Why does Bangladesh flood even when it receives below average rainfall?

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Being a riverine country, astir a large information of Bangladesh is flooded each year. The flood chiefly occurs during the monsoon play of aboriginal July to precocious September. Even successful 2021, erstwhile rainfall passim Bangladesh has been beneath average, floods are being experienced successful immoderate floodplains of the Teesta and Jamuna rivers, arsenic good arsenic the little confederate information of the country.

Bangladesh is 1 of the countries astir susceptible to floods successful South Asia, arsenic good arsenic to the consequences of clime change.

There are 5 main types of earthy floods occurring successful Bangladesh:

  1. Riverine flood
  2. Rainfall flood
  3. Flash flood
  4. Tidal flood
  5. Storm surge flood.

River floods

The main sources of floods are the stream floods from the overbank flows of the large stream systems, the Brahmaputra, the Ganges and the Meghna, successful the monsoon months. Local rainfall floods often travel stream floods caused by runoff from Bangladesh’s high-intensity, long-duration precipitation. This immense discharge of h2o cannot beryllium drained to the Bay of Bengal due to the fact that of precocious outfall h2o levels.

The bluish and northeastern transboundary hilly rivers are susceptible to flash floods from the adjacent hills successful India successful the pre-monsoon play betwixt April and May. The areas adjacent to estuaries and tidal rivers successful the southwest and south-central parts of the state acquisition tidal floods doubly a time owed to astronomical tide from the Bay of Bengal. Tropical storms successful the Bay of Bengal trigger cyclonic storm-surge floods erstwhile successful a while, affecting astir 12,000 sq-km of coastal onshore betwixt April and November.

The important elements that find the grade of flooding are the magnitude, synchronisation of peaks and duration of floods. Smaller differences successful peaks of large floods tin marque a large quality successful presumption of flood-affected areas since it is the spreading of floodwater evenly implicit a wide and level floodplain.

As each the flows are drained successful the Bay of Bengal lone by the little Meghna river, it takes clip and lengthens the duration of the flood. Also, the synchronisation of highest flows successful the Brahmaputra and the Ganges is simply a large determinant of the grade of flooding successful the country.

About 80% of the rainfall successful Bangladesh occurs during the months from May to September. Photo credit: Munir Uz Zaman/AFP

When the peaks of the 2 rivers coincide, terrible flooding occurs arsenic it was the lawsuit successful 1988, 1998, and besides 2004. The state has experienced floods since past times but determination is an expanding inclination successful year-to-year variability successful the annually flooded country from the mid-1970s. Some precise terrible floods were experienced successful 1987, 1988, 1998 and 2004 and immoderate little terrible ones successful 1991, 1993 and 1995.

Geographical factors

There are a fewer geographical, physiographic, and hydro-meteorological factors liable for floods successful Bangladesh. The state is surrounded by hills connected 3 sides: Rajmahal hills successful the west, the Himalayas and the Meghalaya Plateau successful the northbound and Tripura-Chittagong hills successful the east. The rainfall-runoff from this immense hilly country coupled with snowmelt successful the Himalayas brings a immense inflow of h2o to Bangladesh during the monsoon season. About 80% of the rainfall occurs during the months from May to September.

The state is located successful the little parts of the basins of the Ganges, the Brahmaputra, and the Meghna but lone 7% of the floodplain lies wrong Bangladesh which drains astir 91% of the basin runoff. In this process, the country’s onshore consisting of 80% of the floodplain gets inundated by floodwater.

The impacts of this benignant of flood are connected the emergence due to the fact that of a alteration successful hydrological authorities successful the floodplains owed to unplanned operation of antithetic types of infrastructures, specified arsenic dams, barrages, roads, bridges and culverts.

Also, the siltation of riverbeds and encroachment of wetlands successful the floodplain is 1 large crushed for unexpected flooding. Another origin of interest is the harm caused by abrupt floods owed to the nonaccomplishment of flood power embankments.

Anthropogenic activities successful the signifier of operation roads without capable drainage capableness done them, roadworthy alignments transverse to the main drainage paths, blocked drainage channels owed to siltation, cross-dams oregon sportfishing activities, and inadequately sized drainage sluices are expanding municipality floods.

Urbanisation

Recently, flood events are becoming much terrible due to the fact that of the river-bed siltation, stream encroachment and inadequate drainage capacity. Because of urbanisation, radical are filling up the wetlands (ponds, beels) which antecedently functioned arsenic a reservoir for the rainwater successful the floodplain. People propulsion a ample measurement of coagulated wastes successful the h2o bodies, and so, the h2o carrying capableness of the rivers and lakes is decreasing. These are starring to flooding successful the localities causing tremendous distress to quality life.

With the summation of population, much and much radical are settling successful flood-prone areas, leaving them vulnerable. An investigation conducted with 2001 colonisation census information revealed that immoderate 45.5 cardinal radical were exposed to terrible and mean floods.

Flood-prone zones are the worst disconnected among antithetic disaster-prone areas successful presumption of nutrient shortages, the incidence of highly poor, insufficient income, illiteracy, and a precocious attraction of wage labourers. Proper absorption of floods successful a state similar Bangladesh is simply a crying need, and the integration of each stakeholders successful the absorption process tin execute a fruitful result.

This nonfiction archetypal appeared successful Dhaka Tribune.

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