NSW Coastal, Ocean & Port Engineering Panel (COPEP) Half Day Seminar (August 2012) SYDNEY HARBOUR Sea Level Rise Vulnerability Studies Phil Watson Principal Coastal Specialist Office of Environment and Heritage NSW Department of Premier and Cabinet Acknowledgements… Doug Lord, Manager Coastal DECCW * Cath Snelgrove, Cultural Heritage Manager, Sydney, Parks and Wildlife Division DECCW * * (as at November 2009) Outline of Presentation Background Guided tour and brief history lesson Vulnerability assessment Management considerations Conclusions Background… Plan of Management being prepared for Sydney Harbour National Park (SHNP) SHNP contains some of the key and iconic national heritage assets at obvious threat from projected sea level rise Significant investment of public funds foreshadowed to preserve heritage assets Vulnerability studies would provide fundamental strategic advice to inform the above-mentioned Background… Separate pilot studies for Fort Denison and Goat Island Fort Denison completed November 2008 Goat Island completed January 2009 Both studies available on the internet Outline of Presentation Background Guided tour and brief history lesson Vulnerability assessment Management considerations Conclusions Guided tour..… Fort Denison SYDNEY HARBOUR Courtesy Google Maps Courtesy Tourism NSW Courtesy Tourism NSW Historic Context…… Once a rocky outcrop some 25m high known to Aboriginal people as “Mat-te-wan-ye” In 1839 two American sloops entered the harbour undetected raising fears about the apparent inadequacies of Sydney's defences In response, the island was quarried to create a level gun battery which was completed in 1842 Further concerns about defence capacity arose due to the outbreak of the Crimean War (1850s) Courtesy Tourism NSW Historic Context…… Plans were drawn up for a fortification with barracks and the characteristic Martello Tower Work involved quarrying some 8000 tonnes of stone from the Island itself and from nearby Kurraba Point, Neutral Bay In 1857 the facility was named Fort Denison after Governor Denison and was declared ready for battle with 10, 8 and 12 inch 32 pounder cannons Courtesy Tourism NSW Historic Context…… Guns were never needed outside of practice and no shots ever fired in anger The Fort was abandoned as a military facility in the 1870s. At this time the development of iron clad ships and improved weapons made the facility obsolete Harbour defences moved to the outer harbour from this point onwards Courtesy Tourism NSW Historic Context…… The first measurements in the State Tide Register were recorded at Fort Denison in 1866 Continuous reliable tide measurements have been recoded at Fort Denison since 1914 Fort Denison is one of the 2 longest ocean water level records in the southern hemisphere Courtesy Tourism NSW Goat Island Fort Denison SYDNEY HARBOUR Courtesy Google Maps Courtesy DECCW Historic Context…… Bennelong and his wife Barangaroo, were often seen here claiming a special relationship with the Island During the early 1830s sandstone quarries were established on the Island until it was reserved for future defence needs In 1832 Governor Bourke chose the Island as a gunpowder magazine complex with work commencing using convict iron gangs Courtesy DECCW Historic Context…… By 1839 the complex was complete with cooperage, large magazine, sentry compound wall, barracks, kitchen and stone wharf During the late 1830s Colonial Government identified the eastern tip of the Island as suitable for a Water Police Station In 1853 additional gunpowder magazines were added and by 1861 the Island housed over 700,000 pounds of gunpowder Courtesy DECCW Historic Context…… By the 1860s the Water Police Station had been appropriated for storing additional explosives such as guncotton and nitro-glycerine By the 1880s explosives were also being stored at Spectacle Island and the Newington Armoury By the turn of the century Goat Island was only housing low grade commercial explosives and small arms cartridges Courtesy DECCW Historic Context…… With the outbreak of the Bubonic Plague in 1900, the Sydney Harbour Trust was established on Goat Island with a dredging and fire-fighting depot and a grand residence for the Harbour Master The MSB was established in 1936 incorporating the functions of the Trust The MSB constructed wharfage around the Island and developed the shipyard facility Courtesy DECCW Historic Context…… By the 1990s the role of the MSB had changed significantly and Goat Island was determined surplus to needs Goat Island was transferred to NPWS in 1994 and added to the SHNP in 1995 From 1995, the Island was the production home of the long running Australian drama series “Water Rats” Courtesy DECCW Outline of Presentation Background Guided tour and brief history lesson Vulnerability assessment Management considerations Conclusions Vulnerability Assessment…… Survey data (bathymetry and assets) Water level & wave data (current) Up-to-date advice on sea level rise Design water levels for future planning horizons (incorporating sea level rise) Correlating design water levels with assets levels of interest (decks, floor levels, crest of seawalls, etc) Management considerations Vulnerability Assessment…… Survey data (bathymetry and assets) Survey Data DECCW Fort Denison Survey Coverage Vulnerability Assessment…… Survey data (bathymetry and assets) Water level & wave data (current) Design Water Levels (Fort Denison) 2.60 2.40 2.36 2.20 2.16 2.00 1.80 1.60 1.40 Calculated Extreme Maximum Tide Level Extreme Maximum( Level m ISLW) Tide Data (Max Levels) 1.20 1.00 0.001 0.01 0.1 1 10 100 Return Period (Year) Gumbel distribution, co-efficient of correlation = 0.9997 Design Still Water Levels (Fort Denison) ARI Maximum Level (years) ISLW (m) AHD (m) 0.02 1.89 0.965 0.05 1.97 1.045 0.10 2.02 1.095 1 2.16 1.235 2 2.20 1.275 5 2.24 1.315 10 2.27 1.345 20 2.30 1.375 50 2.34 1.415 100 2.36 1.435 200 2.38 1.455 Design Wave Climate (3 Types of Waves) Ocean swell waves (large well defined wave fields, generated remotely with periods generally >6-7 seconds) Local seas (wind generated wave fields, governed by the wind strength and duration and length of water over which waves can build, periods generally <5-6 seconds) Boat waves (highly variable with wave heights commonly <1-2m with periods ranging up to 10 seconds) Design Wave Climate (3 Types of Waves) Ocean swell waves (large well defined wave fields, generated remotely with periods generally >6-7 seconds) Local seas (wind generated wave fields, governed by the wind strength and duration and length of water over which waves can build, periods generally <5-6 seconds) Boat waves (highly variable with wave heights commonly <1-2m with periods ranging up to 10 seconds) These studies combined wind and boat waves into an “equivalent design wave” field based on wave power and applied them in the form of a sensitivity analysis to determine design wave runup levels Courtesy DECCW Boat Waves in Sydney Harbour Location Craft Class Averages Maxima Distance Power From Sail (W/m) (5) Hmax T Hmax T Line (m) (m) (sec) (m) (sec) Hydrofoil 0.45 2.3 0.72 2.0 50-100 1017 Lady Ferry 0.25 2.2 0.44 2.2 418 Sydney Cove Water Taxi 0.38 2.2 0.44 1.8 342 Manly Cove Hydrofoil 0.56 2.4 0.87 2.6 50-100 1931 River Cat 0.32 8.4 0.40 10.0 100-200 1570 First Fleet Ferry 0.45 4.0 0.54 4.3 1230 Drummoyne Cruiser 0.2 2.6 0.25 3.0 184 River Cat 0.45 4.0 0.60 5.2 25-150 1837 Pulpit Point First Fleet Ferry 0.2 2.3 0.25 2.5 153 25m Cat Ferry 0.62 2.0 90 754 Sydney Harbour Lady Ferry 0.39 2.8 418 Source: Edwards and Lord (1995) Wind Waves around Fort Denison Dir. Max Wind Speed Des. Fetch Fetch Hmo Period Power (1) F* Wind (m) eff Limit. (m) (s) (W/m) Speed F* (Y/N) U km/h m/s 10 (m/s) N 70 19.4 17.9 1130 34.5 153.2 Y 0.33 1.5 166 NE 70 19.4 19.9 1330 32.9 130.8 Y 0.41 1.7 276 E 80 22.2 22.8 2950 55.8 107.1 Y 0.71 2.3 1160 SE 100 27.8 28.5 1190 14.4 76.6 Y 0.59 1.9 654 S 110 30.6 31.3 1000 10.0 66.4 Y 0.61 1.9 683 SW 90 25.0 23.1 910 16.8 105.1 Y 0.40 1.6 250 W 90 25.0 23.1 1650 30.5 105.1 Y 0.54 1.9 553 NW 80 22.2 20.5 780 18.2 125.4 Y 0.32 1.4 146 Vulnerability Assessment…… Survey data (bathymetry and assets) Water level & wave data (current) Up-to-date advice on sea level rise Global Average MSL Rise Predictions IPCC (2007) Global Average MSL Rise Predictions 91cm 79cm Regional Variations Ice Sheet Uncertainty 59cm Model Outputs (IPCC 2007) 18cm IPCC (2001) Advised SLR Estimates for Vulnerability Assessment Sea Level Rise Scenario YEAR 2050 YEAR 2100 Lower Bound Estimate (LOW) 4 cm (1) 16 cm (3) Medium Estimate (MED) (5) 21 cm 53 cm Upper Bound Estimate (HIGH) 38 cm (2) 89 cm (4) Note: Prior to NSW Government SLR Policy Statement (2009) Vulnerability Assessment…… Survey data (bathymetry and assets) Water level & wave data (current) Up-to-date advice on sea level rise Design water levels for future planning horizons (incorporating sea level rise) Design Water Levels (incorporating sea level rise) ARI 2008 Design Still SLR Scenario 2050 Design 2100 Design (Years) Water Levels (L, M, H) Still Water Still Water (m AHD) Levels Levels (m AHD) (m AHD) 0.02 0.965 L 1.005 1.125 M 1.175 1.495 H 1.345 1.855 0.05 1.045 L 1.085 1.205 M 1.255 1.575 H 1.425 1.935 0.10 1.095 L 1.135 1.255 M 1.305 1.625 H 1.475 1.985 1 1.235 L 1.275 1.395 M 1.445 1.765 H 1.615 2.125 20 1.375 L 1.415 1.535 M 1.585 1.905 H 1.755 2.265 50 1.415 L 1.455 1.575 M 1.625 1.945 H 1.795 2.305 100 1.435 L 1.475 1.595 M 1.645 1.965 Note: Prior to NSW Government H 1.815 2.325 SLR Policy Statement (2009) Vulnerability Assessment…… Survey