Indian Ocean sea’s and swell combine with longshore currents to generate sediment dynamics in which form wave-breaker sandbanks, producing surfable waves along the majority of Bunburys coast.

Bunbury’s western beaches and surf-waves evolve throughout the year. Isolated surfing breaks, including specific rock outcrops (Hungry Hollow, Whippys, BP reef’s, and Surf Club), natural and artificial headlands (Sidewash, Groyne & Fraggles, Bay and The Wall), and stretches of beach no longer than hundreds of metres (Hungry Hollow, Bay), each produce a diverse range of waves dependent on the seasonal meteo-ocean factors influencing the locations.

In general, the higher quality surfable waves at these locations alternate between dominant seasonal northern (north-south) and southern (south-north) currents and swell, and the sediment dynamics respective of these marine flows. Infra-gravity waves (wind and shorter period waves) do occur throughout the year, and do produce some fun quality surf, but do not compare relative to the larger, longer period swell waves generated during these two dominant seasonal marine states.

Bunbury’s surf waves in winter predominantly break right. The northern marine flows generating these waves arrive from origin storms in the central-west basin of the Indian Ocean, northwards of 20° below the equator. The cleanly formed and organised long-period gravity swell waves maintain the majority of their origin energy, un-impeded along their fetch, and maintain shoreline incident angles which favor low peel rates and longer peel lengths. The northerly winter waves in Bunbury are characterised as tall right-hand wave peaks with longer open-faced right-hand wave walls, conducive to higher quality surf waves in the area (Figure 3).

The marine flows also aid in scouring inshore sediment, moulding the bathymetry with longshore transport and inshore deposition processes. The northern flows develop the inshore bathymetry over the winter season to further produce sandbanks which promote alignment with the northern swells, increasing ride length and surf quality in general, dependent on the the latitudinal and longitudinal origin of the storm (affecting swell direction and fetch, respectively). This developing process further contributes to inshore sediment dynamics, enhancing the sandbanks influence to surf quality, and producing longer right-hand rides with hollow ‘tubing’ wave sections which are desired by surfers above the intermediate level.

The alternate occurs the remainder of the year, with the southern flows advancing around Cape Naturaliste and refracting into Geographe Bay, re-directing deposition processes to produce predominantly longer and more consistent left-hand sandbank formations and waves (Figrue 4). The diffraction of these Southern Ocean swells around the Cape direct the majority of longer period surface-gravity swells to arrive in Bunbury from bearings of ~280° or greater.

Strong Southern Ocean swells regularly transmit through the prevailing northern winter marine flows, with intense austral winter storms generating large (+2 metres), long period (+16 second) swells that either dominate, or combine with the predominant northern winter swells and surf. These conditions create intense and variable surf along Bunbury’s coast that can be dangerous and only for the experienced surfer.

Ideally, the conditions most favored for surf in Bunbury is either one of the two dominant seasonal states, northern flows with long walled right-handers, or southern flows with long walled left-handers. The two dominant marine flows generally occur in Bunbury from northern currents occuring through winter from May to August, and southern currents which occur through summer from September to April. Other wave-types do of course occur within these dominant conditions, producing alternate wave-breaking directions to the general marine flow, such as large wedgeing waves formed from headland reflection (Figure 5).