Nobody ever imagine that Bima City will be struck by great flash flood. When the rainy season started in December 2016, the rainfall intensity was very high in Bima area, West Nusa
Tenggara. A series of flash floods finally hit the area on December 21 and 23, 2016. It endangered people’s lives and destroyed facilities as well as infrastructures. The electricity was disrupted for 4 days, clean water facilities were damaged in 7 points and communication lines were also cut off. There were 26,256 families or 105,797 people affected in 5 sub-district of Bima CIty. BNPB (Badan Nasional Penanggulangan Bencana or National Board for Disaster Management) recorded the loss in Bima is estimated to reach IDR 1,479 trillion.
Based on the analyses of BMKG (Badan Meteorologi, Klimatologi dan Geofisika or Meteorology, Climatology and Geophysics Agency), there were two low pressures in the Indian Ocean in Southern Bali and East Nusa Tenggara that resulted retardation and turn of wind in Sumbawa Island, especially in Bima City. The increased growth of cumulus clouds and rain with moderate to heavy intensity for longer duration triggered flash floods. Advance analysis stated that moderate to heavy intensity of rainfall in Bima City on December 23, 2016 was caused by warm temperature at the sea surface and the tropical cyclone Yvette. This cyclone occurred in the southwest region of Australia that formed convergence area and turn of wind around Sumbawa Island. This condition resulted similar case three days earlier.
BMKG reported that on December 21, 2016 flood with a height reaching 3 meters occurred in some villages of Kodo, Ndodu, Kumbe, Penaraga, Penatoi, Sadia, Rabangodu Utara, Rabangodu Selatan, Rabadompu Barat, Rabadompu Timur, Manggemaci, Paruga, Lewirato, Jatiwangi, Tanju, Dara, Kendo, and Manggge Na’e. The rainfall on December 20, 2016 was quite extreme at 116 mm.
Meanwhile, the government of Bima City reported that the intensity of rainfall on Tuesday night (20/12) was moderate. Moderate to heavy intensity of rainfall was observed at the upstream area.
Even though flash flood was like a small tsunami that hit with a height reaching 3 meters, no casualties had been reported. There are several interrelated factors into an early warning system that works. Firstly is leadership. It can be observed from the role of BMKG in providing the updates of early warning to stakeholders, such as BPBD (Badan Penanggulangan Bencana Daerah or Regional Disaster Management Agency), TSBK (Tim Siaga Bencana Kelurahan or Village Preparedness and Response Team) and rescue teams. The role of BMKG is very crucial to monitor the progress of extreme weather and inform them to the local government, especially BPBD of Bima City. As a part of a chain system, stakeholders also have a role in organizing and informing directly to the people potentially affected by the flash flood. Initiative of each stakeholder becomes a leadership component that should be replicated in various areas in Indonesia that prone to floods.
Rapid information transfer is one of the factors in successful early warning chain. Despite of using some communication approaches, the use of simple communication media is a good option. Simple communication as in Whatsapp message can transmit information on the updates of extreme weather or early warning on weather from BMKG and can be received rapidly by the group of preparedness and response that consists of BPBD, TSBK, Disaster Risk Reduction Forum, Orari (Organisasi Amatir Radio Indonesia or the Indonesian Amateur Radio Organization) community, SAR (Search and Rescue) team and other organizations.
Information on weather was monitored continually by BPBD. BPBD as the focal point of disaster management in the area continued to coordinate with TSBK to get the information of the rainfall and headwater discharge of Wawo and Ambalawi River. Equipped with walkie-talkies, BPBD monitored the preparedness of TSBK at each village. TNI (Indonesian Armed Forces) and POLRI (Indonesian National Police) backed up the communication by radio to ensure the evacuation information was received by BABINSA (Bintara Pembina Desa or Village development non-commissioned officer) at each village. TSBK reported that there was increasing water discharge at Melayu River in Jatibaru-Jatiwangi and Padolo River in Lampe, Dodu, Nungga, Kendo, and Ntobo at 10 a.m. local time. The water discharge overflow two hours later. Then on December 21, 2016 at 15:30 local time, the flash flood hit the area.
TSBK quickly informed the people to evacuate and standby. Most of the people were rescued and evacuated to two-story houses. Another crucial factor was how the people were well-informed on the potential hazard of flood. It was a remarkable effort how thousands of people could be evacuated to higher and safer places or nearby their residence and it worked successfully
In addition to the success story of the evacuation, local wisdom can be continued. Such as gotong royong (mutual cooperation) that is formed when other groups need assistance as it occurs in other areas in Indonesia. Mayor of Bima, Qurais H. Abidin, stated how the spirit of gotong royong assisted the affected people. People had the initiative to provide wrapped rice. Each house provided 6 packages of wrapped rice since public kitchen could only provide 20,000 packages, whereas there were 105,000 affected people at that time.
Local government declared Emergency Status of Flood (Flood Disaster Emergency Status) for 15 days from December 22, 2016 to January 5, 2017. It continued from January 5, 2017 to January 19, 2017. Bima is a city that has high category on flood hazard risk index. The geographical condition of Bima City consist of 60% of hills and 2 big rivers surround the residential communities.