List of Biggest Sumatra Floods in Modern History

Floods are a common occurrence in Indonesia during the rainy season. Each year, over 1,000 floods hit this country. Among the Indonesian regions, Sumatra is the most flood-prone island. Therefore, it is not surprising that the history of Sumatra floods recounts several deadly floods.

Sumatra is prone to floods due to its topography. Bukit Barisan spreads from one end to the other of the island. Consequently, valleys along the mountainous region are vulnerable to floods. High rainfall, Sumatra rainforest deforestation, and poor urban development also increase flood risks in this island.

Biggest Sumatra Floods

Sumatra is the home of 10 provinces. Among these provinces, Aceh, North Sumatra, and West Sumatra are the most flood-prone regions. Below are the five biggest floods in Sumatra in modern history.

1. 2025 Aceh, North Sumatra, and West Sumatra Flood

One of the biggest Sumatra natural disasters is the November 2025 flood. This flood affected over 50 regencies in Aceh, North Sumatra, and West Sumatra. Moreover, it submerged several villages under the mud during the mudflow.

The flood hit those provinces at the end of November after days of torrential rains. This extreme high rainfall was due to the Senyar Tropical Storm. On the other hand, these provinces have lost their natural buffers because of severe deforestation.

Consequently, rainwater flowed freely to residential areas, rice fields, and other areas. In many regions, the floodwater level reached 2 m high. Together with the mudflow, the flood damaged hundreds of roads and bridges and over 156 thousand houses.

This big flood also killed over 900 people and caused 250 others to go missing. Moreover, over 850 thousand people are displaced. The flood also showed a unique phenomenon in which tons of wood logs appeared in the flooded areas and on nearby beaches.

2. 2003 Bahorok, North Sumatra Flood

In November 2003, one of the deadliest Sumatra flash floods suddenly hit Bukit Lawang in North Sumatra. Bukit Lawang is a village and a tourism area located in the upstream of the Bahorok River. Before the flood, heavy rains poured in Langkat Hulu, including Bukit Lawang. 

At night, people in Bukit Lawang heard a rumbling sound. Suddenly, a flash flood hit this region. The flood also brought mud, rocks, and wood logs. This floodwater was as high as the house roof in some areas.

The Bahorok flood damaged approximately 400 buildings along the Bahorok River. Moreover, this catastrophe killed 129 people. It also caused over 100 others to go missing. Furthermore, the flood damaged agricultural lands and the tourism industry along this river.

Authorities said the Bahorok flood is a pure natural disaster. They also said Bukit Lawang is prone to flooding because it is a valley located on a riverbank. The region is also prone to landslides because the steepness of the valley  is between 30% and 70%.

However, the appearance of many wood logs had made the locals realize that illegal logging had contributed to this disaster. Therefore, they stop this activity to prevent similar destructive floods in the future.

3. 2018 North and West Sumatra Flooding

The 2018 Sumatra floods are more destructive than the Bahorok flood. This disaster affected four regencies in two provinces, i.e., North Sumatra and West Sumatra. The trigger of this hazard was a heavy rain that lasted from 11 to 12 October 2018. 

However, an environmental NGO reported that environmental damage on the upstream caused by companies’ exploitation also triggered these floods. After the rain, the floodwater level reached 2 m. 

The floods submerged thousands of houses and many public facilities. The torrential rain also caused landslides in several areas. The landslides damaged many houses and a school. According to the report, 22 people died and 15 were missing due to the flood and landslides.

4. 2017 North Sumatra Floods

A year before the 2018 floods, a flash flood submerged Tebing Tinggi and two other regencies in North Sumatra. This hazard was triggered by heavy rains that led to river overflow and environmental damage in the river basin.

This flood occurred in September 2017 and affected thousands of houses and over 1,500 families. The floodwater submerged houses and roads 1.5 m deep. Consequently, thousands of people must evacuate to higher places. 

In addition, this condition caused authorities to have difficulties accessing the affected areas and distributing aid. Despite the widely affected areas and the large number of displaced people, this hazard did not cause fatalities.

5. 2019 Bengkulu Flood

At the end of April 2019, a massive flood and landslides hit 8 regencies in Bengkulu Province, Sumatra. The causes of these hazards are excessive rainfall, deforestation, river silting, and urban development.

This flood affected over 12,000 people. They must live in shelters for days until their homes are habitable. Moreover, this disaster killed 17 people and hundreds of livestock and damaged numerous houses, 7 schools, and infrastructure.

Sumatra floods have become more severe recently. Damaged environment and climate change contributed to the increased severity of this hazard. Thus, the government must take effective measures, including establishing an EWS, to reduce Sumatra flood risks. Please visit smsbroadcaster.com if you want to establish an advanced EWS.