Daryono, a member of the Indonesian Disaster Experts Association\n(IABI), has analysed the causes of the flash floods that struck Solok,\nWest Sumatra. Daryono stated that rainfall was not the sole cause of the\nflash flood\u2019s occurrence.<\/p>\n
Daryono noted that a rainfall rate of 94 mm\/day acted as the trigger\nfor the flash flood. However, to conclude why the flow developed into a\nflash flood carrying so much material, he believes it is necessary to\nanalyse the upstream conditions, including slope gradient, soil\nsaturation, landslides, sedimentation\/loose material in the river\nchannel, land cover, and runoff concentration.<\/p>\n
\u201cTherefore, it is inaccurate to conclude immediately that rain is the\nonly cause. Essentially, the Solok \u2018Galodo\u2019 (flash flood) demonstrates a\nparadox common in meteorology: a month can be drier than normal, yet\nheavy rain of 9lag94 mm can still occur in a single day, triggering a\ndisaster,\u201d Daryono said on Wednesday (23\/09\/2026).<\/p>\n
Daryono detailed that heavy rain with an accumulation of\napproximately 94 mm\/day caused the water supply to the River Basin (DAS)\nto increase rapidly. Rain lasting several hours caused both infiltration\nand surface runoff to rise.<\/p>\n
\u201cWhen the soil\u2019s ability to absorb water is exceeded, water\nconcentrates directly towards the river channel,\u201d said Daryuno.<\/p>\n
Daryuno also explained that the upstream area of Solok has a\nhilly-mountainous topography with relatively steep slopes. These steep\nslopes accelerate surface runoff and provide significant gravitational\nenergy, enabling the water to erode and transport soil, rocks, and wood\ninto the river.<\/p>\n
\u201cContinuous rain fills the soil pores until they approach saturation.\nPore water pressure increases, causing soil shear strength to decrease,\nwhich subsequently makes slopes more prone to landslides,\u201d Daryuno\nadded.<\/p>\n
Daryuno noted that landslides on slopes or upstream areas can\nintroduce soil, rocks, trees, and other materials into the river\nchannel. This is what distinguishes a flash flood from ordinary\nflooding.<\/p>\n
\u201cThe flow can transform into a mixture of water and solid material\nwith much greater destructive power,\u201d said Daryuno.<\/p>\n
This can be worsened if there were already deposits of sand, gravel,\nboulders, wood, or landslide material at the riverbed and banks.\nConsequently, a sudden increase in discharge can re-mobilise these\nmaterials, increasing the volume and energy of the flash flood flow.<\/p>\n
\u201cA reduction in vegetation or disturbances to the land surface can\ndecrease interception and infiltration while increasing erosion and\nrunoff. However, the contribution of land cover changes to the Solok\nincident must be proven with land-use data,\u201d Daryuno stated.<\/p>\n
Furthermore, water from many slopes and tributaries eventually\ngathers in valleys and the main river channel. In steep river basins,\nthe concentration time is short, meaning that according to Daryuno, the\ndischarge can rise very rapidly.<\/p>\n
\u201cWhen combined with the supply of landslide material and sediment, a\nrapid flow laden with mud, rocks, and wood\u2014known as \u2018galodo\u2019\u2014is formed,\u201d\nsaid Daryuno.<\/p>\n
The Regional Disaster Management Agency (BPBD) of Solok Regency, West\nSumatra, recorded that four residents were injured due to the flash\nfloods that hit several areas in Arosuka, Gunung Talang District, on\nMonday night (21\/09\/2026). Subsequently, one resident was reported dead\ndue to the disaster, while another was reported missing.<\/p>\n
In addition to the injured, the Solok Regency BPBD noted that nine\nheads of households, or 32 individuals, were forced to evacuate due to\nthe flash flood. The evacuees have been placed in two locations prepared\nby the local government to handle disaster-affected residents.<\/p>\n
Furthermore, 11 government offices were affected by the flash flood.\nThe BPBD also recorded that 21 cars and seven motorcycles were damaged\nby the disaster.<\/p>\n
The flash flood hit the Solok Regent\u2019s Office Complex in Bandar\nBaliang, Jorong Kayu Aro, Nagari Batang Barus, and Nagari Koto Gaek\nGuguk, Gunung Talang District.<\/p>", "url": "https:\/\/jawawa.id\/newsitem\/expert-analysis-on-solok-flash-floods-rain-is-not-the-sole-cause-1790168156", "image": "" }, "sponsor": "Okusi Associates", "sponsor_url": "https:\/\/okusiassociates.com" }