Coastal Damage and Coastal Protection in NSW

James Carley

Senior Coastal EngineerWater Research Laboratory

University of New South Wales

Indigenous coastal engineering

Aboriginal fish traps Arrawarra NSW, circa 1000 ADAlso at Point Plomer, (near Crescent Head)

Chronology: Pre 1900• Circa 1000 AD: Rock fish traps were constructed at Arrawarra near Coffs

Harbour by indigenous inhabitants.• 1818-1846: “Macquarie Pier” at Hunter River mouth, Newcastle – a

breakwater/training wall.• 1854: Australia’s first reported breakwater was constructed at Port Elliot

(SA), with a paper on this structure presented to the Institution of Civil Engineers in London in 1858 – the first for an Australian civil engineering project (Gourlay, 2000).

• 1877 and 1885: Visit to Australia by Sir John Coode, engineer in chief for the British Admiralty.

• 1890s: First seawalls commenced on Sydney beaches (eg Manly).• 1890 to 1910: Construction of numerous breakwaters/training walls on

the NSW coast.

Coffs Harbour (1914)

First stone breakwater 1914 (SLNSW)

Coffs Harbour (1916)There are now approximately 70 breakwaters (/training walls) in NSWThe north coast railway in 1910s reduced the reliance on coastal shipping

Manly 1870s

MANLY 1870s (ENGRAVING)

Manly 1895

Manly 1912

MANLY, MAY 1913

Newcastle Beach c1900

Chronology: 1900s 1938: The work of Spanish engineer Iribarren (1938), “A formula for the

Calculation of Rock-Fill Dykes” published in Spanish, which was translated to English by the US Beach Erosion Board in 1949. This related the size of rock armour required to the incident wave height.

1953: The work of Hudson (1953), “Wave Forces on Breakwaters”. This related the size of rock armour required to the incident wave height.

1957: US Army Corps of Engineers/ US Beach Erosion Board “Shore Protection, Planning and Design, Technical Report Number 4”, with revised editions in 1957, 1961 and 1966.

1973: Publication of the US Army Corps of Engineers “Shore Protection Manual”, with revisions in 1975, 1977 and 1984.

1984: BS 6349 – 1984, “British Code of Practice for Maritime Structures”. 1990: First IPCC report on climate change. 1991: Publication of the CIRIA Rock Manual, which was revised in 2007. 1998: Oliver et al (1998), “Condition and Performance Rating Procedures

for Rubble Breakwaters and Jetties”.

Sydney’s sea defences (Gordon, 1989)

SYDNEY’S 23 km of open coast sandy foreshore• Seawalls 5.6 km• Rubble revetments 1.4 km• Dunes (artificial) 13.5 km• Featureless 2.6 km

• Most seawalls built 1880s to 1930s• Typical seawall toe level +2 m AHD• Toe level range 0.0 to 4.7 m AHD• Crest level range 2 to 7 m AHD

Seabee seawall, Cronulla (constructed 1980s)

Sandstone seawall and promenade - Manly

Stockton

Groynes and NourishmentLady Robinsons Beach

Documented damage and failures• CIRIA (1991) found that 36% of seawall failures (1980s) in the UK

were due directly to erosion of the toe and a further 14% were partly due to it (50% in total)

• Blumberg and Rhodes (1995), PBP (1995) identified nine episodes of damage to portions of the Manly seawall over 108 years – once every 12 years on average (typical ~200 m)

• Blain Bremner Williams (1985): • >40 NSW houses lost to coastal hazards in last 100 yrs.• Emergency management has saved more than 200

structures.

• Many structures have been removed from active zone.

North Steyne, Manly 1950

Belongil, Byron Bay13/07/1972

SEPTEMBER 1977

c1999

2001

Freshwater SLSC 1974Near miss for surf club - Sewer lines lost

Bilgola 1974

Sheltering Palms/North Beach

1977:17 houses abandoned

19761975

Beachfront house collapse Wamberal 1978

Dee Why 1998

Old Bar 2008 - 2009

COFFS HARBOUR MAY 9:30 am 24 May 1999

Northern breakwater, Coffs Harbour

Fairy Bower, Manly 27/06/2003

Chronology: 2000s

Numerous PIANC synthesis documents. 2006: Publication of “The Coastal Engineering Manual” coastal

structures chapter. 2007: ISO 21650:2007, “Actions from waves and currents on coastal

structures”, from the International Standards Organisation. 2007: EurOtop overtopping manual

Upgrade of toe of historic seawalls. Rebuilding of damaged structures. Temporary and trial structures from sand filled geotextiles. (Outside of NSW) Sand as protection.

Upgrade of toe

Cronulla - Damaged gabions (14/08/1986) and repair (2008)

Upgrade of toe: South Curl Curl

August 1976

July 2002

South Curl Curl, 2006

North Steyne, Manly upgrade of toe

1974

2010

Replacement: Dee Why (1998 – 2000s)

Collaroy-Narrabeen 1920 (early “geobags”)

Stockton SLSC: First modern geobag structure NSW

1996 1999

20012009

Temporary groynes and seawallMaroochydore QLD early 2000s

Trial geocontainer offshore breakwater (early 2000s SA)

Kirra 1936 and 2004

With sand bypassing/nourishment

Summary and chronology

• Low impact pre colonial structures (eg fish traps).• Breakwaters, training walls and ports.• Seawalls for promenades.• Hard seawalls for protection.• Repairs or replacement of old seawalls.• Temporary and trial geotextile structures.• Sand as protection.

Discussion