126 10th International Conference on Urban Climate 6th to 10th August, New York SURFACE URBAN HEAT ISLAND EFFECT OF A POLYNUCLEAR MEGACITY DELHI

MORPHOLOGICAL AND THERMAL EVALUATION OF THREE SUB-CITIES

Bakul Budhiraja*1, Girish Agrawal2 and Prasad Pathak3

Department of Civil Engineering, Shiv Nadar University, Gautam Buddha Nagar, India; [email protected] *1 School of Art and Architecture, O.P. Jindal, Sonipat, India2 Department of Physical and Natural Sciences, Flame University, Lavale, Pune, India3

Abstract

Delhi has been built over centuries on unique urban planning concepts. A megacity such as Delhi has several heat islands, as it’s an amalgamation of several cities. It comprises of cities built in different centuries and based on unique urban planning concepts. The climate of the city is essentially characterized by the urban form and function. A sustainable urban city has to strike balance between its morphometric and climatic performance. Prioritisation of one over other gives either gives thermally efficient cities with low socio-economic gains or otherwise. Thus, testing the new notion of dense cities with mix-land use on the thermal climatic scale is of prime importance. Three sub-cities have been selected to analyze the surface urban heat island and socio-economic performance. The oldest city is Shahjahanabad built in the 1640s with the organic urban form on the banks of Yamuna River with highest population density in Delhi. Second is Lutyen’s Delhi, built in the 1930’s as a result of garden city movement under the influence of British architecture. A comparatively new city Dwarka has been selected, built in the 1990s to decongest the population load of core Delhi. It was built according to mix land use concept and has twenty times more population than Lutyen's Delhi. Surface UHI Intensity is estimated using Landsat 8 data for 2015 in the local climate zones of the sub-cities. Morphometric matrixes such as mixed-used index and space syntax have been computed for estimating the socio-economic connectivity. Shahjahanabad experiences the least thermal range, Lutyen’s Delhi performs well to keep the thermal temperature at minimum and Dwarka performs better in morphological parameters.

Keywords – Urban form, LST, thermal remote sensing, Local Climate Zones

1. Introduction

Urbanization is bound to have climatic ramifications due to its interference with the surface energy balance. The urban form and function essentially characterize the climate of the city. A sustainable urban city has to strike balance between its morphometric and climatic performance. Delhi is presently the second most populated with 26 million people but by 2030 it will be the most populated urban area in the world. The urban area, described as the “urban microclimate,” has a different climate from the countryside (Barry and Chorley, 1998). Compared to open country, built urban sites have larger areas of exposed surfaces per unit area of ground cover. Because of the larger area, potentially more solar radiation can be collected on a built urban site than on a flat, open terrain. The emergence of “sustainable development” as a popular concept (Jabareen 2004) has revived discussion about the form of cities. Undoubtedly, it has motivated and provoked scholars and practitioners in different disciplines to seek forms for human settlements that will meet the requirements of sustainability and enable built environments to function in a more constructive way than at present. Various urban planning concepts have been followed worldwide to design cities for either dominance of colonial power or having sustainable cities. The paper aims to compare the different cities which originated from different concepts on the thermal scale, in the megacity of Delhi.

Delhi has been the seat of power for more than 650 years, thus many dynasties have built their capitals here. It is one of the most populated megacity but only in the last two decades. Due to its geological location, it faces heat waves each year. Three sub-cities have been selected to analyze the surface urban heat island and socio-economic performance. The imperial capital Shahjahanabad was built by Mughal emperor Shahjahan between 1639 to 1648 along the banks of river Yamuna. Shahjahanabad was also the ‘exemplary’ of the sovereign city model as the city was an extension of the imperial mansion (Blake, 2002). Though the pattern of land use is totally urban, it was still essentially a pedestrian city retaining a human scale (UNESCO WHC, 2012). The residential areas 126 10th International Conference on Urban Climate 6th to 10th August, New York are introvert spaces and independent social and environmental entities, while commercial activities are located along the spines, closer to areas of administrative or institutional importance.

Second is Lutyen’s Delhi, built in 1930’s under the influence of the British Empire. It has geometrical designs and seventy times less population than old Delhi. The design of New Delhi blends the two themes of early twentieth-century city planning – the City Beautiful (vistas) and Garden City (verdure). But New Delhi is not an orthodox baroque city, the king’s way is lined not by the house but by trees, open spaces and canal (Ridley, 1998). Superimposed on the rectangular grid is a second, distinct geometrical system, composed of two overlapping hexagons which are further divided into smaller hexagons and further into triangles (Greenberg, 1969). The colonial city is a city of wide, tree-lined roads designed for cars fronted by bungalows where a significant proportion of space is allotted to visual and ceremonial areas (UNESCO WHC, 2012). Zoning was also an integral part of the planning of New Delhi, the core and the secretariat comprised of the government complex zone, the residential area parallels to Kingsway was termed as bungalow zone and Connaught place comprised of the commercial zone. A comparatively new city Dwarka has been selected, built in the 1990s to decongest the population load of core Delhi. ). It was built according to mix land use concept and has twenty times more population than Lutyen's Delhi. The mixed-use concept slowly found its way back in the late nineteenth century into the rigid zoning land use models (Chadchan, 2012). There is a general consensus among planners and scholars that mixed land use has an important role in achieving sustainable urban form. Mixed-use or heterogeneous zoning allows compatible land uses to locate in close proximity to one another and thereby decrease the travel distances between activities (Parker 1994). In real, Dwarka is majorly residential with few commercial spaces and the absence of proper entertainment spaces. It has been divided into gridded sectors with urban villages and informal settlements on the fringe of the zone. The principles governing the development in the sub-cities are unique, thus it’s interesting to compare them to identify which planning pattern performs best.

Figure 1. Three Sub-cities a) Shahjahanabad b) Lutyen's Delhi c) Dwarka d) Local representation of Local Climate Zone’s (LCZ)

126 10th International Conference on Urban Climate 6th to 10th August, New York

2. Methodology

Three sub-cities namely organic city of Shahjahanabad (1638), garden city or Lutyen’s Delhi (1911) and mixed-land use city of Dwarka (1992) have been selected to test the notion. The estimation of thermal behaviour is based on Land surface temperature (LST). It is estimated using Landsat 8 data for 2015 in the local climate zones of the sub-cities. The Land surface temperature has been corrected for atmospheric and emissivity errors. Local Climate Zones (Stewart and Oke, 2012) incorporates the four properties of the urban environment that contribute to the UHI, namely – fabric (construction and natural materials); cover ( built-up, paved, vegetated, bare soil, water); structure ( dimensions of the buildings and the spaces between them, the street widths and street spacing) and; metabolism (heat, water and pollutants due to human activity) (Stewart, 2011). LCZ has been adopted by World Urban Database and Access Portal Tools (WUDAPT) with an aim to use LCZ as the starting point for characterizing cities. Seasonal trend of Land Surface Temperature has been calculated in the Local Climate Zones of each sub-city to estimate Surface Urban Heat Island Intensity for the year 2015.

The morphological analysis has been performed using Space Syntax maps for understanding road integration and Spacematrix to understand compactness. The Space Syntax maps are produced using Depthmap with angular radii, which highlight the most axial roads and their integration with sub- roads in the city. Also, Space matrix (FSI, GSI and N) is computed to understand built density related to the high socio-economic performance of the city. The intuitive hypothesis is that Dwarka will perform best in the aggregation of morphometric and thermal scores, as it emphasizes on implementing new urbanism.

Figure 2. Aspects of three sub-cities a) Planning maps b) Land Surface Temperature c) Space Syntax d) Normalized Difference Vegetation Index e) Local Climate Zones composition

126 10th International Conference on Urban Climate 6th to 10th August, New York

3. Results

In the morphological analysis, Space syntax values are highest in Dwarka indicating a good integration in sectors, followed by Lutyen's Delhi and Shahjahanabad. In terms of density, the organic city has the highest FSI and GSI. Dwarka has a greater FSI than Lutyen’s since it has mid-rise structures as compared to low-rise buildings in Lutyen's Delhi. GSI for both the sub-cities is comparable to Dwarka, as its still has significant agricultural land.

Seasonal variation of LST in three sub-cites a) b) 42 c) a) 39

36

33

30

27

24 Mean LST (ᵒC)LST Mean

21

18

Shahjahanabad 15 Lutyen's Delhi Dwarka 12 12 01 02 03 04 05 06 09 10 11 Month

c)

d)

Figure 3. a) Space matrix (FSI, GSI and N) b) Seasonal variation of LST in three sub-cities c) Inter- LCZ SUHI intensity in Summer d) Inter-LCZ SUHI intensity in Winter

The thermal analysis yielded a maximum SUHI intensity in the month of May within the sub- city of Dwarka LCZ 5-LCZ D = 7.41ᵒC, Lutyen's Delhi LCZ 5-LCZ A = 4.02ᵒC and Shahjahanabad LCZ 8-LCZ B = 3.52ᵒC. Large low-rise (LCZ 8) has lower temperatures, the maximum deviation from the mean is observed in Open mid-rise (LCZ 5). In residential areas, compact low-rise (LCZ 3) is 2- 4ᵒC cooler than Open mid-rise (LCZ 5), supporting the idea of denser cities. Sparsely built spaces (LCZ 9) and low plants (LCZ D) in summer also have a higher deviation from the mean on the positive side. 126 10th International Conference on Urban Climate 6th to 10th August, New York

The seasonal trend seems to be the same over the three sub-cities, only the quantitative value of SUHI intensity varies with seasons.

In assessing the three sub-cities, Shahjahanabad experiences least thermal range. As expected, Lutyen’s Delhi has less thermal score due to the presence of huge green space available for evapotranspiration. Dwarka performs best in road integration and Organic city with respect to its compactness.

4. Conclusion

The notion of mix-landuse compact cities applied in Dwarka, is far from an ideal thermal environment. New modern sub-city of Dwarka is denser but thermally experiences a high range. The urban form and planning excels in only few aspects of road integration. Revisting the Lutyen's garden city which performs well thermally but has a meager density. The organic city is the densest city with the thermal mean being high, yet sustaining a smaller intervariability in thermal range. The dense cities with mix-land use perform equivalently to the organic city on the thermal scale. Morphologically, the planning is showcasing sigificant outcomes. The seasonal trend for thermal behaviour within the local climate zones is similar in the three sub-cities, with high quantitative SUHI intensities. The residential urban form of compact low-rise has a high thermal performance than open mid-rise. Every sub-city offers an optimum solution to a thermally and morphologically optimum city. The urban planning of the modern city on the mixed land-use concept, questions if our new urban cities are built to create heat islands? Or maybe new urbanism ideas are well implemented in old cities of Delhi. The trends observed seasonally and different thermal behaviours of urban form need to be looked, to understand the partition of energy taking place. Thus, the ultimate aim would be to adopt morphological planning from Dwarka, incorporate density and minor thermal range from Shahjahanabad and adopt startegy of green spaces in urban form from Lutyen’s Delhi.

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