Università degli Studi di Salerno - Facoltà di Ingegneria – A.A. 2012-2013 Laurea Magistrale in Ingegneria per l’Ambiente ed il Territorio

Corso di Frane Prof. ing. Michele Calvello

Gestione del rischio da frana (Fell et al. 2005)

Corso di Frane, Laurea Magistrale in Ingegneria per l'Ambiente ed il Territorio, Università di Salerno (Prof. ing. Michele Calvello, A.A. 2012-2013) - Gestione del rischio da frana: parte A - Pagina 1 di 14

“Landslide Risk Management” (2005) Proceedings of the International Conference on Landslide Risk Management (May 31 - June 3, 2005. Vancouver, Canada) Editors: O. Hungr, R. Fell, R. Couture, E. Eberhardt

1st Part (state-of-the-art and invited lectures) SOA 1. A framework for landslide risk assessment and management (Fell, Ho, Lacasse, Leroi) SOA 2. Hazard characterization and quantification (Picarelli, Oboni, Evans, Mostyn, Fell) SOA 3. Probabilistic stability analysis for individual slopes in soil and rock (Nadim, Einstein, Roberds) SOA 4. Estimating landslide motion mechanism, travel distance and velocity (Hungr, Corominas, Eberhardt) SOA 5. Estimating temporal and spatial variability and vulnerability (Roberds) SOA 6. Risk assessment and management (Leroi, Bonnard, Fell, McInnes) SOA 7. Landslide hazard and risk zoning for urban planning and development (Cascini, Bonnard, Corominas, Jibson, Montero-Olarte) SOA 8. Landslide risk assessment for individual facilities (Wong)

2nd Part (selection of papers submitted to the conference)

Corso di Frane, Laurea Magistrale in Ingegneria per l'Ambiente ed il Territorio, Università di Salerno (Prof. ing. Michele Calvello, A.A. 2012-2013) - Gestione del rischio da frana: parte A - Pagina 2 di 14

“A framework for landslide risk assessment and management” (Fell et al. 2005) Terminology Danger (Threat). The natural phenomenon that could lead to damage, described in terms of its geometry, mechanical and other characteristics. The danger can be an existing one (such as a creeping slope) or a potential one (such as a rockfall). The characterisation of a danger or threat does not include any forecasting. Hazard. Probability that a particular danger (threat) occurs within a given period of time. Likelihood. Conditional probability of an outcome given a set of data, assumptions and information. Also used as a qualitative description of probability and frequency. Probability. A measure of the degree of certainty. This measure has a value between zero (impossibility) and 1.0 (certainty). It is an estimate of the likelihood of the magnitude of the uncertain quantity, or the likelihood of the occurrence of the uncertain future event. Risk. Measure of the probability and severity of an adverse effect to life, health, property, or the environment. Quantitatively, Risk = Hazard x Potential Worth of Loss. This can be also expressed as “Probability of an adverse event times the consequences if the event occurs”.

Corso di Frane, Laurea Magistrale in Ingegneria per l'Ambiente ed il Territorio, Università di Salerno (Prof. ing. Michele Calvello, A.A. 2012-2013) - Gestione del rischio da frana: parte A - Pagina 3 di 14

“A framework for landslide risk assessment and management” (Fell et al. 2005) Terminology Risk analysis. The use of available information to estimate the risk to individuals or populations, property or the environment, from hazards. Risk analyses generally contain the following steps: definition of scope, danger (threat) identification, estimation of probability of occurrence to estimate hazard, evaluation of the vulnerability of the element(s) at risk, consequence identification, and risk estimation. Consistent with the common dictionary definition of analysis, viz. “A detailed examination of anything complex made in order to understand its nature or to determine its essential features”, risk analysis involves the disaggregation or decomposition of the system and sources of risk into their fundamental parts.

Corso di Frane, Laurea Magistrale in Ingegneria per l'Ambiente ed il Territorio, Università di Salerno (Prof. ing. Michele Calvello, A.A. 2012-2013) - Gestione del rischio da frana: parte A - Pagina 4 di 14

“A framework for landslide risk assessment and management” (Fell et al. 2005) Terminology Risk assessment. The process of making a decision recommendation on whether existing risks are tolerable and present risk control measures are adequate, and if not, whether alternative risk control measures are justified or will be implemented. Risk assessment incorporates the risk analysis and risk evaluation phases. Risk management. The systematic application of management policies, procedures and practices to the tasks of identifying, analysing, assessing, mitigating and monitoring risk.

Corso di Frane, Laurea Magistrale in Ingegneria per l'Ambiente ed il Territorio, Università di Salerno (Prof. ing. Michele Calvello, A.A. 2012-2013) - Gestione del rischio da frana: parte A - Pagina 5 di 14

“A framework for landslide risk assessment and management” (Fell et al. 2005) Landslide risk analysis Scope definition

To ensure that the risk analysis addresses the relevant issues, satisfies the needs of those concerned, and to avoid misunderstandings, it is important to define the scope of the risk analysis. Hazard analysis

1. Landslide (Danger) characterisation 2. Frequency analysis There are several ways of calculating frequency (IUGS 1997): (1) Historic data within the area of study, or areas with similar characteristics, e.g. geology, geomorphology. (2) Empirical methods based on correlations in accordance with slope instability ranking systems. (3) Use of geomorphological evidence (coupled with historical data), or based on expert judgement. (4) Relationship to the frequency and intensity of the triggering event, e.g. rainfall, earthquake. (5) Direct assessment based on expert judgement, which may be undertaken with reference to a conceptual model, e.g. use of a fault tree methodology. (6) Modelling the primary variable, e.g. piezometric pressures versus the triggering event, coupled with varying levels of knowledge of geometry and shear strength. (7) Application of probabilistic methods, taking into account the uncertainty in slope geometry, shear strength, failure mechanism, and piezometric pressures. This may be done either in a reliability framework, or taking into account the frequency of failure (for example by considering pore pressures on a frequency basis). (8) Combinations of the above methods. Corso di Frane, Laurea Magistrale in Ingegneria per l'Ambiente ed il Territorio, Università di Salerno (Prof. ing. Michele Calvello, A.A. 2012-2013) - Gestione del rischio da frana: parte A - Pagina 6 di 14

“A framework for landslide risk assessment and management” (Fell et al. 2005) Landslide risk analysis Scope definition

To ensure that the risk analysis addresses the relevant issues, satisfies the needs of those concerned, and to avoid misunderstandings, it is important to define the scope of the risk analysis. Consequence analysis

1. Elements at risk 2. Probability of landslide reaching the element at risk (PT:L) 3. Temporal spatial probability (PS:T) 4. Vulnerability (Vprop:T and VD:T) The probability of the landslide reaching the element at risk (PT:L) depends on the relative location of the element at risk and the landslide source, together with the path the landslide is likely to travel below the source. The temporal spatial probability (PS:T) is the probability that the element at risk is in the area affected by the hazard at the time of its occurrence. It is a conditional probability, given the landslide occurs and the element at risk is on or in the path of the landslide (Vprop:T = vulnerability of the element at risk to the landslide event, VD:T = vulnerability of the person to the landslide event).

Corso di Frane, Laurea Magistrale in Ingegneria per l'Ambiente ed il Territorio, Università di Salerno (Prof. ing. Michele Calvello, A.A. 2012-2013) - Gestione del rischio da frana: parte A - Pagina 7 di 14

“A framework for landslide risk assessment and management” (Fell et al. 2005) Landslide risk analysis Risk estimation Risk calculation Annual Risk for property (annual loss of property value)

R(prop) = P(L) x P(T:L) x P(S:T) x V(prop:T) x E P(L) is the frequency of the landsliding P(T:L) is the probability of the landslide reaching the element at risk P(S:T) is the temporal spatial probability of the element at risk V(prop,T) is the vulnerability of the element at risk to the landslide event E is the element at risk (e.g. the value or net present value of the property)

Annual probability that a particular person may lose his/her life

P(LOL) = P(L) x P(T:L) x P(S:T) x V(D:T) V(D:T) is the vulnerability of the person to the landslide event

Corso di Frane, Laurea Magistrale in Ingegneria per l'Ambiente ed il Territorio, Università di Salerno (Prof. ing. Michele Calvello, A.A. 2012-2013) - Gestione del rischio da frana: parte A - Pagina 8 di 14

“A framework for landslide risk assessment and management” (Fell et al. 2005) Landslide risk analysis Risk estimation Multiple landslide hazards

R(prop) = Σi [ P(L) x P(T:L) x P(S:T) x V(prop:T) x E ]i

Uncertainty and sensitivity analysis Qualitative risk estimation

Corso di Frane, Laurea Magistrale in Ingegneria per l'Ambiente ed il Territorio, Università di Salerno (Prof. ing. Michele Calvello, A.A. 2012-2013) - Gestione del rischio da frana: parte A - Pagina 9 di 14

“A framework for landslide risk assessment and management” (Fell et al. 2005) Landslide risk assessment Property or financial loss Annualised risk cost Financial capability Impact on corporate reputations Indirect costs (e.g. loss of road access) .. Loss of life Individual risk to life Societal risk (frequency versus number of deaths (known as f - N) or cumulative frequency versus number of deaths (known as F - N) criteria) Annualised potential loss of life Cost per statistical life saved (when mitigation measures are being considered)

Corso di Frane, Laurea Magistrale in Ingegneria per l'Ambiente ed il Territorio, Università di Salerno (Prof. ing. Michele Calvello, A.A. 2012-2013) - Gestione del rischio da frana: parte A - Pagina 10 di 14

“A framework for landslide risk assessment and management” (Fell et al. 2005) Landslide risk assessment Risk acceptance criteria

Acceptable risk. A risk which everyone impacted is prepared to accept. Tolerable Risk. A risk within a range that society can live with so as to secure certain net benefits.

Factors that affect an individual's attitude to acceptable or tolerable risk (Resources available to reduce the risk, individual's commitment to the property, age and character, …)

General principles that can be applied when considering tolerable risk to loss of life criteria (IUGS 1997): • The incremental risk from a hazard to an individual should not be significant compared to other risks to which a person is exposed in everyday life. • The incremental risk from a hazard should, wherever reasonably practicable, be reduced: “As Low As Reasonably Practicable” (ALARP) principle should apply. • Higher risks are likely to be tolerated for existing slopes than for planned projects, and for workers in industries with hazardous slopes, e.g. mines, than for society as a whole.

Corso di Frane, Laurea Magistrale in Ingegneria per l'Ambiente ed il Territorio, Università di Salerno (Prof. ing. Michele Calvello, A.A. 2012-2013) - Gestione del rischio da frana: parte A - Pagina 11 di 14

“A framework for landslide risk assessment and management” (Fell et al. 2005) Landslide risk management The outcomes of the Risk Assessent will be either: (a) The risks are tolerable, or even acceptable and no mitigation options need be considered (b) The risks are intolerable, and risk mitigation options need to be considered.

The risk management process is iterative, requiring consideration of the risk mitigation options and the results of the implementation of the mitigation measures and of the monitoring.

Examples of options for mitigation of risks for a slope or group of slopes: Reduce the frequency of landsliding Reduce the probability of the landslide reaching the element at risk Reduce the temporal spatial probability of the element at risk Avoid the risk Transfer the risk Postpone the decision if there is sufficient uncertainty (this would usually only be a temporary measure)

Corso di Frane, Laurea Magistrale in Ingegneria per l'Ambiente ed il Territorio, Università di Salerno (Prof. ing. Michele Calvello, A.A. 2012-2013) - Gestione del rischio da frana: parte A - Pagina 12 di 14

“A framework for landslide risk assessment and management” (Fell et al. 2005) Benefits and limitations of landslide risk management BENEFITS 9 It encourages a rational, systematic approach to assessing the safety of natural and engineered slopes. 9 It can be applied to situations which are not amenable to conventional deterministic analysis. 9 It allows comparison of risks. 9 The process requires consideration of risks for all levels of loading, rather than relying on "extreme event" loadings. 9 It focuses attention or what happens if the slope fails. 9 It provides a framework to put uncertainties and engineering judgement into a system. 9 It provides an open and transparent process on the nature and key contributors of landslide risk.

LIMITATIONS 9 The potential uncertainty in estimating frequencies, travel distance and vulnerability. 9 The variety of approaches, and the need for expert judgement to assess frequency of landsliding in many cases. 9 Poor estimates of risk because significant hazards have been overlooked. 9 Acceptable and tolerable loss of life criteria for slopes and landslides are not well established. 9 There is still a lack of general acceptance of the method by the profession.

Corso di Frane, Laurea Magistrale in Ingegneria per l'Ambiente ed il Territorio, Università di Salerno (Prof. ing. Michele Calvello, A.A. 2012-2013) - Gestione del rischio da frana: parte A - Pagina 13 di 14

Dispense Articoli principali A framework for landslide risk assessment and management. Fell R., Ho K.K.S., Lacasse S., Leroi E. (2005). In: Landslide Risk Management, 3-25. Taylor & Francis, ISBN-13: 978-0415380430.

Corso di Frane, Laurea Magistrale in Ingegneria per l'Ambiente ed il Territorio, Università di Salerno (Prof. ing. Michele Calvello, A.A. 2012-2013) - Gestione del rischio da frana: parte A - Pagina 14 di 14