Analisis Hubungan Intensitas Urban Heat Island terhadap Temperature Criticality Value di Kota Denpasar

Abstract

Pemadatan bangunan di Kota Denpasar menyebabkan terjadinya urban heat island (UHI) yang bisa diukur dengan Urban Thermal Field Variance Index (UTFVI) dan Environment Criticality Index (ECI). ECI adalah perbandingan suhu permukaan lahan terhadap Normalized Difference Vegetation Index (NDVI). Penelitian ini mengembangkan ECI menjadi Temperature Criticality Value (TCV) yang diperoleh dari suhu udara dan Index-based Built-up Index (IBI). Penelitian bertujuan mengetahui intensitas UHI, pengaruh perubahan tutupan lahan, dan hubungan TCV dengan intensitas UHI. Analisis menggunakan data citra satelit Landsat 8 dan pengukuran lapang. Wilayah kajian didominasi oleh lahan terbangun yang meningkat dari 2015 hingga 2021. UTFVI menunjukkan dominasi intensitas UHI sangat kuat (>0,02) yaitu pada lahan terbangun. Rata-rata NDVI mengindikasikan penurunan kerapatan vegetasi. IBI mengindikasikan peningkatan kepadatan bangunan, berbanding terbalik dengan kondisi vegetasi. TCV pada 2015 berkisar antara -11.15°C.IBI hingga 6.42°C.IBI; 2018 antara -9.96°C.IBI hingga 6.79°C.IBI; dan 2021 antara -10.84°C.IBI hingga 6.87°C.IBI. Hal tersebut menunjukkan kondisi lingkungan semakin kritis. Intensitas UHI yang lebih kuat, bangunan yang lebih padat, dan lingkungan yang lebih kritis terjadi di pusat kota dibandingkan suburban berdasarkan analisis transek. Koefisien korelasi (r) TCV dan UTFVI tergolong cukup kuat (0,75–0,82), sehingga peningkatan intensitas UHI berhubungan dengan lingkungan yang lebih kritis. TCV memiliki korelasi paling kuat dengan indeks keterbangunan (r=0,99) dan korelasi kuat (r>0,80) namun berbanding terbalik dengan NDVI. Oleh karena itu, kekritisan lingkungan dapat dikontrol dengan pembatasan lahan terbangun dan penambahan vegetasi.

The buildings’ compaction in Denpasar causes urban heat island (UHI) which can be measured by Urban Thermal Field Variance Index (UTFVI) and Environment Criticality Index (ECI). ECI is the ratio of land surface temperature to the Normalized Difference Vegetation Index (NDVI). In this study, ECI was developed into Temperature Criticality Value (TCV) that was obtained from air temperature and Index-based Built-up Index (IBI). This study aims to determine the UHI intensity, the effect of land cover changes, and the relationship between TCV and UHI intensity. The analysis uses Landsat 8 imagery and field measurements data. This study area is dominated by built-up land, which increased from 2015 to 2021. UTFVI shows very strong UHI (>0.02) domination that occurs on built-up land. Mean value of NDVI indicates a decrease in vegetation density. Built-up density (IBI) has increased, inversely with vegetation. TCV in 2015 ranged from - 11.15°C.IBI to 6.42°C.IBI; 2018 between -9.96°C.IBI to 6.79°C.IBI; and 2021 between -10.84°C.IBI to 6.87°C.IBI. This shows that the environment is increasingly critical. Stronger UHI intensity, denser buildings, and more critical environment occur in the urban centers than in suburbs based on transect analysis. The correlation coefficient (r) of TCV and UTFVI is quite strong (0,75–0,82), so the increase of UHI intensity correlated with a more critical environment. TCV has the strongest correlation with Built-up Index (r=0.99) and strong (r>0,80) but inverse correlation with NDVI. Therefore, environment criticality can be controlled by limiting the expansion of the built-up area and increasing vegetation.