A solar-powered flood warning system
Nepal is a beautiful country with a varied landscape: from rolling flat plains, to the mighty Himalayas. The country is said to have 6,000 rivers and rivulets flowing down from the mountains, passing through the valleys and passing by settlements located on the high hills and in the low plains. However, in August 2014 one such river – which is normally considered to be a blessing – proved to be a curse.
Every year the Bheri River (in Surkhet District, mid-west Nepal) rises to an ‘annual flood level’; every 2-3 years it rises to a ‘periodic flood level’; and on average every 10 years it rises to an ‘extreme flood level’. In 2014, extreme flooding occurred suddenly, in the middle of the night. A massive flood on the Bheri River swept away the livestock and property of thousands of people and took the lives of others. In total, the flood destroyed 1,465 houses, 24 people died, 91 disappeared and 26 were injured.
Disaster arrives in the middle of the night
69-year-old Man Bahadur and his 70-year-old wife Sita Mahatra live in Berichaal Chepang community, which is situated at the confluence of two rivers (the Bheri and Sodh Khola) and lies just a few metres above the river water level. Berichaal Chepang was one of the communities worst affected by the 2014 flood.
Man and Sita came to live in Berichaal Chepang 47 years ago. Since their arrival, they have seen the river that lies behind their house rise and fall annually. But in 2014, the river rose to a level that they had never seen before and it flooded their community. At about 2am on that fateful night, the river flooded its banks and rushed towards Man and Sita’s house.
Although it had been raining all day, no one expected such a sudden, huge flood. The village had no flood warning system and was totally unprepared for this terrifying disaster that came in the dark. Luckily for Man and Sita, they were roused by the commotion being made by neighbours running into the street and shouting warnings, and so managed to escape to safety.
In Man and Sita’s village, lots of cattle were lost and 12 houses were swept away, but fortunately no lives were lost. Sadly though, across the region, not everyone was as lucky as Man and Sita. The rain caused havoc that night, with people buried by landslides or swept away by the flood. In the next village, four people were swept away and, tragically, their bodies have never been found.
This tragic event is still impacting on people’s lives today. Many of those displaced by the disaster are still sheltering in makeshift tents across the district.
With Nepal’s climate changing faster than the global average, the risk of extreme flooding will likely increase, and we can expect to see these devastating events occur far more regularly.
In 2020, we are again seeing extreme rainfall across Nepal. According to the Department of Meteorology and Hydrology, in the first month of the monsoon, Nepal has already received 736mm of rain, nearly 150mm more than the average for this time of year. Worryingly, some of these weather events are cloudbursts – concentrated localised rain that can be very destructive. Man told us: “We are scared of flooding in the future. A flood warning system would be very good – we could save everything except the house with the right warning.”
The solution: a community based Flood Early Warning System
Enhancing community resilience against climate change-induced disasters is an underlying commitment of Renewable World.
To ensure that in the future, at-risk households receive advance warning if there is a sudden rise in the water level in the surrounding rivers, Renewable World has set up a solar-powered early warning system. This system benefits 300 households in Berichaal Chepang and was carried out in coordination with the Department of Hydrology & Meteorology and local government.
The flood Early Warning System was installed on 23 November 2019 by our partner, Real Time Solutions, and in collaboration with our locally-based partner, Sundar Nepal Sanstha.
The system is situated on top of a centrally-located school, and consists of an Audio Remote Terminal Unit (a microprocessor-based digital device that can be used to sound a warning siren). It has sufficient memory to store hours of recorded sound messages that can be triggered locally or remotely via radio, cellular network, satellite network or internet. And it can also be connected to cloud-based systems to automate mass notifications.
A 3m aluminium mast has been erected to install the solar panel and all the Early Warning System components. The weatherproof box housing the Audio Remote Terminal Unit, amplifier, solar charge controller and battery was mounted on the mast. The solar panel is mounted on the same mast inclined at an angle of 45°, facing south. Two horn speakers are mounted on the same mast. The system is properly grounded.
The Department of Hydrology & Meteorology, with whom we have worked closely to install and operationalise the Early Warning System, is the mandated organization in Nepal for monitoring flood hazards and providing flood warnings to communities, organizations, and relevant stakeholders.
The department has established hydrological stations upstream on the Bheri River. Water level data from these stations is automatically transmitted to their server in real time and the data is being continuously monitored and verified by the department. Whenever the water level crosses the warning or danger level, flood warnings are disseminated via internet, display boards and SMS texts. Then, local people who receive the alert at downstream communities (such as Berichaal Chepang) can trigger the siren by sending the SMS to this system. The Department of Hydrology & Meteorology office can also trigger the siren by sending a message via mobile phone or internet. The system will provide at least a three to four-hour lead time to this community which will help them prepare to evacuate. The working principle of the system is shown in the diagram below. The system has been designed to be able to sound alerts not only for floods, but also for other disasters such as fires.
Triggering the siren
The system can trigger the siren in two different ways:
a) Manual SMS: The siren can be triggered through an SMS sent manually by authorized mobile numbers. A list of mobile numbers has been registered into the system. In case of receiving any information about the possible hazard, any of these numbers can send an SMS to the Early Warning System to trigger the siren. This will be the most common way the system is triggered.
b) Automatic SMS: The Department of Hydrology & Meteorology can forecast the flood and the areas likely to be affected, based on river gauge readings installed upstream, as well as data from meteorological stations. They can select the flood prone areas in the digital map of their software and trigger all the sirens installed in that selected area simultaneously. Similarly, the department can also send mass SMS to the mobile phones of the people living in that area.
The project team from Real Time Solutions and Renewable World’s regional team provided training to the community on the operation and maintenance of the Early Warning System, as well as training on the system’s functionality and the importance of the warning message delivered.
The system is owned by the community, and a Disaster Management Unit has been formed within the community who are responsible for the operation of the Early Warning System and dissemination of flood forecasts and warnings. The Disaster Management Unit will hold regular interactions with the wider community and major stakeholders to review and update the evacuation and rescue plan.
Two community members, Gobinda Thapa and Lal Krishna Thapa, have been selected to manage the day-to-day operation of the flood warning system. The operating cost of the system is very low, and the local government has committed to providing necessary funds to cover future operation and maintenance.
Testing the system
With monsoon fast approaching, in May 2020 it became necessary to complete the final testing on the Early Warning System and handover to the community. However, due to the national COVID-19 lockdown, this activity was more complex than usual and precautions including social distancing and mask wearing had to be taken. On 29 May, the Early Warning System was put through a live test and a number of key community members were selected to attend the test and receive refresher training on the operation of and response to warnings triggered by the system.
The system was triggered a number of times, using a range of methods. Firstly, Real Time Solutions staff, based in their Kathmandu office 600 km away, triggered the siren remotely. Secondly, the system was triggered by sending a warning SMS from a mobile phone within the community whose number was registered with the system. Finally, both operational and maintenance personnel (Lal Krishna Thapa and Gobinda Bahadur Thapa) succeeded in triggering the system through their mobile phones, which were also registered in the system. Each time the system was triggered, the warning message (recorded in Nepali) and an alarm sounded loudly across the community. The system test was a success and all who attended, along with the project team who were listening in from Kathmandu, were delighted to have the system up and running.