An examination of decision making in adjustment to the flood hazard with particular reference to the lower Manawatu region : a thesis presented in partial fulfilment of the requirements for the degree of Master of Arts in Geography at Massey University

Copyright is owned by the Author of the thesis. Permission is given for

a copy to be downloaded by an individual for the purpose of research and

private study only. The thesis may not be reproduced elsewhere without

the permission of the Author.

AN EXAMINATION OF DECirno;J ~·1AKING IN ADJUSTMENT TO THE FLOOD HAZARD VJITH PARTICULAR REFERENCE TO THE LOWER MANAWATU REGION.

A THESIS PRESENTED IN PAR'rIAL FULFILMENT OF THE REQUIREMEtJTS

FOR THE ^DEGR~E OF MASTER OF ^~RTS IN GEOGRAPHY AT MASSEY UNIVERSITY.

BE

DONALD BRUCE JOfN.Srl'ON MASSEY UNIVERSITY

1976.

ACKN0¹i/UrnGEMENTS •

Appreciati on i s extended to ~ number of people for the advice and assi stance received.

Acknowledgement must first B~ tc Dr. Pet~r Phillips for the guidance received, particul&rly in regard the methodologiual approach adopted. In this ~rcn, the help received fro~ the member s of the Massey Uni vcrsi ty Ma t:1emRtics, Economics and aomputcr Rdsearch Department~ ~re al so appreciated.

Special thanks must al so go to Mr Brown, retired chairman of the Mannwatu C3tchment 9oardt Mr. E~3ns, the Catchment Board,

Chief Engineer at the time the Flvod Scheme w~s design~d ~nd bui lt , and to al l who gave their tim6 to answer questionaires and various queries.

ABSTRACT

'l'he relationship bat~mcn man .:md his environment is in a const.'.l.Ilt state of chn.n.ge. The study of this interrelationship has commanded the attention of many disciplin0s, yot no one discipline can adequately comment on all essential r0lQtionships involved.

Geography with a tr1ditional interest in tho study of man and his environment is ideally suited to a role as a Dynthesiser of various interdisciplinary findings. This study is concerned with man-

environment interactions in the floodplain and in particular with the varying 'levols' of mans adjustment to the flood hazard.

Th8 prinary aim of this research \ns the identification of tho inter-relation of various elor.1ents in a decision making model for flood hnzard adjustment. Th0 study is based on the analysis of

adjustr:wnt to tho flood hazard in the lower Manm•?.tu rogion, al though it is intended th~t tho research findings and methods bo of more general applicability for th0 study of such adjustnont decisions.

The data used in the study was obtained fron local

Catchment Board files and from floodplain occupants. Tho variation in attitudes towards flooding and flood protection botuoon those two groups is etlphasised and the ef'fect of this on floodplain land use \ri th and without flood protection is outlined.

Floodplain protection has a long history in the lower Manawatu region. The range of adjustment decisions, the reasons for these decisions, and aspects of the inpact of those decisions arc cxtunined within the analytical fra.ciework of Kates model of

adjustment to natural hazards. .An examination of the environ.mental processes and tho human use processes are undertaken.

In the: oxamination of' the hULJ.an use processes the role of' the decision makers h~zard perception, soar ch cf al tcrn:i.ti ve ad.justments, and evaluation of these adjustments are uxGLJined. The factors

influencing tho Catchment B0ards hazm·d perception, adjustnsnt search, and evaluaticn are discussed within the ccnstraints of legal and

financial limits, as well o.s the predisposition of this organisation towards conventional "engineered solutions" to flood protection.

V.'ll'iations between this body and the resource users, and the impact of this on post scheme land use is discussed.

The evaluative procedure used in tLis study then is

der:ionstrated in an analysis of protection nee.suros in the lower Manawatu region. The application of the decision Dc'l.king Dl)dcl is demonstrated and its effectiveness evaluated. It is suggested that floodplain protection should be viewed within a w:i.dor planning context and floodplain protection can bo seen cs a co.so of inappropriate land use unless viabl0 'economic' protocticm can be provided. T!i..is implies that post locational errors shOl~ld not be comj,10undGd by automatically providing flood protection. Tho timcsco.lo of 8nvironmontal processes and the sensitivity of tho environmental system should be considered, and a system of land use planned to minimise the socin.l costs of use.

Chapter 1 Introduction

Research Topic Area

TABLE OF CONrEN'J'S

Kates Natural Hazards Model

Structural Components of the Decision Ma.king System Tho Human Use System

The Natural Events Syste~

The Natural Hazard

Tho Adjustment Decision Process

The Management ^Adjust~ent Decision Model Perception

Search of Alternative Adjustments Evaluation of Alternative Adjustments The Aggregate Adjustment Decision Model Chapter 2 - The Manawatu Setting

The Ma.navratu Natural Events Ranges and Hill Country Plains

Sand Country Soil Types Climate Vegetation Erosion

Drainage System

The Menawatu Human Use System Extensive Sheop Farming Intensive Sheep F~ing

Dairy Farming

The Flood Hazard in the Ma.nawatu Chapter 3

The Adjustment Decision Role of Perception

The Technical Experts Hazard Percenption The Flood Plain Managers Hazard Perception Variation between the Technical Experts and the

Floodplain Managers Hazard Perception The Theoretical Range of Alternative Adjustments The Evaluation of Alternative Adjustments

Chapter

4

Page 1 10 10 11 11 11 i 3 14 14 17 17 17 18

21 21

23 25 28 25 33 34 35

36 39

40 41 42

44 52 53 54

56

57

63

The Decision Making Process in the Lower Manawatu Region 67

Prescheme decisions 68

Individual Floodplain Managers decisions 68

Collective Action Adjustment 69

Emergency Action Adjustment 72

Me.nawatu Catchment Boards Decision Making Process 74 Role responsibility of the Manawa tu Catchment Board 76

Soil Conservat ion and Rivers Control Act 1941 76 Manawatu Catchment Boards Hazard Perception 82 Comments on Catchment Board Perception 89 Alternative Adjustments and Adjus'bnent Search by

Manawatu Catchment Board 94

Structural Protection Works 95

Watershed Management 97

Flood Insurance 98

Floodplain Regulations Emergency Action

Hu.nmw.tu c-..tchment Bc2.rd Evaluation Process Econordc Report to the Council ··

Estimated Flood Damage

~sti~ated increase in Market V~l~e of Land Estii:ie.ted Incre:.so in Production

SUIJTI:;.ry of Estim.:i.tcd Costs e.nd Boncfi ts Cor:inents on Catchment Board Evaluation Procosn Chapter 5

The Lower Ma.nawatu Flood Control Schor:i0 Design Chapter 6

The Effect of Floodplain Managers Hazard Perception on adjustments adopted

Sample Frame Design

Catchnent Boards Hazard Perception Floodplain Managers Hazard Perception

Farmers Perception of River Flcod·;.ng Farmers Perception of Local Flooding

Comparison of Floodplain 1-ianagers and Catchment Boards Hazard Perception (River Flooding)

Variation in Perception a.raong Farmers

Effect of Past Flood Experience on Hazard Perception of River Flooding

Eff 0ct of Past Flood Experience tov.ards Future Flooding

Effect of amount of F.9.I'IIl in Floodplnin in P~rception

of River Flooding

Effect of Flooding from Different River:; on ii.?.zard Perception

Variation in farmers Perception of Local Flooding Farmers Perception of Effect of Scheme on Fr.i..."'Ill Producticn

River Flooding Local Flo.od.i.ng Conclusion

The Environmental II!lpact on the Lo\.Ter ~.!ruw.vm.t"t; Rc,gion Chapter 7

Effect of Flood Scheme of Land Values Conclusion

Appendix A

Bibliography

100 102 102 103 105 110 113 117 119

126

132

134

141 141 1 Li.2 143 145 151 153 157 161 163 164 167 .... ~ 167 171 171 172

180 183 192 197

I I I III

IV

v

VI

VII

VIII

IX

x

XI

XII

XIII

XIV

xv

XVI XVII

XVIII

XIX

xx

XXI XXII XXIII

XXIV

xxv

XXVI

XXVII XX.VIII .XXIX XXXI XXXII XXXIII XXXIV

IJIST OF TABLES

Moan Jfonthly P.nd Annu'.ll Rainfall Figure::; for Selected s·c,,:t:LGnR in tho Vianav;e.tu Catchnent Storr:l Typer:.; C::msir:g :Flooding in the }fonex1atu Flood Darnae:o Reduction Moas'l.}.res diScu§sed.::in Papers published in N.Z. Periodicals 1957-67

i'.bnawatu River Fl0us over 13 feet (50,000 cusecs) at Fitzherbert Bridge ·1929-1972

Theoretical Hanavmtu River Flows

Tuionthl.y Distribution of Flows pvcr 13 feet at Fitzherbert Bridge 1929-1972

Return Per iods for Tributary Ri vcrs

Ifanavratu R!iver FlO'i?S OV8r 50,000 ^CUSGCS at Fitzherbert Bridge (Actun.l and 'l'hooretical) 1929-1972

Su;mnary cf EstiL1atod Floc•d De.mage in £' s Estimated Increase in Le.nd Values

Estimated Increase in Production R8vcnue

Estimated Incr8ase in Production with Che.n:;e of Land Uso

Estimated Capital Cost of Scheme

Distribution of Sample F2rms and Number of Farm Units F'C)mers Pe;_'coptfrn of Riv•3r Flooding and Local

. 'Flooding

F::.rmers Percept ion of River Flr.oding (Assumption Set Number Ono)

Fe..rners Percept ion of River Fhoding (Assunption Sot Number Trm.)

Farmers Overestimation and Und(:restimation of the River Flooding Hazard

Farmers Perception of Flooding by Pr\st Fl·~od

Experience

Effect of Flood ExporiGnce on F->.rnors .~,tH ti.1"1()8

tm7ards Future Fl r'oding

Bffoct of Flood Experience and. F::trr:: Loc'ltion on F2.rr:.1ers Att:. ~ude tovr1rds Future Plooiiing

Explanation for At t itudes tow~~~8 Future Flooding F3.rmors H::i.zard Percopt ion by ~'aj er 2.i1d S:~condD.ry I~loodplain

Farmers Perception on Ri var Fl r•oding by Source of Flood

Farmers Perception of Local Fl ricding by Ydars on tho Farm

Farner;:\ p,.,,,.l"leption of Effect of _i;.l tt:.rt::d Ri ver Flcoding on Productfon

Farmers Perception of· Gffoct of Al tu:ced Loc::-.1 Flooding on Production

Effect of Farmers Past Flood Expe~i0nce on PDrception on Eff'ect of Flood Sche:rie

Environmentc.l :rapact Matrices for the; r~anawatu

Average Value per h9ctare by Fl cod Frequency 1~reP..s

Intorvaluation percentage increases in unimproved land Percentage Annual Increase in Value ($) por hecto.re Average $ value per hectare by Flood Frequency .Area and Drainage Boe.rd f\rea

Ranges in value per hoctare by ,,.lood Frequency Arca and Drainage Beard Arce.

29 32 50

87 88

91 106 111 113 114 117

11 .. 0

147 149 151

155

1 58 159 160 162

165 166 168

169 169 176

·183

183 185 187 188

1 .1 1 .2 2 .1 2.2

2. 3

3.1

3. 2 3. 3 3.4

4.1

4.2 4.3 6 .1

LIST OF FIGURES

Human Adjustments to Natural Hazard The Managerial Adjustment Decision Model

The Manawatu River Catchment and Drainnge Pattern Soil Pattern of the Manawatu

The Manawa tu Rainfall Net~-mrk

Elements Involved in Adjustments to Floods The Process of Making an f'.djustncnt Decision Flood Dn.nage Prevention r5easures

An Abridged Scheme of Human Adjustments to the Flood Hazard

The Distribution of Authority for Soil Conservation and River Control Work

Flows over 50,000 cu.secs at Fitzherbert Bridge The Manawatu Catchment Boards Hazard Identification

Distribution of Flood Frequency and Drainage Board Areas

Pa.B_e 12 15 22

26

30 49 51

60

61

78

85

104

137