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NELSON REGIONFL CURVE
BEOUCEO Y VRRIÊTE
FETUNN PEBIOO (YEHRS)
Figure 3.23 Mass probability plot and fitted curve for the Nelson a¡ea.
3.14 was fiued ro rhe combined set of original and new 3.4 FlOod ffequency acculacy
averages using the optimisation technique.
Figures 3.24 and,3.25 show, for the combined western 3.4.1 Accuracy of flood frequency tat¡o Or/õ
and eastern areas, respec
was fitted to the two types
the extension method arç
tern generalised curve id
marised in Table 3.7.
T¡ble 3.7 Summary of the characteristics of the generalised
curves.
al curve, it is
of statistical
sets of flood
peak data used to define the curye _ if different sets
of records of equal length had been available the curve
would be different; and
(b) tne spatial variation due to the curve being taken as an
of the flood frequencv relation-
ï"t#iltriiLt iJerage
Since in this study a regional curve is interpreted as the
o./o_
o,o/_o
Oro/O
O.o/õo,@/_o
O'æ/Q
O¡æ/O-
Oroo/O
u=
o= k:
General
Eq;ation:
4
Western N.Z.
1.18
1.42
1.67
2.O4
2.36
2.71
3.23
3.68
0.788
o.234
-o.1s6
O/O = -0.714+
1.502 exp (0.1 56yl
o/o
Eastern N.Z.
1.49
1.87
2.23
2.71
3.06
3.42
3.88
4.24
o.724
0.509
=O.724+
O.6O9y
var (a.b) = E(a),.var(b) + E(b),.var(a) 324
where E ( ) denotes the expected value and var ( ) the variance.
Errors of estimation in Q can be considered statistically
independent of errors of estimate in the regional curve ordinate
Q.¡/Q. Hence, applying the expansìon in Equation
Water & soil technical publication no. 20 (1982)