Motunau Beach is situated upon a small coastal promontory which is approximately 3
km in length. Around this promontory a complex of coastal processes are interacting.
In the past there has been concern for people s property due to eroding sandstone
cliffs. In response to the erosion hazard piecemeal structural solutions have been
sought; however, due to their short longevity have proved inadequate.
Based on regular shoreline profiling and observations in conjunction with a broad
international literature base, the processes of wave refraction, cliff erosion, river
mouth dynamics, and sand beach adjustment have been discussed. Sediment transport
pathways have been inferred based upon the natural and human processes around the
promontory and the morphological response since the 1950s.
To analyse the coastal processes and morphological change at Motunau Beach a
combination of qualitative and quantitative research methods have been used. The
field study period of three months, July to September 2009, has focussed on the shortduration
and high-frequency processes of change and nested within a broader context
of coastal change since the 1950s.
Initial results suggest that between the years 1950 to 1968 there was a loss of beach
width on Sandy Bay of approximately 25 m. This was then followed by an increased
rate of cliff erosion during the 1980s. Analysis of historical hindcast wave data since
1979 suggests the wave climate at Motunau is not distinctive from the rest of the east
coast; however, the processes of wave refraction within the nearshore create a
turbulent and dynamic nearshore wave environment which has implications on
shoreline morphology. Results from this study indicate that nearshore sediment
supplies are being exhausted by a increasing wave height of approximately 4 mm yr-1
since 1979. The turbulent wave environment of the nearshore zone at Motunau Beach
is encouraging the offshore transfer of nearshore sediment supplies to a depth beyond
the reworking of waves during swell condition. This has obvious implications for the
long-term shoreline morphology at Motunau and shoreline protection from highintensity
low frequency wave events.
| Identifer | oai:union.ndltd.org:canterbury.ac.nz/oai:ir.canterbury.ac.nz:10092/4170 |
| Date | January 2010 |
| Creators | Foster, Duncan James |
| Publisher | University of Canterbury. Geography |
| Source Sets | University of Canterbury |
| Language | English |
| Detected Language | English |
| Type | Electronic thesis or dissertation, Text |
| Rights | Copyright Duncan James Foster, http://library.canterbury.ac.nz/thesis/etheses_copyright.shtml |
| Relation | NZCU |
Page generated in 0.0022 seconds