Four approaches to size armourstone have been investigated to account for uncertainty within nearshore wave estimates. A deterministic design approach combined with a joint probability analysis resulted in a stable rock armour weight of 9 tonnes. The use of an ultimate limit state based the unlikely scenario of a 200-year wave, water level and 95th percentile climate change estimate occurring simultaneously resulted in rock armour of 13 tonnes. The use of a probabilistic design incorporating partial safety factors resulted in rock armour of 20 tonnes. The use of Monte Carlo approach indicated an armour weight of 12 tonnes would capture 95% of the uncertainty within simulated 200-year extreme events, which is supporting the ultimate limit state calculations.
Index Terms—Breakwater, probabilistic design, rock armour.
The authors are with JBA Consulting, Broughton Hall, Skipton, UK (e-mail: danielrodger@jbaconsulting.com, joshharris@jbaconsulting.com).
Cite:Daniel Rodger and Josh Harris, "Reducing Design Risk for a Nearshore Breakwater in the Orkney Islands," International Journal of Environmental Science and Development vol. 5, no. 5, pp. 479-483, 2014.