Pár geologických dat z Bangladéše

Bangladesh is a developing country in South Asia located between 20°34˘ to 26°38˘ north latitude and 88°01˘ to 92°42˘ east longitude, with an area of 147,570 sq km. It has a population of about 128 million, with a very low per capita Gross National Product (GNP) of US$ 370 (WB, 2000). It has a border on the west, north, and east with India, on the southeast with Myanmar, and the Bay of Bengal is to the south. Geologically, Bangladesh is a part of the Bengal Basin, one of the largest geosynclinals in the world. The Basin is bordered on the north by the steep Tertiary Himalayas; on the northeast and east by the late Tertiary Shillong Plateau, the Tripura hills of lesser elevation, and the Naga-Lusai olded belt; and in the west by the moderately high, ancient Chotanagpur plateau. The southern fringe of the basin is not distinct, but geophysical evidence indicates it is open towards the Bay of Bengal for a considerable distance. The formation and growth of the Bengal Basin is directly related to the origin and morphology of the Indo-Gangetic trough, which itself is overlaid and filled by sediments thousands of metres thick (Rahman, 1994). The broad geological features of the Bengal Basin and its prominent tectonic elements are Indian platform, Bengal foredeep, Arakan Yoma folded system, and the Sub-Himalayan Foredeep. Other features are Rangpur Saddle, Dinajpur slope, Bogra slope, Hinge Zone, Barisal High, and Troughs of Sylhet, Faridpur and Hatiya, etc. The floor of the Bengal Basin consists of quaternary sediments deposited by the Ganges, the Brahmaputra, and the Meghna rivers, known together as the GBM river system, and their numerous tributaries and Geographical Location of Bangladesh distributaries. The sediments are washed down from highlands on three sides of the Basin, particularly from the Himalayas, where the slopes are steeper and the rocks less consolidated. Over 92 per cent of the annual runoff generated in the GBM catchment area flows through Bangladesh, although it comprises only about 7 per cent of the total catchment (Coleman, 1969). The whole country consists of mainly low and flat land, except for the hilly regions in the northeast and southeast. A network of rivers, with their tributaries and distributaries, crisscross the country. Physiographically the country can be divided into hills, uplifted land blocks, and the majority alluvial plains with very low mean elevation above sea level (Rashid 1991). Figure 2.1.1 shows the geographical location of Bangladesh in the context of the GBM river system. The physical environment of Bangladesh is diverse, and there is a mix of both traditional and modern methods of land use, all very closely adapted to the heterogeneous conditions. This complexity of environment and utilization patterns has important implications for the vulnerability and depletion of the natural resource base. Moreover, neither the physical environment nor technologies remain static. For example, rapid and frequent natural changes are taking place in the river systems, and they are also subject to the influence of various human interventions. Thus, there are dynamic changes taking place in the hydrological system all the time. These in turn influence land use patterns. Bangladesh has a comparatively low natural resource base, but a high growth rate of population, with almost half of the population below fifteen years of age. Most of the people are among the poorest in the world, and depend mainly on the natural resource base for their livelihood. But now the resource base is under serious threat, as many natural resources are either being over exploited or used sub-optimally. Besides the effects of anthropogenic stresses, the low ?land-man? ratio in the country is often further threatened by natural hazards.Thus, for the survival of Bangladesh?s dense population, it is essential to have environmental planning and management that conserves and sustains the ecosystems that support their livelihoods. The high population density, low economic growth, lack of institutional infrastructure, an intensive dependence on agriculture and agricultural products, geographical settings, and various other factors, all contribute to make the country weak in its economic development and quality of life. ZDROJ:MOeF Bangladé?