The threat of hydrometeorological disasters has once again emerged in Indonesia, as the frequency of extreme weather events increased from January to April 2026. The Meteorology, Climatology, and Geophysics Agency (BMKG) has warned that moderate to heavy rainfall may trigger floods and landslides in several vulnerable areas, including Jakarta, West Java, the northern coast of Java, and East Nusa Tenggara.
These disasters have not only ruined thousands of homes and disrupted national transportation routes but have also claimed many lives.
Professor of the Department of Geological Engineering at Universitas Gadjah Mada, Professor Wahyu Wilopo, explained that extreme weather phenomena are closely linked to shifts in global climate dynamics that trigger weather anomalies, including the emergence of tropical cyclones in equatorial regions that were previously considered theoretically impossible.
Climate change has altered cyclone formation patterns, making them increasingly frequent in several areas. The Cyclone Cempaka and Cyclone Seroja events, for example, demonstrated how cyclone seeds forming south of Java Island and in the Nusa Tenggara region caused extremely severe and difficult-to-predict weather changes.
“Theoretically, cyclones were once considered unlikely to form in equatorial regions, but that is an old theory. With global climate change, these phenomena are now occurring more frequently,” he said during an interview on Thursday (Feb. 5).
These conditions have made weather patterns increasingly extreme and unpredictable, both in timing and spatial distribution. This situation has resulted in sudden and prolonged periods of high-intensity rainfall, thereby increasing the risk of floods and landslides.
In addition, flood vulnerability is strongly influenced by topography and watershed morphology, which determine how an area responds to extreme rainfall.
“If a watershed is circular in shape, it is more prone to flooding because water from tributaries converges at one point simultaneously. However, if the watershed is elongated, there is a time lag in water flow, so the risk is relatively lower,” he explained.
Beyond watershed shape, Professor Wilopo noted that floods can be classified by their sources and mechanisms: upstream floods caused by runoff from upper catchment areas, local floods resulting from rainfall at the site, often exacerbated by poorly functioning drainage systems, and tidal floods triggered by rising sea levels during high tide.
He explained that the most dangerous conditions occur when all three types of floods occur simultaneously, as is often the case in Jakarta and coastal areas along the northern coast of Java, especially when land elevation is already below sea level, preventing drainage.
“The worst situation is when the complete package occurs, upstream flooding, heavy local rainfall, and high tides at the same time. This is even more severe when the land elevation is already below sea level, because the water cannot flow out,” he said.
Floods and landslides are also strongly linked, as landslides in upstream river areas can form natural dams composed of fragile soil and rock.
These natural barriers may collapse under increasing water pressure, ultimately triggering flash floods. On the other hand, strong flood currents can erode riverbanks and cause landslides along the banks, leading to the collapse of buildings located near rivers.
“If we look at recent cases in Aceh or West Sumatra, houses and buildings located along riverbanks collapsed because floodwaters eroded the riverbanks and caused landslides,” he said.
In terms of disaster mitigation, Professor Wilopo emphasized two main approaches: physical and non-physical measures. Physical mitigation includes infrastructure development such as slope and riverbank reinforcement to prevent landslides, reservoir construction to control flood discharge, and improvements to urban drainage systems.
Meanwhile, non-physical mitigation focuses on spatial planning and development regulations, including restrictions on activities and new construction in disaster-prone zones, the implementation of safe building standards, and enhanced public education and preparedness through early warning systems and disaster response training.
“Safety must be the primary foundation of development. Infrastructure is important, but without strong regulations and risk-aware communities, the potential for loss of life remains high,” he said.
The active role of local governments and Regional Disaster Management Agencies (BPBD) is crucial in preventing fatalities from floods and landslides, particularly through strengthening sustainable non-physical mitigation measures.
According to Professor Wilopo, the first step that governments and BPBD must take is to scientifically map disaster risks and communicate them openly to the public.
Once risk mapping is complete, the government and BPBD must ensure that early warnings are effectively delivered and clearly understood by communities, particularly those living in high-risk areas. He stressed that warnings should not be general in nature but must be specific to each area and the hazards it faces.
“The government and BPBD must map which areas are vulnerable and communicate those risks to the community. People need to know whether they live in a safe area. Without this, early warning efforts and infrastructure development will not be effective,” he said.
In addition to information dissemination, he emphasized that regular disaster training and simulation exercises are a core responsibility of the government and BPBD. Such training is essential to ensure that communities do not panic and know what to do when early signs of disaster emerge.
The government and BPBD are responsible for providing systems, regulations, and warnings, while communities are required to respond proactively and develop safety awareness. In this regard, disaster preparedness efforts will be effective only if the community is fully aware and participates.
“Preparedness is not achieved through a single socialization effort. It requires regular training and drills, followed by evaluation. Otherwise, awareness will decline over time. Even if the government performs well, disaster mitigation will not work if the community does not comply. Safety is a shared responsibility,” he concluded.
Author: Cyntia Noviana
Editor: Gusti Grehenson
Post-editor: Jasmine Ferdian
Illustration: Freepik