Types of maps

There are many different ways to map various hazards and risks, for example:

Each of these are explained in more detail below.

The scale of map is important for its intended use. For example, a 1:250,000 map will not be useful for site-specific land use planning. For examples of different scales of maps and their uses.

Hazard map
Hazard maps include a time frame/likelihood reference. For example, the map (below) shows the 2010 National seismic hazard model for New Zealand showing expected peak ground accelerations for a 475 year return period earthquake for shallow soils (Stirling et al., 2012, p1531).

Hazard map

Risk map
Risk maps show the consequences of an event with a likelihood scale. The example below shows Westport, with a 500 year flood hazard mapped on the left (i.e. a hazard map); and the figure on the right shows a risk map with the 500yr flood with number of buildings per km2 in a damage state of moderate or greater.

Risk maps generated from Riskscape

Susceptibility maps
These maps combine different factors which contribute to a hazard, to give an indication of where hazard is more likely to occur. For example, the figure on the left shows the susceptibility of slopes to landslides from an earthquake by combining slope, geology, rainfall, vegetation, and aspect. No time factor associated with a susceptibility map (unlike hazard map).

Earthquake Induced Slope Failure Susceptibility, Wellington (Kingsbury, 1995)

Inventory Map
Inventory maps show a collection of events that have occurred at a location. The location of previous events is a good indicator of where future events may occur, and allows analyses and testing of susceptibility, hazard, and risk analyses.

The example below shows areas inundated by lahars (or volcanic debris avalanches) and associated floods from Ruapehu, over the last 20,000 and 10,000 years, and since 1860. It is also a simplistic hazard map as it has a timeframe associated with lahars.

(http://gns.cri.nz/Home/Learning/Science-Topics/Volcanoes/New-Zealand-Volcanoes/ Volcano-Geology-and-Hazards/Ruapehu-Geology)

Evacuation map
An evacuation map is used by emergency managers and communities to plan for evacuation in an event. For example, the tsunami map on the left shows three different zones that may be required to be evacuated. A map like this is based on modelling of events.

Red zone Shore-exclusion zone that can be designated off limits in the event of any expected tsunami.
   
Orange zone Area evacuated in most if not all distant and regional-source official warnings (i.e., warnings that extend beyond the red zone, for tsunami from sources more than one hour of travel time away from the mapped location).
   
Yellow zone The yellow zone should cover all maximum credible tsunami, including the highest impact events. The intention is that the yellow zone provides for local-source maximum credible events, based on locally determined risk.
   

Wellington City tsunami evacuation map