Volume One 11. Natural Hazards 11. Natural Hazards Introduction A natural hazard is defined in the Resource Management Act 1991 (RMA) as any atmospheric, earth or water related occurrence that may adversely affect human life, property or other aspects of the environment. They include earthquake, tsunami, liquefaction, erosion, volcanic and geothermal activity, landslip, subsidence, sedimentation, wind, drought, fire and flooding. On their own, natural processes do not constitute a hazard; they only become hazardous when they adversely affect human lives, property and infrastructure. Marlborough is characterised by its physical contrasts. The diversity of landscape, climatic conditions and coastline, combined with dynamic geological forces mean that most of the hazards described above can be experienced in Marlborough. The only exceptions are volcanic and geothermal hazards. Civil defence emergency management in New Zealand is based on four principles – reduction, readiness, response and recovery. The Marlborough Civil Defence Emergency Management Plan (CDEMP) provides strategic direction for the effective and efficient management of all hazards in the District. The CDEMP details the frameworks for readiness, response and recovery. A risk assessment of all likely hazards and consequences is identified in the CDEMP. Earthquakes are identified as having an extreme risk rating, flooding and wildfire have a high risk rating, while coastal erosion and tsunami have a low risk profile. The Council can act to reduce the risk of natural hazards adversely affecting life, property and regionally significant infrastructure. Using its functions under the RMA to control the use of land to avoid or mitigate natural hazards, the Council can influence the location and management of new developments to ensure that they are not subject to unreasonable risk. Other land uses may adversely affect hazard mitigation works and these can be similarly controlled to ensure that the integrity of the works is not compromised. Issue 11A – Natural hazards in Marlborough, particularly flooding, earthquakes and land instability, have the potential to cause loss of life and significant damage to property and regionally significant infrastructure. Marlborough is subject to a wide range of naturally occurring hazards. Earthquakes, tsunamis, land instability, severe rainfall, flooding, wind, drought, fire, hail and snowfall can occur in Marlborough. From experience, the two most potentially damaging natural hazards in Marlborough are major floods in the Wairau River catchment and high magnitude earthquakes from the rupture of a fault. However, the likelihood of any of these hazards occurring in any given year varies significantly. Similarly, the consequences of any natural hazard will depend on the nature, size and location of the hazard event and the land use in the area. Flooding has been the most regular natural hazard experienced in Marlborough. Historically it has caused considerable damage to properties and infrastructure, especially to residential properties in both rural and urban environments, farm properties (including stock losses) and transportation links. Significant investment has been made to reduce the risk of flooding, including flood protection works along the Wairau River and its tributaries, and along the Waitohi and Waikawa Rivers in Picton. These works include changing the location of rivers through the construction of diversions and blocking off alternative outlet channels through the provision of 11 – 1