Kinerja dan Kerentanan Drainase Permukiman Kota Mataram pada Skenario RCP: Pendekatan SWMM–GIS

Abstract

Perubahan iklim yang meningkatkan intensitas dan variabilitas curah hujan menimbulkan tantangan serius bagi kapasitas drainase perkotaan; studi terdahulu jarang mengaitkan kapasitas saluran eksisting dengan proyeksi iklim berbasis skenario RCP sehingga prediksi kinerja jangka panjang masih terbatas. Penelitian ini bertujuan untuk mengevaluasi (to assess) kapasitas sistem drainase permukiman eksisting di Kota Mataram terhadap curah hujan aktual dan proyeksi iklim (RCP4.5, RCP8.5). Studi dilakukan di tiga kecamatan rentan (Ampenan, Cakranegara, Selaparang); data historis (2000–2020) dan proyeksi CMIP6 dikumpulkan dan didownscale, survei 120 segmen saluran dilakukan, serta pemodelan hidrologi–hidraulika dilakukan menggunakan SWMM dan analisis spasial di ArcGIS. Simulasi memperlihatkan intensitas puncak 1-jam median 42 mm·jam⁻¹ (10-tahun) dengan kenaikan ≈+12% (RCP4.5, 2030s) dan ≈+28% (RCP8.5, 2050s), yang mendorong Q_runoff naik ≈+14% (RCP4.5) dan ≈+33% (RCP8.5). Kapasitas median saluran Q_saluran = 1.12 m³·s⁻¹, exceedance segmen meningkat dari 24% (historis) menjadi 48% (RCP4.5) dan 72% (RCP8.5); kedalaman genangan median naik 0.18 → 0.38–0.62 m, luas terdampak 3.6% → 7.9–14.2%, dan durasi median 6 → 12–28 jam. Model divalidasi (NSE kedalaman 0.68; NSE debit 0.75; R² = 0.73; RMSE = 0.14 m). Penelitian ini shows that integrating downscaled RCP scenarios with SWMM–GIS provides robust, quantitative evidence for revising design standards, prioritizing retrofit (35–65% segmen) dan nature-based solutions (reduksi puncak 12–22%), serta memperkuat kerangka teoretis Hydrologic Continuity, Open-Channel Hydraulics, dan Resilience untuk perencanaan adaptif drainase perkotaan.

Climate change–driven increases in rainfall intensity and variability pose critical risks to urban drainage capacity; prior studies seldom link existing channel capacity with downscaled RCP projections, limiting long-term performance forecasts. This study aimed to assess the capacity of existing residential drainage systems in Mataram (Indonesia) against observed and projected rainfall (RCP4.5, RCP8.5). The analysis was conducted in three high-risk districts (Ampenan, Cakranegara, Selaparang); historical (2000–2020) and CMIP6 projection data were downscaled, 120 channel segments were surveyed, and hydrologic–hydraulic modelling was performed using SWMM with GIS spatial analysis. Simulations showed a 1-hour design median intensity of 42 mm·h⁻¹ (10-yr) and projected increases of ≈+12% (RCP4.5, 2030s) and ≈+28% (RCP8.5, 2050s), yielding Q_runoff rises of ≈+14% and ≈+33% respectively. Median channel capacity Q_saluran = 1.12 m³·s⁻¹; segment exceedance rose from 24% (historical) to 48% (RCP4.5) and 72% (RCP8.5); median ponding depth increased 0.18 → 0.38–0.62 m, affected area 3.6% → 7.9–14.2%, and median duration 6 → 12–28 h. Model validation produced NSE(depth)=0.68, NSE(peak)=0.75, R²=0.73, RMSE=0.14 m. The study concludes that integrating downscaled RCP scenarios with SWMM–GIS yields actionable, quantitative evidence for updating design return periods, prioritizing phased retrofits and nature-based measures (peak reduction 12–22%), and advances theoretical understanding by operationalizing Hydrologic Continuity, Open-Channel Hydraulics and Resilience Theory for climate-adaptive urban drainage planning.