Rapid Flood Assessment, September 10, 2025, to Support Climate-Resilient Development Planning: A Case Studies of the Tukad Mati and Tukad Badung River Basins, Bali

Abstract

On 10 September 2025, severe flooding affected Badung Regency and Denpasar City, disrupting economic activities, tourism, and infrastructure, highlighting the urgent need for climate-resilient development planning. While previous studies have focused on structural flood control, limited attention has been given to rapid post-disaster assessments integrating infrastructure evaluation, policy analysis, and community-level runoff control in Balinese traditional settlements. This research conducted a rapid assessment of flood control operations and formulates climate-resilient planning recommendations, focusing on infrastructure performance in the Tukad Badung and Tukad Mati watersheds, Zero Delta Q runoff control policies, and their implementation in traditional Balinese settlements. A descriptive qualitative rapid assessment was employed through field surveys across three watershed segments, infrastructure observations, documentation, regulatory reviews, and expert discussions. The findings indicate that flooding resulted from extreme rainfall, declining infiltration areas, increasing runoff from built-up expansion, and limited infrastructure capacity. The Zero Delta Q principle has been incorporated into national and regional regulations through spatial-use intensity controls including Building Coverage Ratio (KDB), Built-up Area Coefficient (KWT), and Green Coverage Ratio (KDH), though effectiveness depends on consistent community-level implementation. In traditional Balinese settlements, increasing concrete and paving in residential yards has reduced infiltration and accelerated runoff. This study concludes that flood management should integrate infrastructure improvement with source-based runoff control by implementing Zero Delta Q in individual residential yards as the smallest hydrological units within a watershed. The findings contribute to climate-resilient planning by providing empirical evidence on integrating infrastructure, policy, and community interventions, offering actionable recommendations for policymakers and planners.