Assignment On Hazards in Dhaka City

Hazard may be defined as “a dangerous condition or event, that threat or have the potential for causing injury to life or damage to property or the environment.” Hazards in Dhaka city can be grouped into two broad categories namely natural and manmade.
Natural hazards:
Natural hazards are hazards, which are caused because of natural phenomena (hazards with meteorological, geological or even biological origin). Examples of natural hazards are cyclones, tsunamis, earthquake and volcanic eruption, which are exclusively of natural origin. Landslides, floods, drought, fires are socio-natural hazards since their causes are both natural and man-made. For example flooding may be caused because of heavy rains, landslide or blocking of drains with solid waste.

Manmade hazards:
Manmade (anthropogenic) hazards are hazards, which are due to human negligence. Manmade hazards are associated with industries or energy generation facilities and include explosions, leakage of toxic waste, pollution, dam failure, wars or civil strife etc.

Geographical background of the Dhaka City:
Bangladesh dictated by its inherent geology and conditioned by it’s conditioned by its geographical location, suffers from natural calamities on regular basis, Dhaka city the capital of the country. Dhaka is situated between latitudes 23°42' and 23°54'N and longitudes 90°20' and 90°28'E. The city is bounded by the rivers Buriganga to the south, Turag to the west, Balu river to the east, and Tongi Khal to the north. The city has three distinct seasons: winter (November-February), dry with temperatures ranging from 10° to 20°C; the pre-monsoon season (March-May), with some rain and hot temperature reaching up to 40°C; and the monsoon (June-October), which is very wet with temperatures around 30°C. Dhaka experiences about 2,000 mm of rain annually, of which about 80% falls during the monsoon. Urbanization in Dhaka is restricted mostly to the north bank of the river Buriganga. Rapid urbanization without considering the geological aspects has brought significant changes in the geo-environment of the city area. Water logging, pollution, changes in the hydro-geological system, localized land subsidence, and building collapse are the hazards associated with these changes in the geo-environment. Groundwater withdrawal has increased more than 90% over the last 30 years resulting in groundwater mining and lowering of the water level by 20 m. Water resources of the city are being polluted by the indiscriminate disposal of untreated industrial and municipal wastes in swamps and natural channels in and around the city.