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Bangladesh | A Topographical Approach

(R. Ahmed)


The Bangladesh coast-line spreads about 750 km, including island borders and creeks. The coast-line morphology is significantly influenced by three factors, such as the fast-changing nature of low flat lands, the climate, particularly the coastal surge and cyclones and thick density of population in the region. The accelerating interaction between the three, as a result of increasing human interference, has influenced the coastal environment to shape up. The basic three ecological/geographical regions those are distinct are the mangrove forest zone in the western part, the vast estuarine zone (of the Meghna-Brahmaputra-Ganges) in the central part and the eastern coastal lowlands. All the three maintains three groups of eco-environment-geomorphic characters.


The eastern low lands stretched from the Feni River down to the St. Martins Island is a relatively narrow north-south elongated strip, modified by several active rivers and streams by their deposition and erosion activities. The notable rivers are the Karnaphuli, the Matamuhuri and the Sangu. This region is mostly sea-storm and sea-water-surge affected as this stands on the frontline of the main coastal cyclone paths. The margin of this plain land strip is bordered by north-south elongated mountainous range of Tertiary period. However, the coastal plain does not stretch more than 50 Km. So, there has developed a concentration of settlement due to fertile soil and easy land utilization possibility resulted in high density of population and accelerating increase of land use intensity. The southern tip is an estuary of the river Naf and a tiny island named St. Martins is located there. The island is believed to be either coral or formed of coral depositions took place on a tectonic hump which suppoirts a coral ecosystem around the island.


The central estuarine part is the gift the depositions of the mega-rivers and is very active. Geomorphic changes has been taking place almost continuously. The region includes a good number of islands such as Bhola, Hatiya, Swandip etc. and parts of Noakhali, Lakshmipur, Barisal, andBarguna. Frequent coastal erosion and accretion turned the land unstable, but emergence of patches of new lands attract poor land less people from around. Thus the region has become characterized by relatively high density of population (if not very high). This part is also just on the major coastal cyclone and water surge route, make the livelihood highly disaster vulnerable. The relatively recent and unstable nature of the soil the region developed its own land use pattern.

The western mangrove forest is more a natural and protected zone. The region is characteristically inter-tidal and most of the forest species are saline water and tidal-difference resistant. Generally, this part is less vulnerable to coastal cyclone and water surge but more vulnerable to ecosystem damage due to mismanagement of the forest. Main trees are Sundari, Gewa, Goran, Kankra and Pasur. There is a distinct geographical pattern in their distribution which is based on the amount of tidal difference and amount of water salinity. In fact government initiative has extended the mangrove forest by adding some more smaller and narrow strip located further east along the coast and in many small off shore islands, which stands as protection for nature against the coastal cyclone and water surge.


The regular phenomena of coastal cyclones and water surges have made the lives of coastal people harder and full of struggle. They have their own indigenous protection system as well as have government supported shelters and medical systems (but believed to be insufficient). There are hundreds of elevated cyclone shelters located in almost each and every off shore islands and coastal areas, many of those were constructed by the German Red Cross. Although the rate of human death is rapidly decreasing but it is difficult to stop completely because of technological limitation of weather prediction.


There prevails a regular social conflict among the poor and between the poor and the urban rich to grab/occupy the newly accreted land in the coastal islands, which are, according to law, owned by the government, called ‘Khash Land’ or public land. Continuation of this problem is certainly due to weakness in the land ownership law, weak implementation of security system and uncontrollable long handedness of the urban political hoodlums results in loss of human lives every year in power struggle. The lands close to the mangrove forest in its north and in the eastern plain lands are threatened by increasing intensity of land use land utilization due to economic pressure and high population growth. The threat comes up mainly with the conversion of rich agricultural lands to economically benefiting shrimp cultivation. This temporarily helps but in long run a huge amount of good lands become unusable for agriculture. In this regards the most affected parts are locate in the western (Satkhira, Khulna and bagerhat) and in eastern low land regions (Chittagong and Cox’s Bazar). Apart from this hazard of land use change the next important is the biodiversity loss in the shore-line regions. The indiscriminate catching of shrimp fry from the coastal waters damages the overall ecosystem and biological species (other unconsumable species) which are caught and destroyed unknowingfully results in severe bio-diversity loss.


What would happen in case sea level rises even of a single meter? That is a question that confuses people as the influencing components and affected parameters are still undefined. The possible sea-level rise may be a segment of standard climate change but would influence the socio-economic system to adjust with the change. Or it may be more dangerous than we predict, there might be a huge displacement of population and economic setback. Almost the entire part of estuarine central part and the western mangrove zone is below 5m elevation. So, a predicted sea-level rise of just 5 m will be potential to flood about one-forth of the country – to displace about one-forth population! But more than this, there would be a back water logging at many parts of the tectonic basin regions in the country (such as the Chalan Bill, Chanda Bill etc. In addition there would be an extensive saline water penetration to reduce the agricultural production and disturbing crop rotation system.


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