Home' Greymouth Star : August 16th 2014 Contents Greymouth Star
6 - Saturday, August 16, 2014
his river is
a good ford, at the same place next day
you may find 10 feet of water, or quite
as likely, a dry shingle bank instead of
the river.” — Warden D Macfarlane, in
a letter to the West Coast Times, April
Known to Maori as the Waiau, in
reference to its swirling, swift waters,
and misheard and consequently
misnamed by European sur veyors as
the Waiho, this river has been causing
problems for as long as man has tried to
live within its reach.
In March 31, 1911, the Grey River
Argus reported a great flood had put
Batson’s Hotel (formerly the Toi Toi
Home) in danger.
“The water is over the plates of the
building and the people in it have had
to leave the house, the river being a
So they moved the hotel, hoisted it
up the hill on a crude wooden ramp,
tottering on its journey to safety. It was
not the first building to be evacuated
out of harm’s way, and even today
others will follow in its path.
In 1998, a report to the West Coast
Regional Council by M J McSaveney
and T R H Davies had the job of trying
to piece together the complex history of
The Waiho is an ‘alluvial fan’ which
means the river widens as it leaves a
confined channel in a narrow valley. It
is always coloured grey due to the large
amount of ‘fine glacial flour’ from the
ice river just a few kilometres upstream.
The Waiho and its immediate
tributary the Callery River together
generate what the scientists call large
‘slugs’ of sediment. Some of these
‘slugs’ are flushed out from beneath the
glacier. Some occur when large sections
of high terraces of gravel collapse, and
some when debris avalanches fall into
the Callery River gorge, or into any of
the steep tributaries.
In a nutshell, huge quantities of
sediment are continually eroded from
the mountains, and end up in the
riverbed. Nowadays constrained by
stopbanks, the riverbed therefore just
keeps on rising.
Old photographs offer the scientists
a glimpse of the past, before the
stopbanks went up. One shows the
construction of the first road bridge in
1927, with huge boulders that persisted
for many decades.
In the 1930s the airstrip was flooded
and a ‘dam break’ was recorded. The first
permanent river control works were
erected in that decade to keep the river
off this terrace.
By 1948, the first aerial photos show
the extent of the gravel build-up.
However, it would be 20 years before
that began to be a problem at the
By then the solution had became part
of the problem. As scientists recorded,
the ad hoc stopbanks attempted to
hold this “powerful river in too small a
portion of its historic flood plain”.
By April 1985, the gravel build-up
was so great that the State highway
bridge had to be raised. This was
repeated in 1996 and again in 1998.
“ Bigger, higher stopbanks will lead
in the short-term to a further need
for even bigger, higher stopbanks,” the
In 2012, another scientist, Robert
Hall, concluded that the river
protection works were constraining
the active riverbed within artificial
His report makes grim reading.
Stopbank failure along the true left
(south) bank upstream of State highway
6 would result in loss of the access
road to the glacier, and flood damage
to the State highway, the motels,
backpackers and any dwellings in its
As well as describing a series of
catastrophic scenarios, he also puts
for ward some solutions.
One is boundary relaxation — that
is, a stopbank should be removed
altogether to allow the river to
re-occupy part of its natural alluvial
fan surface. That would mean
abandoning extensive farmland on the
Another option is the rapid
abandonment of the current channel,
letting the river flow into the Tartare
River, which is just north of the Waiho.
Of course, the stopbanks could be
raised again. But the higher they go, the
more they tower over the flood plain,
and the more constrained the ever-
rising riverbed becomes.
“ It hardly needs saying but the
management of this river now in the
interests of minimising risk to life and
property is an extraordinarily complex
and difficult exercise. Inevitably, there
must be losers,” Mr Hall concluded.
PICTURES: West Coast Regional Council collection
The Waiho (Waiau) River at Franz Josef Glacier poses a major dilemma. For at least 75 years the bed
of this river, which issues from the glacier itself, has been building up steadily, recently by an incredible
20cm a year. Forty years ago the riverbed was 8m lower than it is today. As the riverbed rises, the risk
of floodwaters overtopping the rock stopbanks worsens, to the extent that civil defence alarms are
now a regular occurrence after heavy rain. Raising the floodwalls repeatedly is not sustainable. That
leaves another option — relax the river boundaries, allow it to migrate naturally, and sacrifice land in
the process. The West Coast Regional Council plans to meet with affected ratepayers to discuss a way
forward. LAURA MILLS looks at the science and the troubled history of the Waiho River.
Batson’s Hotel was the first casualty of flooding. It was moved to higher ground in 1911.
Former regional council staff member Rick Lowe checks the
narrowing gap beneath the temporary bridge.
The river in flood, 1989.
The river in 1991, even closer to the old bridge.
Flood protection work under way, 1991.
The old suspension bridge in September, 1991 next to the ‘temporary bridge’ which is still there today.
Waiho in flood in January, 2013.
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