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Forecast Model to Potentially Warn About Lahar Floods in Indonesia

Indonesia Short Term Rain Forecast Model

A Civil Engineering Doctoral Program student from the Gadjah Mada University has developed a short-term rain forecast model, which is based on radar rain using the High-Resolution Pixel-based QPN method that utilises PLKOF or HPLK models.

According to a recent press release, the research was centred on the slopes of Mount Merapi, which has unique topographic and climate characteristics.

Information on the short-term rainfall spatial distribution, obtained through the forecasting process, is very much needed for applications that are associated with lahar flood mitigation efforts.

When done with high accuracy, it will provide results that potentially be significant contribution to the development of the lahar flood warning system.


Heavy rains can transport sediment deposits on Mount Merapi, through surface runoff, to cold lava.

The deposits will travel quickly in large quantities, which may cause floods that will have affect the environment along its path.

Lava flow, according to the researcher, can occur if triggered by rain that has a specific intensity. Findings from studies show that the minimum threshold of lava trigger is a rainfall intensity of 9 mm/hour.

So far, the Merapi Multiparameter (MP) X-band radar device, which was made possible through a collaboration program between the Japanese and Indonesian governments, had only been used for monitoring rain data.

As such, the development of a short-term rain forecasting model using it is very timely and relevant.

About the Initiative

Although the use of MP X-band radar data can provide significant benefits in the short-term rain forecasting model, there should still be an evaluation and correction of radar rain value to surface rain.

Errors may still possibly occur as it is dependent on the estimated rainfall value of the radar.

There are three main issues to be considered. These are:

  1. The characteristics of the short duration rain in the Mount Merapi region
  2. The suitability of the radar rain value to surface rain
  3. The form of an appropriate forecasting model for the characteristics of the mountainous region with distinctive characteristics

The development of HPLK’s short-term rain forecasting model has been successfully completed. Meanwhile, the algorithm used for tracking rain movements with the PLKOF method showed good results, especially for small displacements.

The short-term rain forecasting model generated from this study has the potential to be applied to applications that are related to the warning of lahar floods in the Mount Merapi region.

However, there are still improvements that need to be addressed before the model could actually be used for practical purposes.

Moreover, in order for the model to be applied to other regions, there needs to be a consideration of various factors such as the similarity of regional characteristics and the similarity of radar rain data characteristics.

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