Beach erosion at Waihi Beach Bay of Plenty, New Zealand

Abstract Since the 1940s, severe dune erosion has threatened property at Waihi Beach. This paper investigates beach erosion and dune recession in relation to wave climate, sedimentoldgy and mineralogy of the beach sediments, cyclical beach changes and sediment budget, and the littoral drift. Average dune recession along the entire beach between 1948 and 1977 was 27 m, although maximum recession recorded to 1977 was 83 m. Sand loss rates 1948–1977 average 3.4 m 3 per metre of beach per year. The sediment budget of the entire beach is about 850 × 10 3 m 3 and up to 74% of this was recorded as being ‘cut’ from the beach in one erosive episode. The cut and fill cycles are dominantly controlled by wave steepness, which has a critical value of 2.1 × 10 −3 for breaking waves on Waihi Beach. Net littoral drift is towards the south‐east, and the basic reason for beach erosion at Waihi Beach is the lack of sediment to supply the littoral drift.