**7. Application**

In the last 10 days of November 2016, Piemonte region was affected by a flood event with meteorological characteristics similar to other events of the past. According to ARPA Piemonte (*Regional Environment protection Agency of Piemonte*), the flood severity was similar to the most severe historic event occurred in the past in the Tanaro river watershed.

The flood event on November 24–25, 2016, has also significantly affected the basins of the Bormida di Millesimo and Bormida di Spigno rivers. In particular, the Bormida di Millesimo flood involved important production companies in the Bormida valley, as well as residential buildings and farms, causing considerable damage to the agricultural cultivation [19, 20].

According to the flood report ([20], p. 2), the event caused extensive damages to flood control structures, sediment deposits, bank erosions, and meander changes and extensive flooding with serious involvement of inhabited settlements and productive activities.

According to the report ([20], p. 3), important economic activities, generally insured against flood damage, risked not to benefit from reimbursements by insurance companies; these in fact generally cover the damage only in the presence of a *declaration* of an emergency *status,*

by the Council of Ministry. Consequently, some companies, which were affected by the flood and suffered extensive property damages, asked for the *declaration* of the emergency *status* and also claimed the restoration of damages and the reinstallation of adequate defenses in order to continue to stipulate insurance with adequate contractual conditions. The Council of Minister declared the emergency *status* on December 16, 2016, only for Turin and Cuneo Provinces. Afterwards, Regione Piemonte public administration asked to extend the *declaration* to Asti and Alessandria. On February 23, the Council of Ministers approved the resolution, extending the emergency *status* to the provinces of Asti and Alessandria, providing the allocation of financial resources.

The IRP model can be easily used to rank flood risk, according to quantitative criteria. At present, it can be used to calculate the risk (and the damage) on receptors (buildings), as well

The model has been extensively applied to different case studies, in Piemonte region, for the

In this work, a sort of validation of the model has been tried by comparing the IDP computed

The term "validation" is not appropriate, as the comparison is not simple. Actually, it should be highlighted (see Section 8) that the real damages suffered by residential or commercial receptors may not be equal to the indemnifications by public administration [18]. This point

However, a comparison between the computed index damages and the requested indemnification for residential or commercial activities has been tried, in order to estimate the gap

In the following paragraphs, three applications will be shown and discussed, referring to 2016 flooding in Chisola river, Bormida river, and Tanaro river. A comparison between the

In the last 10 days of November 2016, Piemonte region was affected by a flood event with meteorological characteristics similar to other events of the past. According to ARPA Piemonte (*Regional Environment protection Agency of Piemonte*), the flood severity was similar to the most

The flood event on November 24–25, 2016, has also significantly affected the basins of the Bormida di Millesimo and Bormida di Spigno rivers. In particular, the Bormida di Millesimo flood involved important production companies in the Bormida valley, as well as residential buildings and farms, causing considerable damage to the agricultural cultivation [19, 20].

According to the flood report ([20], p. 2), the event caused extensive damages to flood control structures, sediment deposits, bank erosions, and meander changes and extensive flooding

According to the report ([20], p. 3), important economic activities, generally insured against flood damage, risked not to benefit from reimbursements by insurance companies; these in fact generally cover the damage only in the presence of a *declaration* of an emergency *status,*

as for risk mapping (**Figure 2**).

26 Natural Hazards - Risk Assessment and Vulnerability Reduction

risk assessment and the cost/benefit analyses [14, 15].

will be discussed in the next paragraphs.

between the computer IDP and the available data.

by the model and the damages recorded in the recent 2016 flood.

computed IDP and the requested indemnifications is also shown.

severe historic event occurred in the past in the Tanaro river watershed.

with serious involvement of inhabited settlements and productive activities.

**6. Model validation**

**7. Application**

After the flood event, the Regional Departments started some activities, aiming to map and assess the flood effects, upon which the hazard evaluations of the IRP model have been based. These activities are the following:


Flood maps were the basis upon which the hazard estimation procedure of IRP started from. The procedure to obtain the flood depth maps has been described elsewhere [14, 15].

In this application, the exposure of receptors in the flooded area refers to the 2018 OMI database. The variability in time of the asset value (i.e., from the date when the flood occurred to present days) is negligible. The total number of flooded receptors and municipalities is summarized in **Table 6**.

After the 2016 flood, data of damages have been collected by public administration according to the civil protection procedures [18]*"Procedure for the recognition of the needs for the restoration of damaged public and private structures and infrastructures, as well as for the damages to economic and productive activities, to cultural heritage, and to the housing assets."* The procedures are followed by Regione Piemonte administration [19, 20] and are available to public. According to them, the requests for residential and productive damage indemnification have to be collected in the so-called *B-sheet* (*Recognition of the needs for the restoration of private buildings* sheet, which contains all the requests regarding residential damages*)* and *C-sheet* (*Recognition of damages suffered by economic and productive activities* sheet, which contains all the requests regarding damages to economic/productive activities), respectively. These have to be filled by privates and confirmed by technical assessments.


The total number of receptors is referred to the flooding mapped area as described before. The analyses were focused only on the river reaches where damage data were available.

**Table 6.** Applications of the model to the case studies.

The interpretation of the comparison, shown in **Figures 3** and **4** and summarized in **Table 7**,

The IRP model, extensively applied to different case studies in Piemonte region, demonstrated to be a suitable tool to risk and damage estimation, either for the aims of the implementation of flood directive or for the design of the countermeasures. The model aims at expressing an "index," where estimation is based on a scientific approach (i.e., on the definition of damage and of risk) and on the basis of databases available at regional and national scale. The usability of the model has been proven elsewhere, and it is confirmed by the application to the 2016

The comparison shows that IDP can lead to an under/overestimation of the collected data. The use of the term "collected" is preferable to others, as it substantially refers to the kinds

is not immediate, and a discussion is provided in the following paragraph.

**Figure 4.** Comparison among the IDP and collected data in Bormida and Tanaro case studies.

Chisola € 6,933,305.00 € 21,520,781.16 € 51,191,427.49 Tanaro € 751,473.12 € 451,153.28 € 496,860.00 Bormida € 2,757,522.90 € 2,116,426.00 € 13,885.00

**Table 7.** Comparison among the IDP and the collected data.

**River IDP (total) Damage to private properties Damage to productive activities**

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29

case study, to Tanaro, Bormida and Chisola rivers (**Figures 3** and **4**).

**8. Discussion**

**Figure 3.** Comparison among the IDP and collected data in Chisola case study.

Comparison of IDP index has been made by referring to the total requests in B-sheet and C-sheet. The results of the comparison are shown in **Figures 3** and **4**.

It should be highlighted that the categories of damages refundable by Public administration are specified by the Council of Ministry. Actually, the recent deliberation of the Minister council (July 28, 2016; *Directional criteria for the determination and granting of contributions to private individuals for damage to buildings and housing assets*.) contains the list of the damages that can be eligible for indemnification. They may not match with the real damages.

Moreover, as it can be seen from the figures, the rate of residential and productive damages to the total damage varies in a wide range.

Index of Proportional Risk (IRP) Flood-Risk Assessment Model and Comparison to Collected Data http://dx.doi.org/10.5772/intechopen.79443 29

**Figure 4.** Comparison among the IDP and collected data in Bormida and Tanaro case studies.


**Table 7.** Comparison among the IDP and the collected data.

The interpretation of the comparison, shown in **Figures 3** and **4** and summarized in **Table 7**, is not immediate, and a discussion is provided in the following paragraph.

#### **8. Discussion**

Comparison of IDP index has been made by referring to the total requests in B-sheet and

**Municipalities included in the analysis**

d'Asti, Revigliasco d'Asti, Asti, Azzano d'Asti

170 (159 residential) Vesime, Cessole, Loazzolo, Bubbio, Monastero Bormida, Sessame e

Tanaro reach 104 (85 residential) Govone, San Martino Alfieri, Costigliole d'Asti, Antignano, Isola

Chisola reach 1858 (1243 residential) Candiolo, Cumiana, La\_Loggia, Moncalieri, None, Piobesi\_Torinese, Piossasco, Vinovo, Volvera

The total number of receptors is referred to the flooding mapped area as described before. The analyses were focused

Bistagno

It should be highlighted that the categories of damages refundable by Public administration are specified by the Council of Ministry. Actually, the recent deliberation of the Minister council (July 28, 2016; *Directional criteria for the determination and granting of contributions to private individuals for damage to buildings and housing assets*.) contains the list of the damages

Moreover, as it can be seen from the figures, the rate of residential and productive damages to

that can be eligible for indemnification. They may not match with the real damages.

C-sheet. The results of the comparison are shown in **Figures 3** and **4**.

**Figure 3.** Comparison among the IDP and collected data in Chisola case study.

the total damage varies in a wide range.

**Case study Total number of** 

Bormida di Millesimo reach **involved receptors**

28 Natural Hazards - Risk Assessment and Vulnerability Reduction

only on the river reaches where damage data were available.

**Table 6.** Applications of the model to the case studies.

The IRP model, extensively applied to different case studies in Piemonte region, demonstrated to be a suitable tool to risk and damage estimation, either for the aims of the implementation of flood directive or for the design of the countermeasures. The model aims at expressing an "index," where estimation is based on a scientific approach (i.e., on the definition of damage and of risk) and on the basis of databases available at regional and national scale. The usability of the model has been proven elsewhere, and it is confirmed by the application to the 2016 case study, to Tanaro, Bormida and Chisola rivers (**Figures 3** and **4**).

The comparison shows that IDP can lead to an under/overestimation of the collected data. The use of the term "collected" is preferable to others, as it substantially refers to the kinds of damages reported by privates for indemnification. These categories of damages may, or may not, match with the categories of "refundable" damages by Ministry. Moreover, the quantification of damage made by "not expert" privates after the flood can overestimate/ underestimate real damages assessed by professionals.

The gap between the collected damages (contained in the B-sheet and C-sheet) and the refundable damages can lead to an over (or under)estimation of the former with respect to the latter. **Table 8** shows a list of the main factors for this gap.

Consequently, the quantification of real damages, and the calibration of the model, is a very difficult task. The computed IDP cannot be easily compared to collected damage "data," as the latter refer to conditions which are highly influenced by regulations, personal attitudes, and so on.

For this reason, the proposed model aims at the computation of an *index* (the Index of Proportional Risk, or the index of proportional damage) more than to the precise computation of physical damages.

(i) costs for people rescue; (ii) costs for highly urgent interventions: restoration of public services and infrastructures of strategic networks; (iii) interventions to reduce the residual risk (strictly connected to the event); (iv) costs contained in the *Recognition of the needs for the restoration of private buildings (B-sheet);* and (v) costs contained in *Recognition of damages suffered* 

**Figure 5.** Total flood costs referred to 2016 flood event, recorded by public administration [19, 20] in Alessandria and

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As shown in **Figure 5**, the total flood costs are by far higher than the "collected" damages from private (residential and productive). The IDP can allow an estimation of the (iv) and (v)

In spite of the fact that model calibration is a very difficult task, the computation of IDP can

Actually, the estimation of the (iv) and (v) components by means of the IDP can indirectly allow the estimation of total costs. For example, by referring to the damages to Alessandria and Asti provinces in 2016 flood, the total cost is 1.6 or 3.9 times (respectively) the private

The variability of the total damage with respect to the private one depends on variables that

At present, it is preferable, for public administration, to focus on simple and robust models that can predict the order of magnitude of damages (preferably based on free- and opensource software [21]), more than to complex models hard to be applied in practical conditions.

The IRP model, extensively applied to different case studies in Piemonte region, demonstrated to be a suitable model to risk and damage estimation, either for the aims of the implementation of flood directive or for the design of countermeasures. The model aims at expressing an "index," where estimation is based on a scientific approach (i.e., on the definition of damage and of risk) and on the basis of available databases at the regional scale (Piemonte region) and

prove to be a useful means for the estimation of the total damages after a flood.

are highly dependent on the kind of processes and the affected area of flooding.

damage (i.e., given by the addition of the (iv) and (v) components).

*by economic and productive activities (C-sheet)*.

components.

Asti provinces.

**9. Conclusions**

national scale (Italy).

Moreover, it should be considered that the total flood damages can be by far higher than the residential and/or productive ones. Actually, in the recent *flood report* of Regione Piemonte administration ([19], p.84), "flood costs" have been divided into different groups:


**Table 8.** Main factors that cause a gap between the total amounts of real damages suffered by residential/commercial receptors and damages that can be eligible for public indemnification.

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**Figure 5.** Total flood costs referred to 2016 flood event, recorded by public administration [19, 20] in Alessandria and Asti provinces.

(i) costs for people rescue; (ii) costs for highly urgent interventions: restoration of public services and infrastructures of strategic networks; (iii) interventions to reduce the residual risk (strictly connected to the event); (iv) costs contained in the *Recognition of the needs for the restoration of private buildings (B-sheet);* and (v) costs contained in *Recognition of damages suffered by economic and productive activities (C-sheet)*.

As shown in **Figure 5**, the total flood costs are by far higher than the "collected" damages from private (residential and productive). The IDP can allow an estimation of the (iv) and (v) components.

In spite of the fact that model calibration is a very difficult task, the computation of IDP can prove to be a useful means for the estimation of the total damages after a flood.

Actually, the estimation of the (iv) and (v) components by means of the IDP can indirectly allow the estimation of total costs. For example, by referring to the damages to Alessandria and Asti provinces in 2016 flood, the total cost is 1.6 or 3.9 times (respectively) the private damage (i.e., given by the addition of the (iv) and (v) components).

The variability of the total damage with respect to the private one depends on variables that are highly dependent on the kind of processes and the affected area of flooding.

At present, it is preferable, for public administration, to focus on simple and robust models that can predict the order of magnitude of damages (preferably based on free- and opensource software [21]), more than to complex models hard to be applied in practical conditions.
