è Adverse effects on the built resource, infrastructure, people and communities arising from the impact of natural hazards.
Natural processes can impact on amenities and can impose a significant threat to buildings and infrastructure. Such hazards exist over large parts of the District. Flooding can occur at any time of the year with rivers in Westland rising and falling rapidly. A combination of the District’s topography and climate accentuates the flood risk. Flood damage, for example to roads and bridges, can isolate some small communities and individual households and can cause damage to farmland, buildings and communication links. The West Coast Regional Council has a series of flood hazard maps which can be used to indicate the level of hazard in particular areas.
A potentially devastating hazard in Westland is earthquakes. The Alpine Fault runs through Westland and is one of the world’s largest faults. Consequently, earthquakes are probably the most destructive hazard threatening the District. One of the most damaging features of the earthquake hazard is their potential to trigger other hazards such as landslides and tsunami. There is also concern regarding liquefaction and post earthquake flooding by rivers being dammed. The coastal location of some of the District’s settlements means substantial losses could occur.
While most of the coastline in Westland District is eroding, it presents a hazard only where there is a threat to existing development and infrastructure. For example, both commercial and residential properties in Hokitika are especially vulnerable to flooding and coastal erosion, however the cost of moving buildings is such that it is not practicable to remove urban zoning from Hokitika.
As well as coastal erosion, blockage of some lagoons and river mouths occur periodically, for example at Okarito, causing surface flooding of the township.
Significant landslide, stability and flooding hazards exist elsewhere. Otira township and the Mount Adams/Poerua River are known examples.
3.13.1 Rules for the avoidance and mitigation of natural hazards have been incorporated in the District Plan given that severe hazards pose a significant threat to the built resource and infrastructure of the District and people and communities.
Rules for the avoidance and mitigation of natural hazards have been incorporated in the District Plan given that severe hazards pose a significant threat to the built resource and infrastructure of the District and people and communities.