Remote Sensing-Based Approach to Identify the Influence of Land Use/Land Cover Change on the Urban Thermal Environment A Case Study in Chattogram City, Bangladesh
Human actions are responsible for significant changes in the character of urban ecology, as well as for decreases in the vegetated area, which point towards indicative change in the environment, particularly decreased diversity in the terrestrial ecosystem, on both local and global scales (Meyer and Turner 1992, Connors, Galletti, and Chow 2013, Moore, Gould, and Keary 2003). These environmental changes mainly occur as a consequence of the rapid expansion of urban areas, which is one of the most noteworthy human impacts (Lin et al. 2013). The growing expansion of cities and towns worldwide has now reached the point where over 54% of the global population resides in urban areas, and the UN expects that this proportion will reach up to 68% by 2050 (Alfraihat, Mulugeta, and Gala 2016, Alqurashi, Kumar, and Sinha 2016, UN 2015, Collins et al. 2013, IPCC 2014, Karim and Mimura 2008, Rimi et al. 2019). Urban areas primarily alter, transform, and replace natural vegetation and agricultural land into less- or non-evaporating and non-transpiring surfaces (Kafy, Faisal, et al. 2020, Kafy, Rahman, et al. 2020, Rahman et al. 2018, Ahmed 2018, Tomlinson et al. 2011. Xiang 2017. Zaksek and Ostir 2012). One of the significant environmental changes due to urban expansion is the increase in surface temperature (Saleh 2011). Changing the form of land use/ land cover (LULC) also affects heat absorption, evaporation, and transmission (Aboelnour and Engel 2018, Swetnam et al. 2011, Wang et al. 2017). The major causes for this urban expansion are population growth, economic development, improper urban management, and inappropriate planning (Aboelnour and Engel 2018, Kafy, Mansour, Al-Belushi, and Al-Awadhi 2020, Rahman, Aldosary, and Mortoja 2017, Ullah et al. 2019). Such changes in LULC profoundly affect the urban thermal environment, which is associated with land surface temperature (LST), urban heat islands (UHI), and urban field variance index (UTFVI).
The LULC change due to rapid urbanization and its effects on LST is a matter of great concern. The increase in LST in the urban context results from the UHI effects (Ahmed 2018, Fernando 2018, Silva, da Silva, and Santos 2018, Zhang et al. 2006, Zhou et al. 2013). Climate change, induced by urban growth, is an effect of UHI, and UHI highlights the variation in the ambient temperature of the metropolitan area compared to its neighbouring rural areas (Ahmed 2018, Fernando 2018, Lai and Cheng 2010, Santamouris 2014). Many researchers nowadays use thermal remote sensing (RS) and geographic information system (GlS)-based applications for describing the relationship between LULC and LST (Bokaie et al. 2016, Fernando 2018, Ullah et al. 2019, Weng, Lu, and Schubring 2004, Kafy, Faisal, et al. 2020, Kafy, Rahman, et al. 2020). Multi-spectral and multi-temporal remote sensing-based data are most suitable for displaying the LULC impact on LST (Ahmed 2018, Kafy, Rahman, et al. 2020, Kim 2008, Mou 2019, Santamouris 2014, Sarkar, Islam, and Akter 2016, Silva, da Silva, and Santos 2018, Yang et al. 2020).
The use of RS and GIS to measure land cover changes and LST has flourished significantly in recent decades (Balogun and Ishola 2017, Lilly Rose and Devadas 2009, Ahmed 2011, Kafy et al. 2019, Kafy, Rahman, et al. 2020. Rahman et al. 2018, El-Hattab, Amany, and Lamia 2018, Rahman, Aldosary, and Mortoja 2017c, Rahman, Aldosary, and Mortoja 2017a, Silva, da Silva, and Santos 2018). GIS and RS applications today receive a great deal of attention, as they can estimate changes in the landscape, ecosystem biodiversity, and heat stress of the urban environment (Al-Hathloul and Rahman 2003, Li and Zhao 2003, Streutker 2003, Celik et al. 2019, Swetnam et al. 2011, Trolle et al. 2019). Gathering information by direct field visits to understand LULC and LST transition scenarios often takes more time, requires more labour, and involves greater chances of error (Hart and Sailor 2009, Lilly Rose and Devadas 2009, Kafy, Rahman, et al. 2020). Several studies have described the LULC influence on UHI in various parts of the word (Hart and Sailor 2009, Bokaie et al. 2016, Silva, da Silva, and Santos 2018, Gaur, Eichenbaum, and Simonovic 2018, Sejati, Buchori, and Rudiarto 2019, Huang et al. 2019, Ahmed 2018). The earliest efforts began in 1972, when Rao first tested the pattern of surface temperature distribution and UHI in American coastal towns on the Atlantic Ocean, using remote-sensing technology (Krishna 1972). Huang et al. (2019) used the land contribution index method to describe the periodic thermal contributions in UHI for China for 2005-2015 for each type of LULC (Huang et al. 2019).
Chattogram is the second largest metropolitan area in Bangladesh, as well as being its industrial and business capital. Studies have been conducted to demonstrate the LULC pattern and its impact on the LST for Chattogram (Hassan and Nazem 2016, Roy et al. 2020). Chattogram (formerly, Chittagong) is one of the fastest-expanding metropolitan cities and is the second most-populated city in Bangladesh. To date, no study has focused on the LULC change and its impact on the urban thermal environment of Chattogram, using LST, UHI, and UTFVI. Therefore, this present study was undertaken to assess the LULC change and its impact on the thermal urban environment of Chattogram City, using the Landsat data for the 1999-2019 time period.