Key objective of this research is to understand the geographical characteristics of a tornado in Bangladesh. In Bangladesh, there are several tornadoes in different parts of the country. But for the lack of proper source of data and identification system, they remain unnoticed most of the time. The country has no tornado warning system, nor any tracking or measurement system of tornado. As a result, no effort can be taken to assess the elements at risk of tornado for the country, for the lack of proper data.

A tornado database was developed by Jonathon Finch in 1996 which was highly generalized and lack of detail information about each tornado in Bangladesh. So, a research like this is hoped to develop a new way to learn about the tornado in context of Bangladesh [1].

Many parts of Bangladesh are regarded as high risk zone for tornado. During 1961-1996 local newspapers reported 10,766 tornado deaths. During the thirty five-year period, twenty of 199 tornadoes killed more than 100 people and seven of them killed more than 500 people [1]. On an average 179 people dies every year tornado in Bangladesh [2]; most of which become unnoticed because of highly localized in nature.

A violent tornado swept over the eastern part of Bangladesh in Brahmanbaria Sadar Upazila (sub-district) and AkhauraUpazila (subdistrict) of Brahmanaria Districts on 22nd March 2013. The incident occurred around 17:10 hours in local time (GMT +6) and lasts for 15 minutes [3].

The most significant feature of this tornado is there was no past record of any tornadoes in Brahmanaria or surrounding areas [1,3]. As a result people of this area didn’t know about the characteristics of the tornado and the necessary measure to save their life and properties.

The target of this research is to find out the geographical characteristics of the tornado in Bangladesh also point out the elements at risk of tornado in the perspective of rural Bangladesh.

The research has done with the combination of two methods. An immediate field visit and survey to the tornado affected villages was done on 26 March, 2013 by the researcher and his team. Several interviews were taken to understand experience of the affected people, to find out the elements at risks and also the nature of damages done by the tornado.

The tornado track map was created using the local administrative map, Google satellite image and GPS technology during field visit. As in Bangladesh, there is no immediate source of tornado track or location primarily the relative location of the tornado was identified from the situation reports (Figure 1).

Figure 1: Track and area of influence of Brahmanbaria tornado.

Local cadastral maps (scale 1:50000) were collected and was overlapped with Google satellite images. Field maps were prepared with identification of roads, rivers, important landmarks etc. During the field visit the first attempt was to identify a point or place where the tornado was first noticed. As the tornado left a track of damage, we followed this track of damage and identified the tornado track, width, area of influence and other characteristics of tornado. GPS was used to precisely identify the location. Later on, all this data were compiled to develop the tornado track and map (Figure 1).

Newspaper reports, situation reports by the government and different NGO’s were collected and analysed to get the actual figure of damages and relief facilities done after the tornado. From the analysis of damage data, and the field survey the elements at risks of tornado were identified.

Geographical coverage

The tornado travels a distance of more than 12 kilometer. The tornado begins at Ram rail Village of Ram rail Union and ended at Ahmedabad Village of North Akhaura Union. The identified villages over which tornado traveled are listed in Table 1. Among them Dubla is damaged most severely followed by Fulbaria and Chinnari among thirteen villages of six unions reported to be visited by this tornado.

Table 1: Affected villages of Brahmanbaria Tornado.

As observed from the field survey, the average radius of the tornado on earth surface was sixty to eighty meter. It affected an area of seventeen square kilometer [3], of which around one square kilometer area was heavily damaged. Anything within this area was devastated. Almost ninety percent of the causalities occurred within this area of influence of the tornado.

Meteorological condition

The regional meteorological condition of affected area on the tornado day (22 March, 2013) and during the tornado is in Table 2. It was definitely very high temperature on that day of tornado occurrence. At noon the average temperature of that area is more than 35°C and it creates the perfect triggering factor for tornado.

Table 2: Meteorological condition of the affected area on 22nd March, 2013.

Local peoples and government officials said that during the tornado the wind speed was up to 70 km/hour (43.5 mile/hour). As there was no local weather station, the exact meteorological details of the tornado were unknown. According to the wind speed this tornado is within F0 scale the Fujita Tornado Damage Scale this. In this scale this is the lowest level of tornado [4](Figure 2).

Figure 2: The Brahmanbaria Tornado. Source: YouTube video [4].

According to the local people before the tornado on March 22, weather became cloudy suddenly. People thought that, it was a Nor’wester. But when they saw the funnel shaped wind and cloud with heavy rainfall, they begin to think that it was something different.

Damages

The Brahmanaria tornado is one of the severe disasters in this region of the country. The total population of these unions are28913, and 8615 have been affected partially or fully, which represents almost 29 percent of the total population of the affected areas (Table 3) [5]

Table 3: Damages done by Brahmanbaria Tornado.

Thousands of trees were uprooted [3], electric lines and poles were heavily damaged. Tube wells were damaged and malfunctioned. One of the most devastating features of the tornado was, it collapsed 200 feet boundary wall and 420 feet of security boundary wall of Brahmanaria District Jail, which was highly fortified. The road and rail communication was halted for several hours, mainly due to blockage from tree fall.(Figure 3)

Figure 3: Damages done by the Brahmanbaria tornado.

The most devastating effect of this tornado was the loss of thirty five lives just within fifteen minutes. This was unbearable to the local people. The dead bodies were reportedly found ten to thirty meter away from the original spots [3]. The loss of means of livelihood, like crops and livestock or poultry brought further havoc to their miseries. These created a long lasting economic problem for the affected people. Almost 1300 livestock and poultry died in this tornado, which are a major source of income of people living in those villages.

In this area, the tin made houses were abandoned which was completely destroyed. The roofs were blown away, wall collapsed; home furniture and utensils were flown away to a further distance. The brick built buildings were not spared. Most of the brick built houses within the tornado track collapsed partially or fully, causing casualties. The reason behind this is mainly poor construction.

Elements at risks

The Brahmanaria tornado caused heavy fatal damages to human and animal life considering its small geographic nature and less intensity. This is because of the completely unawareness of the population about the tornado and the necessary measures to save life from tornado. If those populations were aware of this natural hazard, such devastating fatalities would never happen. This kind of unawareness about tornado is very much common in rural Bangladesh. So, human life is top element at risk of tornado in rural Bangladesh [6].

Loss of more than a thousand household livestock and poultry is a massive economic loss for a rural area in Bangladesh. Peoples livelihood and nutrition supply are dependent on these. So, these are another most highly risked element for tornado in rural Bangladesh.

The houses were mainly teen shaded with wood and tin wall. There were many brick built houses also. But all these houses were poorly contrasted. Even the brick built houses were devastated by the tornado –as they were not tornado resilient in any way. Moreover there were no underground chambers of houses to take shelter during tornado. So taking shelter within the houses did not help anyone from not getting injured or killed.

Electricity supply was great hampered by the tornado, as the polls were weak not tornado resistant.

From the field interviews and surveys, we can list following items as at risk of tornado:

1. People without awareness about what to do during tornado. Especially women and children

2. Livestock and poultry are heavily at risks

3. All types of houses and other structures like mosques, schools etc.; as those are very poorly constructed.

4. Electricity, telephone and water services are also vulnerable.

There is a need of an extensive research to find out the adaptation strategies for tornado in the context of rural Bangladesh. Bangladesh is a densely populated country and for this reason any tornado with small size and intensity can do a much greater loss to life and property than any other countries in the world. Additionally, development of tracking and warning system for tornado is also very important as thus we can predict the vulnerability of any region and population.