Publication Date:
2017-04-04
Description:
A natural hazard is a geophysical, atmospheric or hydrological event (e.g., earthquake, landslide, tsunami, windstorm, flood or drought) that has the potential to cause harm or loss, while a natural disaster is the occurrence of an extreme hazard event that impacts on communities causing damage, disruption and casualties, and leaving the affected communities unable to function normally without outside assistance (Twig, 2007).
The definition of natural disaster impact (NDI) can change according to both the aim of the study and the scientist assessing it. It can be defined as constituting the direct, indirect and intangible losses caused on environment and society by a natural disaster (Swiss Re, 1998).
Direct losses include physical effects such as destruction and changes that reduce the functionality of an individual or structure. Damages to people (death/injury), buildings, their contents, and vehicles are included, as are clean-up and disposal costs.
Indirect losses affect society by disrupting or damaging utility services and local businesses. Loss of revenue; increase in cost; expenses connected to the provision of assistance, lodging, and drinking water; and costs associated with the need to drive longer distances because of blocked roads are included.
Intangible losses include psychological impairments caused by both direct and intangible losses that individuals personally suffer during the disaster.
The Natural Disaster Impact Assessment (NDIA) is crucial in helping individuals to estimate replacement costs and to conduct cost-benefit analyses in allotting resources to prevent and mitigate the consequences of damage (UNEP-ECLAC, 2000).
A general NDIA procedure has not yet been developed; several approaches are available in literature and their applicability depends on the accessibility of damage data.
Possible end users of NDIA include the following (Lindell & Prater, 2003):
1.Governments, with an interest in estimating direct losses to report to taxpayers and to identify segments of the community that have been (or might be) disproportionately affected
2.Community leaders, who may need to use loss data after a disaster strikes to determine if external assistance is necessary and, if so, how much.
3.Planners, who can develop damage predictions to assess the effects of alternative hazard adjustments. Knowing both the expected losses and the extent to which those losses could be reduced makes it possible to implement cost-effective mitigation strategies.
4.Insurers, who need data on the maximum losses in their portfolios to guarantee their solvency or even to undertake additional measures to alleviate the risk that they would face in case of a disaster (i.e., the use of catastrophe bonds which are risk-linked securities that transfer a specified set of risks from a sponsor to investors) (Noy & Nualsri, 2011).
Data availability and reliability, especially for old events, represent constraints in the NDIA context because of several issues of very different type:
1.Data availability, for current events, depends on the time at which data gathering started. It is impossible to decide a priori when data have to be gathered: it primarily depends on the type of phenomenon causing the disaster and its magnitude, and secondly on the scope of the assessment (for example, the assessment should not be unnecessarily delayed as there is an urgent need to elicit support from the international community) (ECLAC, 2003).
2.Long-term losses must sometimes be determined over a period of years. Slow landslides, for example, can cause damage over long periods. Intangible damage like disaster-related stress also requires years to be detected (Bland et al., 1996).
3.In most countries, there are no agencies responsible for gathering damage data. Damage caused by severest events can be mined from international databases, while data on less severe events can be obtained by means of specific historical studies.
4.Data on property damage can depreciate the value of property, thus they would not be available or not completely reliable (Highland, 2003).
5.For some type of disasters, as landslides or floods, the costs of damages to structures such as roads are often merged with maintenance costs and are therefore not labelled as damage. In addition, when heavy rains trigger both landslides and floods (Petrucci and Polemio, 2009), it is difficult to separate landslide damage from flood damage.
6.Developing countries have an incentive to exaggerate damage to receive higher amounts of international assistance; thus, in these cases, data may not be entirely reliable (Toya & Skidmore, 2007).
This chapter starts with a panoramic of the different approaches reported in the literature to assess the impact of natural disasters, and then presents some simplified approaches to perform a relative and comparative assessment of the impact caused by phenomena as landslides and floods triggered by heavy rainfall during events defined as Damaging Hydrogeological Events. Finally, some indices to assess the relative impact of landslides are presented.
Description:
Published
Description:
109-132
Description:
open
Keywords:
natural hazards
;
05. General::05.08. Risk::05.08.99. General or miscellaneous
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
book chapter
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