Investigation of Land Use and Land Cover Change and Urban Heat Island Phenomenon in Nakhon Ratchasima Province

Abstract

Background and Objectives: Urbanization constitutes a significant physical and sociodemographic transformation of the 21st century, exerting considerable influence on global ecosystems and local microclimates. Human-induced alterations in the previously vegetated and permeable soil structure of natural landscapes, along with their transformation into concrete, asphalt, and decorative architectural developments, significantly affect the Surface Energy Budget (SEB). These alterations generate an artificial environment that disrupts the natural equilibrium of the Latent Heat Flux. Latent Heat Flux decreases exponentially because of insufficient evapotranspiration, concurrently leading to an increase in the storage and re-release of Sensible Heat Flux. The Urban Heat Island (UHI) Effect refers to the phenomenon where urban areas experience higher temperatures than their rural surroundings due to human activities and alterations in land cover. The Urban Heat Island (UHI) Effect refers to a temperature phenomenon where urbanized areas exhibit markedly elevated atmospheric and surface temperatures compared to nearby rural regions. The Urban Heat Island (UHI) Effect refers to a temperature phenomenon in which urbanized areas exhibit markedly elevated atmospheric and surface temperatures compared to nearby rural regions. The UHI Effect has significant implications, including increased energy demands for air conditioning, deterioration of air quality due to heightened ground-level ozone production, and substantial risks to human health and urban living conditions. Nakhon Ratchasima Province is strategically located as the Gateway of Isan, serving as the biggest economic, industrial, and transportation center of Northeastern Thailand. The province has undergone significant structural urbanization in the last two decades. The expansion has been driven by major infrastructure assets and an increase of industrial areas. The city is experiencing thermal challenges due to its expansion. The previous study on the UHI phenomenon in this domain has been mainly descriptive. Literature often exhibits insufficient statistical validation to quantify temperature variations among various Land Use and Land Cover (LULC) types and is frequently hindered by methodological limitations concerning satellite image data calibration. Addressing these significant studies problems. This study aims to: (1) analyze the spatiotemporal changes in land use and land cover (LULC) from 2006 to 2021 and (2) assess the impact on structural changes in urban heat island (UHI) intensity and dynamics, by using high-quality radiometric data and robust statistical methods to verify the accuracy and reliability of the results.

Methodology: This study employed a Hybrid Classification method for the analysis of Land Use and Land Cover (LULC) for optimal accuracy of data and consistency. The 2006 LULC database published by the Land Development Department (LDD) was used as the baseline for this study. In 2021, LULC classification occurred by using multispectral imagery from the Landsat 8 Operational Land Imager (OLI) sensor that was acquired during the dry season in February to avoid cloud influence and variations in the season. The classification process used the Maximum Likelihood Classification (MLC) algorithm, that is a parametric supervised learning method based on the assumption of a normal distribution of image pixels within each training class. The classification accuracy was assessed through Stratified Random Sampling involving 205 reference points, results in an Overall Accuracy of 95% and a Kappa Coefficient of 0.90, which refers to an excellent level of agreement between the LULC classified map and in-situ data. The temperature evaluation focused on capturing Land Surface Temperature (LST) and identified data quality through the selection of USGS Collection 2 Level-2 Science Products (L2SP). The measurements of temperatures have been acquired from Landsat 5 Thematic Mapper (TM) for February 2007 and from Landsat 8 Thermal Infrared Sensor (TIRS) for February 2021. A selection was taken to apply data from the same temporal season (dry/cool season), and the selection of 2007 LST as a baseline estimate effectively reduced discrepancies associated with seasonal variability and atmospheric absorption. This study uses advanced statistical methods to evaluate the relationship between LST and various LULC types, expanding higher than simple descriptive statistics. Welch’s One-way ANOVA was used to improve its resistance against violations of homogeneity of variance assumptions, which are often present in environmental datasets. Post-hoc pairwise comparisons were performed utilizing the Games-Howell method. The spatial impact of heat island variation has been evaluated by using the Urban Heat Island Ratio Index (URI) and the Temperature Grade Change Index (TGCI) to show and quantify heat island expansion.

Main Results: The Transition Matrix analysis showed that the city's urban morphology changed a lot in terms of structure throughout the 15 years of research. Urban and built-up areas grew by a net of 73.66 square kilometers, which is a huge growth rate of 34.46% compared to the baseline. This urban and built-up area expansion primarily occurred on agricultural land (55.32 sq. km.) while other of LULC (23.35 sq. km.). Additionally, the analysis found that forest land decreased by 49.83%, which shows how significantly people are placing stress on natural resources and their buffers. Statistical analysis of the 2021 LST data found important proof of the UHI effect. The average surface temperature in urban and built-up areas was 28.4°C, which was significantly greater than the average surface temperature in forests land (25.40°C), with a statistical significance of p < .001. The average temperature difference of about 2.99°C shows how urbanization impacts the temperature. The result is distinct from the baseline LULC data from 2007, that showed a lack of statistical significance between urban and built-up areas and forest area temperatures. This indicates that the city has changed from a temperature balanced condition to a distinct island. In 2021, the mean temperature in the area decreased into slightly because of the La Niña phenomenon, which decreases the region. However, the location inside thermal structure became more severe. The URI analysis showed that the number of regions classified as "High Temperature Grade" increased from 7.30% to 7.39% of the whole area studied. This indicates that the increase due to urbanization is strong enough to cause local cooling patterns in the surrounding environment. The Linear Regression study also showed a strong positive relation between the Normalized Difference Built-up Index (NDBI) and LST. The coefficient of slope increasing higher in 2021 shows that the current urban surface elements in Nakhon Ratchasima are becoming increasingly prone to heat accumulation and retention.

Conclusions : This study shows that the fast urbanization of Nakhon Ratchasima during the past fifteen years has greatly exacerbated the UHI phenomena. The city has transitioned from thermal equilibrium to a fully developed heat island, mostly due to alterations in urban morphology rather than regional climatic influences. The results have serious effects on urban planning and policy. Statistical evidence indicates that there is a major negative relationship between LST and NDVI and MNDWI. Therefore, city planners require that they quickly add "Blue-Green Infrastructure" to the city's overall strategy. Several actions that should be implemented are to protect the original forest areas, build green spaces in cities, and restore water bodies. These actions have been shown to be the most effective approaches to decrease UHI intensity, increase Nakhon Ratchasima more comfortable in hot weather, as well as making it more resilient to climate change as the future urban expansion.