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or more annual peaks, however, the annual peaks themselves were not considered for the mass plot. Condition (v) was necessary because the flood estimation method sought was intended for rural catchments, not urban ones. Condition (vi) was imposed in the belief that flood frequency characteristics of the very small and the larger catchments would be markedly different. It was anticipated that the effect of catchment storage in dampening the flood hydrograph would be less in the very small catchments, producing a steeper frequency curve of Q/Q than that for a laiger catchment with the same rainfall excess. An area of 20 kmt was chosen as the lower limit on the size of a catchment. It was later found, however, that catchments of smaller size could have been included in some of the regions (section 3.5.6). An exception to the lower limit of 20 km'z was made for the Northland-Auckland area. In this part of the country there are relatively few large catchments, and without a relaxation on the minimum catchment size any flood estimation method would have only limited application. Moreover, the presence of swamps had caused the rejection of a number of annual series samples for flow stations in the area. Therefore, to ensure that a reasonable amount of flood peak data was obtained for the area and to enhance the practicability of the resultant flood estimation method, the lower limit on catchment size was reduced in the Northland-Auckland area to 2 km'. The data samples collected were plotted on Gumbel probability paper and, after checks were made of their repiesentativeness (section 3.2.2), samples for 152 stations were finally accepted for use. For 148 of these stations - 96 in the North Island and 52 in the South Island - the annual series was eight years or longer; the remaining four stations had historical information and an annual series of between fltve and seven years in length. Five of the stations were later omitted for the derivation of the regional curves (see Table 3.2 and Appendix B). The location of all the staiions, and their associated catchments, are shown for the North and the South Islands in Figures 3.4 and 3.5, respectively. Information on the stations is listed in Table 3.2' grouped according to the regions into which the stations were initially classified (section 3.3.1). The annual flood peak data for the stations, statistics of the data, and comments on the data and the catchments are summarised in Appendix B, again according to the initial regional classification. Attempts to extend short records by correlation with adjacent longer records for a sample of stations in the northern half of the South Island were unsuccessful and the approach was not Pursued. 3.2.2 Minimum record length and outliers ferent distribution' on the use of an outlier are given by Irish and Ashkanasy are as follows: Water & soil technical publication no. 20 (1982) (i) lf 5
'o ,l\, I zl l- I Water & soil technical publication no. 20 (1982)
Page 1 and 2: WATER & SOIL TECHNICAL PUBLICATION
Page 3 and 4: Regional flood est¡mat¡on in New
Page 5 and 6: Tables 1.1 Risk ofexceedence for sp
Page 7 and 8: Preface Water & soil technical publ
Page 9 and 10: annual flood Q (the mean of the ann
Page 11 and 12: Water & soil technical publication
Page 13 and 14: Doto ovoiloble on TIDEDA Figure 2'1
Page 15 and 16: P=45 O= 15 x4 (l) '= o o t.25 2'.O
Page 17 and 18: Êv2 ( ko) Reduced Voriote y I'O t1
Page 19: turn period. A plotting position fo
Page 23 and 24: Table 3.2 Flow stat¡ons used. SITE
Page 25 and 26: e process of examining the simtrend
Page 27 and 28: Iì_ t_ I I I I I I I t-. I I tñ I
Page 29 and 30: Þ I"IEST COFST 0 o I E 6o o o 25 3
Page 31 and 32: SOUTHEBN REDUCEO Y VRBIßTE NETURN
Page 33 and 34: SOUTH ISLFND HEST COFST I]ÊTR èo
Page 35 and 36: SOUTH CÊNTERBURY DRTÊ NEOUCEO Y V
Page 37 and 38: COMB I NED ,,IE5T CORST DRTR o rt
Page 39 and 40: BÊY OF PLENTY DRTF o o o NEOUCEO Y
Page 41 and 42: NOBTH ISLRND ßEGIONÊL CUBVES 1.50
Page 43 and 44: data for this area are required bef
Page 45 and 46: NELSON REGIONFL CURVE BEOUCEO Y VRR
Page 47 and 48: 46 EÊSTEFìN NEI,,I ZEFLÊND DÊTI
Page 49 and 50: Table 3.9 The grouping and the grou
Page 51 and 52: allowing curves rather than just st
Page 53 and 54: 3.5.5 Extension method The NERC (19
Page 55 and 56: Table 4.1 South lsland catchment ch
Page 57 and 58: I 2 t l¡ 5 5 7 I 9 l0 t1 ,12 I5 1{
Page 59 and 60: decided instead to use estimates of
Page 61 and 62: \Í l{ I t, ìj( Fþurc 4.4 Distrib
Page 63 and 64: 62 Fþurc 4,6 Logarithmic rcsidual
Page 65 and 66: Table 4.6 Final equations for South
Page 67 and 68: I ++ ++ * E 4.6 Analysis of North l
Page 69 and 70: Non Pumice = õ = 3-24xto'6 AREA'7
Page 71 and 72:
Northlond f C"ro^ondel f Eost Cope
Page 73 and 74:
Table 4.11 Comparable equations for
Page 75 and 76:
Poo led cv Pooled o.40 F¡guro 4.12
Page 77 and 78:
mates of Cp typically range between
Page 79 and 80:
-J æ 'll o Eo !¡ Assemble llood p
Page 81 and 82:
Year 1958 1959 1960 l96r t962 1963
Page 83 and 84:
The estimate of Q from the regional
Page 85 and 86:
Water & soil technical publication
Page 87 and 88:
Maguiness, J.A.; Blackwood, P.L.; B
Page 89 and 90:
The liequency factor K is a functio
Page 91 and 92:
e.9., Linsley et ol. (1915); lrish
Page 93 and 94:
Maguiness, J.A.; Blackwood, P.L.; B
Page 95 and 96:
sltt 930 t [rûltRÀict ¡ l? s;¡t
Page 97 and 98:
3950't flrlÀRt R tr îlt¡Ît ;tP
Page 99 and 100:
S ITI 29202 RuNttiltcl I ¡t tllEtt
Page 101 and 102:
ïI-'_____ ::19: lt¡IPt0r n À1 i
Page 103 and 104:
9100r GNE? R ¡T DOBSO| s¡18 93207
Page 105 and 106:
6800 1 sBlrri R tT SrITEC¡,tttS 6I
Page 107 and 108:
APPENDIX C Summary of tho data for
Page 109 and 110:
oæ ON LAT. STATION NA ATION LAT. N
Page 111 and 112:
o NUI,IBER HHAKAIIARU 854801 38 L7'
Page 113 and 114:
l9 AT NU¡IB ËR AR',tËtlANA ÂRAI
Page 115 and 116:
A ON LAT. STATION NA NUMBER AHUNA 5
Page 117 and 118:
â NUI,IBER Lü{G.E ON NU14EER I,IU
Page 119 and 120:
æ TATI ¡rouNT sor.tERS 7L740? 43
Page 121 and 122:
N) o STATIoN NAr{gmLfï3---ffij NUI
Page 123 and 124:
APPENDIX E Compadson of Regional Fl
Page 125 and 126:
Table F.2 Flood peak data. NEW OTAG
Page 127 and 128:
F.3 Analysis and results tatively p
Page 129 and 130:
ét êt REOUCEO VßFIHTE 2. 33 5 l0
Page 131 and 132:
SOLITH I EA l') COAST soUTH CANTERB
Page 133 and 134:
0tiftflt a itÉitut5 ü¡. il/5 tg?
Page 135:
Water & soil technical publication
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