Rural roads now have a flood damage function model: A case study in Bangladesh of the Teesta River basin

Climate change is causing an intensity and frequency of exacerbated extreme flooding events and the number of moderate floods have decreased. Further, an article according to the United Nations Environment Program mentions that the new normal is reflecting how climate change is creating a record-breaking flood pattern across the world. These flood patterns have become a new normal and can be witnessed in Bangladesh.

There has been research conducted on how flooding affects road transportation conditions but there has been limited research focused on road characteristics and the direct damage of floods on roads. Therefore, field studies were undertaken to fill in the missing gaps which were conducted in rural Bangladesh's Teesta River Basin. The method of the study was questionnaire based to gather information on flood characteristics such as a qualitative measure on flood velocity and flood depth. Additionally, road structure which includes: length, height and width for each road segment that is above the ground, as well as the damaged part dimensions and damage mechanisms. A flood damage functions model which analyses flood factors and road characteristics. This model examines statistical parameters and integrated results which showed that roads have been damaged significantly.

One of the most destructive natural hazards is floods, as it affects human life, damaging infrastructure, livestock, industrial production and hampers agriculture. Due to many negative effects occurring by floods there have been studies taken to assess the flood damage by agriculture and residential houses. The factor that is equivalent to agriculture and residential damage which is not mentioned as much is road damage. An article by ScienceDirect, written by Haque and other researchers mention that, “Previous research has demonstrated that transportation infrastructure considerably contributes to direct tangible flood losses, often in the order of 5–10% and up to 50–60% in rare circumstances”. Further, transport disruptions lead to an indirect economic loss and evacuation problems due to damaged roads making it difficult for people to escape during an event of a flood.

An undiscovered topic that needs more attention is flood damage on road structures. Moreover, researchers have investigated areas in Malaysia and the Netherlands on how flooding is affecting road structures. Both these studies have however classified roads under land-use. The data was analysed through a grid method which did not involve the physical characteristics of the road, such as the road height from the ground and the width. Further, a methodology specifically to analyse a damage curve for various road types regarding road properties and flood parameters are absent. Additionally, flood characteristics pertaining to baseline information on river basins are neglected. This is the case in Bangladesh where there is a lack of information on rural roads and their structural properties. Furthermore, after each flood incident a road development authority analyses an entire flood affected area that needs to be repaired. This method that is taken out by the road authority is not sufficient as there is not a concrete relationship between the road type damage and the flood characteristics. Therefore, to have accurate information the flood damage function model is vital as it will consider road questionnaire surveys and in depth field investigations. In order to get an intense accurate database, a local survey should be conducted on the details of the damage the flood had bestowed upon an area regarding road and flood characteristics.

About the Teesta river in Bangladesh

The Teesta river in Bangladesh originates in the Eastern Himalayas of the Pauhunari mountains. The river flows through India and Bangladesh and the downstream area of the river is mostly rainfed but the rainfall intensity of the area has increased. Further, the upstream areas of the river are in crucial need of rainfall. The rainfall is however, mostly crucial in the downstream areas of the floodplain in Bangladesh as the rainfall keeps the Teesta River and its tributaries flowing. The article mentions, “Using daily data from the Bangladesh Meteorological Department, a time series analysis of seasonal rainfall in Rangpur revealed an increasing trend during the pre-monsoon (March to May), monsoon (June to September), and post-monsoon (October to November) seasons but no discernible trend during winter (December to February).” The residents who live on the banks of the Teesta River generally experience night time flooding which affects their agricultural crops, homes and roads due to the intense rainfall events. 

The method of the study

The methods of the study were done in two ways: road types in rural Bangladesh and a questionnaire survey as well as  a development of flood damage function.

Road types in rural Bangladesh and questionnaire survey

This method observed the flood events over the years from 2017 to 2021 and a questionnaire was answered based on road types in rural Bangladesh. Moreover, two types of roads were compared in the study, namely, Earth road and a BC road. The data that was collected in the study was around road characteristics, flood characteristics and information around structural damage.

This method was purely based on calculations around the road damage rate where, “The total volume of the damaged road segment was estimated from the length, width and thickness of the damaged part of this road segment.”

At this point in time, Bangladesh is missing a database about damage phenomena of roads regarding road characteristics and flood parameters. This study gathered a complete database through questionnaire surveys of flood-related road damage. Further, the study mentions that “this kind of database has not previously existed in underdeveloped nations such as Bangladesh, in part because it is challenging to undertake a qualitative assessment of flood velocity through a question-and-answer session with local responders.” For the rural roads of Bangladesh, it was best examined through the flood damage function. The article further gives some recommendations, “the goal of the study is to recommend an efficient approach for estimating flood losses to support efforts in reducing flood risk in developing nations such as Bangladesh. The rural transportation roads in Bangladesh can significantly reduce the flood damage to their road structures by altering the earth roads with higher-quality materials on the top surface”. The purpose of the study is to “act as a valuable support in flood disaster risk management works in Bangladesh.”

Climate change is occurring at an accelerating rate and we need to act fast during natural disasters of flood and drought. In the above case-study of Bangladesh, I do agree that flood damage on road infrastructures need to be explored more. Alternatively, residents who are residing near a river or floodplain should be relocated to another area as they are vulnerable and in high risk of being affected by the floods. 

Climate change affects many sectors and things. Each sector needs to be explored as everyone and everything has a significance and if we solve the small issues, it will help in overcoming the larger issues related to climate change events.