> \!l

UJ 0 2· 4 f-

Z 0 E VI Z UJ 0 2'3 0 :r ~ I « 0 u..

UJ :r 2'2 ~0 f- f'3 III « z 0 a:0 UJ UJ. N 2" ~ ....J

> UJ UJo ~ a:f- III 1.1 « « ~ ....J 2· 0 UJ > UJ ....J a: UJ ~ 1·9 II G'l c: ;0 rrJ 0·2 0'5 1· 0 2 5 10 20 50 100 200 00 RETURN PERIOD - YEARS RETURN PERIOD OF RECORDED WATER? LEVELS AT FORT DENISON FOR PERIOD 1883 TO 1975 I ~t I

I 2

I x x x x x 0 ::r: x I ill ill x I E

+J .c 1 I OJ . ..-i OJ ::r: I OJ TI X X • ..-i X X X x x x x l- x x x x x x x x I x x x x x x Predirted Tide, Fort Denison - Measured Tide, Batemans Bay I 0 2 3 4 5 6 7 B 9 10 11 12 13 14 15 I August 1986 Datum: Batemans Bay Hydro D.atum I E .3

I .-; .2 CO :J TI . ..-i .1 I U) OJ IT .0

.-; I CO -.1 TI . ..-i I I- -.2 Residual = Measured - Predicted I I Tide Height, Batemans Bay Zwarts Gauge August 1986 I Source 0 f· Data: PWD/MSB FIGURE 9 I I I ':.-:. I

I 2

I "" x x x 0 x I x I (]] x x (]] x x x I E x

+J .c 1 01 I' . .-1 UJ I x ~ x I UJ x X TI X X . .-1 x x f- x x x x x x x I x x x x x Predicted Tide, Fort Denison Measured Tide, Batemans Bay I 0 " : 15 16 17 1B 19 20 21 22 23 24 25 26 27 2B 29 November 1966 I Datum: Batemans Bay Hydro Datum I E .3

I r-1 .2 CO ::J TI . .-1 .1 I U) UJ IT .0 1 16 17 1B 19 20 9 r-1 I CO -.1 November TI . .-1 I· f- -.2 Residual = Measured - Predicted I I Tide Height, Batemans Bay Zwarts Gauge November 1986 I Source of Data: PWD/MSB FIGURE 10 I I I I 2 / ...... I /' ENVELOPE~:'­ / ENVELOPE 0 I I CD CD - - ,/ ..- .>--:::: / ...... --- ./ I E .... ------" +.J .c 1 I ...... CI (lJ I -- -- I Ql /'...... , U ...... / ----V7"" t- I /LLW ENVELOPE --2 - ...... " , HLW ENVELOPE ----' Measured Tide, Floatwell Gauge Measured Tide Envelopes, Zwarts Gauge I 0 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 I November 1986 Datum: Batemans Bay Hydro Datum

I -E - .3 Ql u I C .2 (lJ L Ql .1 .....'I- I ...... 0 .0 16 17 r-t I 10 -.1 ...... u t- -.2 I Difference - Zwarts - Floatwell

I Comparison of Tides, Batemans Bay I Zwarts and Floatwell Gauges November 1986 I Source of Data: PWD I FIGURE 11 I '. -,. I .. •• .. •• I .. II 10 .0 • I ~ ~.. Maxl.u. Wave Helght " DO !!'".. "~.. :I: • :I: • u , .. I ..> ..> • " "

I •

Height 0 1 .0 II • 2 I> I. II II 2. ., • • .. .. t7 •• ...... I August 1986 November 19B6 !! ..II !! II "~ !!" " L L U .. I a. a." u 10 > ~ '" • ~ .. '"u '"u I a. a. -.. .. L · -L O' O' ..U • U.. • C1 0 C1 0 I In I 1 • .0 II .. I> .. .. In •• tI t7 II •• ...... August 1986 November 1986 " A. Offshore Botany Bay. August 1986 B. Offshore Botany Bay, November 1986 I Source of Oata: HSB/PHO Source of Data: MSB/PHD ".. ••.. I II II

10 10

§ § I Maximum Wave Hetght • Haxlmum ~ave Helght O' O' 7 !!'" !!'" .. u :I: • :I: • u I "..> • ..> • " " I

Significant Wave Height Significant Wave Height 0 7 .0 II I. 17 tI ., 2 • I • ...... •• ...... " ...... August 1986 " November 1986 .!! •• !! II "0 .. !!" .. I <- Ii <- .2 -u a. a." 10 .0 .."> .."> I ".. • ".. • '"u '" a. a..." ~ ..<- -<- O' 2 O' U U • U I C1 0. " 0 In • 10 II 12 .. .. In •• .. 17 II .. .. 21 .. 23 2' .. ,. 27 2 • August 1986 " November 1986 " C. Offshore Batemans 8ay. August 1986 O. Offshore Batemans Bay. November 1986 I Source of Data: PHD Source of Data: PHD f I Wave Height ar:)d Per i od, Botany Bay and Batemans Bay FIGURE 12 I I 'f" 62' )000 II I I I I I

II " 6, 6 I BEACH I I Q: • ~,"7. ~ I ~ I,.. 5'5 I,.. Q..- WHALE" I BEACH I I

I AVALON BAGALLEY I HEAD I ...... <> <> <> <> <> <> I m... CLAR EVILLE .... m 627 'I000N ~ o 250 500 m LEVELS IN METRES ON AHD , , I AMG COORDINATES SCALE I MAXIMUM RUN-UP LEVELS, PALM' BEACH TO AVALON I AUGUST 1986 FIGURE 13 a I I 'f, 6277000 N I

I •

I BILGOLA I PLATEAU I I I I I I I

I \ I I MONA VALE I I w w <> <> <> o <> <> N ... I ... 6271000 N :. '" o 250 500 m LEVELS IN METRES ON AHD , I I AMG COORDINATES I MAXIMUM RUN-UP LEVELS, AVALON TO MONA VALE 1986 I AUGUST FIGURE 13 b I I 6271000N I I WARRIEWOOD I I I I I I I I I I I

I (OLLAROY I I UJ UJ <> <> C> <> <>'" I '" 626 SOOON ;;, o 2S0 SOO m LEVELS IN METRES ON AHD I I I AHG COORDINATES SCALE I MAXIMUM RUN- UP LEVELS, NARRABEEN TO·· COLLAROY AUGUST 1986 FIGURE 13 c I \ \ I I 626500011 I I I I I I I I I I I HARBORD I I I I )( 6- 0 I UJ o UJ o o o o o I '" 6259000 N ~ o 250 SOO m LEVELS IN METRES ON AHD ! , I AMG COORDINATES SCALE I MAXIMUM RUN- UP LEVELS, LONG REEF TO QUEENSCLIFF I AUGUST 1.986 FIGURE 13 d I I & I I I I I I

I BATEHANS BAY I ZWARTS TIDE 2-8 CATALINA " GAUGE + I HE IGHTS • '" I PER ISLAND

OBSERVATION HEAD I () I I BATEHAVEN I I I

....o o o I ...'" '" o 250 SOOm LEVELS IN METRES ON AHD ! , AMG COORDINATES I SCALE MAXIMUM RUN UP LEVELS, BATEMANS BAY WEST I AUGUST 1986 (NOVEMBER 1986) FIGURE 14 a .1 I" I 6046000 N

I LONG BEACH • • • V• . MURRAMARANG I r.> ~:> r.> ~ <- .~~~~ NATIONAl V 'oNG BEACH./ ...., ;,- PARK I f~

I( -: -...... I ~~ ,J) t;;; ("-So- :.> ~ :/ I ~ ) <9~., I

ACHE RON I LEDGE I \ ~.. .. .' I BATEMANS BAY I I I , I , I I w w <> <> <> <:> <> <:> I 0- N ~ N '"N 6039000N o 250 SOOm LEVELS IN METRES ON AHD , I I AMG COORDINATES I SCALE MAXIMUM RUN- UP LEVELS, BATEMANS BAY EAST I AUGUST 1986 (NOVEMBER 1986) FIGURE 14 b I I 'i " I; 6040000 N

I DENHAI1S BEACH DCNHAHS I SEACH I I I I

I CIRCUIT SEACH _~.r:;:; I ~LL BCACH ? I q -

I 4t

MO GO I STATE REST I I I1ALUA

I " I I w PRETTY POINT 0 w 0 0 0 r- 8 ~ I ~ N 6034000 N '"N lEVELS IN METRES ON AHD 0 250 AHG COORDINATES I I I SCALE MAXIMUM RUN UP LE VELS, BATEMANS BAY SOUTH I AUGUST 1986 (NOVEMBER 1986) FIGURE 1·4 c I I I x I I I I I x I

I x

I .' I I x I

I ·uL-______~ x x I

Key to pial of beach I ~ o sO 100 m iJp of bxk beach OSCXIrpmenl 1. These graphs portray the difference in sub~rial sand voh.mes Q'l the beach between the yeers v..t:rter line of photography sh:>wn, '~I SCALE' x 2. Sand volumes were determined from beach:c.ross-sectians obtained photognll"1'1tnetriCXllly on a ; a .f Rood formation I NOTt: p,LANIMETRIC INFDRMATION OBTAINED Wild AC1 stereo-restitution instrument f~m eM.A. photography. Location of beach profiles 3. The differences in sand volume were analytically and were measured above Om A..H.O. PHOTOGRAMM£TRICALL Y FROM AU6. '"4 ! i I! I i I ol;ltai~d C.M.A .. !\ERIAL PHOToGRAPHY; AUSTRALIAN (appro><, mean sea leve!) between tN toe 'of, tN bxk beach escarpment. measured from the MAPPINj;, OR 10 Key 10 graph ", . 1979 photography. and !he 2m beach berm'lcontour line fe>- each date of photography· The croSs­ se:c_~.i.?n~ __,,:,.!~_! .. _~ed at 10m interval~ __ ~~ t~ beach. I DIfference " sand 'IOiumes between surveys , 23/8/84- 18/8/86 P"riod of Comparison Storm Event I A M6 Co ordinClte. 23/8/84-18/8/86 5-B/8/U' I I BEACH CHANGES, FORRESTERS BEACH FIGURE 15

I :;. . I I I -. I I

SCS Surve Wamberal Y I L,ne 4 I

SCS Surve I Wamberal Y LIne 1 I I I I I

NarES:

- KlP of back boach·. .._ ...... ~~ 1. These graphs of photographurnes wportray. 1M ditte' 10 sand' ,-, . I WJter line p ..e'll' 2. Sand vol y srcwn. renee In sub-aer" t . . Wild AC1 ere determin ' ~l.mes an Rood forr:ootion , ~ ,," '_-_'M~~ ,-- ,-' ~ _. - ,.- ::;::"' ,. ,- "" '. .Locat ion of bee . ~";::"'".~ ,::::~ -,~ ~ ch profiles '''"•• , ~ ~,- ___,,_, _ ..,~ .., ._,m" ~ • -" I sections ;eraphy." and the 2m b the top .of the ba~~'CaIlY and were mea . Key to graphs , " """" _. ~ ~'" . '", . " .",,0 do "' •• • ".'w, ... AA. o the ferosion "'~,dem S datong the beach,,~, or each='--. date of - ..from ~ the Difference n sand vol.umes between enyelope~ma actual h' an I In'e s hi' p~,::d.""raphy. The 23/11'184 _ 1 survt')'S' . Changes'In beach Islorlcal s I arm ave bee n adopl d cross- • 27/6/8 818186 e . I 6 c,ompari son', . S eeYO~:'Ho detse~minedn 1'2 of from S c,rOSlonS data values. ha e ( R~fm P~Dsi deralions19850) DeSIQll storm 6 - 131 8 I 8 5 report. YO been added f -150 eroslCl'l demand: I or .. , I A"6 (0 ...... ulnat · .. Period of C' omparison Storm Event , 23/8'184-18/8/86 ' 5-8/8186 I " ,'Ii" I BEACH CHANGES WAM BERAL AND TERRI GAL BEACHES I • FIGURE 16 I .l I

+)h ISC": I / .J I / '- I I I I , I ! I

S,= I .~ ;'."7! ,~ '';:: I =::. I I

/' ~" ,: '':'\ , , I /' , , f beach v''''--; Key to phrl 0 beach esoorpment -.- -.-.- - lOp of bock . b-oerlot sand voh.mes en the beach be-" the years NOTES the dIfference In su hot rommetroCXIlly on a I ¥.btpr line 1 These graphs portroy hons obtaIned p og , Rood formation . ' of photography s'""':iermoned from beach c:~-,:: photography, easured above Om "-HO It· , i Location, 0 f boach profiles I 1 ! ~ .; ' :;,7 ::':-:::'::'.'~"":::' ::'.::.:::~ -:'::'"!:'':'::. -=::'';;-Th~;=. I 3 TheI dIfferences Inlevel sand I betweenu the top of thetour boc lone for eac h date of p, _..,., v , ' Key to graphs between surveys : (appro>< mean sea odd the 2m beaCh berm coothe boach Difference n sand volumes con~ideratlons 1978pMtogrophy. an at 10m .,tervols along L e be ..n ajopted trom PWD 198501 I SectIonS wer. spac rosion demond linestorm nav erosion vo lues! Re ..' , The design lstorm es ofe QC tua! historical s 23/8/84 - 18/8/86 I of the enve op t I I ' I CMsign storm eros icn demmd : I -""~--ilJ")--- I Period of Comparisan Storm Event I AMG coordinates 23/8/84 -1818/86 5-8/8/86 I

I' 'j

BEACH CHANGES, AVOCA BEACH .....; .. I .. , FIGURE 17 I I I I I " I x I

.., . , . I x I I Block .. I x x

I .~ I x TT.rrrr~rrT~T~T·TT·TTTTTTTTTTTT~"'nrrrrrrrrrrr~- I ";-, I Xi iii I t iii .. iii iii I iii iii Iii I . .' no I ... -

'" ~J:. .. ~ I .. !~ . - I \ L-~~ ______~~ ______J .• I x

I Koy to !?len of boocI1 s' Top of back beach O0_ tho toe .of tho back beach 6CQrpment. moasur.cl· from the 1978 photography. and IIw 2m booth bonn contour Ii,. far lOCh dale of phaIograJ1hy. Tho <","­ PHOTOGRAMHETRlfALLY FROM AUG. 1984 . i . Key 10 grophs CM.A. AERIAL PHOTOGRAPHY ; AUSTRALIAN sKtions _! spaced at 10m iltenals along IIw boach. Diff-.ce n sand ""'umes between surwys , I MAPPING GR 10 23/8/81,.; 1SIM86· Period of Comparison Storm £'HIlt

2318/84 - 1S/8/86 5-618/86 •

BEACH CHANGES, COPACABANA AND Mac MASTERS BEACHES I FI GURE 18 I ------_. ------

10

8

o J:

~ Starting Chainage for area calculation = 10m E

c o 4 .r< +J co > OJ rl 2 I ...... ~~ =----- " W . . ~ """ """ '" 27/6/86

'>..IJ/IV/OU a i ( I 10 20 30 40 50 60 70 80 90 100 110 Chainage (m)

I] -2 Source of Data: Soil Conservation Service H G1 Beach Pro files, Gosford Area C IJ rn Wamberal Beach, Line 1

--" ..0 P ------', - . ------

0 :r: <{ Chainage for area calculation = 5m ,~". E

C 0 • .-1 +J ro > III r-1 2 w 27/6/86 2110186 o 15/10186 10 20 30 40 50 . 60 70 80 90 100 110 Cha inage (m)

Source 0 f Data: So i 1 Conservat ion Serv lce TJ -2 H Gl Beach Profiles, Gosford Area C II rn Wamberal Beach, Line 2

-" -.0 CT ------

.~

10

B

0 I Starting Chainage for area calculation = 15m

C 4 0 . .-t +J ru > OJ rl W 2 I 13/8/86/.,~ ~ " "" 27/6/86

15/10/86 0 10 20 30 40 50 60 70 BO 90 100 110 .~ Cha inage . (m)

Source of Data: 5011 Conservation Service 11 -2 H Gl Beach Profiles, Gosford Area C JJ rn Wamberal Beach, Line 3

....>. '-D n ------~------,

.', 10

8

o :r <{ 6 Starting Chainage for area calculation = SOm E

c: 4 o • ...-f +J ro > Ql 2 I ,/0/00 ,,==------=-:..", 5 ~ ':..., rl W c::::::::: """ 2/10/8G 27/6/86

o 10 20 30 40 50 60 70 .80 90 100 110 Cha inage (m)

Source of Data: Soil Conservation Service I] -2 H Gl Beach Profiles, Gosford Area C JJ Wamberal Beach, Line 4 rn

~ -.D 0. --I ------

10

8

o I 4: 6

~ E Starting Chainage for area calculation = 20m c 4 o .~ +J co > III r-t W 21-; 1 - ~ ~- ,§~ "~ 27/6/86

.1719/86 01 10 20 30 40 50 6'0\5/10186 7'0 80 90 100 110 Chainage (m)

Source of Data: Soil Conservation Service 11 -2 H Gl Beach Profiles, Gosford Area C ::rJ rn Terrigal Beach, Line 1

-" -.0 CD I

I Time (Days) 1986 o~----~------1 0 170 190 200 210 220 230 2~0 250 260 270 280 290 300 310 320 330 3~0 350 380 -20 $ '" -: S S $ ~ ~ :: -40 ~', ~ ~ ~ ~ ~ ~ ! ~ I III C1 C -60 IV .r:. U " -80 "" " I -~--. ------1----- .... I III " ~---y- E .....:J -100 'l----+"'---- o I > -120 A. Wambera 1 Beach, Line 1 Time (Days) 1986 E o~----~------"'­ 1 0 170 190 200 210 220 230 2~0 250 260 270 280 290.300 310 320 330 3~0 350 360 (T) lID , -tG:I CD til .. • -20 S " • S., ~ ~ ~ I .§ 0, 0 0 , ~o ~ ~ -40 ~ " :;;; ~ ~ 'C\i ~ ~ III C1 . C IV -60 I .r:. u 0 -80 """I~- I~ III . ------+ E -­ .....:J -100 ~--~---~--~~-~------o I > -120 B. Wambera 1 Beach, Line 2 Time (Days) 1986 I E Or---~~------1 0 170 190 200 210 220 230 240 250 260 270 280 290 300 310 320 330 340 350 380 "'­(T) -20 :: " - ::: : = : :3 •.§ ...... • ~...... n. ~', Ii !! ~ ~ ~ ~ ~::: -40 tv " I\; III ~~ ~ ~ ~ ~ ~ I 01 C IV -60 .r:. u -80 III I E """,1 ." ...... I ...... :J -100 "'- .,,- _--+----- o --+----~ ------.-..-+ > -120 C. Wambera 1 Beach, Line 3 I Time (Days) 1986 E Or-----~------1 0 170 190 200 210 220 230 240 250 260 270 280 290 300 310 320 330 3~0 350 380 "'­(T) • -20 .§ I '" . r I ~ ~ ~ ~ a~ ~ I ....." a...... N~ .... ~ Wi ..... ~ ~ ~. 0'" .~ ~ III r;" 01 C IV -60 .r:. ////.---+------1------+ U "\, 1 I , ~¥ -80 III " ~~ E ... r~ .....:J -100 o y/ > I -120 D. Wamberal Beach, Line 4 Time (Days) 1986 E Or---~~------~ __ ~~~~=_~ __~~_==_~~~ I "'- 1 0 170 188- 190 200 210 220 230 2~0 250 260 270 280 290 300 310 320 330 340 350 360 f1 --20 = " __ -.....1...... 1.. I I ....10 I ..... '...... 0 ,01_ .§ .. ~ o!::~ II

Ill. ~ """'...... : ~ t ~ ~ ~ ~ 01 I C IV -60 .r:. u -80 E.. "l--~----~---~--·------l----· I .....:J -100 o I > -120 E. Terrigal Beach, Line 1 Change in Beach Volume Vs Time, Wamberal and Terrigal Beaches FIGURE 20 I I

I J f I f J I ii ii S ~ i ~ I ~

I ~ " . :. A ~ " "- 'j-. .;'. I _J, 21 • -, 'c

Y TO GRAPHS " . DIU,renceKE In .and volum ••. I + + + -+- 1072 - 1974 I 18815 - 1988

I ..~' --1..'" I < :"::~:--1:0.\".', 1~7 __ -+- + ...' .,...! I o

I I ! I \ I + + "~ ','0, \ I :<, '\ 'I I i , i I NOTES, • _ .wla' ...... _ •• -"., .. -- -- tM ,ho_"- •• Tho.. "':CM ...... pCH1rI' thodltf , •• ... ,.. ~. of P-:;~.Ptt' _ I !

•• ... ..Ium ...... d •••tric._, ~ .... 011 ".m • W ::":~ ~:';':~: •• ,""", j 2. Slftd "'? pllolo".""lIe hologflp"" I ...... ".mC ...... ,...... ! In...... •• _ ... _ .... _ .. , + i ~ .. ". T...... , ..... InOm ...... • .HoO ..,;." ' '."': ..w.~ ... :...... tho... ~:::.'...... _ '""! I. .od ..... tho bodo.... Th...... _ • ...... 11oftO. hotogrlph,_Hac:A. In,arbftr.ry ,~ •• e "dat.Om _, .....0 P .-one tIM ! I apeced.t 2 . I J I I ~ ~

BEACH CHANGES, NARRABEEN BEACH I FIGURE 21 I I

I I I I ~ ~ ~ ---~-~----,------_.------.. _------,------" --,------_.-. ,." 1 .;; c

21 .. I . .! ·1 .. -t- ee i I 1 + + + + -I 1 I I I I I

I -j + I I

1 NOTEI: ,. T ...... rap .. port,s, ftM; dm...... c ...... "b - eeriel ~."d .0...... 0" .11. b ••,;" "I ••• " .... ,. •• ,. o. pllotopap"r .M .... KEY TO GRAPHS ...... d "0""'•••• .,.. d ...... d kom beach Ct••• - MctktM obtalneet pftolo.a_otrtce.., on o. Wild AC 1 .t.re. - , •• tthfttoo DUr.rence In •• nd volum ••. I Inatr..o", troca·C.f.IIA...... ograp .. ,. i. o UiI72 - 187. i + + + a. TIM dttf.....o..... UtMI ~ ..... obtelned .,..~ • .,. IIftd ..... + -I ~-.,- ...... d abo". Oat A.M.D. C ...., ••• M ...... ".t I betw._. an 1885 - ,&88 arbttre'Y .an. aloft, the bee. Mach and ttl. a ... Mach berwI OMtow I .... tOf eec" o.e .r ..... ' • .,.11,.. The cr... - OHt......

I ~ J I I I I I- I I i i ~ • ~ 1 • i i i - iI § ~ i

BEACH CHANGES, COLLAROY AND SOUTH NARRABEEN BEACHES I FIGURE 22 I ------

, ,

6300000

,.'.

.••'~~ 1>', • ., ,'.f'O ',,",,,,, Mamb.er.·" 1" ·,"174'" '-. B8<' ',' " ,.,~.,,1 .•;,., .... ' "'" /"'- • I' , ".' ~" t· .. ".'",.' , \""" ,;,"'" .,,'.' Be'a'Ch'" r~ - . 6299000

t;

Terriga1 6298000 I Beach -- l ~ 107 ~83 81 Line 13

6297000. • ./ L1ne 12

(~i. AVDca 6,296000 t Beach /'U..,. 173 " ~~-.. 59 61 60 64 ~~ --- 66 --e Line 9 6295000 '

i?~ 6294000

. 6293000

i'}; 6292000

6291000

~, 6290000 !~~

Line 5 6289000 I , , I , , , I I I I I I I I I I I I I . I· -.----.. ···353000· ··354000 -35500·()-'-356000;':'--::JS?OOO-· ·358000- 359000---3,60000- 361000" 36~000- . 363000'" AMB CDDrdinates

+ Shore Station If. <;> 1983/84 a Samp Ie Locat ion (Above line)

1986 x Samp'le Location (Below line)

Location of Gosford Offshore Profiles and Samples ., .~ FIGURE 23 ------_. ------, ---- Origin at Station 32. AMG 353765.2 E. 6292613.8 N Chainage (m)

1000 2000 3000 4000 5000 6000 7000

-E ~ -.J (f) H

~ 0 -30 r-f OJ ..Cl .c -40 -+-J Cl.. OJ 0 -50

I] -60 H 27/10/83 Sediment Sample Location a Gl C 28/ 8/86 - - - Sediment Sample Location # :rJ rn OFFSHORE PROFILES, GOSFORO LINE 5 N +- MacMasters Beach p ------_. ------. ---- Origin at Station 32, AMG 353765.2 E, 6292613.8 N Chainage (m)

400 600 800 1000

)'".

I] -15 H 27/10/83 + Sediment Sample Location 0 G1 C 28/ 8/86 x- - -x Sediment Sample Location {I ]) f1l OFFSHORE PROFILES,· GOSFORD LINE 5 N +- MacMasters Beach cr -- -' --- _. ------Origin at Station 24. AMG 354573.6 E. 6296151.9 N

""'::. Chainage (m) ·0 1000 2000 3000 4000 5000 6000 7000

169. :-. t"~\56 -10 .-'"'E

.~ ....J -20 (J) H

.<1'., 3 a -30 ,...-t OJ ..D .r::. -40 +J a. OJ 0 -50 I .." 66

~'I'(. -60 "H 2/11/83 Sediment Sample Location 0 G1 C .26/ 8/86 - - - Sediment Sample Location # II rn OFFSHORE PROF ILES, GOSFORD LINE 9 N lJl Avoca Beach p

~ , ------.. --- .. ------Origin at Station 24. AMG 354573.6 E. 6296151.9 N Chainage (m) a % ' ?Gn 400 600 BOO 1000 x, .., 168 x...... , , E , --- , , ~ , -5 -.J ~ -~~ (fJ \ \ H , ,~AREA = 320 m 2 ~ 0 \ r-f \ QJ \ .a , , -10 1: \ .j.J \ a. QJ 0

~., ." -15 H 2/11/83 + + Sediment Sample Location 0 Gl C 26/ 8/86 x- - -x Sediment Sample Location # JJ rn • OFFSHORE PROFILES . GOSFORD LINE 9 N U1 Avoca Beach 0------. - ,------Origin at Station 19. AMG 355137.9 E. 6298714.9 N Chainage (m)

o t M 2000 3000 4000 5000 6000 7000 fQ~\

-10 -E --- ~ '-20 --1 PROFILES POORLY U) ALIGNED. UP TO 75m H t ~" APART. ~ 0 -30 r-t OJ .0

.c 108 +J ~ 9 107 D. 11 106 -- -e OJ l --- .... - 0 -50

11 -60 ~ . .- IH 24/01/84 Sediment Sample Location 0 G1 C 26/ 8/86 -- - Sediment Sample Location # JJ rn OFFSHORE PROFILES. GOSFORD LINE 12 N 0- Terrigal Beach D ------.------, -- -- Origin at Station 19. AMG 355137.9 E. 6298714.9 N Chainage (m) 0 200 400 600 BOO 1000 ~:" ('164 i X \ , --E \1/ \ - \ \ 3: 2 ...:J -5 \~AREA = 100 m (J) H

~ 0 r-I OJ """ .a -10 .!: ~ 0.. OJ 0

......

-15.L ~...... ~ H " 24/01184 + + Sediment Sample Location ~'. .IeG1 0 IJ 26/ 8/86 x- - -x Sediment Sample Location # rn OFFSHORE PROFILES. GOSFORD LINE 12 N Q' Terrigal 8each c::r ------_. ------, ----

LIJ -60 H 24/01/84 Sediment Sample Location 0 G1

~,. ,e 27/ 8/86 - - - Sediment Sample Location # :u rn OFFSHORE PROFILES. GOSFORO LINE 13 N -.l Wamberal Beach (:) -- -- -' _. ------Origin at Station 18. AMG 355509.8 E. 6299729.9 N Chainage (m) 0 200 400 600 800 1000 I

~""" t I ~ _I( ,, -5 + \ X 2 " 'yAREA = 260m ,, ,, ,, ..... -10 + '\., t ~ i...... , ......

-i5 J. ~ "H 24/01/84 + + Sediment Sample Location 0 G1 C 27/ 8/86 x- - -x Sediment Sample Location # "'!- ,:0 rn OFFSHORE PROFILES, GOSFORD LINE 13 N -.J Wamberal Beach c- I .1 I I Warrie.ood Tur.metta Head I I I 19 I I I I I I I I Colla roy

I _. _.__ • 20/21.8.88 .oundlngUn•• I 0 __ 0_ 1878 to 1883 .oundlng nn •• ... I 8t24 e Shore Station No. 24 g .". ,.at .••• : Reef I A.M.G. CO-ORDINATES COLLAROY NARRABEEN BEACHES I OFFSHORE SOUNDING LINES /

------o

NOTES : Cruised Line shown in Figure 28. Reef locations shown In Figure 28. '?-t \ x Chainages taken along cruised nne. .--, \ en \ w \ Chainage origin is arbitrary. a::: \ f- \ Full survey details given In Appendix A. w \ L \ '-'~ \ I \ CAUTION : Comparison. between this and other offshore 3: \ -len ~ , profiles shQuld be made only after detailed' , , 3: 'x consideration of the above notes. IS:) -l 'X w~ x, ; 't 'X 0.- W 0 x, , 'X_ ~f -X- 'X 'X_ -x_ -x - ~+ - -x- - - ¥ ~Reef

~I I I I --t--+- I I +~.~ .. -~+---~-_+_--t_ I I I I I I 0 100 200 300 400 500 600 700 800 900 1000 lIDO 1200 1300 1400 1500 1500 1700 1800 1900 2000 CHRINRGE [METRES] i!>'i ~FFSH~RE PR~FILE COLLRROY-NRRRRBEEN LINE 1 [20.08.86-21.08.86J ; .~ ------.- - --- ClT .l-

NOTES : Cruised Line shown in Figure 28. \ Reef locations shown in Figure 28. \ x ~! Chainages taken along cruised -line. I (f) LL! Chainage origin is arbitrary. IY. l, l- \ Full survey details given in Appendix A. LL! X 2::: , '-I~ \ , \ CAUTION : Comparison between this and other offshore .3: , -l X (f) profiles shQuld be made only after detailed' ><., 3: consideration of the above notes. x -x- ;J

Lfl N, +t ;;:;, 1 I I .-+---'---r----+-----+---+-- .. -j------t----j------.+-----+------+--+------+------j---I-----+----j o 100 200 300 100 ;;00 bOO 7(10 '3D:: ':llll 1 (100 1!. DO 1,'00 1500 1400 1500 1 GOO 1700 1300 1 'lOO 200,: CHRINRGE [METRES] OFFSHORE PROF I cf- i=LJLLRROY -NRRRR8Ui'j LINE 2 [20.08.86-21.08.861 !t .;-~ ; ~ ------C)

\ tl NOTES: Cruised line shown in Figure 28. \ Reef locations shown in Figure 28. 1I1 \ 1 .l \ Chainages taken along cruised line. ~ X (f) \ UJ \ Chainage origin is arbitrary. IY I­ \ UJ \ Full survey details given in Appendix A. L '-'~ ~ , 1 , CAUTION : Comparison between this and other offshore 3: , -1 I x, profiles should be made only after detailed­ (f) ! consideration of the above notes. ~ t '>( UJ:'::.l m'l >-. ~ t ,< v-n, >.. / ' ./ ~ i ."'\ , x-' .. ~, .' .' ~+ 'X.- -- - ).('

lI1 N I I--~) Reef

~I +-- I I -f------!---t----t----+-- --+------+---t------f----t--+---+---f-----t-----+---I----t o 100 200 300 ,100 SUO 000 7[]0 3(1U ,)OU ! ODD lIOn !LoD 1500 1400 1500 1600 1.700 1300 1900 2000 CHRINRGE [METRES] "T1 OFFSHORE PROFILE CDLLRROY-N~RRRBE~_:-! LINE 3 [-20,08.8~-21.08.86J d'S" ", E; CD ...~ ------.------° 1, NOTES : Cruised line shown in Figure 28. j\ Reef locations shown in Figure 28. I 1 \ + \ Chainages taken along cruised line. (f) 1 ' W I Chainage origin is arbitrary. >\ , Full survey details given in Appendix A. ,-"01~ I , , \ , CAUTION : Comparison between this and other offshore ~,. t X profiles should be made only after detailed' ~ t consideration of the above notes. ~~~ " x co' i ;',

W _ " t t \ o 1 :'\- ~~ --. .. ;'\- "- - -;.<-

~ ;" x-- --'-- -;>~ >~~ / / ,- - "t ,'- / + t '-;< en c,,

~Reef ~ I---~) Reef

c ~, +----+----+----+--- t------1------1------f------+-- -\--- --. - 1------+------1--·- -- --I------f----I------f------1 ______1·------I----! o 100 200 30Cl

ClT 1

i NOTES : Cruised line shown in Figure 28.. : x.. -I- , , Reef locations shown in Figure 28. Cfl, x, Chainages taken along cruised line. ~ en "x UJ Chainage origin is arbitrary. 0:: ; I­ \ Full survey deta ils given in Appendix A. UJ \ :7t CAUTION : Comparison between this and other offshore ....J x en profiles should be made only after detailed

3= consideration of the above notes .. El . \ ....J i..LJLn m';' \ \ X Ii. " ,-' Cl.­ UJ >.,. o ." -- -". Cl N , ? x / >~ / , / , / x---"-

lf1 Ni ·1'

Reef ";;<--1 I--~~ Reef I

~, t-~ ,-- -+-, -<-- !.. . .,.-..... 1-· ...... ·/ ...... --/-.. ·--~ .. - .. -·-f-----t---.. -·.. I- .. - .... I-··-·.. -I-·--I-.. --/ o 100 200 3110 ·:[l'i ';lil) 1oI1i) 7011 'JilU 'lUll l0ll0 11(]O 1',:00 :5[10 1400 1500 'GllO 1700 1300 1900 ?OO,) CHq!NRG~ iMETRES]

"TI OFFSHORE PROF I U: UJi LPRCJi- !\jRRRRf3:~:; ; ,_IfJE 5 120.08.86-21.08.861 cO' c: •. CD... ~ i ------. ------.- - -- °T .+.

NOTES : Cruised line shown in' Figure 28. 1-~, Reef locations shown in Figure 28. :f) 1 " '1>;, Chainages taken along cruised line. ~ 1 \ \ Chainage origin is arbitrary. \ ~ t X Full survey detalisgiven in Appendix A. \ Lo \ '-'~ W I C'AUTION : Comparison between this and other offshore ~ i ;, --1 (j) profiles should be made only after detailed ;;." consideration of the above notes. \ . ~ 1 ., .-~~\ ,<:;- '- - )/:.' ",' d~+ .'"

'V'.- .- -->~ ~ I 'it, x , W o \ \ \ o N X I \

\ \ x- --x

Reef ....(f--~ I--~~ Reef

;J1 ~+ x t ~t-, , --+_ .._ .. 1--.... (- .....-+-_ .... ,...... f-.--.+- ..... ,.---.+.--.+----I-...- ... , o 100 200 300 JDr: 'iU(1 SliD JOO ,][1'1 :Oei ! [lUO liDO ! iOO 1.~OO 11)00 ! 'iOO ! GOO ! 700 1300 1900 :·:CJOD [HR!~JRGE [METRES] OFFSHORE PROFli.~~ ~ iRc;!.lt··fJRRRRt3f!'·' LINE G [20.08.86·'21.J8.861 ~c til ".'.~ ------Cl Jri '~

\ \ NOTES : Cruised line shown in Figure 28.

\ Reef locations shown in Figure 28. x' "'tI ' \ Chainages taken along cruised line. ,-, \ if) \ UJ \ Chainage origin is arbitrary IY. \ I- Fu" survey details given in Appendix A. w , L "- , '-';: \ I CAUTION : Comparison between this and other offshore 3: x, ,-1 profiles should be made only after detailed . if) x consideration of the above notes. x x "-

I x I- tL x~~ UJ ;)(--~ 0 X -- 7(,- - X.. t / \ \ / , \ , , / , / X / X ,'- - X \ , \ X \ \ \ ~+ \ x

Reef

I I I j-- I I I -, --t-- +----j-- I I I --j ~tI 0 100 200 300 ,j00 SOD bOO 700 300 ''lOO 1000 1100 1200 1300 1400 1500 1600 1700 1300 1900 2000 CHRINRGE [METRESJ

"T1 OFFSHORE PROF [Lt: [OU_RROY -NRRRRSEU: LINE 7 [20,08.86-21,08.86J e'; (.t,) -. (J'I ------.------Cl

". NOTES: Cruised line shown in Figure 28. .~ " " Reef locations shown in Figure 28. Vl " I 'x .I- Chainages taken along cruised line . 'fJ 4- \ Chainage origin is arbitrary. cr \ f­ Full survey deta ils given in Appendix A. UJ 2: \ ,-,0 \ I CAUTION : Comparison between this and other offshore :3 .-J K Ul profiles Should be made only after detai'led ';.~~ consideration of the above notes. :3 o --;-<',. '-, .-J UJVl :-<: Q)'-;< :r ',:, f­ CL UJ Q~i

I ><

-Xc - - ., ~Y:;- -- ,~- -* -- - -"\ ~ ":-' LI1 \ N \ I \ \ x" RMf~ x, ":' x, ~, I -f-- -~-~ - ---- ._~ __ .. _n . --+- ---- ,-----+----t----..... +-.-----1------1-.--+------f-.. ---- -. -1-----t---::..x-t------I o 100 200 300 10[1 SOD GUO "liD 'we lOD 1000 1100 1200 1300 1400 1500 IGOO 17 00 1300 1000 2000 CHRINRGE [METRES] OFFSHORE PROF J U-~!: . _PROY -i,iRF:RRBt~:.! ~INE 8 [20.08.86-21.08.86] "TI ~. a (,) (I) ------

C)

\ NOTES : Cruised line shown in Figure 28. \ Reef locations shown in Figure 28. 1I1 1 \ I , \ \ Chai.nages taken along cruised line. x \ Chainage origin is arbitrary. et:: \ e- \ , Full survey details given in Appendix A. UJ~ f \ - ! L \ ~a I x CAUTION : Compari~on between this and other offshore 3: I '- --.l (J) profiles should be made only after detailed v -, ,~ J. 3: l 'v consideration of the above notes. 0 + ,~ ..;J w:.f1 '~~ CD""; -,."'.,~

:r " ~... :. "- Q.. ;.:'..... UJ Cl -x

C) N 'x , I "x

;~. -K r -", - 1I1 N --x.. 'X- -~'<

I I ------1------'----,------+------+---- - f----_ ... -+------l--f I I I-----I---j ~I I o 100 200 300 ,IOD 'ill 0 GilD 7110 ,lOU 'lllO IUClO I; 00 1:'00 1300 1400 1 ~)OO I GilD lIDO 1300 1900 2000 CHRINRGE [METRES] OFFSHORE PROFILE Cn~LRROY-NRRRRB[EN i_INE 10 [20.08.86-21.08.86J «5. "c: CD Cot) ..... ------. ------aT 1 1 ',1.. NOTES : Cruised lines shown in Figure 28. Reef locations shown in Figure 28.

(f] W Chainage origin is arbitrary. 0::: f­ "'-- Full survey details given in Appendix A. W L: ,-,0 I CAUTION: Comparison between this and other offshore 3: .-J (f] profiles should be made only after detailed consideration of the above notes. 3: 18 x, .-J "" "" w~ " OJ I "'''. I '- 'X. (L w o + / "'. ~ .~ ... ~ // ",~, ~I ""'-x'/ "<."-. "- " ",-v ~t " ~ I--~' Reef -+---I--.u-I.----- ,I . ---.------j- ---. -i------t-.------f------j--I----j--...... ,--+_ ::;;I t o 100 200 300 "Del 'illl hi.lO )(10 emu ,)ClO ll1DD 11 DO 1LOO 1500 1400 1'iOO 1GilD 17(]O 1800 1'l00 2000 CHRINRGElMETRESJ OFFSHORE PROF I i..t C,Ji.!Jli\lJr'-r·JRRRR8f-;: L I ~I[ J) (25.09.79) ~; ~ - - -. - - -. _. ------, - .------o

NOTES: Cruised line shown in Figure 28. '", Reef locations shown in Figure 28. ,-, en Chainages taken along cruised line. i.IJ 0:: Chainage origin is arbitrary I­ i.IJ :L Full survey details given in Appendix A...... ,0, :3: CAUTION : Comparison between this and other offshore en--J . . profiles should be made only after detailed o~ consideration of the above notes. --J QJ;"i.IJ'" I '- i:L i.IJ o

o N,

en N,

~, I I I I I I I I I I I o 100 200 300 400 500 600 700 300 900 ! DOD ! 100 1200 ! 30Q 1400 ! SOD 1600 1700 ! 500 ! 900 2000 CHRINRGE [METRES] "T1 . ~FFSH~RE PR~FILE COLLRROY-NRRRRBEEN LINE 18 (19.11.79) <5' c: @ CA) co ---- - .- _. ------o

NOTES : Cruised line shown in Figure 28. Reef locations shown in Figure 28. ":'t Chainages taken along cruised line. ~ (J') Chainage origin is arbitrary w a::: I­ Full survey details given in Appendix A. w :::E ....,::::J CAUTION: Comparison between this and other offshore I ~ --.J profiles. should be made only after detail~d (J') ..... consideration of the above notes . 3: o --.J LJ..JLf' CD";' I L- a.... i.L.J o

o N I

"-"-", N '"I Reef ~ x t ~R~f ~ I I I I o 100 200 300 .100 500 000 700 300 900 1000 11 00 1200 1:;00 1400 ! 500 1600 1700 1300 ! 900 2000 [HRINRGE [METRES]

"T1 OFFSHORE PROFI~E COL~AROY-NRRRqB~EN LINE 19 (19.11.79) cO· c: (])... oJ:o. ------.-~------Cl

NOTES : Cruised line shown in Figure 28. '", Reef locations shown in Figure 28. ~ + Chainages taken along cruised line. w i Chainage origin is arbitrary v '~::: 1 Full survey details given in Appendix A.

CAUTION: Compar·il?on between this and other offShore profiles should be made only after detailed ~io + GJ~l consideration of the above notes. OJ , 1 ~ t ~~

°'11 1 I IE Reef )1 J~~ " r<">., o 100 200 300 400 seD 600 7QO 380 300 1000 I!OO i200 1300 1400 1500 1600 1700 1600 1900 2000 CHR!NRGE [METRES]

"'~i:'SH"'·""'E p~",~ T' .- r(' "f'1p~r-.:::>-·NI U!I I :... Ji~. : (\~i _L....t: L.\•• J:_~:--t~\ "):;lClv ! -!-:~:\r\~u:'. ,'-- T... I"cc \ t- !'. 11.... 1 (10.. 02 83) "TI cO· t: CD ~.... 1_.- _ ... - -.- or ------

•1.fr ... :Il I NOTES: Cruised line shown in Figure 28 ...... , Reef locations shown in Figure 28 . en w 0::: Chainages taken along cruised line. I­ W Chainage origin is arbitrary ::E ...... 0 I Full survey details given in Appendix A. :3: -.J en CAUTION: Comparison between this and other offshore :3: o profiles should be made only after detailed -.Jw'" CO-;' consideration of the above notes. I L- i:L w o ~ ° '"I

'" ~--+, '"I Reef

'J.,

~ +----+----+----+----+----+----+----+----+----+----+---~----+_--_r----+_--~--~----;_--_+----+_--~ a 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 CHAINRGE CMEiRESJ ." OFFSHORE PROF I LE CLlLLARClY -NARRRBEEN U NE 1112 (10.02.83) ell c: CD ~ I\) -----o - _. ------

'", NOTES : Cruised line shown in Figure 28. ,--, ~ Reef locations shown in Figure 28. i.U '\ Q::: \ !- Chainages taken along cruised line. '-'.J \ L ,-,:::1 Chainage origin is arbitrary 3:'1 -l Full surv~y details given in Appendix A. ttl CAUTION: Comparison between this and other offshore o3: -l profiles should be made only after detailed COli.U'" ~. '\ consideration of the above notes. \ 1 \ C~ I \ 1 \ OJ N I

\ \ \

\ " "'/ \v~ ~!

1 Reef ~

'I ' I I I I ;;;;I t o 100 ZOO 300 lOO 500 COD 700 SOD 900 ! 000 1 ! 00 ! 2ao ; 300 1400 1500 lSGO 1700 1300 ! 900 :2000 ~HnT~ln~- rME-Rc~J :"""1 ~.!. 1~~UC. L I 1-,:) "'FFSHr'lR~t. DRr'lC c ORr'I)' _loI"Pt::' n c ',j U U I \L!j I:'-~ ...... "n' U:.....~,.!.~ . ~r-1 \: \"1 3:::....._1. UNE 151 (10,02,83) cO' "c: ~ ,Jl. Cot) -,- -- - - _.------,- .. --" 0_+

.L

NOTES : Cruised line shown in Figure 28. ",I Reef locations shown in Figure 28. -,. ~. i Chainages taken along cruised line. Chainage origin is arbitrary ~ l' LLJ Full survey details given in Appendix A. ~c:1 :'1 CAUTION: Comparison 'between this and other offshore ~ 1 1,. profiles should be made only after detailed 3: • i o 1 consideration of the above notes. -l,~ LLJ';:.; CD 1 :J: ~ CL LLJ o

C ',' N I

.;:-: ~t

-". ~ to 100, 200" 300 400 500"'" 600 700 300 900 1000 1100 1200"" 1300 1400 1500 1600 1700 ISOO 1900 2000, CHqINRGE [METRES] , -n ClFFSHClRE PRClF Itt COLLRROY -NRRRRBEEN LI NE 254 (07.04.83) cC c: CD t ______. ______-_tH-iiiti:6_--·b"·"W~1t .I

0- I 1 •

",1\~ NOTES: Cruised line shown in Figure 28. 't \, Reef locations shown in Figure 28. ., t8 + \\ Chainages taken along cruised line . ~. \ I- .L Chainage origin is arbitrary ~ t 'X Full survey details given in Appendix A. ,-,0 ~i'I CAUTION: Comparison between this and other offshore ~ t profiles should be made only after detailed ~ t consideration of the above notes. w'" en";' I L- a.. w c ~f \ • ~t r Ree!

"(: ... ;, OLf~~~~~~~~~~~~ a 100 200 300 400 500 600 700 aDo 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 CHRINPGE [METRES] ""T1 ~FFSHORE PR0FIL~ COLLRROY-NRRRPBEEN LI NE 255 (07.04.83) d5" ~ ~ (71