5.2.1 The Foredune
The foredune was a narrow (18-m wide), low (3.5 m above mean sea level) flattopped terrace that had been significantly modified in the past. It extended 150 m
alongshore. As with many foredunes on New Zealand coasts with moderate to high
recreational activity, the dune crest had been flattened, some unknown amount of
building fill had been emplaced in the dune, clay had been laid over the surface, and
the soil had been planted with exotic kikuyu grass (Pennisetum clandestinum). The
area behind the ‘‘dune’’ was open grass and trees and utilized as a recreation/picnic
area. The seaward face of the dune commonly displayed an erosion scarp along its
length (Fig. 5.2). The only naturally functioning portion of the dune was this stoss,
or seaward face, which on occasions, between storms, would fill with aeolian sand.
Following discussions with the local New Plymouth District Council, a plan was
developed with the objectives of reshaping the foredune to a more natural shape,
improving the natural functioning of the foredune (i.e., enabling beach–dune
interaction; see e.g. Hesp 1989), and carrying out dune re-vegetation utilizing Spinifex sericeus, the primary indigenous foredune species in northern New Zealand.
5.2.2 Foredune Reshaping
The reshaped dune seaward slope (or stoss face) should ideally lie within the slope
range of 1:5 (around 11°) to 1:3 (around 18°). These slopes approximate natural
(unmodified or non-scarped) foredune stoss slopes in the region. However, at
Oakura there were five significant factors that limited the dune reshaping exercise:
1. There was very limited space in which to reshape a foredune (approximately
10 m maximum from the dune scarp crest), since it was the Council’s wish to
retain the maximum lee dune recreation area.
2. The seaward toe of the reshaped foredune should not extend further seaward
than the toe of the dune scarp and should preferentially be landward of that
Fig. 5.2 View of the Oakura
Beach site prior to restoration
70
P. A. Hesp and M. J. Hilton
The foredune was a narrow (18-m wide), low (3.5 m above mean sea level) flattopped terrace that had been significantly modified in the past. It extended 150 m
alongshore. As with many foredunes on New Zealand coasts with moderate to high
recreational activity, the dune crest had been flattened, some unknown amount of
building fill had been emplaced in the dune, clay had been laid over the surface, and
the soil had been planted with exotic kikuyu grass (Pennisetum clandestinum). The
area behind the ‘‘dune’’ was open grass and trees and utilized as a recreation/picnic
area. The seaward face of the dune commonly displayed an erosion scarp along its
length (Fig. 5.2). The only naturally functioning portion of the dune was this stoss,
or seaward face, which on occasions, between storms, would fill with aeolian sand.
Following discussions with the local New Plymouth District Council, a plan was
developed with the objectives of reshaping the foredune to a more natural shape,
improving the natural functioning of the foredune (i.e., enabling beach–dune
interaction; see e.g. Hesp 1989), and carrying out dune re-vegetation utilizing Spinifex sericeus, the primary indigenous foredune species in northern New Zealand.
5.2.2 Foredune Reshaping
The reshaped dune seaward slope (or stoss face) should ideally lie within the slope
range of 1:5 (around 11°) to 1:3 (around 18°). These slopes approximate natural
(unmodified or non-scarped) foredune stoss slopes in the region. However, at
Oakura there were five significant factors that limited the dune reshaping exercise:
1. There was very limited space in which to reshape a foredune (approximately
10 m maximum from the dune scarp crest), since it was the Council’s wish to
retain the maximum lee dune recreation area.
2. The seaward toe of the reshaped foredune should not extend further seaward
than the toe of the dune scarp and should preferentially be landward of that
Fig. 5.2 View of the Oakura
Beach site prior to restoration
70
P. A. Hesp and M. J. Hilton