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Climate change and Urban Vulnerability in Africa Assessing vulnerability of urban systems, population and goods in relation to natural and man-made disasters.

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Presentation on theme: "Climate change and Urban Vulnerability in Africa Assessing vulnerability of urban systems, population and goods in relation to natural and man-made disasters."— Presentation transcript:

1 Climate change and Urban Vulnerability in Africa Assessing vulnerability of urban systems, population and goods in relation to natural and man-made disasters in Africa 1 Training on the job Course on Hazards, Risk and (Bayesian) multi-risk assessement Napoli, 24.10.2011 – 11.11.2011 12/06/2014Fatemeh Jalayer

2 R = H V E 12/06/2014Fatemeh JalayerSlide 2 Risk assessment: The engineering point of view R : risk H : hazard V : vulnerability E : exposure

3 12/06/2014Fatemeh JalayerSlide 3 What is hazard? A dangerous phenomenon, substance, human activity or condition that may cause loss of life, injury or other health impacts, property damage, loss of livelihoods and services, social and economic disruption, or environmental damage.

4 12/06/2014Fatemeh JalayerSlide 4 Risk assessment: The engineering point of view R = H V E R : risk H : hazard V : vulnerability E : exposure

5 12/06/2014Fatemeh JalayerSlide 5 What is the vulnerability?... a human condition or process resulting from physical, social, economic, and environmental factors which determine the likelihood and scale of damage from the impact of a given hazard (United Nations Development Programme, 2004) The fraction of the total value at risk that could be lost after a specific adverse event (Principles of multi-risk assessment, EU, EUR 23615, 2009).... Vulnerability is the characteristics and circumstances of a community, system or asset that make it susceptible to the damaging effects of a hazard (2009 UN International Strategy for Risk Reduction)

6 12/06/2014Fatemeh JalayerSlide 6 What is the climate change vulnerability?... Vulnerability is the degree to which a system is susceptible to, or unable to cope with, adverse effects of climate change, including climate variability and extremes (United States Environmental Protection glossary for climate change).... Vulnerability is a function of the character, magnitude, and rate of climate change and variation to which a system is exposed, its sensitivity, and its adaptive capacity (United States Environmental Protection glossary for climate change).

7 The concept of Vulnerability seems always to involve a system. The system is a set of interacting or interdependent components forming an integrated whole. system boundary surroundings Some general aspects of the vulnerability

8 The definition of a system is very broad; it can stand for the environment, the community, the assets, the buildings, the roads and so on. Some general aspects of the vulnerability

9 12/06/2014Fatemeh JalayerSlide 9 Technical (Physical) Vulnerability of urban structures and life-lines Environmental Vulnerability of agriculture Environmental fragility (e.g., groundwaters, land) Social The specific social inequality of people in the context of a disaster … in broad terms, how susceptible people are to a hazard Economic Vulnerability of different economic sectors Institutional Effectiveness and failure of organized structures and institutions And hence, different types of vulnerability

10 12/06/2014Fatemeh JalayerSlide 10 A system is consisted of many components. It is not trivial to take into account the interaction of the components. Some general aspects of the vulnerability

11 Vulnerability is subjected to variability: Temporal: The hazard on the system can change with time The system can change in time. Spatial: The system is usually distributed spatially. Some general aspects of the vulnerability

12 Some general aspects of the vulnerability Vulnerability assessment is usually characterized by incomplete information and its assessment is a probability-based procedure. Incomplete information regarding the hazard evaluation Incomplete information regarding the system parameters

13 12/06/2014Fatemeh JalayerSlide 13 Some general aspects of the vulnerability The concepts of hazard, vulnerability and risk have quite a dynamic nature. What is called vulnerability from a point of view, would be called risk by some and hazard by some other at the same time and nobody is wrong! R = H V E

14 12/06/2014Fatemeh JalayerSlide 14 Capacity The combination of all the strengths, attributes and resources available within a community, society or organization that can be used to achieve agreed goals. Capacity may include infrastructure and physical means, institutions, societal coping abilities, as well as human knowledge, skills and collective attributes such as social relationships, leadership and management. Before to start we need the definition of capacity:

15 12/06/2014Fatemeh JalayerSlide 15 A quantitative definition for vulnerability rooted in engineering The vulnerability of a system or its components can be defined as the probability of its failure: C is the system capacity D is the demand a system can be subjected to C and D are attributes of the same property or quantity (they have the same units)

16 12/06/2014Fatemeh JalayerSlide 16 What is the system demand and how its related to hazard Demand: An urgent requirement or need Demand can be interpreted as the requirements imposed to the system by the hazard.

17 12/06/2014Fatemeh JalayerSlide 17 Linking hazard and vulnerability In order to link vulnerability to hazard in an efficient way it is useful to introduce a variable that links hazard to system demand. In the earthquake engineering jargon, this variable is called an intensity measure (IM). It can be thought of as an interface variable representing the intensity of hazard.

18 12/06/2014Fatemeh JalayerSlide 18 Vulnerability and Hazard Vulnerability can be calculated by expanding for all possible intensities of hazard: p(IM) represents hazard P(D>C|IM) is called the system fragility

19 12/06/2014Fatemeh JalayerSlide 19 System vulnerability vs Component vulnerability The system vulnerability is a function of the vulnerability of its components. There are different ways to calculate the system vulnerability: Employing a generalized definition of demand and capacity (the cut-set theory) for the system. Calculating the vulnerability of the system as a function of components vulnerability. Using simulation methods and calculating directly the system vulnerability.

20 12/06/2014Fatemeh JalayerSlide 20 System Reliability The system reliability is the probability that a system its able to carry out a given mission. If the reliability is a time function, then its possible to define a mission time interval (0,t) in which the system not fails. Structural Reliability the concept of reliability specializes through the following assumptions: - (0,t) is the time interval for which is designed the structure; - The reliability is the probability that the structure does not collapse; - Its more common to talk about collapse probability than reliability.

21 12/06/2014Fatemeh JalayerSlide 21 Limit State Concept We define failure the achievement of a state (the limit state) for which the structure is not more able to carry out a given mission. From a mathematical point of view, the failure and the limit state are correlated by the limit state function. This function depends by the uncertainties (random variables) that involved during the structure life. LIMIT STATE FUNCTION R ANDOM V ARIABLES no collapse collapse after collapse R ELIABILITY C OLLAPSE

22 12/06/2014Fatemeh JalayerSlide 22 Demand – Capacity Approach J OINT PROBABILITY DENSITY FUNCTION D OMAIN R n RANDOM VARIABLES FOR WHICH G IS NOT POSITIVE A simple way to understand the limit state function is to divide the random variables array so to create the Demand function (D) and the Capacity function (C).

23 12/06/2014 Fatemeh Jalayer Slide 23 Some general aspects of the vulnerability The Bayesian framework for inference lends itself very well to vulnerability assessment. Normalizing Constant Probability Distribution a posteriori Likelihood Function Vector of uncertain parameters Data D Modeling assumptions M Probability Distribution a priori

24 12/06/2014Fatemeh JalayerSlide 24 Demand – Capacity Approach

25 The Cornell Reliability Index 12/06/2014Autore25

26 The Cornell Reliability Index Variation 12/06/2014Autore26

27 The Interpretation of Cornell Reliability Index 12/06/2014Autore27

28 Simulation-Based Approach 12/06/2014Autore28

29 12/06/2014Fatemeh JalayerSlide 29 Reliability Single Component System Series Component System Parallel Component System

30 12/06/2014Fatemeh JalayerSlide 30 Reliability Cut set theory

31 F RAGILITY (1 STRUCTURE ; 1 BUILDING TYPOLOGY, K BUILDING TYPOLOGY ) 12/06/2014Fatemeh JalayerSlide 31 Reliability of informal settlements To evaluate the mean annual rate of exceeding of a given flood height respect to the structural capacity height its necessary to calculate the follow integral: where: H AZARD Is the collapse probability for a class of structures, given a specific rain height value, that can be represented as B ETA distribution as below showed; Is the mean annual rate of a given rain height, function of rain duration;

32 12/06/2014Fatemeh JalayerSlide 32 Reliability of informal settlements Example

33 12/06/2014Fatemeh JalayerSlide 33 Reliability of informal settlements Example Fixed 32 1 123 Hinged

34 12/06/2014Fatemeh JalayerSlide 34 Reliability of informal settlements Example 100 % 75 % 50 % 25 %

35 12/06/2014Fatemeh JalayerSlide 35 Reliability of informal settlements Example 100 % 75 % 50 % 25 %

36 12/06/2014Fatemeh JalayerSlide 36 Reliability of informal settlements Class of structuresx y BUILDING TYPOLOGY IDENTIFICATION Informal settlements N type,1 Type,1 N type,2 Type,2 N type,i Type,i N type,k Type,k … … … … N Buildings the construction techniques the method used for constructing the bricks type of the mortar used presence or absence of lintel beams foundation type and height from the ground the existence of drainage system the material used for roof beams the material used for roof cover type and number of openings the division of internal spaces possible reinforcing used in the wall corners the techniques used for anchorage of roof inside the wall general geometrical characteristics - the construction techniques - the method used for constructing the bricks - type of the mortar used - presence or absence of lintel beams - foundation type and height from the ground - the existence of drainage system - the material used for roof beams - the material used for roof cover - type and number of openings - the division of internal spaces - possible reinforcing used in the wall corners - the techniques used for anchorage of roof inside the wall - general geometrical characteristics

37 12/06/2014Fatemeh JalayerSlide 37 Reliability of informal settlements Class of structures ( TYPE 1; TYPE 2; …; TYPE i ; …; TYPE k) Type i n m Into Type i its possible to study n structures with a particular mechanical procedure trough that are recognized m collapse (survey sampling). The target is to evaluate the collapse probability based on survey sampling given the information (flood height and structural typology). h (m)h* 1 i 1 with probability i 1 - i 0 with probability 1 - i Binomial distribution

38 12/06/2014Fatemeh JalayerSlide 38 Reliability of informal settlements Class of structures Normalization factor Likelihood: binomial distribution Prior distribution: uniform B ETA DISTRIBUTION For the evaluation of i its possible to calculate the expected value:

39 12/06/2014Fatemeh JalayerSlide 39 Reliability of informal settlements Class of structures Example 18 survey sampling on 18 buildings 2 5 -TYPE 1 2 collapse on 5 buildings 56 -TYPE 2 5 collapse on 6 buildings 37 -TYPE 3 3 collapse on 7 buildings 1 0.4286 =0.0306 1 0.4286 =0.0306 2 0.7499 =0.0208 2 0.7499 =0.0208 3 0.4444 =0.0247 3 0.4444 =0.0247 Expected value Expected value P 0.542

40 12/06/2014Fatemeh JalayerSlide 40 Reliability of a network For the networks and lifelines, generally definable like system spatially distributed, the reliability can be obtained considering the conditions of the single part of the system (logic structure) and is function of the target that we want to achieve. Than its important to know: Detailed description of the network Position of the network respect to hazard sources 1 234 5 I1I1I1I1 I2I2I2I2 O1O1O1O1 O2O2O2O2 IiIiIiIi Input point into the network OiOiOiOi Output point into the network Network elementi Element centroid Possible direction

41 12/06/2014Fatemeh JalayerSlide 41 The network components Roads (paved and unpaved) Bridges Critical nodes Point of interest (e.g. schools, Emergency services, hospital) Open public concentration areas Parking areas Tunnel Culverts Side drainage ditches Understrains storm drains Sewage system …

42 12/06/2014Fatemeh JalayerSlide 42 Reliability of a network Vulnerability of the single part Functionality target ONE to ANY ANY to ANY

43 12/06/2014Fatemeh JalayerSlide 43 Reliability of a network The vulnerability of a road network component can also be defined in terms of its lack of connectivity or failure: p(h rain ) represents hazard P(D/C>1|h rain ) is the component fragility h (m)h* 1

44 12/06/2014Fatemeh JalayerSlide 44 From component to system The system vulnerability is calculated as a function of vulnerabilities for different structural types within the system (e.g., using cutset theory).


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