Climate change and Urban Vulnerability in Africa

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

21/04/23 Fatemeh Jalayer, Francesco De Paola, Raffaele De Risi

Case study: from climatic data to flooding risk assessment -

Application for Informal settlements in Tanzania.

221/04/23 Fatemeh Jalayer, Francesco De Paola, Raffaele De Risi

21/04/23 Slide 3

Risk assessment:

The engineering point of view

R : risk

H : hazard

V : vulnerability

E : exposure

Fatemeh Jalayer, Francesco De Paola, Raffaele De Risi

R = H• V • ER = H• V • E

𝜆𝐹=න 𝑃(ℎ𝑆𝑑 > ℎ𝑆𝑑𝐶 |ℎ𝑆𝑑) ∙ȁ�𝑑𝜆(ℎ𝑆𝑑)ȁ�ℎ𝑆𝑑

FRAGILITY(1 STRUCTURE; 1 BUILDING TYPOLOGY, K BUILDING

TYPOLOGY)

21/04/23 Slide 4

Reliability of informal settlements

To evaluate the mean annual rate of exceeding of a given flood height respect to the structural capacity height it’s necessary to calculate the follow integral:

where:

HAZARD

Is the collapse probability for a class of structures, given a specific flood height value;

Is the mean annual rate of exceeding given flood height;




21/04/23 Slide 5


Class of structures

xx

yy

BUILDING TYPOLOGY IDENTIFICATION

Informal settlementsInformal settlements

Ntype,1Type,1

Ntype,2Type,2

Ntype,iType,i

Ntype,kType,k

…

…

…

…

N BuildingsN Buildings - the construction techniquesthe construction techniques - the method used for constructing the bricksthe method used for constructing the bricks - type of the mortar usedtype of the mortar used - presence or absence of lintel beamspresence or absence of lintel beams - foundation type and height from the groundfoundation type and height from the ground - the existence of drainage systemthe existence of drainage system - the material used for roof beamsthe material used for roof beams - the material used for roof coverthe material used for roof cover - type and number of openingstype and number of openings - the division of internal spacesthe division of internal spaces - possible reinforcing used in the wall cornerspossible reinforcing used in the wall corners - the techniques used for anchorage of roof inside the wallthe techniques used for anchorage of roof inside the wall - general geometrical characteristicsgeneral geometrical characteristics


21/04/23 Slide 6


Example


21/04/23 Slide 7


Example

Fixed

3 2 1

1 2 3

Hin

ged

Hin

ged


21/04/23 Slide 8


Example

100 %100 %

75 %75 %50 %50 %25 %25 %


21/04/23 Slide 9


Example

100 %100 %

75 %75 %50 %50 %25 %25 %


21/04/23 Slide 10


Example

Structural Population


3m 4m 5m

Thickness3 values:20 cm30 cm40 cm

Mechanical Material Property:25%50%75%100%

Total: 72 cases

21/04/23 Slide 11


Example

Structural Fragility

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 1 2 3 4 5 6 7

Prob

abili

ty o

f fai

lure

h - flood height (m)


21/04/23 Slide 12


Example

Flood hazard TR=10years


21/04/23 Slide 13


Example



21/04/23 Slide 14


Example



21/04/23 Slide 15


Example



21/04/23 Slide 16


Example



21/04/23 Slide 17


Example



21/04/23 Slide 18


Example

Flood hazard For a given grid point


21/04/23 Slide 19


Example

Flood hazard For a given grid point


21/04/23 Slide 20


Example

Vulnerability ∙ Hazard


21/04/23 Slide 21


Class of structures

xx

yy

BUILDING TYPOLOGY IDENTIFICATION

Informal settlementsInformal settlements

Ntype,1Type,1

Ntype,2Type,2

Ntype,iType,i

Ntype,kType,k

…

…

…

…

N BuildingsN Buildings - the construction techniquesthe construction techniques - the method used for constructing the bricksthe method used for constructing the bricks - type of the mortar usedtype of the mortar used - presence or absence of lintel beamspresence or absence of lintel beams - foundation type and height from the groundfoundation type and height from the ground - the existence of drainage systemthe existence of drainage system - the material used for roof beamsthe material used for roof beams - the material used for roof coverthe material used for roof cover - type and number of openingstype and number of openings - the division of internal spacesthe division of internal spaces - possible reinforcing used in the wall cornerspossible reinforcing used in the wall corners - the techniques used for anchorage of roof inside the wallthe techniques used for anchorage of roof inside the wall - general geometrical characteristicsgeneral geometrical characteristics


21/04/23 Slide 22


Class of structures

( TYPE 1; TYPE 2; …; TYPE i ; …; TYPE k)

• Into TypeType ii it’s possible to study nn structures with a particular mechanical procedure trough that are recognized mm 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 1 with probability ii

0 with probability 1 -1 - ii

Binomial distributionBinomial distribution


𝑃൫ℎ𝑆𝑑 > ℎ𝑆𝑑𝐶 หℎ𝑆𝑑൯= 𝑃൫ℎ𝑆𝑑 > ℎ𝑆𝑑𝐶 หℎ𝑆𝑑,𝑇𝑦𝑝𝑒൯∙𝑃(𝑇𝑦𝑝𝑒)𝑘𝑖=1

21/04/23 Slide 23


Class of structures

ii

iii PmnPC

mnP

PmnPmnP

|,

,

|,,| 1

Normalization factorNormalization factor

Likelihood: binomial distributionLikelihood: binomial distribution

Prior distribution: uniformPrior distribution: uniform

BETA BETA DISTRIBUTIDISTRIBUTI

ONON

For the evaluation of i it’s possible to calculate the expected value:

n

mdmnPImnE iiiii ,|,,|


21/04/23 Slide 24


Class of structuresExample

survey sampling on 1818 buildings - TYPE 1 22 collapse on 55 buildings

- TYPE 2 55 collapse on 66 buildings

- TYPE 3 33 collapse on 77 buildings

11 0.42860.4286 =0.0306=0.0306

22 0.7499 0.7499 =0.0208=0.0208

33 0.44440.4444 =0.0247=0.0247

• Expected valueExpected value

P 0.542


21/04/23 Slide 25

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 it’s important to know:

Detailed description of the network

Position of the network respect to hazard sources

11

22 33 44

55

II11

II22

OO11

OO22

IIii Input point into the network

OOii Output point into the network

Network elementii

Element centroid

Possible direction


21/04/23 Slide 26

The network components

Roads (paved and unpaved)BridgesCritical nodesPoint of interest (e.g. schools,Emergency services, hospital)Open public concentration areasParking areasTunnelCulvertsSide drainage ditchesUnderstrains storm drainsSewage system…

21/04/23 Slide 27


Vulnerability of the single part

Functionality target

ONE to ANY

ANY to ANY


21/04/23 Slide 28


The vulnerability of a road network component can also be defined in terms of its lack of connectivity or failure:

rainrainhFF dhhpPC

DPP

rain )()1( |

• p(hrain) represents hazard

• P(D/C>1|hrain) is the component fragility

h (m)h*

1


21/04/23 Slide 29

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).

)1min(max ij

ijF C

DPP


Climate change and Urban Vulnerability in Africa

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