Is Indonesia Prone to Floods? Understanding Indonesia’s Flood Hazards

The rainy season in Indonesia lasts from October to March. During this season, rains typically fall with heavy outbursts, but last for a short time. However, prolonged heavy rains usually occur at the peak of the season. Is Indonesia prone to floods?

Decades ago, floods occurred less frequently in Indonesia. They usually happen in low-lying urban areas or river basins. Nowadays, this hydrologic hazard has hit many regions recurrently.  Some areas even experience floods more than once a year. Moreover, the flooding severity in some cities is increasing.

Is Indonesia Prone to Floods? Why?

As a tropical country, Indonesia is vulnerable to floods during the rainy season. According to a report, this country experiences an average of 1,100 floods per year from 2020 to 2024. Moreover, the flood in Indonesia killed over 900 people and injured around 7,000 people in the last five years.

Why is Indonesia prone to flooding? This country experiences recurrent flooding because of the following causes.

1. Prolonged Heavy Rains

At the peak of the rainy season, prolonged rainfall of over 100 mm per day may occur. This weather event will cause the river water to overflow. Therefore, river basins and downstream river regions experience inundation.

2. Topography

Many areas in Indonesia are low-lying coastal areas, steep slopes, river basins, and low-lying flood plains. These areas are naturally vulnerable to flooding. Thus, it is not surprising that floods become an annual weather event in many Indonesian regions.

3. La Niña

The weather in Indonesia is affected by La Niña and El Niño. La Niña typically occurs during the rainy season. This phenomenon increases sea surface temperature and creates more rain clouds. Consequently, heavy rains intensify and may cause flooding.

4. Inadequate Drainage System 

Many regions in Indonesia have inadequate drainage systems due to poor urban planning, poorly maintained drainage systems, etc. This condition makes the system unable to manage water flows during heavy rains. As a result, flash flood risks in this country increase.

5. Deforestation

The practices of illegal logging and burning forests are common in Indonesia. Indonesian people do these actions to open new plantations. Consequently, there are not enough trees to absorb water. Thus, floods occur in many regions.

6. Peatland Degradation

Flood in Indonesia is also triggered by peatland degradation. Peatland is vital for water absorption during the rainy season because it acts similarly to a sponge. Thus, flood risks will increase if peatland is ruined.

7. Land Subsidence

Some Indonesian coastal regions also experience severe land subsidence. Cities, including Jakarta and Semarang, experience land sinking of up to 20 cm per year.

On the other hand, climate change causes the sea level to increase. Those phenomena cause the land to be lower than the seawater level. Therefore, some coastal areas in Indonesia are vulnerable to tidal floods during high tides.

Indonesian Regions that are Prone to Floods

Is Indonesia prone to floods? Yes. However, not all districts in this country are vulnerable to inundation. Below are some flood-prone areas in Indonesia. 

1. Jakarta

Flood in Jakarta is a common weather phenomenon. This coastal region is prone to floods because of severe land subsidence, rapid urbanization, inadequate drainage systems, and rising sea level. Moreover, many rivers flow through this low-lying city before flowing to the sea.

Consequently, flood risks in Jakarta increase when prolonged heavy rains occur on the upstream of those rivers. In 2025, this city experienced at least three floods. They occur due to various factors, such as prolonged heavy rain, broken embankment, and river overflow.

2. Semarang

Semarang’s topography is almost similar to Jakarta’s. It lies in a coastal area with several rivers passing through the city. Moreover, extreme groundwater extraction and urban development have caused land subsidence and inadequate drainage systems.

Therefore, this coastal city has high flood risks during the rainy season and high tides. In October, Semarang was hit by a prolonged flood. This hazard occurred because of river overflow and tidal flood. 

3. Bali

Decades ago, Bali was less prone to flooding. However, the tourism industry and urban development have cut the size of water absorption areas and narrowed the rivers. Consequently, heavy rains that last for days will submerge some areas in this Island.

In September 2025, Bali was hit by the worst flood in years. A torrential rainfall of over 380 mm in 24 hours was the trigger of this hydrologic hazard. This flood killed 14 people and displaced many others.

4. West Kalimantan

West Kalimantan is also vulnerable to inundation. The flood risk in this area increases because of deforestation and peatland degradation. Last September, several subdistricts in West Kalimantan were inundated. This hazard disrupted trade and a major transportation route in the region.

Is Indonesia prone to floods? Yes. Many regions in this tropical country are vulnerable to inundation during the rainy season. Therefore, an early flood warning system is vital in this country. The Indonesian government will have an excellent flood early warning system if it uses the cell alert broadcast technology from smsbroadcaster.com.