WATER & SOIL - These are not the droids you are looking for.

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d qgoinst CATCHMENT AREA for South Istond x
64
x+O
¡XOs
Xt
x
o
74314 Toieri
1é
x V,/est CoqsT
+ Eqst Coost
O Intond Morlborough/
Conterbury
O Mqckenzie, Inlqnd Ofogo,
Southlond
10
Iotch me n I
100
A¡e u (kmz)
1000 10000
Fþure 4.3 O vs AREA, South lsland catchments.
the inland hill country of Marlborough and Canterbury.
The southern part includes the Waitaki River basin, inland
Otago and most of Southland. This division is made on the
basis that with the exception of coastal Southland, the
southern part is a low rainfall area for which Q rvas overestimated
by the equation.
The regional division is evident in Figure 4.3. When the
catchments were identified according to the region including
them, it was found that data for West and East Coast
regions tend to lie in an upper band. Those for Inland Ma¡lborough/Canterbury
tend to lie in a central band, whereas
those for Inland Otago and Southland tend to lie in a lower
band.
The data were grouped according to these regions and regional
stepwise regressions were calculated (Table 4.5). In
all cases AREA is the most important variable, although in
all regions additional variation in log Q is explained by
other variables. In the West Coast, and Inland Otago and
Southland, rainfall intensity (I2Z)'signifïcantly improves
the fit of the estimating equations.
For the East Coast, MARAIN is the second most important
variable. The reason this is more important than I2Z is
therefore preferred.
Water & soil technical publication no. 20 (1982)
not obvious. It naay be that, because the East Coast catchments
are relatively small (the largest, Station 64301 is
464 km'z), the 2-hour storm intensity may be more important
than the Z4-hour figure used. However, such information
was not generally available. The appropriateness of
annual rainfall for estimating a flood parameter is open to
question, but it is supported by Figure 4.5. This figure
shows that, with the exception of Station 65Ð2, there appearsto
be a linear relationship between log MARAIN and
the residual of log Q, after the effect of AREA is removed.
This is the justification for including MARAIN in the estimating
equation.
For Inland Marlborough/Canterbury FOREST appears
as significant in the best-fit equation. However, this is a little
deceptive since only 4 of the 15 of the catchments in this
region are more than l09o forested and the ma¡