Copyright is owned by the Author of the thesis. Permission is given for
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Frontispiece: Aerial view of Otaki river mouth and beach foreshore.
Photo courtesy of Professor D.W. McKenzie, Victoria University, Wellington.
Massey University library New Zeaiand & Pacific Colleci:1on
BEACH MORPHOLOGY AND SEDIMENTS OF THE WEST WELLINGTON COAST: WANGANUI TO
PAEKAKARIKI
A thesis presented in partial fulfilment of the requirements for the Degree of
Master of Science in Geography at Massey University
by
RONALD GRAEME GIBBARD
1972.
ACKNOWLEDGEMENTS
I wish to thank the many people who gave assistance in the course of my research and this presentation of results. In particular I wish to acknowledge:
The following staff members of Massey University:
Dr. J.L. McArthur, Geography Department, for his valued supervision of field and laboratory procedures, and whose suggestions and
constructive criticism were greatly appreciated; Professor K.W.
Thomson, Geography Department, for the provision of transport; and Dr.
c.
Fife, former Head of Soil Science Department, for the use of the Soil Science Laboratory facilities.The staff of the N.Z. Meteorological Service and the N.Z.
Oceanographic Institute, Wellington, for the supplying of climatic data and bathymetric charts, respectively; and Mr. S. Ellen, Area Engineer (Paraparaumu), Hutt County Council, for providing background information and personal comments on beach conditions in the vicinity of Paraparaumu.
Fellow students at Massey University, especially Nanyang Lee, A. Taylor, P. Tayler and D. Stewart, who gave assistance in the field.
Professor D.W. McKenzie of the Geography Department, Victoria University, for the frontispiece photograph; Mrs M.
McCamish, Massey Illustrator, who completed a number of diagrams;
and Mrs R. McGee for typing the thesis copy.
TABLE OF CONTENTS
ACKNOWLEDGEMENTS TABLE OF CONTENTS List of Tables List of Figures List of Plates 1 •
2.
INTRODUCTION
1.1 Introduction 1.2 Thesis Format 1.3 Previous Research THE ENVIRONMENT
2.1 THE TERRESTRIAL ENVIRONMENT 2.11 Introduction
2.12 Geologic and Geomorphic History 2. 121
2 .122 2.123
Development of the Wnnganui Bc:.sin
Hnwera St.:i.ge
Post-Glacial Development of the Sand Country
2.13 Climi:tte 2,131 \Hind 2. 132 Rainfall 2.133 Temperature 2.14 The Drainage System
2 .141 2 .142 2.143 2. 15 Summary
Northern Rivers Southern Rivers
Sand Country Drainage
2.2 THE MARINE ENVIRONMENT 2.21 Introduction 2.22 Bathymetry
2.23 Offshore Sediments 2.24 Coastal Currents
iii.
Page ii iii vi vii
ix
1 2 3 3 6 7 7 8
9 9
10
12 12 13 13 14 14 15 16 16 18 18 18 20 23
3.
iv.
Page
2.25 Waves
2.251 General Setting
2.252 Environmental Factors
2.253 Wave Climate
2.254 Survey Data 2.26 Wave Refraction 2.27 Summary
FIELD AND LABORATORY INVESTIGATION OF BEACH SEDIMENT AND BEACH MORPHOLOGY
3.1 FIELD AND LABORATORY PROCEDURES 3.11 Field Procedures
3.12 Laboratory Procedures 3.2 BEACH SEDIMENTS
24 24 25 27
28
30 34
40
41 41 42
44
3.21 Introduction 44
3.22 Mineral Composition and Source Areas 45 3.23 Hydraulic Equivalence
46
3.24 Justification of Sieve Analysis 47 3.25 Mean Grain Size Vuriation 48
3.251 Longshore Variation 49 3.252 Se~sonal Variation 51 3.26 Environmental Differentiation 52
3.27 Summary 55
3.3 BEACH MORPHOLOGY Introduction Beach Profiles 3.321
3.322
Monthly and Seasonal Variation
~ind Patterns and Volumetric Change
Foreshore Slope, Grain Size and Sorting Summary
57 57 58 59
62 64 67
4. RECENT COASTAL CHANGE 4.1 Introduction 4.2 Coastal Change
4.3 Effects of Erosion near Raumati 4.4 Erosion Factors
I+. 41 4.42 4.43 4.44
Sub-Aerial Beach Offshore Conditions Energy Considerations
Sediment Supply, Deposition and Depletion
4.5 Summary CONCLUSIONS APPENDICES
BIBLIOGRAPHY
v.
Page
71 72 72 74
75 75 76 77
78
Bo
84
87
93Table I
II
I I I
IV
v VI
VII
VIII
LIST OF TABLES
Temperature statistics of sel ected Sand Country stations.
Offshore gradients to 50 fathom contour at four localities.
Swell ~ave heights at ~aipipi
Point, 1959.
Breaker wave hei ghts for Surveys 1 t o 6.
Comparison of t i tano-magnetite and resi dual sample properties.
ApplicQtion of t-test to Grain-size pcr nmeters of sampl es obtained from mid-tide, backshore and dune
environments.
Average depth change per unit l ength of profi le on the basis of station sets.
Uind regimes and volumetric change, May-July, AuGust-October incl., 1971.
IX Statistics, tests of hypotheses and estimates of sampl e par~meters for slope and gr ain size regression nnalysis.
vi .
page
13
19
28 29 1+7
61
66
Figure 1
2
3
4
LIST OF FIGURES
Location of west Wellington coast study area.
Percentage frequency of wind speed and direction at Ohakea, 1940-49.
Mean annual rainfal l distribution, west Wel l ington province.
Offshore bathymetry of eastern Cook Strait.
5 Sediment distribution over the continental shelf west of central
Ne~ Zealand.
6
7 8
9
10
11
12
13
14
15 16 17 18
Surface coastal currents of central New Zealand.
Linenr fetch at selected sites.
Refraction diagram of north-westerly wave system: period ten seconds.
Refraction diagram of westerly wave system: period ten seconds.
Refraction diagram of south-westerly wave system: period ten seconds. Refraction di agram of southerly wave system: period ten seconds.
Location of sampling stations.
Source areas of mineral suites supplied to the west Wellington coast.
Levels of hydraulic equivalence of selected heavy minerals.
Longshore mean grain size variation of foreshore samples.
Idealised profile types.
Average inter-survey change across each profile.
Net volumetric change per profile on basis of station sets.
vii.
following page
2
12
13 18
20
23
32 32 32 32
41
45
46
60 61
Figure 19
LIST OF FIGURES (continued)
Rel utionshi p bet ween mean grain si ze (M z ) and beach foreshore slope. .
20 Nature of interaction bet ween the major elements of a 3each-erosion model .
21
22
Refraction of westerly wave trai n around Kapi t i Island: period ten seconds.
Sediment source-sink areas for the Waikanae-Paekakariki foreshore zone.
viii.
following page
65
75
77
78
Plate frontispiece
1
2
LIST OF PLATES
Aerial view of Otaki river mouth and beach foreshore.
View of foreshore berms and beach cusp development, south of Otaki river.
View of beach conditions, Raumati South.
ix.
following page
59 75
