ANALISIS REDUKSI LIMPASAN MENGGUNAKAN INVEST-UFRM BERBASIS NBS DI DAS SELOWOGO

Abstract

Flooding in the Selowogo Watershed, Situbondo Regency, has increasingly occurred due to extreme rainfall, Land Use/Land Cover (LULC) changes, and declining land infiltration capacity. The flood event on February 3, 2025, with a daily rainfall of 253 mm, highlights the need for sustainable flood mitigation strategies through a Nature-based Solutions (NbS) approach. This study aims to analyze existing runoff conditions, evaluate the effectiveness of NbS implementation in runoff reduction, and determine the most optimal mitigation scenario for the Selowogo Watershed. The study employed the InVEST Urban Flood Risk Mitigation (InVEST-UFRM) model, the Analytical Hierarchy Process (AHP) method to identify priority NbS alternatives, and the Weighted Overlay method to determine priority implementation areas. The event-based simulation results showed a total flood volume of 4.816.731,73 m³ with an AUC validation value of 0,772, indicating good model performance. Under the 10-year return period rainfall condition, the total runoff retention reached 7.483.936 m³, while the total flood volume was 4.008.789,75 m³. The AHP results identified wetlands and reforestation as the priority NbS alternatives. The reforestation scenario increased runoff retention by 11,40% and reduced flood volume by 21,22%, while the wetland scenario increased runoff retention by 0,14% and reduced flood volume by 0,19%. The combined wetland and reforestation scenario produced the best results, increasing runoff retention by 11,49% and reducing flood volume by 21,39%. Therefore, this scenario is recommended as the most optimal flood mitigation strategy for the Selowogo Watershed.