Chapter 17 - Natural Hazards Tsunami Tsunamis are large waves triggered by earthquakes, landslides, underwater slumping or underwater volcanism. Tsunamis can result in marine flooding of large areas of land with its associated impacts. Tsunamis in this area may result in marine inundation of the Rarangi settlement, low- lying farm lands, Lake Grassmere and the Wairau Lagoons. The frequency or size of tsunamis and the extent of inland flooding has not been estimated and would be very difficult to quantify. 17.4.2 Objectives and Policies Objective 1 Management of areas prone to coastal hazards to avoid loss of life, and avoid or mitigate damage to property, infrastructure and the environment as a result of the occurrence of natural hazards. Policy 1.1 To assess the likely need for coastal protection works when determining appropriate subdivision, use or development in the coastal environment and where practicable avoid those for which protection works are likely to be required. Policy 1.2 The ability of natural features and systems to provide a natural defence to coastal hazards, including erosion, inundation and sea level rise, should be recognised and the integrity of such features or systems be protected where appropriate. Policy 1.3 To avoid developments or other activities that are likely to interfere with natural coastal processes including erosion, inundation, except as provided for in Policy 1.5. Policy 1.4 To monitor and research coastal processes and the extent to which they constitute a hazard. Policy 1.5 To allow the establishment of coastal protection works only where: • The works are justified by a community need; • There are substantial capital works or infrastructure at risk; • Alternative responses to the hazard (including abandonment or relocation of structures) are impractical, impose a high community cost, or have greater adverse effects on the environment; • It is an inefficient use of resources to allow natural processes to take their course; and • Protection works will not generate further adverse effects on the environment or transfer effects to another location. Policy 1.6 Provide warnings and emergency response procedures for areas at risk from or affected by predictable coastal hazards. 17 - 9