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restriction on the location of dwellings – given the existing beachfront yard setback requirement. 4.12 Whangapoua Whangapoua is a medium to coarse grained beach located to the east of the Whangapoua Harbour entrance. The beach, approximately 1.6 km long, is exposed to waves from the Northwest to east (though partially sheltered from easterly waves by the Mercury Islands) and is backed by beachfront development along most of its length (Figure 43). Figure 43: Whangapoua Beach Beach profile data is collected at three sites along the beach. All sites have nearly 30 years of data and are reasonably representative of adjacent beach areas. The sites have therefore all been used to establish recommended setbacks as part of this review. Data from CCS11 and CCS12 dates from January 1979, while surveys at site at CCS11/1 were started in January 1981. Charts showing the calculated erosion profiles against the beach profile record are included for all sites in Appendix A. Other information available at this site including information from long-standing property owners (some September 2009 Coromandel Beaches – Coastal Hazards: Review of Primary Development Setback 79 owners dating back to the early 1960’s) and limited historic photography (the earliest aerial photographs dating from 1944). There are also a number of property specific reports relating to properties at the northern, central and southern ends of the beach. 4.12.1 CCS12 Beach profile site CCS12 provides a record of beach change at the northern end of Whangapoua Beach, with the transect line in the lee of the small island immediately offshore (Figure 43). Field observations confirm that the shoreline at the profile site is influenced by a salient formed behind the island, with the dune line curving inland to the south. This salient effect could be one of the reasons for the greater fluctuations in dune toe observed at this site when compared with other profile sites at Whangapoua Beach. The most landward erosion profiles in the record were surveyed in 1997 and 1998, with the eroded dune toe position about 22 m landward of the most seaward dune toe. Interestingly, the profile surveyed in January 1979, approximately 6 months after the July 1978 storm, is one of the more accreted dunelines in the record with the most accreted duneline surveyed 2 years later in 1981. Therefore, this storm did not cause significant erosion at the northern end of the beach, with the more severe erosion experienced during the late 1990s – a period also noted for erosion at some other eastern Coromandel sites as discussed earlier (e.g. Buffalo Beach). The local Beachcare group has actively planted the eroded dune face since the early 2000s and the dune in this area was in early stages of recovery at the time of our initial field inspection in April 2008 (Figure 44. Figure 44: View south from CCS 12 in April 2008 showing early stages of dune recovery The predicted worst estimated erosion extends approximately 10-11 m landward of the worst measured erosion and is located in the swale behind the frontal dune. All available evidence for the site suggests the estimate is reasonable and approximately 8-11 m landward of any erosion recorded over at least the last 50 years. September 2009 Coromandel Beaches – Coastal Hazards: Review of Primary Development Setback 80 Figure 45: Location of worst estimated erosion in swale behind frontal dune. 4.12.2 CCS11 Beach profile site CCS11 lies near the centre of the beach. The most serious dune erosion at this site occurred in the late 1990s and early 2000s, with the most eroded dune toe about 10 m landward of the most prograded (the latter surveyed in the mid 1980’s). The January 1979 dune profile lies about midway between the most eroded and most accreted dune profiles, indicating that the erosion accompanying the July 1978 storm was not as serious in this area. The dune in this area was eroded again in the storms of July and August 2008, but not as severely as the dunes further south (see discussion in next section). The worst estimated erosion intercepts ground level about 8-10 m landward of the worst measured erosion (see graph for CCS 11 in Appendix A). Field inspections (Figure 46) and available community information indicate that this is well landward of any erosion observed since at least the early 1960s and probably earlier. Data collected at CCS11 is representative of the central area of the beach and accordingly has been used to revise setback recommendations in this area – though grading to CC 11/1 for areas to the south. September 2009 Coromandel Beaches – Coastal Hazards: Review of Primary Development Setback 81 Figure 46: Worst estimated erosion at ground level at Whangapoua Beach, profile site CCS11. 4.12.3 CCS11/1 Beach profile site CCS11/1 lies near the southern end of Whangapoua Beach. The most severe erosion in the profile record occurred in the storms of July and August 2008, with the eroded dune toe (at RL 3.5 m) nearly 5 m landward of the previous worst measured erosion surveyed in 1981. However, the latter profile was surveyed over 2.5 years after the storm of July 1978 when the beach and dune were recovering. Photographs of the 1978 erosion held by property owners indicate the 1978 erosion was as severe in some areas towards the southern end of the beach as the recent (August 2008) erosion. The earlier erosion was not as widespread along the beach and in places the August 2008 erosion was more severe. Erosion protection works placed in the 1970s (permeable fences with little to no effect on erosion) were located close to the recently eroded dune face at the more southern end of the beach. Further north on the beach, August 2008 erosion extended landward of these works. The erosion of July and August 2008 was extensive, with severe erosion extending 750 m northward from the southern end of the beach (Figure 47) and lesser erosion for at least a further 250 m. In places, the erosion severely threatened houses (Figure 48). Erosion mitigation works (dune reinstatement using beach scraping) were subsequently designed (Eco Nomos, 2008) and implemented. September 2009 Coromandel Beaches – Coastal Hazards: Review of Primary Development Setback 82 Figure 47: View looking south from centre of beach before (top, June 2007) and after (bottom, November 2008) erosion of July and August 2008 September 2009 Coromandel Beaches – Coastal Hazards: Review of Primary Development Setback 83 Figure 48: View of erosion scarp in central-southern beach following storms of July and August 2008 (Photo: Meg Graeme – taken August 2008). The of worst estimated erosion calculated using the data from CCS 11/1 intercepts ground level about 8 m landward of the top edge of the erosion scarp measured following the July and August 2008 storms (the worst erosion since at least the early 1960s). There is no field evidence of more severe erosion. We believe the estimate is sufficiently precautionary to use to revise the PDS in this area of the beach. Trend analysis of the variation in dune toe at this site raised the question whether or not the southern end of the beach is experiencing a long-term trend for erosion (Environment Waikato, pers. comm.) . Planning maps also show a 16 m wide reserve fronting development. At present, little width of reserve land remains in many areas. Community photographs we viewed dating from the 1960s (held by the Goldsmith family, long-term property owners at Whangapoua) also seem to show the duneline at the southern end of the beach further seaward than has been observed since. Historically, sand was extracted from the ebb tide delta at the entrance to Whangapoua Harbour and the sand grade removed was similar to that on Whangapoua Beach. Other eastern Coromandel beaches subject to sand extraction often show evidence of some long-term erosional response (see discussion in Section 2.1.2). We analysed trends evident in the beach profile data at CCS 11/1; inserting a data point for the July 1978 erosion based on the position of shoreline armouring works placed at that time. The variation over time is shown in Figure 49. With insertion of data for the 1978 erosion, the figure tends to suggest that shoreline change from 1978 to the present was dominated by a multidecadal shoreline fluctuations – with a period of 30 years for the ‘cycle’ from severe erosion in 1978 through a period of sustained shoreline recovery/advance and back to severe erosion in July 2008. No significant long-term trend can be reliably assessed from the data. The similarity of the 1978 and 2008 erosion suggests there is either no ongoing long-term trend for erosion or that any trend is slow (e.g. less than 5 m per century). While there is no conclusive evidence for long-term trends since July 1978, it is possible that some adjustment to the earlier sand extraction occurred before or up to this time. Accurate analysis of shoreline change using rectified historic photographs and any available historic surveys would be required to more reliably assess this. However, regardless of any such adjustment, we believe that no additional allowance for ongoing long-term erosion can be justified on the basis of existing data. September 2009 Coromandel Beaches – Coastal Hazards: Review of Primary Development Setback 84 Figure 49: Trends in duneline (RL 3.5 m) position from 1978 to 2008 at CCS 11-1. 4.12.4 Discussion and Setback Recommendations Primary development setbacks at Whangapoua Beach are based on beach profile data and include a 10 m safety factor.

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