Journal of Iranian Architecture & Urbanism(JIAU)

Abstract Extended Abstract
Background and Objectives: Landscapes in general and townscapes in specific are susceptible to various natural and non-natural risks. Flooding is considered one of the primary factors that contribute to the vulnerability and problems faced by landscapes and townscapes. Although these conditions are present worldwide, they are more severe in Iran compared to other countries. On the one hand, natural disasters such as floods and earthquakes threaten this region. On the other hand, the built environments of this country are threatened by the weakness of inadequate building construction trends. In many cases, the structural systems and materials used in buildings do not meet the risk management requirements of the development process. The negative impact of the threatening development process has relatively different consequences on place dimensions. The impacts of disasters are often linked to the sensitivity of the specific features of a place. Among these features, townscapes and landscapes are particularly vulnerable to various disasters, more so than other dimensions of a place such as function and management. The future of a place is shaped by the consequences that occur in different zones and areas of communities. The measurement of vulnerability and resilience should consider the normative qualities of the environment, especially in terms of geographical contexts. The aim of this research is to assess the resilience of townscapes in relation to their environmental qualities, such as efficiency, richness, attraction, and variety, through the use of a case study approach. The research aims to assess the flood vulnerability of the Pole-Dokhtar region and city, with a particular emphasis on the spring 2019 flood. The study will use a case study approach and evaluate the resilience of the townscapes in relation to environmental qualities, such as efficiency, richness, attraction, and variety. The region of Pole-Dokhtar in Lorestan province, Iran, will be the specific area of focus.
Methods: The research method will involve the application of the development category to identify and address the major problems related to flood vulnerability. By this condition, the city engine analytical software has been used for analysis and finding trends of case study area data and information process. The research methodology involves three actions in field study techniques, which are the examination of current documents, site observation, and interviews with relevant stakeholders at the local and national levels. These studies incorporate data gathering stages. For data gathering trends, three sources have been used: 1- the information from the Pole-Dokhtar city’s master and detailed plans, as well as any written documents relating to any regional development plans and studies 2- Official data from 2019 flood variables. 3- Field survey, with emphasis on direct observation in the Pole-Dokhtar urban area. Observation trends encompass a journey to Lorestan province, Pole- Dokhtar County and Pole-Dokhtar city in spring 2020. In addition, the data has been analyzed through GIS and SPSS logic, techniques, and tools. Then, using the SWOT matrix helped researchers to compare the basic influential factors in terms of contextual strengths, weakness, threats, and opportunities.
Findings: The research has produced three main findings. Firstly, it highlights the vulnerability of areas like Pole-Dokhtar not only to floods but also to other natural and man-made disasters. Secondly, the research reveals the importance of specific attention to the land slope, river basin, and soil foundation to maintain environmental quality in urban landscapes. Lastly, the study emphasizes the need for a comprehensive examination of various planning documents at different levels, including master, structure, and detail plans.
Conclusion: In summary, the achievements of this study encompass various research outcomes regarding both townscape resilience and vulnerability of national, regional level and scale on various geographical contexts. In spite of this, long-term experiences in disasters like wars, earthquakes, droughts, floods and the same Iranian communities could not benefit from their valuable lessons. Learning from these valuable experiences should be the key lessons to solve and resolve ongoing problems and challenges which are essential for the comprehensive development of a country.

Abstract Extended Abstract
Objective and Background: The present study analyzes the urban skyline and natural ventilation of land parcels in two urban blocks in Velenjak region of Tehran simultaneously. This study tries to assess the efficiency of the urban blocks not only from the visual aspects– what has been considered by most researchers so far- but also from an environmental perspective. For this purpose, a part of the urban texture in Velenjak region of Tehran is modeled in two patterns, and the airflow with a reference velocity of 4.5 m/s is applied to the models. The models are prepared in two patterns:1. The current status; a situation in which vacant lands have been massed according to existing data and ultimately resulted in a heterogeneous skyline; 2. A pattern in which 4 and 5 story buildings are added to the site, resulting in a homogenous skyline. The modeled area comprises 17 urban blocks and has an area of approximately 483,000 square meters. Wind simulation has been performed by Ansys Fluent Software and k-ε turbulence model, regardless of the atmospheric thermal stratification. Comparing the data obtained from the numerical solutions by Fluent Software to the reference wind tunnel results indicates acceptable accuracy of the selected method.
Methods: The information of the nearest meteorological station to Velenjak region is used to assess the data in this area. The data achieved between 2007 and 2016 show that the wind speed is less than 5 meters per second 93% of the time. Therefore, the reference wind speed in this study is considered to be 4.5 m/s at the height of 10 m. Based on the continuity and the frequency of wind in any direction during the mentioned time, an average for the coefficient of importance is defined for each wind direction (Table 1). In this study, a velocity of 1.7 m/s at the height of 10 m above the ground is considered the criterion for wind stagnation state. The reference for the assignment of this velocity is Beaufort’s table.
Findings: According to equation 1, a velocity of 1 m/s at 1.75 m balance is equal to a velocity of 1.7 m/s at 10 m balance (α= 0.33). Figures 9 to 12 show the absolute wind speed contours at 10 m balance above the ground on two samples for four wind directions. The areas marked with light blue color are areas of air stagnation. In these areas, the rotational airflow motion, also known as a vortex or a sequence, can be seen (Figure 7). The magnitude of the sequence area around the buildings is directly related to the building’s geometry and architecture and the urban fabric formation. Wind speeds in these areas are minimized, and they are prone to the accumulation of pollutants. A point grid with 100×100 points (Figure 8) is considered over the target area at the height of 10 m to compare the sample data and the velocity value at each point. Outdoor points with velocities greater than 1.7 m/s are separated from points with velocities less than 1.7 m/s, and their frequency percentages are calculated. Since the importance of wind blow in each direction varies, a coefficient of importance is applied to the frequency percentage of the points, shown in Table 1. Comparing airflow in two urban patterns with regular and irregular skylines indicates that air stagnation is seen at 29% of time/place in an area with a balanced skyline. However, in the first sample, at about 45% of time/place, the average wind speed at 10 m balance above the ground is recorded as 1.7 m/s, and thus we experience air stagnation phenomenon.
Conclusion: According to the results, considering buildings to cover 60% of the land parcel according to the construction regulations, and given the wind characteristics of the study area and its urban texture pattern, natural ventilation is provided better in 4 and 5 story buildings with a maximum height of 12 and 15 meters for buildings that cover 60% of the land parcel. This is while 7 story buildings are also allowed to cover 60% of the land parcel due to the relatively highly constructed urban blocks. Based on the results, it can be argued that a balanced skyline is more favorable both aesthetically and environmentally, and that creation of tall buildings in residential areas is only recommended when the building has a symbolic value and plays a special role in the region and affects the skyline.