The just-released Ōtaki Beach coastal hazards report is an interesting read. While Ōtaki Beach is not Waikawa Beach, nevertheless it is our next door neighbour and a boundary line on a map doesn’t mean a clear demarcation in physical processes. It would be reasonable to think that the comments about Ōtaki Beach could well apply to Waikawa Beach too. Surely at the very least, the following paragraph could be generalised to Waikawa Beach too:
The open coast at Ōtaki Beach is mostly sandy beach (photo A) backed by sand dunes. It also has gravels from the Ōtaki River (D). Sand is supplied to this area by the persistent southward longshore transport of sediments from the four large rivers to the north (Whanganui, Whangaehu, Rangitikei and Manawatu Rivers). The supply rate is greater than the transport losses to the south, resulting in long-term shoreline growth. The dunes provide protection to the Ōtaki Beach settlement, acting as a 30–80 m wide buffer between the beach and Marine Parade. The almost continuous dunes and stopbanks provide good protection from coastal flooding, but there are low areas around accessways where water can run up into the dunes in large events.
For more read the Kāpiti Coast District Council Coastal report pages.