Geography, rivers, climate vulnerability & disaster management
Bangladesh's physical geography, the Ganges-Brahmaputra-Meghna river system, climate vulnerability and its world-leading disaster-management architecture for the BCS.
A deltaic nation
Bangladesh occupies the world's largest delta, the Ganges-Brahmaputra-Meghna (GBM) delta, drained by some 700 rivers totalling roughly 24,000 km of waterway. About 80% of the territory is floodplain lying less than 10 metres above sea level; only the Chittagong Hill Tracts (the Keokradong/Saka Haphong massif, the highest points, c. 1,000 m) and the Madhupur and Barind tracts rise above the alluvial plain. The country covers approximately 147,570 sq km, shares a 4,156 km border with India and a 271 km border with Myanmar, and fronts the Bay of Bengal to the south.
The three great rivers
Three systems define the hydrology. The Padma is the name the Ganges takes after entering Bangladesh near Rajshahi. The Jamuna is the lower course of the Brahmaputra, which shifted westward into its present channel after the great earthquake of 1762 and floods of 1787. The Meghna, fed by the Surma and Kushiyara from the Barak in India's Manipur/Assam, is the deepest. The Ganges and Brahmaputra join at Goalando; the combined flow meets the Meghna near Chandpur before discharging into the Bay—the world's largest combined freshwater discharge after the Amazon and Congo. The delta's seaward fringe holds the Sundarbans, the largest mangrove forest on earth (UNESCO World Heritage Site, 1997) and habitat of the Royal Bengal Tiger.
Transboundary water disputes
Because 57 of Bangladesh's 57 transboundary rivers originate in India and Myanmar, water sharing is a permanent strategic concern. The Farakka Barrage (commissioned by India in 1975, 16.5 km above the border) diverts Ganges water into the Hooghly and reduced dry-season flow at Hardinge Bridge, intensifying salinity intrusion and desertification of the southwest. The dispute was settled by the Ganges Water Sharing Treaty signed 12 December 1996 (Sheikh Hasina–Deve Gowda), a 30-year accord guaranteeing minimum dry-season shares. The Teesta river-sharing agreement, initialled in 2011, remains unsigned owing to West Bengal's objections—a recurring current-affairs flashpoint.
Climate and physiography
Bangladesh has a tropical monsoon climate: pre-monsoon (March–May) bringing nor'westers (kalbaishakhi) and cyclones; the southwest monsoon (June–October) delivering 80% of the c. 2,300 mm annual rainfall; and a dry winter. Sylhet's haors (back-swamp wetlands) and the flash-flood-prone northeast contrast with the drought-prone Barind in the northwest. The coastal zone—covering 19 of 64 districts—faces tidal surge, salinity and erosion. This physiographic diversity, concentrated population (over 170 million; one of the highest densities on earth), and low elevation make the country a textbook case of climate exposure.