Efficient factors for assessing urban resilience were determined based on the literature review and area conditions. A part of the criteria layer is presented in Fig. 4. The DEMATEL based ANP method was used since that multiple criteria had different effects on the process of assessing urban resilience. Considering the fact that the ANP model investigates the relative importance of criteria in the network, it was essential to apply the DEMATEL approach to resolve the issues of interactions or interdependence among the criteria. Thus, the current study has three results that involved: building the Network Relation Map (NRM), determining the weights of criteria, and generating Urban Resilience Map (URM).
3.1. Building the Network Relation Map (NRM)
The first result was the dependent relationships between the criteria. Tables 5 and 6 show the amount of the interaction between the criteria and dimensions. Figure 5 shows INRM for a visual representation of the four dimensions and their criteria.
Table 5
Sum of influences given and received on dimensions
Dimension
|
di
|
ri
|
di+ri
|
di-ri
|
A
|
5.96
|
4.77
|
10.73
|
1.18
|
B
|
4.97
|
5.55
|
10.52
|
-0.58
|
C
|
6.02
|
5.40
|
11.42
|
0.62
|
D
|
5
|
6.22
|
11.22
|
-1.22
|
Table 6
Sum of influences given and received on criteria
Criteria
|
di
|
ri
|
di+ri
|
di-ri
|
A1
|
2.46
|
1.35
|
3.81
|
1.11
|
A2
|
1.35
|
1.79
|
3.14
|
-0.44
|
A3
|
1.97
|
1.58
|
3.56
|
0.39
|
A4
|
1.06
|
2.13
|
3.19
|
-1.06
|
B1
|
3.13
|
1.94
|
5.07
|
1.19
|
B2
|
2.71
|
2.33
|
5.04
|
0.38
|
B3
|
1.43
|
3
|
4.43
|
-1.57
|
C1
|
4.47
|
3.35
|
7.82
|
1.13
|
C2
|
3.92
|
3.45
|
7.37
|
0.48
|
C3
|
3.29
|
3.63
|
6.92
|
-0.34
|
C4
|
3.20
|
4.46
|
7.67
|
-1.26
|
The value of (di – rj) listed the criteria in cause-and-effect classes. As can be seen in Table 5 and Fig. 5, the environmental dimension (D1) has the highest (di – rj) value with 1.18, which has a direct impact on other dimensions. In addition, the influential impact degree of (D1) is 5.95 (Table 5), which is ranked as the second-highest degree among all causal dimensions. ‘Socio-economic (C)’ dimension has a significant impact on other cause group dimensions with the second highest (di – rj) value of 0.61. Additionally, (C) has the first highest ri value (6.01) among the causal dimensions in terms of prominent impact degree. Institutional (D) aspect has the lowest value of (di – rj) with (− 1.22), which is the most vulnerable to influence. Generally, A affects C, B, and D dimensions (A → {C B D}), C affects B and D dimensions (C → {B D}), and B affects D dimensions (B → {D}). Understanding these cause-and-effect relationships helps planners and urban managers make decisions for solving resilience issues. For instance, urban planners should first take action to develop the D (Environmental) dimension, and then C (Socio-economic), B (Physical), and D (Institutional) dimensions, respectively. Furthermore, the causal diagram shows that among the four dimensions, the socio-economic (C) dimension has the highest prominence (di + rj) value with 11.42 (Fig. 5). Prominence ranking is listed from the highest to the lowest value as follows: C (Socio-economic), D (Institutional), A (Environmental), and B (Physical).
Figure 5 and Table 6 demonstrate the most significant causal criteria. As can be seen, A1 affects A3, A2, and A4 criteria (A1 → {A3 A2 A4}) in the environmental dimension. According to Table 6, the (di – rj) values of the A1 (Disasters and natural hazards) and A3 (Environmental pollutants) criteria are positive. Hence, this criterion is classified as the cause group. Disaster and natural hazard criteria (A1) have the maximum positive value (di – rj) (1.11), and indicates that it has an significant effect on all of the criteria. Further, the A2 (Water resources) and A4 (Topography) criteria were located in the effect class due to the negative amount of (di – rj) values. Topography (A4) has the minimum negative value (di – rj) (-1.06) and receives a significant effect from cause class criteria. The results indicate that urban managers in Tehran can improve urban resilience in the environmental dimension by identifying types of natural hazards such as floods, earthquakes, and landslides and preparing vulnerability maps to identify safe situations for citizens in hazard situations.
Further, B1 affects B2 and B3 criteria (B1 → {B2 B3}) in the physical dimension. This finding indicates that the (di – rj) values of the B1 (Urban infrastructure) and B2 (Land use) are positive between these criteria and can influence all criteria. Urban infrastructure (B1) has the highest (di – rj) value with 1.19, which impacts the other sub-criteria of the physical dimension. In addition, the results show that B3 (Green space) is negative, has the minimum negative value (di – rj) (-1.57), and is affected by other criteria. Therefore, urban managers can improve urban resilience in the physical dimension by observing international standards of design and planning for providing the infrastructure and facilities. Additionally, they can protect vital and infrastructural public facilities through reconstruction.
C1 affects C2, C3, and C4 criteria (C1 → {C2 C3 C4}). The employment rate (C1) is another significant criterion since the (di – rj) value is the maximum value (1.13) in the socio-economic dimension. Furthermore, the results indicate that C3 (Health status) and C4 (Insurance type) are negative and are influenced by other criteria. C4 has the minimum negative value (di – rj) (-1.26). Therefore, urban managers can improve urban resilience by stabilizing the economic activities in the district, providing employment facilities, and taking measures to attract investment to diversify economic activities and increase people’s financial capacity. Similar influential relationships could also be defined for the other criteria, as illustrated in details in Fig. 5. Fontela and Gabus (1976) stated that due to internal relationships between factors, more attention should be paid to the cause class criteria due to their impact on the effect class criteria. This method is a useful tool for urban decision-makers to identify priorities for increasing urban resilience. Urban decision-makers can define regular prevention programs based on causal factors to increase urban resilience. Table 7 presents a preventive program for the most important causal factors in urban resilience according to Tehran situation.
Table 7
The preventive program for the most important causal criteria in urban resilience
Code
|
Causal Criteria
|
Preventive Program
|
A1
A3
|
Disasters and natural hazards
Environmental pollutants
|
• Identifying types of natural hazards in Tehran
• Preparing vulnerability maps to identify safe locations for citizens in hazard situations.
• Repair infrastructure vulnerabilities in the shortest possible time after the crisis.
• Granting incentives and financial facilities and tax exemptions for factory owners to purchase and use machines and machines with high standards and less pollution.
|
B1
B2
|
Urban infrastructure
Land use
|
• Updating the facilities of fire centers.
• Updating the facilities of medical centers.
• Build and upgrade the facilities of crisis management support bases in districts and neighborhoods with a suitable access radius.
• Creating multi-purpose land uses with emphasis on green space and open space for temporary housing in times of crisis.
• Paying attention to the compatibility of land uses and their impact on the crisis.
|
C1
C2
|
Employment rate
Population and education
|
• Promoting economic activities in the district for economic recovery after the crisis.
• Increase business and investment opportunities to increase urban economic resilience.
• Implementing regulations that limit building density to increase resilience.
• Implementing regulations that limit population density to increase resilience.
• Educating citizens to prepare for a crisis through photos, posters, seminars, etc.
• Implement programs for citizens to identify hazards, increase awareness of hazards, safety training, etc.
|
3.2. Determining the weights of criteria
The second result is related to determining the weights of the criteria. Based on the performance matrices of DEMATEL method, ANP was used to measure the criteria weight in a network structure. Finally, the limits of the super-matrix Wα were applied to obtain the criteria weights presented in Table 8 and Fig. 6.
Table 8
Influence weights of urban resilience assessment
Dimension
|
Global Weight
|
Ranking
|
Criteria
|
Global Weight
|
Ranking
|
Sub-criteria
|
Global Weight
|
Ranking
|
A
|
0.27
|
1
|
A1
|
0.120
|
2
|
A1-1
|
0.077
|
1
|
A1-2
|
0.061
|
2
|
A2
|
0.073
|
9
|
A2-1
|
0.044
|
7
|
A2-2
|
0.027
|
17
|
A3
|
0.099
|
5
|
A3-1
|
0.028
|
16
|
A3-2
|
0.031
|
14
|
A3-3
|
0.031
|
14
|
A4
|
0.0583
|
11
|
A4-1
|
0.003
|
27
|
A4-2
|
0.004
|
26
|
B
|
0.24
|
3
|
B1
|
0.126
|
1
|
B1-1
|
0.020
|
23
|
B1-2
|
0.028
|
16
|
B1-3
|
0.021
|
22
|
B1-4
|
0.020
|
23
|
B1-5
|
0.041
|
8
|
B2
|
0.109
|
3
|
B2-1
|
0.014
|
24
|
B2-2
|
0.011
|
25
|
B2-3
|
0.010
|
26
|
B2-4
|
0.058
|
3
|
B2-5
|
0.025
|
18
|
B3
|
0.062
|
10
|
B3-1
|
0.034
|
12
|
B3-2
|
0.028
|
16
|
C
|
0.26
|
2
|
C1
|
0.105
|
4
|
C1-1
|
0.054
|
4
|
C1-2
|
0.050
|
5
|
C2
|
0.093
|
6
|
C2-1
|
0.047
|
6
|
C2-2
|
0.037
|
10
|
C2-3
|
0.040
|
9
|
C3
|
0.078
|
7
|
C3-1
|
0.024
|
19
|
C3-2
|
0.023
|
20
|
C3-3
|
0.030
|
15
|
C4
|
0.077
|
8
|
C4-1
|
0.032
|
13
|
D
|
0.23
|
4
|
|
D1-1
|
0.022
|
21
|
D1-2
|
0.036
|
11
|
As shown in Table 8, the environmental dimension with a weight of 0.27 has a more important effect on urban resilience in comparison to other dimensions. It is noteworthy that the weights of the percentage of critical infrastructure vulnerabilities in the event of a natural disaster (0.077), the degree of the vulnerability of the infrastructure to hazards (0.061), the worn-out texture rate (0.058), the employment rate (0.054), the poverty line (0.05), and the population density (0.047) are the most important sub-criteria in comparison to other sub-criteria. Therefore, these six sub-criteria are the key factors for assessing urban resilience.
3.3. Urban Resilience Map (URM)
In the third result in related to applying the Weighted Overlay method for generating the urban resilience map. In this approach, the criteria weights obtained by the DANP model was multiplied into the criteria layer, and the layers were integrated. The urban resilience map was calculated based on the following equation:
URM = [(A1-1 🞩 0.077) + (A1-2 🞩 0.061) + [(A2-1 🞩 0.044) + (A2-2 🞩 0.027) + (A3-1 🞩 0.028) + (A3-2 🞩 0.031) + (A3-3 🞩 0.031) + (A4-1 🞩 0.003) + (A4-2 🞩 0.004) + (B1-1 🞩 0.02) + (B1-2 🞩 0.028) + (B1-3 🞩 0.021) + (B1-4 🞩 0.02) + (B1-5 🞩 0.041) + (B2-1 🞩 0.014) + (B2-2 🞩 0.011) + (B2-3 🞩 0.01) + (B2-4 🞩 0.058) + (B2-5 🞩 0.025) + (B3-1 🞩 0.034) + (B3-2 🞩 0.028) + (C1-1 🞩 0.054) + (C1-2 🞩 0.05) + (C2-1 🞩 0.047) + (C2-2 🞩 0.037) + (C2-3 🞩 0.04) + (C3-1 🞩 0.024) + (C3-2 🞩 0.023) + (C3-3 🞩 0.03) + (C4-1 🞩 0.032) + (D1-1 🞩 0.022) + (D1-2 🞩 0.036)] (8)
Then, the urban resilience map was classified into five categories for visual interpretation. Figure 7 displays the final resilience map.
Figure 7 shows the spatial pattern of Tehran metropolis resilience as well as the districts which need additional attention. The spatial patterns of resilience rates show that districts with very high to high resilience (Districts 4, 1, 2, 5, and 22) are located in the northwest to northeast parts of the study area (Table 9).
Table 9
Area and percentage of resilience degree in 22 districts of Tehran
Classes
|
District
|
Area
|
ha
|
Percent
|
Very low
|
10, 12
|
2162
|
3.5
|
Low
|
9, 17, 14, 11, 7, 8
|
8286
|
13.5
|
Moderate
|
3, 6, 13, 15, 16, 20, 19, 18, 21
|
23118
|
37.7
|
High
|
1, 2, 5, 22
|
20450
|
33.5
|
Very high
|
10, 12
|
7243
|
11.8
|
The household economy situation in these districts is moderate to high. These districts include mostly old residents and immigrants with high economic and social status. Furthermore, access to welfare facilities, urban infrastructure, social services, and large green spaces such as Chitgar, Koohsar, and Kan forest parks for local communities is better than other districts. The districts with moderate resilience (Districts 3, 6, 21, 18, 19, 16, 15, 20, and 13) are mostly located in the southern, southwestern, and western areas of the study area. According to Fig. 8, 17% of the total area of Tehran is located in ‘very low’ and ‘low’ resilience classes. Districts with very low to low resilience (Districts 7, 8, 9, 10, 11, 12, 14, and 17) are in the central and eastern areas of the study area. These districts have a very low to low degree of resilience due to high population density, worn-out texture, the vulnerability of infrastructure to hazards, air pollution because of compact urban structure, and many commercial land uses. This study aimed to provide opportunities for urban planners and decision-makers to reflect their decisions based on the DANP method. The advantages of DEMATEL based ANP technique for decision-makers could be stated as follows:
-
It is a proper method of MCDM which is used to identify the pattern of causal relationships between the variables.
-
This method has clarity and transparency for showing the interrelationships between an extended range of criteria as compared to the network analysis approaches, which can help experts express their views on the direction and intensity of the effects among factors with more knowledge.
-
It expresses the direction and intensity of the effects between the criteria in a quantitative way by presenting diagrams for visual interpretation.
-
It determines the importance and weight of the factors by considering all available factors and dimensions.
-
Structuring complex factors in the form of cause-and-effect groups is one of the most important functions, which could be considered as one of the most important reasons for its widespread use in problem-solving processes. By dividing a wide range of complex factors into cause-and-effect groups, it puts the decision-maker in a better position to understand relationships, which can result in a greater understanding of the position of factors and their role in the interaction process.
-
The ANP technique used in this study is a suitable tool for network ranking and does not require a hierarchical structure. Thus, it shows the more complex relationships between different levels of a decision in a network. In fact, it considers the interactions and feedback between the criteria and provides a suitable framework for analyzing the problem.