Bangladesh is a low land and deltaic country almost a drainage system of three major rivers in the world meeting to the Bay of Bengal. Bangladesh lies between 20o30’ and 26o40’ north latitude and 88o03’ and 92o40’ east longitude. The annual distribution over the country is unevenly distributed over different regions such as annual average precipitation is 2,300 mm, varying from 1,200 mm in the north-west to over 5,000 mm in the north-east. India borders the country in west, north and most part of east. The Bay of Bengal is in the south, Myanmar borders part of the south-eastern area. It has 405 rivers including 57 transboundary rivers, among them 54 originated from India including three major rivers the Ganges, the Brahmaputra and the Meghna (Annual Flood Report, 2014).

Bangladesh experiences natural disasters like floods, droughts because of the location of the country and meteorological forcing. For instance, flood is a common disaster that is experienced almost every year. Current climate changes, the meteorological forcing are accelerating and enhancing these disasters to be intense and infrequent. Due to geographical locations and river basins, there are several kinds of floods are experienced in Bangladesh such as river flood, flash flood, rain-fed flood and tidal floods due to storm surges. River flood is occurred typically in monsoon due to heavy rainfall. Flash floods are experienced due to convective storms. Rain-fed is classified due to heavy rainfall even in pre-monsoon and post-monsoon period. Tidal floods are seen in coastal areas due to storm surges in tropical cyclones and high tides (nearby coasts only). Figure 1 shows the type of natural disasters that are experienced in Bangladesh in different regions.  The figure shows Bangladesh is mostly affected by floods and droughts. There are also places experience both floods and droughts. These disasters damages human lives, agricultural crops, and properties significantly. It also affects the growth of development of country’s economy. Thus, it is very important for Bangladesh to assess climatic variations of floods in taking warning and safety measurements for saving lives and properties.

Since the disasters of Bangladesh is very diverse, the current study has been taken for the capital city. The latitude and longitude of Dhaka city is respectively 23.46oN and 090.23oE. The altitude above sea level is 8 m. The total area is 270 Square Km. Dhaka City is besides by the river Buriganga which is meeting to Jamuna.  The weather station of Dhaka city is 41923 and the synoptic data is collected from 2000 to 2015 from online source OGIMET. Dhaka metropolitan usually faces flash floods and also droughts. Another reason for choosing this site is the availability and accessibility of data from online source in climatic studies. The study site of Dhaka city and river basins are shown in figure 2. Some figures of the capital city are shown in figure 3 (a), (b), (c), and (d) respectively from 1850 to current situations. The evolution of the metropolitan also explains the reasons of the flash floods since the most places are occupied by localities where there was used to be open space, canal markets and vegetation. The population is also increasing significantly as the current population is around 7 million. The crowded building structures are also hindering the drainage systems and causing flash floods.

Objective: This current project is intended to study the climatic variation over the Dhaka city to assess flash floods by scrutinizing rainfall distribution. The climatic rainfall distribution is assessed from 2000 to 2015 to find a trend of rainfall and seasonal variation for Dhaka city. For flood assessment, the paper finds probable forecasting studies, climate model’s trends, and adaptation and mitigation measurement that can be considered in the context of Bangladesh, Dhaka city. 

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Methodology: The primary and synoptic data is collected from the OGIMET of 15 years daily precipitation. Moreover as secondary data, several climate model forecasts of rainfall several years of late 19th century and 20th century were compared and assessed. The climate model descriptions are given in table 1. Later, the feasibility and role of climate model and short term rainfall forecast models were suggested in assessing flood and managing flood. The observation data for Dhaka city were collected for 15 years monthly rainfall (mm/d). The observation data were compared with the two model forecasts shown in result section. The importance of models are also discussed in results and discussion sections followed by several suggestions and projected by future studies’ references.