Vulnerability assessment of urban areas exposed to natural disasters - floods and earthquakes - using IHWP method in GIS environment

One of the most important issues that has always threatened human societies throughout history has been the occurrence of natural hazards. Hence, urban thinkers and planners seek to develop approaches to reduce urban vulnerability and increase resilience. District 1 of Tehran Municipality is considered as one of the most dangerous and vulnerable areas of Tehran metropolis with its North Tehran fault, Niavaran fault, Mahmoudieh fault. Zone one is also constantly exposed to floods due to the high slope in the northern parts and the presence of runoff. High density of impermeable surfaces and high volume of runoff in zone one, as well as being at the foot of the mountain, are the main reasons for flood-potential in the study sample (Salmani Foumani et al., 1398: 51). The question is what is the vulnerability of district one of Tehran municipality against natural hazards (floods and earthquakes)? To identify the current situation, prioritize the necessary management and planning actions and planning in the face of a possible crisis of future risks.

The present study is applied in terms of purpose and descriptive-analytical in terms of method. First, using library and documentary studies, such as the study of texts related to the subject and previous research, and the use of expert opinions in this field, effective indicators on vulnerability in cities were identified. The raw data of the research are extracted from the statistical blocks of Tehran Region 1 and the GIS map of the study sample and for data analysis, reverse hierarchical analysis or IHWP is used.

In this part of the research, documentary studies were used to extract the indicators for assessing the vulnerability of urban areas to hazards. These indicators include: population density; Maximum ground acceleration; Distance from the channel; Fault; Access to medical centers; Width; Access to fire stations; Access to open and green spaces; Distance from gas station and CNG; Distance from worn tissue; Sewage cover; Distance from bridges. In the last step, the final map is obtained by classifying the data into 5 distinct categories in terms of vulnerability and by overlaying the layers. According to the results, of the total area of ​​District 1 of Tehran Municipality, 14.95% of the area with very low vulnerability, 23.28% of the area with low vulnerability, 27.03% of the area with moderate vulnerability, 23.59 with high vulnerability And 11.14% have a very high vulnerability. As can be seen in Map 4, the center and west of the region are more damaged and the damage is reduced from west to east. 

Due to the climatic and physical conditions of the region, the plan to widen the passages for narrow passages of the city, especially in the center of the region, should be considered. The rivers Jamshidia, Darabad, Darband, Darkeh, Lark, Maghsoud Beyk, Velenjak and Golabdareh may be flooded, so the river area in this section should be controlled; At the same time, in this field, with proper planning and management, steps can be taken to eliminate the shortcomings and problems.