The Impact of Natural Disasters: Simplified Procedures and Open Problems

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 hazardous event that impacts on communities causing damage, disruption and casualties, and leaving the affected communities unable to function normally without outside assistance (Twig, 2007).


Introduction
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 hazardous 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.
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 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 & 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.

Short-medium-term effects directly involving people and goods affected by a disaster
The articles included in this group employ the simplest approach: the impact is expressed by the list of damaged elements and neither monetary figures nor other assessment are performed (Ngecu & Ichang'i, 1999;Whitworth et al., 2006;Bilgehan & Kilic, 2008). Frequently used impact indicators include numbers of victims and damage to buildings, roads and agriculture. In these studies, damage data are obtained by state agencies or even collected by directly asking people involved in the disaster. Both the number of victims and the percentage of people affected are used to compare the impact of a disaster on various communities (Msilimba, 2010) or that of disasters that have occurred in different time and places. Some of these articles focus on damage to people, analysing the circumstances leading to loss of life and assessing them in relation to vulnerability factors (e.g., age, race, and gender) (Jonkman et al., 2009).

Medium-and long-term socio-economic effects
In these articles, after individuating the affected population and the pre-disaster situation, the researchers isolated effects on social sectors (the population, housing, health and education), service infrastructure (drinking water and sewage, communications, electricity and power), and production sectors (agriculture, industry and trade) in order to measure the disaster's impact on the macroeconomic indicators during a period of one to two years after the disaster (ECLAC, 1991).
Natural disasters are seen as a function of a specific natural process and economic activity (Raschky, 2008). The indicators used to detect the impact on national economies include a) long-term recovery businesses (Webb et al., 2002); b) changes in flow variables such as annual agricultural output (Patwardhan & Sharma, 2005); c) variations in fiscal pressure (Noy & Nualsri, 2011); and d) effects on the labour market (Belasen & Polachek, 2007;Zissimopoulos & Karoly, 2010).
The value of human life can be tentatively assessed using two approaches that assign different values to people in different income groups or in countries at different stages of development (AusAID, 2005): 1. The human capital approach involves calculating the average expected future income that the deceased would have generated assuming that he (or she) had achieved normal life expectancy. 2. In the willingness to pay (WTP) approach, surveys assess how much an individual is willing to pay to reduce the risk of death. Even environmental damage can be assessed using the WTP approach, either by asking people to state a WTP amount or by inferring this amount based on costs incurred for environmental services (Dosi, 2001).
Economically, disasters can act as a barrier to development, increasing poverty and having a small but significant negative effect on economic growth (Raschky, 2008). This effect can return a society to the level of human development it had achieved two years prior to the disaster (Rodriguez-Oreggia et al., 2010). Indirect societal effects such as decreases in productivity in people affected by disaster can influence economic growth (Popp, 2006). Human capital can be directly affected by these disasters through death or injury and indirectly affected when damage to schools decreases human capital accumulation (in poor countries, decreasing school attendance rates caused by reductions in family expenses can occur). Even demographic effects such as migration have been detected (Smith & McCarty, 1996).
Nevertheless, natural disaster can also produce positive effects. Disasters can create Schumpeterian creative destruction (Cuaresma et al., 2004), especially if there are injections of funds for assistance and/or reconstruction. They can represent an opportunity to update capital stock and improve an economy, thereby producing a long-term positive effect on the growth of the Gross Domestic Product (GDP) (Skidmore & Toya, 2002). Activities in the construction sector may reactivate the economy, and the demand for construction materials may generate windfall profits (ECLAC, 1991). Outside the disaster area, income increases can accrue for owners of commodities whose price is inflated by disaster-induced shortages (CACND, 1999). For instance, in the case of drought, when agricultural production decreases, farmers in affected areas experience the negative effects of the disaster, and the price of agricultural products increases. Then, farmers outside affected area, who are experiencing normal production, will reap the benefits of these higher prices (Wilhite et al., 2007). Even ways of thinking and acting can be modified by major disasters, resulting in personal and community growth (Birkmann et al., 2008).
Disasters are more costly for developing countries: as economies develop, there are fewer disaster-related deaths and damages/GDP (Toya & Skidmore, 2007). Nevertheless, increasing wealth causes relatively higher losses in high-income nations (Raskly, 2008). Increases in income increase the private demand for safety; higher income enables individuals (and countries) to employ additional, costly precautionary measures. Nevertheless, in countries that experience a concentration of assets that is larger than the counter-measures put in place, the income-vulnerability relationship can be inverted, especially in the case of disasters related to behavioural choices such as floods and landslides.
Disasters in South, Southeast, and East Asia are more costly than those occurring in the Middle East and Latin America. These results might be tied to the higher population density of Asian countries. Small island developing states are severely impacted by such events (Meheux et al., 2007): the number of victims and affected individuals and the degree of damage are twice as large on average as in any other region (Noy, 2009).
Normalization procedures are used to assess what the magnitude of economic losses over time would be if a past disaster took place today. It seems that societal change and economic development are the principal factors responsible for the increasing losses from natural disasters to date (Pielke et al., 2008;Barredo, 2009;. For weather-related disasters, Bouwer (2011) pointed out no trends in losses -corrected for increases in population and capital at risk -that could be attributed to anthropogenic climate change.

Short-to-long-term physical and physiological effects on people
These articles focus on natural disasters and their effects on people's health from either a physical or a psychological point of view. Pre-and post-disaster conditions were compared in these studies to detect the onset of diseases and/or the worsening of pre-existing illness, and to assess if and when disaster-related symptoms appear/disappear. The data collection processes mainly involved standardized questionnaires used to collect self-reported information on symptoms quantified using numerical scores (Catapano et al., 2001;Cao et al., 2003) that could measure the disaster's impact.

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The Impact of Natural Disasters: Simplified Procedures and Open Problems 113 Fig. 1. Damage caused to roads by landslides and floods in Calabria.

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The risk of developing physical and/or psychiatric disorders is related to the extent of the losses suffered (Cao et al., 2003), and it is greater in families that have lost a family member in a disaster (Lindell & Prater, 2003), have experienced evacuation, or have worse finances (Bland et al., 1996). This probability can also be increased by a lack of information on the probability that the event will re-occur (Catapano et al., 2001). Two sub-sets of articles were isolated that focused on psychological and physical effects, respectively.

Psychological effects
According to the Conservation Resource Model, people try to protect resources such as objects (housing, possessions, etc.), social roles (employment, marriages, etc.), energy (time and monetary investments), and personal characteristics (e.g., self-confidence). The threatened or actual loss of these resources as caused by a natural disaster leads to psychological distress (O'Neill et al., 1999). Frequently observed conditions such minor emotional disorders seldom come to the attention of psychiatrists but may negatively affect social relationships and work performance. Commonly detected symptoms are fatigue (Lutgendorf et al., 1995), tics, and cognitive experiences such as confusion, impaired concentration, and attention deficit disorder. Emotional signs such as anxiety, depression, and grief, as well as behavioural effects such as sleep and appetite changes and substance abuse, were also reported (Lindell & Prater, 2003). Even effects on suicide rates were detected: earthquake victims (people who had lost family members residing with them, were injured, or experienced property loss) were 1.46 times more likely than non-victims to commit suicide (Chou et al., 2003).
All these effects can be mild and transitory or can lead to Post Traumatic Stress Disorder (PTSD). The mental states of victims can include three stages (Sadeghi & Ahmadi, 2008): a) an immediate reaction involving distressing symptoms accompanying adaptive stress; b) the post-immediate phase, which includes symptoms of maladaptive stress (confusion, agitation, and occasionally neurotic or psychotic reactions); and c) the long-term sequel phase, which involves a return to normal health or the onset of PTSD, which can sometimes yield a chronic phase that involves personality changes. These surveys make it possible to monitor the most fragile segments of the population, including people with pre-existing mental illness, racial and ethnic minorities, and children, in which symptoms may differ depending on age (Lazarus et al., 2002;Overstreet et al., 2011). Gender differences arise as well: for instance, after an earthquake, women report greater emotional distress and mental health problems than do men (Norris et al., 2002), but the occurrence of addiction disorders among women is much lower (Montazeri et al., 2005).

Physical effects
Physical effects encompass symptoms affecting people who have not been directly involved in a disaster. The deterioration of hygiene, housing, and basic services can induce the outbreak of diseases such as leptospirosis (AusAID, 2005) or increase the risk of morbidity and mortality caused by communicable diseases (Waring & Brown, 2005). In developing countries, for instance, contagious and non-contagious diseases are reported during the first weeks after floods. Moreover, in some environments, even the incidence of snake bites can increase (Shajaat Ali, 2007).

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The Impact of Natural Disasters: Simplified Procedures and Open Problems 115 Disaster-related stress can have several secondary impacts on human health, such as effects on the human immune system (Solomon et al., 1997), diabetes (Ramachandran et al., 2006;Fonseca et al., 2009), and gastro duodenal ulcers (Suzuki et al., 1997). Also increases in serum leptin levels have been detected in subjects with PTSD, which explains the hypervigilance of people who have faced danger and uncertainty (Liao et al., 2004). In addition, after major earthquakes, the number of patients with Acute Myocardial Infarction (AMI) has been reported to increase 3.5-fold, and the part of women with AMI seems significantly greater than in the years preceding the disaster (Suzuki et al., 1997).

The impact of Damaging Hydro-geological Events (DHEs)
This paragraph focuses on climate-related damaging phenomena as landslides, floods, urban flooding, and storm surges which occur during periods of bad weather conditions, lasting from one to a few days, and characterised by intense rainfall and sometimes strong winds. These periods can be defined as Damaging Hydro-geological Events (DHEs) (Petrucci & Polemio 2003, and their impact can be assessed as the sum of the damage caused by all the damaging phenomena triggered through a selected DHE.

Data collection
Data on damage caused by DHEs which occur currently can be obtained from different agencies (civil protection, public works offices, etc.) or even by on-site surveys (interviews with people involved or local administrators). On the contrary, dealing with events that occurred in the past, for which no direct surveys can be performed, historical data have to be found. The availability of historical data changes from one country to another and over time, and it is related to event severity. Actually, information concerning older events is less plentiful than information pertaining to newer events and the greatest amount of data usually exists for the most severe events, whereas less severe cases are rarely mentioned. Historical data can be gathered mainly from non-technical sources (books, newspapers, etc.), and then phenomena are described by non-specialist observers, which often focus on the effects (damage) more than on their causes (landslides, floods and so on).
In Italy, for example, there is no public authority that systematically collects data on damage caused by DHEs. These data can eventually be found in several offices, but none of these offices focus exclusively on collecting them. Moreover, each office stores documents in its archive by using organization criteria that are designed according to the needs of the office itself and not planned for public use. In addition, the archives of some type of offices, as i.e. fire brigades and hospitals, w h i c h c a n c o n t a i n d a t a o n d a m a g e t o b o t h p e o p l e a n d properties, cannot be accessed because of laws ensuring the privacy of citizens. Other requests for both aid and damage reimbursement are usually sent to civil protection offices, but we mustn't presume that these requests are systematically collected, and, this usually happens only for recently occurred phenomena; it is more difficult to find documents concerning damage that occurred several decades ago. Several authors gathered data from press archives (Cuesta et al. 1999, Devoli et al. 2007). Daily newspapers ensure continuity in information flow and, by-passing problems related to privacy, report detailed descriptions of human injuries, supply the age, sex, and names of the people involved and details of the causes of death or prognosis of injuries. However, this information source presents some disadvantages that must be clearly understood.
1. The language of newspapers is not technical, so the articles must be carefully analysed to correctly classify the described phenomena. It is necessary to understand the reporter's perspective and familiarity with phenomena: adjectives to describe the size of a landslide, for example, must be assessed with caution because they are strongly affected by previous experience of the reporter with landslides. 2. Local newspapers are more detailed than national ones: until some decades ago, news coming from regions far from the editorial unit was only related to severe events, and thus, only the local newspaper allows a complete screening of both major and minor events occurred in a selected time-frame. 3. Articles tend to focus on damage, so details on phenomena can be scarce and must be inferred. Similarly, quantitative data on triggers (i.e., rain or wind intensity) are not provided, because newspaper articles focus more on the effects and less on their causes. 4. The articles must be checked in order to avoid duplication: often, newspapers report a damaging phenomenon in several editions (at least until major damage has been repaired). Also the number of victims must be carefully checked: newspapers may provide changing figures until the end of rescue operations.
Despite these disadvantages, especially in countries where there are no public authorities collecting these data, newspapers can be used as proxy data to establish a catalogue of damaging situations that can provide an indicator of the social impact of DHEs. In Italy, a systematic collection of data mined from newspapers was organised in an on-line database named AVI (http://sici.irpi.cnr.it/), and the use of newspaper data or, more recently, of internet-sourced news is a common practice to gather data (Kirschbaum et al., 2009).

Approaches to the assessment of damage caused by DHEs
The record of damage caused by DHEs in a selected region during a certain study period can be obtained by means of the systematic analysis of daily newspapers. Then, the damage caused by these DHEs can be assessed by various criteria, and the events can be classified according to their damage severity. In this way, data can be used for different types of analyses, as for example: a) the study of triggering rainfall thresholds, b) the comparisons between the severity of DHEs occurred in a selected area through the time, to understand if climatic change can modify their impact, and c) the comparisons between the severity of DHEs o ccurred in the same place s but in different peri ods, to v erify if and how t he development of urbanised sectors can affect their impact.
The approaches to assess the impact of DHEs can be more or less complex; nevertheless, their applicability depends firstly on data availability and secondly on the scale of the study. The simplest damage classification, which can be applied at both local and regional scale, can be performed establishing a priori three damage levels (Petrucci & Versace, 2000): To perform an in depth analysis, further steps can be done, by defining some descriptive indices that can be used to summarize the effects of a DHE.

Index of Damaged Area (IDA)
This index represents the relative size of the area affected by floods or landslides during a DHE, and it is assessed in reference to small administrative units of the disaster region. In Italy, for example, we relate this index to the municipalities of a selected region.
The IDA is obtained by summing the area of municipalities hit during the DHE (S) and dividing the obtained value by the area of the regional surface (R).

IDA (Index of Damaged Area) = S / R x 100 (1)
S is greater than the area truly affected, but this simplification is necessary to by-pass the impossibility of precisely delimiting areas actually hit, because of the low technical level which can characterise historical data. IDA represents the percentage of a region's area affected during each DHE; based on IDA, the DHEs that affected a region can be classified as: Local DHE = IDA< 2.5% Wide DHE = IDA: 2.5÷10% Regional DHE = IDA> 10%

Local Damage Index (LDI) and Local Damage Index Density (LDI d )
The Local Damage Index is the sum of damage D i caused in a municipality by the i phenomena that occurred there, and it is based on the concept that damage is the product of the value of damaged element and the level of loss that it suffered (Varnes & IAEG, 1984): Where:

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The Impact of Natural Disasters: Simplified Procedures and Open Problems 119 V i is the value of the damaged element, ranging from 1 to 10 in an arbitrary scale (Figure 3), and L i is the level of loss suffered, a measure of the percentage of loss affecting the element during the event, that can be High=L1 (1), Medium=L2 (0.5), or Low=L3 (0.25) (Petrucci et al. 2003).
By dividing the LDI by the municipal area, we can obtain an index that represents the density of damage in each of the hit municipalities:

LDId (Local Damage Index Density) =LDI/Municipality area
Obtained values can be sorted into a number of classes. For each event, a regional map of municipalities classified according to the LDId can summarise the regional pattern of damage, thus allowing use of a geographical analysis of the pattern of damage density pattern which can be used, i.e., to identify more intensely affected regional sectors. Moreover, by comparing LDI to the return period of rainfall which triggered the damaging phenomena, the proneness of an area to be damaged by DHEs can be classified as (Petrucci & Pasqua, 2008):

The impact of mass movements
Mass movements, defined as the movements of masses of soil, rock, debris, or mud, usually occur because of the pull of gravity, and are a source of great concern because they can impact numerous victims and cause severe damage. Although many types of mass movements are included in the general term "landslide," the more restrictive use of the term refers only to mass movements where there is a distinct zone of weakness that separates the slide material from more stable underlying material (USGS, 2009).
Only a low percentage (12%) of the articles analysed to perform the review presented in the paragraph 2 concern landslides. This low attention to landslides impact depends on two factors: a) if compared to earthquakes or hurricanes, landslides could be classified as minor disasters; b) landslides can be secondary consequence of major disasters such as earthquakes. Nonetheless, both the assessment of damage after landslides occurrence, and the appraisal of damage that could be caused by future landslides have practical usefulness.
Immediately after an event that triggered several landslides, a rapid relative damage assessment allows for the sorting of phenomena according to their relative impact, upon this assessment priorities for structural remediation can be set and the costs and benefits derived from the implementation of different defensive measures can be assessed.
On the other hand, pre-event assessment of the potential impacts of future mass movements can provide information to planners, who must evaluate the consequences of alternative hazard mitigation measures. If the landslide inventory of an area has been conducted, a "consequence analysis" can identify potential outcomes arising from the activation of each mapped landslide. In addition, estimating the potential damage from each landslide can enable preparedness and improve the capacity of governmental agencies to cope with the emergency phases.

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Approaches to Managing Disaster -Assessing Hazards, Emergencies and Disaster Impacts 120

The Support Analysis Framework
The Support Analysis Framework is a spread sheet used to appraise damage caused by past mass movements or to assess the probable damage related to future phenomena (Petrucci & Gullà, 2009. The SAF was organised on the basis of historical damage data available in the Historical Archive of CNR-IRPI of Cosenza which have been partially published (Petrucci & Versace, 2005). Fig. 3. Types and sub-types of damaged elements. For each type and sub-type, the value considered for damage assessment is V i . The multiplying factors for assessing the Local Damage Index are 1, 0.5 and 0.25 for levels 1, 2 and 3, respectively.

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The aim of the SAF is to convert (historical) data of landslide damage into numerical indices describing: direct damage, defined by the effects on 6 types of elements (Buildings, Roads, Railways, Productive Activities, Network services, People), indirect damage, defined by the actions aiming to reinstate pre-landslide conditions, and intangible damage, defining psychological consequences caused to people by the landslide.
In dealing with an approach designed for historical damage data, the SAF does not require on-site surveys: damaged elements and levels of loss are obtained by analysing the available descriptive data. For this reason, the SAF can be filled by non-specialists who should simply be trained on the procedure to mine landslide damage data from historical documents.

Identification and direct damage sections
For each landslide, a SAF must be completed to obtain numerical indices representing its impact. The first part of the SAF is the identification section (A), which accounts for: location of the landslide (province, municipality, place name, coordinates) and map of the landslide area (if not available in analysed documents, we can roughly trace it on a topographic map with the available information); -time of activation (year-month-day/s); -document(s) from which data have been obtained (original title or type of document if no title is available); -reliability of the document(s) from which data have been collected (ranging from low to high, according to the type of document and the skill of the author).
The part of the SAF assessing direct damage is made up of 6 sections (B to G) and it is divided into two parts: the elements (on the left side of the chart) and the levels of loss (on the right) ( Figure 4). Each element is characterised by its value, set on an arbitrary scale (red numbers). The levels of loss (black numbers), are set as: L4: complete loss; L3: high loss; L2: medium loss; or L1: low loss. Depending on the section, these levels have different meanings, but they always reflect the aforementioned levels of loss.
In the working version of the SAF, the yellow cells are empty: by typing the letter x in a cell describing an element and another one in the cell of the suffered level of loss, formulas implemented in hidden columns multiply these two values to obtain dl, which is the contribution to damage of the line l. All the dl values are used to assess both direct and total damage indices.
The elements used for direct damage assessment are organised in the following sections: • Section B: Buildings. Buildings are classified as public or private. For public buildings, according to the social function, the strategic coordination role in emergency management and the number of people who can be inside during night and day, a unique value was set (city hall =1; barracks =1; hospital =1; school =0.75; church =0.75). For private buildings, two criteria were introduced to identify their value: the number of buildings (1 building; 2-10 buildings; >10 buildings), and whether they are inhabited, temporarily inhabited or uninhabited. The level of loss can be selected from: L4 (collapsed), L3 (unusable due to structural damage), L2 (unusable due to loss of functionality), and L1 (habitable with light damage). In this section, the loss of furnishing inside or outside the buildings is also included and classified according to the number of buildings involved (1 building; 2-10 buildings; >10 buildings).
• Section C: Roads. Roads are classified into five types according to relevance, traffic flow, and possible restoration costs: highway, state road, county road, municipal road and country road. Except for country roads, which are characterised by a simple structure, the damage can affect one or more of the following sub-elements: bridge, tunnel and roadway. Then, except for country roads, the value depends on the damaged sub-element(s). According to the degree and duration of inefficiency, the levels of loss were set as follows: L4: road breakage causing traffic interruption for months; L3: road breakage causing traffic interruption for days; L2: temporary interruption without breakage; L1: light damage without traffic interruption.
• Section D: Railways. According to the relevance and the traffic flow, we divided railways into state and regional railways. The value depends on the damaged subelement(s), and the level of loss can be selected from: L4: railway breakage causing traffic interruption for months; L3: railway breakage causing traffic interruption for days; L2: temporary interruption without breakage; and L1: light damage without traffic interruption.
• Section E: Productive activities. These are divided into five types: industrial, commercial, handicraft, tourism and farming. The levels of loss were set as: L4: interruption of production and loss of productive system; L3: interruption of production and loss of products; L2: loss of products; and L1: light damage without loss of products.
• Section F: Network services. This category is divided into five types: gas pipeline, electric line, telephone line, aqueduct, and drainage system. The levels of loss were set according to the duration of the inefficiency and the extent of the suffering area (L4: prolonged service interruption of large areas; L3: temporary service interruption of large areas; L2: local and temporary inefficiencies; and L1: light damage without inefficiencies).
• Section G: People. Damage to people is described by the occurrence of four conditions: victims; badly hurt; light physical damage; and temporary shock conditions. The levels of loss were set according to the number of people concerned (>60 people; 60-30 people; 30-10 people; <10 people).

Indirect damage sections
The indirect damage analysis process includes two sections, H and I ( Figure 5). Section H describes actions concerning the dislocation of people, for which the levels of loss are set according to the number of people involved (>60 people; 60-30 people; 30-10 people; <10 people). Section I accounts for the cost of remedial works, and the interruption and/or delay of economic activities caused by the mass movement. In this case, the level of loss depends on an appraisal of the economic cost of these works, sorted into four nominal intervals (>100,000 €; 100,000-20,000 €; 20,000-10,000 €; <10,000 €).
As for direct damage sections, the numbers in Figure 5 are hidden in the operating version of the SAF, because the yellow cells must be filled in. For each action, we have to select only one of the four levels of loss, by typing the letter x into the relative cell: in this way, the hidden value is placed in the correspondent d l cell. All of the d l values are used to assess both indirect and total damage indices.

Intangible damage section
The intangible damage, assessed in section L, takes into account the psychological consequences affecting people who live in the damaged area. The levels of loss are set according to the number of people involved (>60 people; 60-30 people; 30-10 people; <10 people) ( Figure 5). For each line of the indirect damage sections, by selecting a single level of loss, the appropriate numerical value is inserted in the corresponding cell of d l . All of the d l values are used to assess both intangible and total damage indices.

Assessment of damage indices
The values of d l obtained from the lines of the SAF are converted into damage indices by means of the simple calculations summarised below. For each section, i.e., for the generic section i, we calculate the Damage of the Section i (D Si ) using equation 5: where d l is the damage contribution of each of the n lines of section I. Following the described procedure, the SAF allows to converts damage descriptions into numerical indices expressing -in a relative manner -the direct, indirect, and intangible damage. The procedure was tested in Calabria, on both historical landslides (Petrucci & Gullà, 2009 and more recent events (Petrucci et al., 2010). It must be pointed out that the procedure is based on a relative scale of values and not on monetary costs. Then it can be used for a) current events for which monetary assessments are not (or not yet) available, and for B) past landslides for which monetary assessments of costs are quite impossible to obtain. In both these situations, the SAF represents the minimum amount of information that can be used to define the impact caused by different landslides in order to perform impact comparisons.

Conclusion
The chapter showed a panoramic view of the assessment of the impact of natural disasters as presented in the scholarly literature. The numerous experiences of damage assessment performed in different economic frameworks show that developing countries are more strongly hit than developed ones: as economies develop, there are fewer disaster-related deaths and damages/GDP. Nevertheless, increasing wealth causes relatively higher losses in high-income nations. Increases in income increase the private demand for safety; higher income enables countries to employ additional, costly precautionary measures. Yet, in countries with a concentration of assets that is larger than the counter-measures, the incomevulnerability relationship can be inverted, especially in the case of disasters related to behavioural choices such as floods and landslides.
Two major constraints obstruct the assessment of the impact of disasters: the first is the lack of shared assessment methodologies. In the different literature sectors, several approaches are available, but, as far as academic research are restricted to the detailed discussion of one particular impact, or impacts in a single sector, the result is a somewhat fragmented coverage of impacts. On the other hand, conveying all the different assessments in a single methodological approach is objectively an extremely complicated task which can be handled exclusively by multidisciplinary staffs, having all the skills to cope with a multifaceted task as disasters impact assessment.
The second problem is related to data availability. It is impossible to decide a priori the most opportune time to gather data and to undertake impact assessment, as it will depend on the type of phenomenon causing the disaster, its magnitude and scope of the assessment. In addition, continuous data gathering also once the emergency phase has passed ensures detection of long-term effects, as either economic impacts or psychological consequences on people affected.
On the contrary, dealing with the impact of phenomena occurred in the past, data gathering becomes very complicated: both the amount of data available and their level of detail can be low and cannot be significantly increased, even by further research. In these cases, simplified approaches can be used to perform relative assessments based on a minimum amount of information. These approaches aim to supply quantitative indices expressing the impact of different disasters in order to make them comparable even if they occurred both at different time and in different areas.
Specifically for landslides, a structured approach aiming to collect data and transforming them into relative damage indices is presented. This approach can be used for a) current events for which monetary assessments are not (or not yet) available, and B) past landslides for which monetary assessments of costs are quite impossible to obtain. In both these situations, the approach focuses on the minimum amount of information that can be used to define the impact caused by different landslides in order to perform impact comparisons. It m u s t t o b e u n d e r s t o o d w h e n u s i n g t h i s a pproach that one is dealing with relative assessments and their reliability strictly depends on the reliability of the data employed.