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Tablo 3.4 Summary of the regional curve characteristics. Region Regional Curve Ordinates Regnl. Parameter Values for Eq. 3.14 or 3.23 O, sglO O¡/O O,o/õ Oro/O O.o/õ O,oo/O OrooiO Regional Cuwe Equation,OO = NORTH ISI.AND 1. Combined N.l. West Coast 1.OO 2. Bay of Plenty 0.96 3. N.l. East Coast 1.OO 4. Central Hawke's Bay 1.OO SOUTH ISI.AND 5. S.l. West Coast O.99 6. S.l. East Coast 1.OO 7. South Canterbury 1.OO 8. Otago-Southland O'98 1.30 1.55 1.31 1.62 1.43 1.78 1.49 1.89 1.22 1.41 1.31 1.56 1.52 1.95 1.33 1.62 1.78 2.09 1.96 2.46 2.12 2.56 2.27 2.77 1.59 1.82 1.80 2.12 2.39 2.94 1.89 2.25 2.32 2.55 2.87 3.33 2.89 3.21 3.14 3.51 1.99 2.16 2.35 2.58 3.44 3.91 2.51 0.804 0.330 0.762 0.325 0.726 0.469 0.696 0.s32 0.846 0.249 0.809 0.335 o.689 0.529 o.762 0.380 O.8O4 +O.33Oy -O.142 1.53O+2.292exp lO'142Y1 O.726 +0.469y 0.696 +O.532y O.846 +0.249y 0.8O9 +o.335y -O.O52 -9.545+10.234 exp (O.O52y) 0.762 +O.38Oy both regions, and to have included it in either regional plot \r/ould bias the resulting regional curve; down\ryards in the case of the Bay of Plenty curve and upwards for the North Island East Coast curve. The Te Teko station was therefore omitted from the derivation of the regional curve for both regions. Clearly, in deciding which regional curve to use for points on the Rangitaiki River system, consideration needs to be given to such factors as which region contains the greater proportion of the catchment area, and whether the western or eastern part of the catchment contributes most to the peak flows at the point in question (see also section 5.2\. The number of stations near the eastern boundary of the Bay of Plenty region permitted such a detailed examination ofihe boundary line. In general, however, there were insufficient stations to be able to do this' Most lines were subjectively defined and they should be regarded as broad dividing iines between regions. To define the regional boundarils more precisely will require more flow stations with more flood peak data. 3.3.4 Final rog¡onal curves The final regional flood frequency curves that were derived are summarised in Figure 3'20. In general' the curves The excePtion is the minimal amount of gional curve Past 100 years, and the curve is tentative only. The ordinates Q'¡/Q for the final regional curves are listed in Table 3.4 for selected return periods. As well, the the eastern South Island area identical to the annual flood regions defined f,or estimating Q (section 4.5). Regional plots correspondirng to the flood regions in the area were constructed, but the data showed substantially greater variability than was evident in the plots for the original flood frequency regions, i.e., Regions 6, 7 and 8 in Figures 3'14- 3.16. Still pursuing the possibility of having consistent regions, all of the flood peak data for the three flood frequency regions were subsequently pooled together, forming a combined region known as the Eastern South Island region. The regional plot that was obtained for this area, and the resulting regional curve, are shown in Figure 3'21. A comparison of this plot with those for the original three flood frequency regions (Figures 3.14-3.16) shows that the variability in the data for the combined region is much greater. This is borne out by the standard error equation developed for the regional curve of the combined area which gave a C¡ I'alue at the 100-year return period, for example, that was 25 percent greater than that given by the group equation (llable 3.9) for the original regions (see section 3.4.1). This greater variability was not surprising in view of the range in the ordinates of the regional curves for the three regions. For instance, at the lü)-year return period the difference between the South Canterbury and South Island East Coast regional curve ordinates is l.l8' or 50 percent of the ordinate for the latter curve. Because of this iange, and the greater variability in the regional plot for the combined area, tlhe curves for the three original regions offer a more accurate estimate of Q/Q for sites in the area and the three regions were therefore retained as the flood frequency regions. 3.3.5 Consistent regions For th the resul made of 3.3.6 Sub-reglons It will be noted that two small areas in Figures 3.6 and 3.7 have been specially identifl¡ed as sub-regions. The first is that area around Mt Egmont in the combined North Island West Coast region (see Figure 3'6). Flood peak data were available for onìly two stations in the area, although each was associated u¡ith a representative basin. The catchment for the station on the east of the mountain (site 39504, Manganui River at Tariki Road) was included in the North Island West Coast region after its flood peak data were found to conform very well with the regional flood frequency tr€nd. The second station (site 36001, Punehu River at Pihama) was located on the southern side of the mountain. Its flood peak data displayed distinct upwards curvature on a probability plot, a trend markedly different from the regional one,, Because it was uncertain whether this was ase ofaPPlication of a real trend, or simply the result of using a short record an examination was (eight years), the southern area of Mt Egmont was excluded frequencY regions in from the North ltsland West Coast region' More flood peak Water & soil technical publication no. 20 (1982) 39
NOBTH ISLRND ßEGIONÊL CUBVES 1.50 2.?S 3. OO REDUCED Y VRBIßTE 2,33 sl02030 BETUBN FERIOO (YE8BS) 50 75 r00 Flgure 3.2Oa Summary of North lsland regional cury€s. SOUTH iSLÊND REGIONÊL CURVES 1.50 2-25 3.( BEOUCED Y VRBIFTE s r'o ¿'o g'o RETUNN PEBIOO IYERNS) 1t.50 5.2S so 7s t00 200 4 Fþure 3.2Ob Summary of South lsland regional curves. 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 and 20: turn period. A plotting position fo
Page 21 and 22: 'o ,l\, I zl l- I Water & soil tech
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: BÊY OF PLENTY DRTF o o o NEOUCEO Y
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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