point. If it were seaward of the scarp toe, it would be very likely eroded in the
next storm or spring high tide.
3. The foredune was quite low and should ideally be reshaped to a greater height
to allow for, and mitigate against, storm erosion and potential storm overwash.
4. The foredune surface comprised clay and other materials, some of which would
not be desirable for use in the reshaping and this lessened the volume of
material available for dune reshaping.
5. Views from the reserve toward the beach should be maintained where possible.
Given these constraints, the very limited availability of sediment from other
sources, and the potential for storm wave erosion, the reshaped dune profiles were
constructed with a stoss (seaward) slope of around 18° (1:3) (Fig. 5.3). The dune
height was maximized where possible to heighten the dunes a small amount while
still conserving sediment. The dune lee slope was constructed with a slope of
around 20° and, while it was desirable to produce a lower lee slope, dense planting
and fencing ensured the stability of the slope.
5.2.3 Dune Volumes, Sand Placement, and Sand Removal
from Oakura Beach
The approximate volume of sediment (per meter alongshore of the dune) required
for reshaping is indicated in Fig. 5.3. The volumes required to construct the
desired dune profile ranged from 1,200 to 2,700 m
3 /m depending on the location
alongshore. There was a greater amount of sediment available in the northern
section of the area to be reshaped and a deficit in the southern area. That is, the
amount of material required to produce a minimal dune shape in the southern
section was less than that available from the excavated area. Since it was desirable
to build the reshaped foredune as large as possible, and since there was more
sediment in the northern area, some of this northern sediment was transported to
the southern area to make up the deficit.
It was not clear prior to reshaping of the dune exactly how much fill of foreign
materials might be in the dune, and thus, an additional 300 m
3 of sediment was
potentially required for dune reshaping. This sediment was to be extracted from
the beach adjacent to the Waimoku Stream (at the northern end of the beach) when
stream re-alignment works took place. It was then to be transported along the
beach at low tide and emplaced on the southern section.
5.2.4 Dune Planting
Prior to dune reshaping and planting the kikuyu grass was eliminated by spraying
it three times with Roundup
TM at 8-week intervals (Bergin et al. 2000). The dune
was reshaped, restored to a relatively natural profile (Fig. 5.4), and mostly planted
5 Restoration of Foredunes and Transgressive Dunefields
71
next storm or spring high tide.
3. The foredune was quite low and should ideally be reshaped to a greater height
to allow for, and mitigate against, storm erosion and potential storm overwash.
4. The foredune surface comprised clay and other materials, some of which would
not be desirable for use in the reshaping and this lessened the volume of
material available for dune reshaping.
5. Views from the reserve toward the beach should be maintained where possible.
Given these constraints, the very limited availability of sediment from other
sources, and the potential for storm wave erosion, the reshaped dune profiles were
constructed with a stoss (seaward) slope of around 18° (1:3) (Fig. 5.3). The dune
height was maximized where possible to heighten the dunes a small amount while
still conserving sediment. The dune lee slope was constructed with a slope of
around 20° and, while it was desirable to produce a lower lee slope, dense planting
and fencing ensured the stability of the slope.
5.2.3 Dune Volumes, Sand Placement, and Sand Removal
from Oakura Beach
The approximate volume of sediment (per meter alongshore of the dune) required
for reshaping is indicated in Fig. 5.3. The volumes required to construct the
desired dune profile ranged from 1,200 to 2,700 m
3 /m depending on the location
alongshore. There was a greater amount of sediment available in the northern
section of the area to be reshaped and a deficit in the southern area. That is, the
amount of material required to produce a minimal dune shape in the southern
section was less than that available from the excavated area. Since it was desirable
to build the reshaped foredune as large as possible, and since there was more
sediment in the northern area, some of this northern sediment was transported to
the southern area to make up the deficit.
It was not clear prior to reshaping of the dune exactly how much fill of foreign
materials might be in the dune, and thus, an additional 300 m
3 of sediment was
potentially required for dune reshaping. This sediment was to be extracted from
the beach adjacent to the Waimoku Stream (at the northern end of the beach) when
stream re-alignment works took place. It was then to be transported along the
beach at low tide and emplaced on the southern section.
5.2.4 Dune Planting
Prior to dune reshaping and planting the kikuyu grass was eliminated by spraying
it three times with Roundup
TM at 8-week intervals (Bergin et al. 2000). The dune
was reshaped, restored to a relatively natural profile (Fig. 5.4), and mostly planted
5 Restoration of Foredunes and Transgressive Dunefields
71