Decadal Assessment of Built-up Growth in Tirap District of Arunachal Pradesh (1993-2023) Using NDBI

Urban expansion in ecologically sensitive and topographically complex regions requires careful monitoring to ensure balanced land management and sustainable development. This study analyses the spatial and temporal dynamics of built-up growth in Tirap district over a thirty-year period (1993–2023) using the Normalized Difference Built-up Index (NDBI) derived from multi-temporal Landsat imagery. Surface reflectance data from four decadal intervals were processed to generate NDBI layers, which were subsequently classified into built-up and non-built-up categories using a defined threshold. The results indicate a steady increase in built-up area from 14.79 sq. km in 1993 to 76.37 sq. km in 2023, reflecting gradual but consistent spatial expansion. Growth patterns reveal clustering around established settlement nodes and progressive outward extension influenced by terrain and accessibility. Despite this increase, large portions of the district remain under vegetation cover, suggesting that development has been spatially concentrated rather than widespread. The findings demonstrate the usefulness of index-based remote sensing techniques for long-term monitoring of land-use transformation in mountainous districts. The study provides a spatial baseline to support informed planning strategies that seek to balance infrastructural development with environmental sustainability in Arunachal Pradesh’s eastern Himalayan region.