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West Coast flooding - Expert Reaction
The West Coast region of the South Island has declared a state of emergency following torrential rain on Tuesday night and Wednesday morning.
The Waiho bridge - which spans the Waiho River just south of Franz Josef - collapsed on Tuesday afternoon, leaving the road between Franz Josef and Fox Glacier impassable until the bridge is replaced.
There has also been a slip on State Highway 73 between Arthur's Pass and Christchurch, near Candys Creek.
The SMC gathered expert comments on the resilience of remote communities to hazardous events. Please feel free to use these comments in your reporting.
Dr Caroline Orchiston, Deputy Director Centre for Sustainability, University of Otago, comments:
"The West Coast is a long, narrow region, with a road and bridge network that is also long and narrow with very little network redundancy. It is accessible only via alpine passes (Haast and Arthur’s) that are susceptible to closure by landslides during heavy rainfall and earthquakes.
"Because of the high mountains and the westerly weather systems, the Coast also experiences very high rainfall and so perennial flood and landslide hazards, and interruptions to the road network, are quite common.
"The Franz Josef area is a highly dynamic, hazard-prone environment because of the glacial valley and the Waiho River that flows from it. As the glacier retreats, more material (sediment, rock) is coming down the valley and so the river has been aggrading (or raising the river bed) downstream and beneath the Waiho bridge. Flood protection structures in the area have protected the township from floods in the past. The river in high flow presents a very significant risk to downstream communities.
"The human impacts of losing the bridge are significant, particularly for the movement of people and goods, including tourists. The West Coast circuit through the alpine passes won’t be possible until the bridge is repaired.
"NZTA has been working to a schedule of bridge and highway improvements on the West Coast to increase the resilience of the network in recent years. The highly dynamic natural environment of the West Coast means that there will be disruptions to the network, and the recovery of the network will rely on how quickly temporary bridges can be put in place.
"West Coast Civil Defence Emergency Management has been working with communities on the West Coast to develop local community response plans so they can be better prepared to look after themselves if they are isolated by road and air for a period of time."
No conflict of interest.
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