Measuring impacts of "outdoor comfort" on "walkability" in warm humid city : a perspective from new and historical streetscape in the residential area of Dhaka, Bangladesh

Abstract

Walkability- “a measure of the livable urban form” 1 is affected by the rapid and intense urbanization worldwide. A subtropical city like Dhaka, Bangladesh, an example of a fast growing city, is now facing the challenge of livable and healthy urban development, especially in newly planned residential areas where a comfortable setting of walkable streets is almost absent. Automobile dominated newly planned residential sprawl severely compromises pedestrian mobility in terms of accessibility, safely and comfort etc. People’s activities and usages of urban space particularly street which is the most viable and sustainable feature of urban design is directly affected by thermal setting and thus affect walkability. This research investigates the thermal comfort condition on walkability of two different street fabrics of Dhaka. The research starts with theoretical review of ‘pedestrian-friendly community development’ while looking into case studies and standards in order to synthesize ‘walkability’ matrices. The research then proceed to a comparative analysis of the walkability between newly planned residential (Bashundhara R/A) area and historic settlement (Shakhari bazar) while taking into account street fabric as a variable for outdoor thermal comfort in the context of sub-tropical city like Dhaka. The next step is the calculation of thermal comfort indices to find out the comfort condition of the historic and the new street fabric by using a simulation software “City Comfort +” (Jianxiang Huang, 2014). Scientific tools are used to collect site specific microclimatic data for thermal comfort. To understand user’s response to comfort sensation and walkability of the street observation and questionnaire surveys are conducted. Survey data is then synthesized to find out the matrix between street fabric and thermal comfort condition. The aim is to develop and recommend a checklist of comfortable streetscape elements and potential design features from the historic street fabric and reinterpret those features to selected study area to investigate the scope of improvement of outdoor thermal comfort and streetscape thus walkability of that area. The outcome is tested by the computer based simulation software “City comfort +” (Jianxiang Huang 2014).The result interprets that thermal comfort condition is better in historical street due to deep canyon and shadow on street than the street of newly planned area . Both the physical (height width ratio, vegetation, water features, orientation) and functional attributes (amenities, infrastructure, safety) of street fabric has strong impact on improving thermal comfort and walkability. Passive cooling system considering “Shadowing” and “evaporative cooling “design elements are suggested to incorporate with streetscape elements for improving thermal comfort and walkability of streets in newly planned residential area. Finally the research suggests some urban design options for an effective and comfortable streetscape for streets of Bashundhara Residential Area Dhaka, Bangladesh.