Under impact of cyclone Aila.
The analysis of the outcome of the climate change summit held in Copenhagen pointed out a stark reality for Bangladesh and other most vulnerable countries (MVCs) that we can't just rely on greenhouse gas (GHG) emitting developed countries to come to our salvage. We will have to increase our domestic capability in terms of adaptation and mitigation plans. The formulation of Bangladesh Climate Change Strategy and Action Plan (BCCSAP) is a valuable document and a step in the right direction. This document outlines many action plans including strategy for flood protection and management schemes, coastal green belt, cyclone shelters, resilience of vulnerable groups, centre for research on climate change, climate change resilient crops, and coastal embankments.
The infrastructure theme and repair and maintenance of existing polders program (T3P3) of the BCCSAP call for repair, rehabilitation, and building of over 7,000 km of coastal embankments to prevent tidal flooding and incursion of saline water. In a press conference following the Copenhagen conference, the state minister of forestry and environment, Dr. Hasan Mahmud, has reiterated the plan for building more polders and embankments in coastal region. This writer believes that building of coastal embankments and polders as an adaptation scheme against climate change will not be an effective measure. Instead, such action will aggravate the situation on a long run, and will provide a false sense of security to the people living in low-lying coastal regions of Bangladesh.
This writer views the climate change in the context of "big picture." The climate change that we are experiencing is a part of the natural cycle; however, the rate of such change is accelerated by human interference. We are living in a warming phase of climate for the last 10,000 years, and this trend will continue for at least several hundred years into the future. During this rise in sea-level, the delta region of Bangladesh (and for that any other low-lying coastal areas in the world) will undergo increased rate of submergence. Whether or not this submergence will be countered by land-growth will depend on the rates of sedimentation facilitated by tidal and flooding inundations.
Coastal lands grow vertically at the rate of millimeter by millimeter through sediment-capture from such tidal and flooding inundations. If the rates of such sediment-capture on land are higher than the rates of sea-level rise then coastal lands will grow both vertically and seaward at faster rates. As a result, sea-level rise will not submerge coastal lands on a long run. Such land growth, both upward and seaward, against the rising sea-level has been occurring for the last 10, 000 years in Bangladesh.
For example, the location of our shorelines was near Madhupur Tract in Tangail and Barind near Rajshahi about 125,000 years ago. Bangladesh has gained all these lands between Madhupur-Barind and today's shorelines during this time period. Water-flow in all major rivers and their tributaries brought sediments that were dispersed over coastal lands by tides and floods. It is through these natural processes that most of what we know as Bangladesh was created over geologic time. Although sea-level rose by 300 feet over the last 10,000, the shoreline did not migrate landward from its current position. In fact shoreline migrated seaward up until about 200 years ago.
Isolation of coastal areas from tidal inundation and flooding by building embankments and polders may provide temporary relief from the rising sea-level, but over time the coastal lands will be deprived from natural processes of sediment-capture that is necessary to cope with such rise in sea-level. Sediment deprivation on coastal lands will result in lowering of elevations below the sea-level. This phenomenon can be observed first hand in Bhabadah, Jessore, as well as in coastal areas of Louisina, USA, and in the Netherlands. Since sea-level rise will continue for the next several hundred years, we need to facilitate, if not accelerate, the sediment-capture process over coastal lands.
It may sound counter intuitive to allow more flooding and tidal inundation when people in coastal areas are trying to get relief from the rising sea-level. However, alternatives are more disastrous. If coastal lands are isolated from tidal inundation then only thing that will go up is the sea level - not the coastal lands. Not only the lands behind embankments and polders will decline in elevations over time, the salinity will increase in groundwater supply and will it not be potable any longer.
Drainage and sanitation will also become ineffective in those areas. The problem of drainage congestion has been recognized in the infrastructure theme and adaptation against future cyclones (T3P6) programme of the BCCSAP. In addition, if even the people living in areas behind embankments and polders will feel protected from natural sea-level rise, in reality those lands will occasionally get inundated by storm-surges and cyclones. When that happens, the salty waters entering behind the embankments and polders will have no place to go as the elevations within such polders will be lower than the sea-level and river-beds that are located outside of such protected areas.
The cyclone Aila has already devastated many of the existing embankments and polders. Such episodic inundations by cyclones will turn areas behind embankments into permanently water-logged in the future. The situation in New Orleans, Louisiana, following the devastation of the Hurricane Katrina in 2005, exemplifies this phenomenon.
The obvious question that begs answer is, how can the people continue to live in areas that are undergoing submergence due to sea-level rise? The answer to this question really depends on the balance between the rates of future sea-level rise and the growth of lands by such inundations. Adaptation and mitigation measures against climate change need to include plans that will accelerate sediment-capture mechanism and land reclamation process in coastal areas. If such measures cannot ensure sedimentation rates that exceed the rates of sea-level rise then the people will have to consider relocating or adapting to new ways of living and livelihood in coastal zones.
People will also need to follow the "dig-elevate-dwell" principle as long as they can manage to live in coastal areas. The bottom line is, the sea-level will continue to rise for several hundred years into the future, and we have to learn to live with this natural process. Isolation of lands by embankments will only accelerate the process of submergence and water-logging. Now the question is, will the people respect the nature and live in harmony with it, or will they defy the natural forces and will be doomed as many civilizations did in the past?
The future success of Bangladesh's strategy for adaptation against climate change will mainly depend on how successfully the government of Bangladesh can persuade the government of India and other co-riparian countries to come up with an integrated water and sediment resources management plan that will ensure necessary water and sediment inflow in coastal areas during all seasons in the future. As it stands now, India has unilateral control over water resources in all common rivers and doesn't allow enough water (and sediment) flow during dry season, which results in more salinity ingress in coastal rivers.
Several studies documented that the amount of sediment-flow in rivers entering Bangladesh form upper riparian countries has declined from 2 billion tons per years in the 1960s to about 1 billion tons per year in the 1990s. This reduction in sediment-influx has resulted in higher coastal erosion and lower land formation. Once agricultural lands are inundated with salty water from storm surges or cyclones then they are rendered useless for regular food-grain production. On the other hand, when India releases too much water during rainy season from dams and reservoirs then Bangladesh receives flood more than the land can handle.
The government representatives from Bangladesh should raise the issue of integrated water and sediment resources management plan in the context of climate change during negotiations at all levels with India and other upper riparian countries. As a friend, Bangladesh should expect India to respect the principles of water resources management science, i.e. to follow the globally accepted norm of watershed or basin-scale management of water resources. If one looks at the water control structures on all common rivers that enter Bangladesh from India, it will be obvious that India could never implement those water control structures against her own people, because neither science nor politics will support such actions. Bangladesh should seek equality and justice from India and other co-riparian nations, because our survival depends on it.
Md. Khalequzzaman is Professor of Geology, Lock Haven University, Lock Haven. Email: email@example.com