Is Cilacap Prone to Disasters? Identifying Natural Hazard Risks in Cilacap, Indonesia

Cilacap is a regency and a city in Central Java, Indonesia. This region lies along the southern shore of Java Island, bordering the Indian Ocean. This city also boasts attractive tourist attractions. Unfortunately, Cilacap sits on an active subduction zone. Is Cilacap prone to disasters? 

For decades, various natural hazards have hit Cilacap. In addition, this region is home to a power plant and Indonesia’s largest oil refinery. Therefore, potential man-made hazards are also present in Cilacap. What natural and man-made disasters may occur in this region?

Is Cilacap Prone to Disasters? List of Cilacap’s Potential Disaster Types

Cilacap is vulnerable to various types of natural disasters. Topography, geographical location, climate change, and other factors make a vital contribution to the natural disaster risks in this region. Moreover, Cilacap is also at risk of man-made hazards.

Therefore, the answer to the question of ‘Is Cilacap prone to disasters?’ is ‘yes’. What are these disasters? Below are some potential hazards in Cilacap.

1. Earthquake

The southern coast of Java, including Cilacap Indonesia, is a megathrust zone. Two enormous and active tectonic plates, the Indo-Australian and the Eurasian, meet in this zone. Consequently, a megathrust earthquake may occur along this coastal area.

According to research, this earthquake may reach a magnitude of 8.7SR. This catastrophe is extremely destructive. Moreover, this megathrust zone already has a long seismic gap. Thus, the destructive earthquake may hit Cilacap and other Java’s coastal regions sooner than expected.

In the past, powerful earthquakes have hit Cilacap. The recent strong earthquake that shook this region occurred in December 2017. The 6.9-SR earthquake damaged over 100 houses and displaced 21 people.

One of the most powerful earthquakes in Cilacap was the 1923 earthquake. It had a magnitude of IX MMI. This catastrophe destroyed vital infrastructure, a train station, and numerous houses.

2. Tsunami

As a coastal region with a high earthquake risk, Cilacap is also vulnerable to tsunamis. Scientists have predicted that a tsunami risk is present in this region. This wave may reach 20 m in height because it is triggered by a megathrust earthquake. 

According to research, this massive wave may sweep 55 villages in Cilacap city. Moreover, the tsunami will affect hundreds of thousands of people in these villages. 

Scientists have also found traces of prehistoric tsunamis in this region. They discovered layers of ancient tsunamis in Cilacap coastal areas. Each layers have an interval of 600 to 1,200 years. These layers also indicate that massive tsunamis have hit this region.

The latest tsunami that swept Cilacap was the 2006 tsunami. The height of its wave reached 7 m. This tsunami killed 34 people. Moreover, the trigger of this massive wave is a 7.7-SR earthquake offshore of southern Java.

3. Flood

Cilacap is also vulnerable to floods. The flood risk in this city reaches its peak during the rainy season. Cilacap’s sub-districts with high flood risk are Kroya, Bantarsari, Kedungreja, and others located in the depressions or low-lying regions near the shore.

The high flood risk is also the result of factors other than heavy rains and topographic conditions. One of them is inadequate drainage systems. Moreover, river sedimentation and land use change also contribute to the increasing flood risk in Cilacap.

4. Landslide 

The northern part of Cilacap is hilly and mountainous. This mountainous area also has varying sloping degree. Moreover, this sloping area has unstable soil structure. 

Therefore, it is prone to landslides during heavy rains. The risk of this hydrological hazard has also increased recently due to land use change on hill slopes. Since 2020, Cilacap has experienced landslides almost every year.

In 2025, two landslides hit this region. The first was in April. This hydrologic hazard affected two villages. Meanwhile, the second was on 13 November. This landslide damaged 2 villages and killed at least 20 people.

5. Hazards Coming from the Oil Refinery and Power Plant

Cilacap is also at risk of man-made disasters from the oil refinery and power plant. Fires and explosions may occur in those sites. These hazards can be triggered by many factors, including broken equipment, chemical reactions, earthquakes, and lightning.

Since 1995, fires have occurred multiple times in Cilacap’s oil refinery. In some cases, they did not cause casualties or injuries. However, in 2008, the fire in this site killed 2 workers. In 1995, thousands of people lived in shelters for a few days due to massive fires in this oil refinery.

Is Cilacap prone to disaster? Yes, this region is vulnerable to earthquakes, tsunamis, floods, landslides, and man-made hazards. Thus, the local government must have an efficient early warning system to alert the people. Creating this efficient system is easy if the government has a cell broadcaster from smsbroadcaster.com.