A hydrological comparison between two watersheds in Pohangina County : a thesis submitted in partial fulfillment of the requirements for the degree of Master of Agricultural Science at Massey University

(1)

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

the permission of the Author.

(2)

A HYDROLOGICAL COMPARISON BETWEEN TWO WATERSHEDS IN POHANGINA COUNTY

A Thesis Submitted

in Partial

Fulfillment

of

the Requirements

for

the

Degr

ee of

MASTER OF AGRICULTURAL SCIENCE I N SOIL SCIENCE

at

MASSEY UNIVERSITY

by

Shirley Jean Rolston

1973

(3)

towards the Pohangina River

(4)

(5)

SUMMARY

Sequential aerial phot~graphs taken in

1946, 1958, 1966

^and

1972

were used to study the changes in erosion and vegetation over two a'djacent catchments in the Pohangina County,

35

km north east of Palmerston North. Infra red colour and Kodachrome prints were used as well as black and white film for added inter- pretive value.

The major problem in these watersheds is the severe canyon gullying that occurs in the unconsolidated Castlecliffian Sand underlying this area.

Number 1 catchment ( 240 ha ) is in a mor~ critical state with regard to erosion, than Number 2 catchmeat

( 200 ha ). It yielded extremely low dry weather flows, with much of the streambed completely dry except in flood events, or fed only by seepage from small springs. Reasons for the significant differenees in the behaviour of the two catchments are suggested.

Attempts were also made with limited resources to look at the flood levels and sediment loads contributed to the Pohangina River by these catchments. It was calculated from a flood 10/3/72 that sediment loads in the order of

3

tonnes/min could be reached at the flood peak. Mechanical analyses showed that

80

per cent of this load falls in the

size range of fine sand.

Using a mirror stereoscope and simple morphometri8 and photointerpretive methods, the physical factors contributing to the erosion and headward gully movement in the two catchments were compared and a series of deductions made in eonjunction with the history and manageme•t of the

properties involved. Headward gully movement and increased erosion was proposed to result from climatic events and

•hanges as well as the removal of large areas of scrub and regenerating native bush on the gully sides• Feneing off

(6)

v

the gullies, complete withdrawal of stock from them and allowing unrestricted r~generation of native species coupled with the planting cf exotic trees and the erection of conservation structures should have been instigated as soon as the problem became apparent. These measures have also been advocated by other workers and organizations for simi- lar problems in the same ar ea.

* * * * * * * * *

(7)

Temper a ture

••••••••

Wind •••••••••••••••

• • • • • • • • • • • • • • • • • • • 0

General ••...•••••••

Geo

logical

History ••

Stratigraphy

•••••••

Developmen

t

of

Topogr aphy and Struc-

ture ••.•...•.••••.•

iv vi

xi xii

Xi ii

xv

1 1

5

11

17 17 18

20

21

23

31

33

(8)

2.7

2.8

CHAPTER THREE

Soils

Vegetation Erosion

•0•000•••••••••11»••••

General

Desr.ription of the Soils in the Study Area

...

• • • • • • • • • • • • • 0 • • • •

....•...

Erosion Control Types of Erosion Agriculture and Management History •••••••••••••••••••••

2.8.1

2.8.2

^History •••••••••••

Present Agriculture and Management ••••

Literature Review

...

3.1

^{Flow and}^Sediment ^Measuremen^ts

and other Factors Aff8cting Erosion

3.1.3 3.1.4 3.1.5

...

1~nalysis of Stream Flows •••...••••••

Flood Flow Charo.cteristics Stream Sediment Loads • • • • • • • • • o • •

Rainfal l and Climatic Effects on Erosion Miscellaneous Effects

on Erosion

vii

38 40 38

53 59 59 65 71

71

72

75 75

75

78

79 84

90

(9)

3.2

Aerial Photography in Soil Conservation and Hydrological Studies ^{• • • $} • • • • 0 • • • • • • • • • • • • • •

3 .2.1

The Applications of Aerial Photography

3-2~2 Factors affecting Photoi nterpretation •••

3 . 2.3

The Re la ti ve Merits of Different Films

3.3

^Photogrammetric and Mor phometric Techniques

•...•...•.

3.3.1

Ârêa^l Ânalysis ^{• • 0} ^• ^{• •}

3.3.2

^Slope^Ana^lysis

3.3.3

^Drainag^e ^Ana^lysis

CHrl.FTER FOUR

Field and Laboratory Techniques and

Equipment ^• ⁰ • • • • • • • • • • • • 0 • • • • • • • • • • • • •

401

4.,2

Sediment and Flow Measurements

4 .1.1

Monthly Flow Record~ ••

4.1.2

Flood Flow Records

4.1.3

Flood Sediment

Collection and Analysis

4.1.4

Rainfal l Records

4.1.5

Other Measur ements and Observations • • • • • • 0 • •

Comparison of Different Film

Types

.•...•••..•.•...

Photogrammetric and Morphometric Measurements ^{• • 0}• • • • • • • • • • • • • • •

Areal Analysis Slope Analysis Drainage Analysis

94

94 103 107 120

12 0 121 126

12 9

129 129 131 134 134 135

136

137

139 142

147

(10)

CHA!-'TER FIVE Results

5.2

5.3

CHAPTER SIX

...

Sediment and Flow Measurements

5.1.1 5.1.2 5.1 ..

3

5.1.4 5.1.5

Monthly Flow Records ••

Flood Flow Records •••••

Flood Sediment Analysis Rainfal l Records •••••o Other Observations •••

Comparison of Different Film Types

5.2.1 Qualitative Observations of the Different

Applications of Aerial Photographs

Factors Affecting Photo Interpretation •••••••

The Merits of Different Film Types ••••••••••

Phot ogrammetric and Morphometric Measurements ^• ⁰ • • • • • • • • • • • • • • • • •

Ar eal Analysis •••••••

Slope Analysis • · · · Drainage Analysis

Discussion and Conclusions

ix

149

1

L~9

149 153 157 159

161

167

168

172

172 182 191

199

6.1 Field Measurements and Observations 199

6.1.1

6.1.2

6.1.3 6.1.4

Stream and Flood Flows Sediment Loads

Erosion

The Effects of Rainfall and Climate on Erosion

199 201 202 205

(11)

6.2 The Qualitative Use of Aerial

6.3

6 .. 4

Photographs

6.2.1 6.2.2 6.2.3

Applications ••••••••••

Limitations ••••••••••••

Different Film Types

The Use of Fhotogrammetric and Morphometric Measurements for Com- paring and Evaluating Watershed Characteristics and Problems ••••••••

6.3.1 6.3.2 6.3.3

Ar eal Measurements

Slope Analysis •••••••••

Drainage Analysis ·~····

Conclusions

ACKNOWLEDGEMENTS

BIBLIOGRAPHY • o • o o o o • c o e o e o o • • o o o 1 1 o o o e • C ' o o o o o o e •

AFPENDICES o o e o e o o o • o • o • o • • o • • • • o • o o e o o t t o o e . : t o o o o

209 209 210 211

212

212 213 214

215

217 219 245

(12)

Figure

2.1 2.2

2.3 2.4

2.5

2.6 2.7 2.8

5.1

5.6

5 •. 7

5.8 5.9

5.10

5.11

5.12

5.13

5.14 5.15

LIST OF FIGURES

Locality Map • • • • • • • • • • • • • • • • • • • • • o • • • • •

Specific Locality Map • • • • 0 • • • • • • • .,. • • • • •

Stratigraphic Column Culling's Gully •••••

Distribution of Soils Over the Study Area Raumai Sandy Loam Profile No. 1

xi

Page

6 8

34

39 41

Raumai Sandy Loam Profile No. 2 ••••••••• 42 Pchangina Steepland Soil Profile Ne. 1 49 Pohangina St eepland Soil Profile No. 2 50 Monthly Dry Weather Flows, December

1971 - 150

December

1972

• • C 1 0 • • 0 • • • • • • 0 • • · · ·

Relationship Between Recorded Water

Depth and Dischar ge fer Number 2 Catchment Relationship Between Depth of Sediment Deposited at the Flood Level Recorder in Number 2 Catchment and Previous Maximum

( 2 day total ) Rainfal l •••••••••••••••

1972 Monthly Rainfall Totals for Study Area • • • • • • • • ft 0 • • • • • • • • • • • • • • • • • • • • • • • •

Changes in Ercsion over the Study Area from Sequential Aerial Photographs Changes in Regeneration over the Study Area from Sequential Aerial Photographs.

Analysis of the Subwatersheds ••••••••

Contour Map •••••••••••••••••••••••••••

Generali.zed C·ontours •••••••••••••••••

Stream Profiles and Crest Line Profiles Multiple Projected Profiles •••••••••

Area-Height Curves ••••••••••••••••••

Hypsometric Curves •••••••••••••••••••

Drainage Analysis •••••••••••••••••••

Surrounding Drainage Network Between the Pohangina and Oroua Rivers •••••••

154 155

158

174

175

180

183

185

186

188

189

190

192

193

(13)

Table

I

II I I I

IV

v

VI VII

VIII

IX

x

XI

XII

LIST OF TABLES

Variability of Rainfall at Komako and Colyton

Geological Time Scale ••••••••••••••••

Slope Group Table for Soils of the Study Area •••••••••••••••••••••••••••

Measured Flood Flows •••••••••••••••••

Monthly Water Depth Maxima and Silt Deposition in Number 2 Catchment from Flood Events •••••••••••••••••••••••••

Sediment Loads • • • • • • • • o o • • • • • • • • • • • •

Particle Size Distribution in Flood •••

Sediment Loads •••••••••••••••••••••••

Area of the Catchm8nts Calculated by Five Different Methods • • • • • • • • • 0 • • • 0 .

~nalysis of Subwatersheds

Analysis of Drainage • • • • • • • • • • • • • 0 • •

Analysis of Drainage Composition •••••

Changes in He~dward Gullying from

1958- 1966 ••••••••••••••••••••••••••••••••

Page

18 26 47

151 152

153 156

172

181

194

196

197

(14)

P l a te

1

2. 1

2.2 2.3

2. 4 2. 5 2. 6

2. 8 2. 9

2.10

2.11 2.12

2.13

2. 14

2 . 15

LI ST OF PLATES

Fr on ti spi ece - Ob lique Aeri a l View of Study Ca tc hments from Ridge Road Looking towa rds

the PohanBina River ••••••••••• .•••.••••••• ^o

Aeria l View of th e St udy A rca

,

showing Location on the Easte rn Flank of t he

Pohangina An ticli ne be tween the Pohang i na

and Oroua Rivers .••••••••••••.•••••••••••

Confluence of Number 1 and Number 2 Gu llies Erosion Debris a t Foo t of Wat erfa ll, Number 1 Gully

¹¹

K n ickpoint

¹¹

.. .. .... ... ... ... .

Seepage Zone Contributing t o Streamflow

, Number 1 Gully ••••••••••••••••••••••••••

Seepage Flow Mee ting D ry Channe l

St eep Gul ly Wa l l showin g High ly Erodib l e Laminated Cast l ecliffian Sand Substra t a and Pop l a r Poles Pl an te d a t th e Bot tom

.

Burie d Ash Cl ast with Soil Deve loped on one Sur face , i n Matrix of Coarse Pumiceous Sand Raumai Sandy Loam , Profile No

. 1

...

Rauma i Sandy Loam, P:eofile No

. 2

... ...

Holling A re a of Rauma i Sandy Loam So ils with Ter races of Ohakea Si lt Loam in the Background ... ... ... .. .... .... ... ...

Co l on i za tion of St eep G ully Faces by Lup ins Pohangina Steepland Soi l Pr ofi le No

.

1

Pohangina Steepla nd So il, Pr o file No

.

2 Young Pop l a r Po les Planted a t the Reced ing Head of a Tributary of No. 1 Gully showing felled Manuka in the Backgr ound

••

•

••

•

St oc k Water Dam with Rush growth and

Improved Pasture in the Foreground

••••••

xiii

Page

iii

7

10 10

14

14 24

24 43

43

44

44 51 51 55

55

(15)

2 . 16

2 . 17

2. 18

2.19

2 .. 2('J) 2.21

2.22

2.23

4 . 1 4. 2 5. 1

5. 3 5. 4

5. 8

Concrete Dam Installed in Number 1

Gully, April 1971

... .. ...

Undercutting and Slipping on Farm

Track, April 1972 •••••••••••••••••••

Concrete Dam installed in No. ¹Gully in 1973 •••••••••••••••••••••••••••• Wide flat Aggraded Channel behind this Dam showing the Huge Build up of Sand within a few Months ••••••••••••••• • N6W Poplar Poles Planted on Active Slip Degraded Streambed in No. ¹Gully

showing Original Fence Suspended in the air

...

Cut-over Scrub above No. I Gully

showing Incipient Rilling and Gullying Sheep Grazing on the Steep Exposed Gully Faces ^{• • • •}^{• • 0} ^{• • • • •}^• ^• ^{• •}^• ^{• • •}^{• •}^{• • •}

Flood Level Recorder in No. 1 Catchment Flood Level Recorder in No. 2 Catchment Kodachrome herial of the Main Gully and Tributary of No. 1 Catchment ••••••••

Infra Red Aerial of the Main Gully and Tributary of Number 1 Catchment

Black and White 1972 Aerial View of the Lower part of No. 1 Catchment.

Kodachrome Aerial of Part of t he Main Gully of No. 2 Catchment

... .

Infra Red Aerial of Part of the Main Gully of No. 2 Catchment ••••••••••

Black and White 1972 Aerial View of the Lower Part of No. 2 Catchment 1946 Aerial View of Lower Part of the Study Area showing High Incidence of Slipping ••••••••••••••••••••••••••

1958

Aerial of Study Area Showing Increased Regenerative Cover ••••••••••

1966

Aerial of Study Ar ea showing Increased Incidence of Slips

62

63

68

74 74

130 130 162

162

163 164 164

177

178

179

(16)

Append ix I

II

III

IV

v

VI

VII VIII

LIST OF

AP~ENDICES

Summary of th e Main Cli m

a

tic Elements in t he Pohang ina District ...

Stratigraphic Table of the Castlecliffian Stage a t Wanganui

• • • 0 • • • • • 0 • • • • • • • • •• •

Geological Sec tion De scri ptions (1) Culling 's Gully Sec

tion

Measured We stward from A xis

(2)

of the An ticline

••••••••••••

Culling's Gul ly Sec tion

Measur ed Eas twa rd from

A

x

i

s of the Antic line ... "' ...

Soil

Profile

Desc riptions

(1)

(2) ( 3)

(4)

Rauma i Sandy Loam

,

Pro file No

. 1

Rauma

i Sandy Loam ,

Profile

No

. 2

Pohangina

Ste epland So ils,

Profile

No .

1 •••••••••••••••

Pohangina Stccpland So ils, l-rofi l e No

. 2

... ..

Common and Botanical Names of

Plants

Used in the Tex

t

....••....••..•....

Land Cap

ability Cl

asse s Used in the Pohangina Survey, 1951

••••••••••••••

Monthl y Dry Weather Flows

Correla tion of Maximum Flood Levels with Discharge for Number 2 Catchment ( Raw Da t a for Figure 5

.

2 )

••••••••••

xv

Page 245

247

248 248

250

252

252 254 256

258

260

262

263

264

(17)

IX

x

XI XII

XIII

XIV

xv

Sediment Loads

(1) R~w Data ( Means and Standard ) Errors ) for Table VI

(2)

Raw Data ( Means and Standard Errors ) for Table VII

Rainfall Records ( 1 )

(2)

(3)

(4) (5)

Rainfall Reco~d (rum) for 1972 for ~he Study Area

Maximum Daily Rainfall for 1972 1972 Rainfall for the Study Arca c.nd Surround.ins Districts Te

Awa

23-Year Rainfall Figures Maximum Rainfall ir. Selected Time Intc~vals from 10 minutes to 72 hours during 1972

Catchment nreas, Raw Data for Table VIII Analysis of Eros~on and Regeneration.

( Data for Figures

5q5

and

5.6 )

Determinati0:i o: 1iv0r:J.ge Slop: using 100 Foot Contou~ Interval

Stream and Crest-line Profiles, ( Ra~

Data for Figures 5u10 and 5.11

(1) Straam Profiles ^"'•^{• •}^{O •}^{o o o}^e ⁿe • t "

(2) _Cres~_-lin_eProiiles •»>• o• •• o...,.,

Raw Dat.::i. for Construction of Area-height and Hypsometric Curves t:if'lono no o •o o• o c - •

265

266

268 268

269 269

270 271

272

273

275

276

277

A hydrological comparison between two watersheds in Pohangina County : a thesis submitted in partial fulfillment of the requirements for the degree of Master of Agricultural Science at Massey University

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

SUMMARY

TABLE OF CONTENTS

Temper a ture

CHAPTER THREE

CHAPTER SIX

ACKNOWLEDGEMENTS

VI VII

LI ST OF PLATES

K n ickpoint

Rauma i Sandy Loam, P:eofile No

St oc k Water Dam with Rush growth and

Append ix I

Culling's Gul ly Sec tion

Land Cap