BMKG’s 1.61‑metre Reo tsunami reading put in context

Labuan Bajo — — Indonesia’s Meteorology, Climatology and Geophysical Agency (BMKG) confirmed that its tide-gauge network recorded a tsunami with a peak height of 1.61 metres at Reo, northern Manggarai, after the magnitude 7.7 earthquake off northern Flores on Saturday, 15 August 2026.

BMKG describes the 1.61‑metre figure as the maximum sea-level change observed at that specific monitoring point, not a measure of how far seawater travelled inland or the height of waves along every coastline in Flores.

The agency’s instruments detected tsunami waves at multiple stations. BMKG reported peak heights of 1.61 metres at Reo and Manggarai Timur, 0.94 metres at Maurole in Ende, and more than 0.5 metres at Bulukumba (South Sulawesi) and Sape in Bima (West Nusa Tenggara), among other locations.

What the Reo number represents

A tide gauge is an instrument that continuously measures sea level relative to a defined reference point at its installation site. In its post‑event briefing, BMKG stated that the Reo, Maurole, Bulukumba and Sape figures came from this observational network and were used to validate tsunami modelling produced by the national warning system.

BMKG’s releases do not specify whether the 1.61‑metre value at Reo refers to the highest crest above mean sea level, the rise above a chart datum or another technical standard used by the gauge, nor do they disclose the exact coordinates of the instrument.

Those technical details affect how measurements can be compared. Tide gauges record sea-level changes at a single point, and tsunami behaviour can vary sharply over short distances because of differences in shoreline shape, harbour configuration, offshore bathymetry and the direction from which waves approach the coast.

According to BMKG, the tsunami generated observable peaks at 16 stations across four provinces — East Nusa Tenggara, West Nusa Tenggara, South Sulawesi and Southeast Sulawesi — with the highest overall reading of about 1.60 metres at Pota in Manggarai Timur and the lowest at Bakalang in Alor.

Why readings differed between locations

BMKG presents the Reo and Maurole values as local tide‑gauge observations confirming that tsunami waves arrived at those coasts, rather than as island‑wide averages. The agency also categorised potential tsunami heights in its early warning as Siaga (Alert) for expected waves of 0.5–3 metres in northern Manggarai, Ngada, Ende, Flores Timur and Jeneponto, and Waspada (Advisory) for expected heights below 0.5 metres in parts of Flores Timur, Bima, Dompu and Wajo.

Observed tide‑gauge peaks did not occur simultaneously at all stations. BMKG reported, for example, that the highest recorded tsunami at Pota in Manggarai Timur occurred at 05:03 Western Indonesia Time, while the lowest at Bakalang in Alor was noted at 05:41. This illustrates how different coasts can experience different wave heights and timings during the same event.

Neither BMKG’s tide‑gauge data nor its warnings alone describe the extent of inundation or structural damage, which depend on local topography and the vulnerability of buildings, ports and roads.

Warning timeline and aftershocks

The magnitude 7.7 earthquake struck the Flores region at 04:58 Western Indonesia Time on 15 August 2026. BMKG states that it issued its first tsunami warning 2 minutes 16 seconds after the main shock, with a second update about 10 minutes later once earthquake parameters had been refined.

The tsunami early warning was formally ended at 07:30 Western Indonesia Time, equivalent to 08:30 Central Indonesia Time, after BMKG reported no further dangerous sea‑level rise along affected coasts.

In the days following the event, BMKG reported more than 1,600 aftershocks, later rising to around 2,100 and then 2,768, and noted that aftershock activity could continue for weeks. Authorities urged residents and visitors to remain cautious around damaged structures while following official guidance.

Tourism conditions in Nusa Tenggara Timur

The earthquake and tsunami prompted temporary closures at several tourism sites in East Nusa Tenggara while safety assessments were carried out. According to an overview published on 29 August 2026, Wae Rebo tourism village and Ruteng Pu’u in Manggarai, along with the Teluk Maumere marine conservation and tourism area in Sikka, were among destinations still closed pending inspection.

The same report noted that other tourism areas in the province had begun to reopen with adjusted operating hours and visitor caps, including sites in and around Labuan Bajo, as local authorities assessed infrastructure and coastal conditions.

For residents and travellers, BMKG and disaster‑management agencies emphasise that decisions on evacuation or travel should be based on official warnings and local instructions for specific coastlines. Tide‑gauge readings such as the 1.61‑metre peak at Reo are crucial for confirming that a tsunami occurred, but they do not by themselves describe the full impact across Flores and surrounding islands.

Sources

• BMKG – BMKG, Pemerintah Pusat, dan Pemerintah Daerah Kolaborasi Percepat Pemulihan Bencana Gempa Flores
• Okezone News – BMKG: Tsunami di Pesisir Utara Flores Bisa Datang Sangat Cepat
• RMOL – Gempa M 7,7 Guncang Flores, BMKG Keluarkan Peringatan Dini Tsunami
• IDN Times – Gempa Magnitudo 7,7 di Flores Berpotensi Tsunami, Status Siaga dan Waspada
• Metro TV News – Daftar Destinasi Wisata yang Masih Ditutup dan Sudah Dibuka Pascagempa NTT
• Kupastuntas.co