Keppel Sands shoreline changes due to engineering structures: Monitoring and modelling

Keppel Sands beach (Capricorn Coast, Qld) has been vulnerable to the possibility of severe erosion and the existing rockwall may not survive a severe storm (storms having a return period of 50 years). One of the options accepted by the Livingstone Shire Council to improve beach safety and stability was the construction of a groyne. The groyne, 80 m in length, was constructed in 1982 and extended another 100 m in December 2001. This extension was recommended on the assumption that the extended groyne would work as a headland, helping to form a pocket beach and consequently creating the possibility of the natural accretion of sand in front of the existing rock wall. Monitoring of coastal changes along the Keppel Sands beach, before and after construction of the groyne extension has been carried out, together with theoretical analysis of predicted changes to the shoreline. The GENESIS model shows sand accumulation in front of the rock wall as a dynamic process where sand will not stay permanently, whereas the crenulate shaped bay reveals it as a permanent process. In both cases it was found that an extended groyne would not create significant sand accumulation to cover the whole length of the existing rock wall.