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Hazardscape

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Hazards are defined as a natural or technological phenomenon or human action that may cause or contribute to damage to the environment, life or property.

For more information on natural events, natural disasters, natural hazards and risk read Defining Moments in Nature [PDF, 3184 KB]

Hazardscape in Selwyn District

In Selwyn, the higher priority hazards are:

Hazards and Consequences

Earthquake

Canterbury is located in a wide zone of active earth deformation associated with the oblique collision between the Australian and Pacific plates in the area east of the Alpine Fault.

There are a number of active faults in the Selwyn district. The main faults are:

  • The Christchurch Fault;
  • The Porters – Amberley Fault Zone;
  • The Torlesse and Esk Faults; and
  • The Cheeseman, Craigieburn.

Any major seismic activity along the Alpine Fault would impact on the district. However, an impact on the Porters – Amberley Fault will have more significant damage to lifelines and the community. The Selwyn District Earthquake Hazard Assessment (2004) provides more details as to impacts and consequences of movement in these faults.

For more information on earthquakes, read our Earthquake [PDF, 3136 KB] and Liquefaction [PDF, 1880 KB] information booklets.

Key Local Lifeline Failures

The Council, as asset manager of significant community lifelines (water – waste/potable, sewerage systems, roads/bridges and buildings), has in place asset management plans to respond and manage the response to a disaster event. A Utilities Lifeline Response Plan has been developed to manage the response.

Flooding

Lake Ellesmere has flooding potential around the shoreline due to high river flows from the Selwyn River or when the Lake is high due to opening being delayed and a south easterly wind direction. This can impact on lakeside communities such as the Upper and Lower Selwyn Huts and Greenpark.

The district is bounded by two major rivers – the Waimakariri to the north and the Rakaia to the south. Both rivers have high flooding potential especially in lower areas of the Selwyn District. Flooding from the Waimakariri has the potential to affect a wide area of the district between the river and into the Halswell catchment.

The district is also bisected by the Selwyn River which is fed into by the Hororata, Hawkins and Waianiwaniwa Rivers. These three rivers cause localised flooding and disruption to road access.

The Selwyn River has potential to flood areas from Glentunnel to Lake Ellesmere. Areas to be affected include Glentunnel Holiday Camp, farms, farm land and houses down river through Chamberlains and Coes Fords to Lake Ellesmere. Also affected are the communities of Upper and Lower Selwyn Huts. If the Selwyn River breaches out above Dunsandel it has crossed State Highway 1 and entered the Irwell River catchment. The river passes through Brookside and Irwell to Lake Ellesmere.

There is the potential for flooding from the Halswell and Liffey Rivers. These rivers affect the area from the Christchurch City boundary to Lake Ellesmere.

Wild Fires/Rural Fires

Wild fires are a serious hazard both in the hill and high country of the district as well as on the plains.

The hill and high country ranges from low foothills to sub-alpine and consists of farming land and tussock forests.

The plains area is extensively farmed, with the fire risk reducing in some areas due to dairy conversion. However, the fire risk remains high during summer seasons due to land use, hedges and shelter belts. The number of exotic forests continues to reduce due to land conversion. The Council Fire Plan sets out the fire risk management strategies and policies to manage fire risk in the district.

Meteorological Hazard

The district has historically been subject to wind storms and large snow storms.

Wind storms are characterised by weather patterns where a blocking high pressure system is situated to the north of the North Island and a low pressure system approaches from the southwest.

Historically, windstorms have caused damage to utilities, trees and buildings.

Large snow storms are typically as a result of slow moving deep depressions embedded in a cold south-westerly or south-easterly air stream.

Snow storms from the south-west tend to affect the hill and high country and have caused property damage and loss of stock. Road access and lifelines have also been affected.

Snow storms from the south-east affect the Plains area. This area is populated by farms and small towns and snow has caused disruption to everyday life with disruption to utilities, communities and farms.

Are you in a current snowfall area? Are you ready for snow? See our map of township elevations.

The Council accepts it has a role to play in these events under the Ministry of Agriculture and Fisheries (MAF) on Farm Response and Recovery Plans for climatic and natural disasters.

Animal Disease Epidemic

Selwyn district as an agricultural district would be susceptible to a range of agricultural disaster events both on farm and at Research Institutes.

The Council would carry out its role in assisting any response through its Disaster Recovery Plan and required council activities.

Human Disease Epidemic

Selwyn district, as with the rest of New Zealand, may be affected by a large human disease epidemic. The Council has in place a Selwyn District Pandemic Co-ordination Plan to co-ordinate the community response to a pandemic event in conjunction with the Civil Defence Emergency Management (CDEM) Local Arrangements.

Transportation Disasters

Selwyn District is close to Christchurch International Airport and has State Highways and Rail Systems passing through the area.

Both the State Highways and Rail Systems pass through communities and the potential for a disaster event exists.

Otira rail tunnel with portals at Arthur’s Pass and Otira is a high risk area. Police and rail operators have management plans to respond to an event in the tunnel.

Road and Rail carry fuels and hazardous chemicals as well as passengers.

The southern approach to Christchurch International Airport is over communities which would be affected if an aircraft came down in the area.

All Hazard Approach

Selwyn District Council has an All Hazard Approach to Emergency Management and offers support to other agencies leading up to, during, and after an emergency event.

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