Jakarta (ANTARA) - A research team from the Bandung Institute of\nTechnology (ITB) has stated that the flash floods that struck several\nareas in Aceh, North Sumatra and West Sumatra in November 2025 were\ntriggered by extreme weather that exceeded national flood mitigation\nstandards.<\/p>\n
Heri Andreas, coordinator of the ITB Centre for Analysis and Applying\nGeospatial Information (CENAGO) research team, said in a statement\nreceived in Jakarta on Friday that the findings were based on forensic\nanalysis of extreme precipitation, hydrological characteristics of three\nriver basins \u2014 Badiri, Garoga and Batang Toru in North Sumatra \u2014 land\ncover changes, and hydrological-hydraulic simulations.<\/p>\n
The ITB research team\u2019s study found that rainfall of extremely high\nintensity rendered existing flood control systems inadequate, as they\nwere not designed to withstand events of such magnitude.<\/p>\n
\u201cThe extremely intense rainfall was caused by Tropical Cyclone\nSenyar, meaning the capacity of existing flood control systems was not\ndesigned to withstand an event of this scale,\u201d he said.<\/p>\n
Heri explained that high-resolution satellite imagery analysis showed\nthat rainfall in late November 2025 reached extreme levels of 150\u2013300\nmillimetres per day, and very extreme levels exceeding 300 millimetres\nper day.<\/p>\n
ITB\u2019s probability model categorised the event as R700 to R1000 \u2014 a\nreturn cycle of 700 to 1,000 years \u2014 far exceeding the national flood\nmitigation standard, which is generally designed for up to R50.<\/p>\n
In conducting the study, Heri said the team did not rely solely on\nsatellite image digitisation to classify land cover, but also\nincorporated precipitation data from BMKG and the United States\u2019 NOAA,\nwatershed and sub-watershed delineation, digital elevation models (DEM),\nas well as hydrological and hydraulic parameters.<\/p>\n
\u201cQuantitatively, the contribution of land cover changes, which have\nbeen blamed, is relatively small compared to the extreme weather\nfactor,\u201d Heri said.<\/p>\n
The study\u2019s findings were also discussed at a forum titled\n\u201cUnderstanding the Root Cause of the 2025 Sumatra Floods for\nScience-Based Conclusion Reconciliation\u201d held recently in Jakarta,\nattended by representatives from ministries, agencies and professional\norganisations.<\/p>\n
At the forum, BMKG representatives presented findings on the Tropical\nCyclone Senyar phenomenon in late November 2025, which triggered extreme\nrainfall in several areas of West Sumatra, North Sumatra and Aceh. They\ndescribed it as an exceptionally rare event in which the combination of\nextreme rain and landslides triggered flash floods, including in Garoga\nVillage, South Tapanuli.<\/p>\n
ITB geology specialist Dr Ahmad Imam Sadisun added that landslide\nareas affected by the massive extreme rainfall occurred in zones with\nvery steep gradients, predominantly found in the upper Garoga watershed\nand protected forest areas.<\/p>\n
ITB therefore stressed the importance of utilising high-precision\ngeospatial data in disaster-related decision-making, so that every\nconclusion regarding the causes of disasters is formulated in a measured\nand proportionate manner.<\/p>\n
\u201cThere remains a very significant task ahead \u2014 namely the use of data\nand information, such as geoscience data, for the analysis and\ndecision-making of various problems,\u201d said Ahmad Imam.<\/p>", "url": "https:\/\/jawawa.id\/newsitem\/itb-flash-floods-in-sumatra-exceeded-national-mitigation-standards-1771663079", "image": "" }, "sponsor": "Okusi Associates", "sponsor_url": "https:\/\/okusiassociates.com" }