Dynamics of a wave-dominated tidal inlet and influence on adjacent beaches, Currumbin Creek, Gold Coast, Australia

Currumbin Creek on the Australian Gold Coast is a wave-dominated tidal inlet which exhibits a particularly active morphology. The recent history of Currumbin Creek entrance has seen rapid growth of the entrance for access to the ocean by fishermen, as a world class surfing site, and as a recreational area. Before the construction of two groynes in the 70's, Currumbin Creek entrance was highly variable in terms of inlet location and sand bar characteristics due to a cyclical behaviour of spit migration. Nowadays, the entrance is stabilised. However, natural processes continue with the entrance infilling causing flood and navigation issues, resulting in a regular dredging program to maintain an open entrance and for regular beach nourishment plans.This paper investigates the behaviour of the entrance and adjacent beaches from aerial photographs and numerical modelling. Before groyne construction, sand by-passing was intense resulting in channel migration and sometimes the closure of the mouth. After training works, the longshore drift is diverted further north from the mouth leading to new circulation patterns behind the headland. During fair weather conditions, the sand transported by the longshore current is trapped by Currumbin rock groyne resulting in a negative sediment budget in Palm Beach. For high energy conditions, the diverted longshore current splits in the southern Palm Beach, resulting in a circulation cell. The sediment of the southern beaches is stirred up and transported both northward and toward the inlet.