Kingscliff seawall design
Project Partner: Haskoning Australia
Client: Tweed Shire Council
Project Reference: 2011073, 2012031, 2014051
WRL Technical Reports: Alternative Terminal Seawall Designs and Beach Nourishment (2011/25), Groyne Field Assessment (2012/18), Detailed Concept Terminal Seawall Design (2014/15)
Following storm erosion episodes between 2009 and 2012 which severely impacted the Kingscliff Beach Holiday Park and other public assets, Tweed Shire Council engaged WRL in partnership with Haskoning Australia to prepare the design for a long-term terminal seawall.
This seawall would extend along the foreshore between the existing rock seawall at the Kingscliff Beach Bowls Club and the existing secant pile seawall at the Cudgen Headland Surf Life Saving Club to protect built assets at immediate risk from coastal hazards. It would replace existing interim rock and sand-filled geotextile container structures along this stretch of coast.
Following consideration of a range of preliminary seawall design types (including an alternative protection scheme with a groyne field); a composite seawall design was adopted with:
- A rock seawall section at the northern end; and
- A stepped concrete section at the southern end.
As a result of two-dimensional physical modelling undertaken by WRL, the rock armour mass for the rock seawall section was reduced by more than 25%, the structure slope was steepened (reducing its footprint) and the expected wave overtopping rates were found to be lower compared with the preliminary design.
The maximum horizontal wave forces measured on the stepped concrete section in the wave flume were found to be between preliminary design estimates using two different desktop techniques. The physical modelling also demonstrated that, under the same wave conditions, wave overtopping on the stepped concrete section was comparatively higher than the rock section with the same crest level and similar slope. As a result, the crest level of the stepped concrete seawall was increased by 0.5 m (an extra bleacher) from the preliminary design to maintain acceptable wave overtopping under design conditions.
Construction of the stepped concrete and rock seawall sections commenced in March and April 2017, respectively and is expected to be completed by November 2017.
Links to our coastal engineering conference papers on Kingscliff Beach are provided below:
- Concept Groyne Field Design (Coghlan et al., 2013)
- Preliminary Rock Armoured Seawall Design (Coghlan et al., 2014)
- Physical Modelling of Rock Armoured Seawall (Coghlan et al., 2016)
- Physical Modelling of Stepped Concrete Seawall (Modra et al., 2016)
For further information contact:
Kingscliff erosion in the media