Changes in Green Areas and their Spatial Relationship to Flood Areas in Nonthaburi Province

Abstract

Nonthaburi province, a rapidly urbanizing metropolitan area of Bangkok, faces increasing flood challenges in parallel with the decline of green spaces crucial for water absorption and retention. This research aims to: 1) analyze the spatiotemporal changes of green areas in Nonthaburi from 2002 to 2022 and forecast the trend to 2032, and 2) analyze the relationship between green areas and historical floodplains. The study employed geoinformatics techniques, classifying land use from Landsat satellite imagery, utilizing a Cellular Automata Markov Chain model for future projection, and applying Chi-Square statistics to test the relationship. The results reveal a significant decrease in green areas over the 20-year period, from 387.45 km² (60.89%) in 2002 to 300.22 km² (47.18%) in 2022. The model forecasts a further decline to 279.92 km² (43.99%) by 2032 if current urbanization trends continue. The statistical analysis confirmed a significant relationship between green areas and floodwater retention (X² = 8.30, p < 0.05), particularly in the agricultural zones of the province's western region, which serve as natural water receiving areas. This finding provides empirical evidence supporting the strategic plans of the Royal Irrigation Department and the Department of Public Works and Town & Country Planning to designate this area as a water retention zone ("Kaem Ling"). Therefore, the urgent implementation of green area conservation and management policies is not merely an environmental measure but a critical strategic tool for ensuring the long-term flood management security of Nonthaburi province.