Factors that influence hazard maps

The value and use of hazard maps may be influenced by a number of important factors: scale (and detail ), units of measurement, and sampling.

Scale

The flood map of New Norfolk shows great detail at the local level, which can be used for local land use planning and emergency response planning. But what of small-scale maps?

 


Activity 5.5

learning portfolio activity

Consider some small-scale maps. What is the value of the flood maps of Bangladesh shown on pages 144-148 of Disaster mitigation in Asia and the Pacific? Think about this before reading on.

 

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  • Small-scale flood maps that cover a large area, such as a region or country, are valuable for prioritising those areas that may need further analysis, or that are likely to require emergency management planning. They are therefore useful for developing policy, and for making emergency management resourcing decisions.
  • Large-scale maps, such as that of New Norfolk, are of value for detailed emergency management work. They show specific hazards, and may allow the discovery of relationships between the community, hazards and vulnerability.

 

Units of measurement

As you read on you will find som earthquake maps for Australia and Tasmania . You will notice that there are two types of map with different units of measurement, one showing peak ground acceleration, which is the amount of ground movement, and the other showing intensity in terms of the Modified Mercalli scale (refer back to the Table 5.5 ( LINk) to refresh your memory).

 


Activity 5.6

learning portfolio activity

Which of these two units of measurement do you consider to be more useful for emergency management? Explain your reasoning.

 

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In my view, the Modified Mercalli scale is more useful for emergency management because it indicates what people's likely reactions might be, and the types of damage that may occur. Also, given most people's perception of risk and understanding of technical terminology, it is better to express results in a manner that is more accessible, and more readily understood. The Modified Mercalli scale is more concrete, therefore it is likely that more people would be able to understand it.

This highlights a general principle with hazard and risk analysis, as well as with hazard and risk mapping. Simple and understandable is the best when you are trying to communicate. Always keep this in mind.

 

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