4 Identification of natural hazards

Identifying natural hazards is the initial requirement of any programme designed to estimate the risk from natural hazards and design management strategies.

The range of hazards identified as threatening an area depends to some extent on the scale of investigation (both in time and space). Assessment can be carried out at the regional, subregional or site scale. Assessments can focus on present conditions, or can extend into the future to take account of changing environmental conditions (e.g. climate change) or social conditions (e.g. population growth or new settlements). As a result, both actual and potential hazards may be identified. Table 1 provides an example of the range of hazards that might be identified in a region.

Table 1. Natural hazards grouped by main causal agent (Crozier, 2006)

Meteorological / Hydrological	Geological and Geomorphic	Biological	Human / Natural
Drought Low river flows Agricultural * Domestic water supply Groundwater Flood Overbank flows Hyper-concentrated flows Surface flooding Fog Freezing rain (surface ice) Frost Hailstorm Heat wave / cold wave Snowstorm Storm surge (ocean) Lightning strike (fire) Cyclone/tornado/ hurricane Windstorm	Avalanche snow & ice Earthquake Ground shaking Fault rupture Liquefaction Lateral spread Seiche Landslides Tsunami Erosion Coastal Riverbank Slope Agricultural soils Expansive soil Landslides Fall Topple Slide Slump Flows (including lahars and debris flows) Lateral spread Shifting sand Tsunami Volcanic eruption Pyroclastic flow Ash falls Lava flow Earthquakes Gas plumes Weak foundation material	Algal blooms Animal infestations Bacterial and viral diseases Fungal diseases Plant infestations	Avalanches snow Air pollution Bush/grass fire Erosion Landslides Smog

* soil water reducing below wilting point or to a level that reduces crop quantity and quality

Note that categories are not mutually exclusive.

Specialists with appropriate expertise need to be employed for the purpose of hazard identification. They will use a range of information sources, including those identified in section 5.1.1.

Descriptions of New Zealand hazards can be found in Speden and Crozier (1984) and on CRI web sites e.g. http://www.gns.cri.nz/what/earthact/modelling/index.html