PETALING JAYA: The Fire and Rescue Department has advised the public to minimise outdoor activities near rivers or waterfalls during the rainy season and to remain vigilant about the potential dangers of water surges during unpredictable weather.
Putrajaya fire safety division director Datuk Khirudin Drahman Hussain told theSun that recent erratic weather patterns, including unexpected heavy rains upstream, could trigger dangerous water surges.
“Pay attention to weather alerts and warnings from local authorities or weather services, as it’s crucial to take precautions. We urge the public to remain cautious during sudden weather changes. Even if the water downstream seems clear and calm, heavy rainfall upstream can rapidly create hazardous conditions,” he said.
Khirudin added that search and rescue statistics from January to July recorded 101 deaths due to drowning in rivers and waterways.
“The primary trigger is heavy and concentrated rain within a short period, often associated with thunderstorms, tropical storms or hurricanes. Extreme weather events characterised by exceptionally heavy rainfall over a short period can create conditions for flash floods. So, it is important to be vigilant during such occurrences,” he said.
He added that rapidly rising water levels could indicate an imminent flash flood, often preceded by a roar as water rushes through narrow valleys or gorges.
Visitors should be alert if water changes color from clear to muddy and monitor water levels, which can rise in stages.
Universiti Teknologi Malaysia Civil and Environmental Engineering expert Prof Dr Mohd Fadhil Md Din explained that surges often occur in a straight channel when water is suddenly forced to stop or change direction.
“Water surges form a column-like structure, which can be uneven in nature. This often happens when valves are quickly closed or pumps are suddenly shut off, creating a pressure wave that causes water to surge.”
Mohd Fadhil said heavy upstream rainfall can increase the flow of a river, leading to sudden surges and changes in water volume downstream.
The rapid flow can cause a surge if the riverbed is narrow or changes shape.
“When two rivers or a river and its tributary meet, their different flow rates can mix and cause unpredictable surges, which can be worse if the area has been affected by deforestation or other human activities. The merging of rivers, debris buildup and natural features can also lead to sudden changes in water flow,” he said.
Mohd Fadhil added that the probability of surges occurring can be calculated based on the volume of water entering a river within a certain timeframe.
He highlighted that historical data from extreme flash floods reveal that heavy upstream rainfall can lead to downstream flooding and surges, even during off-monsoon periods.
“The Intergovernmental Panel on Climate Change has reported that rising temperatures speed up the melting of snow and ice, increasing the amount of water that rivers carry. In tropical climates such as Malaysia, warmer temperatures can cause more intense and prolonged rainfall. Extreme weather events like hurricanes, typhoons or cyclones can also lead to heavy rain upstream, causing rivers to discharge large volumes of water. Rapid changes in water speed and volume create turbulence and pressure shifts, affecting how water behaves in the river. This is why the public must stay aware of weather changes and monitor warnings from the authorities.”
