Ceremony of Banjir Lahar is a particular tradition held by local people around Mount Merapi, especially in anticipating the lava flood disaster. One of the ceremony can be seen at Dusun Tambakan, Desa Sindumartani, Kecamatan Cangkringan, Kabupaten Sleman, as a small village that is often flowed by lava / lahar (cold or hot) from Mount Merapi.

This ceremony is mainly asking for safety and protection from the Almighty for all people in order to avoid disaster, also it is followed by offerings of giving coconut in the river that might be traced by lahar / lava. It is done by observing natural signs of lava flood disaster for generation to generation.

People on the bank of the rivers from Mount Merapi sometimes heard strange voices in the middle of the night, for instance voice of royal charts. It is said that the voice is a sign, Kraton Merapi is about to have a great wedding ceremony with one of the living at Kraton Laut Kidul. Then it is determined as a mystical sign that there would be lava flood through the river, then they would prepare to make safetry and rescue.

The main goal of the ceremony is to ask for safety and prosperity to the Almighty and also giving particular offerings to the spirits that stay among them in Mount Merapi in order to make the local people calm, peaceful, and free from any danger, therefore there would be a good harmony between human being and the nature.