Urban flooding and it is mitigation strategies: a case study of Bhubaneswar

Abstract

Flood is one of the most common disaster in the world. Flood is generally termed as submerging of dry lands by an overflow of water. It is either localised in small area of land or neighbourhood or a large disaster affecting the entire river basin or a part of it generally in the down streams. It is generally categorised as river flooding, flash flooding, urban flooding and coastal flooding. While most of the flooding occur near the water bodies but the urban flooding is generally occurred by sudden flow of rain water in the urban areas due to sudden flow of surface rain water and accumulating in lower grounds. The rapid increase in the urban areas are also leading to decrease in urban lands which gradually leads to less infiltration of rain water and increase in surface runoff. The overwhelming of the capacity of drainage systems like storm sewers by rainfall causes urban flooding. Due to increase of existing paved streets and concrete roads there is a rapid increase of the speed of flowing water which leads to increase of flood effects in urban areas. Since the impervious surfaces in the urban areas increases which prevents rainfall from infiltration into the ground and causes a higher surface runoff thereby exceeding the local drainage capacity. These floods occur for a short period of time due to fast flow of surface run-off as the built-up area increases and the surface ground soil decreases. Bhubaneswar being the capital of state Odisha with an average population of 8.87 lakhs (as per 2011 Census) and a fast growing city being one of the first planned city after independence, planned by German architect Otto H. Konigsberger. The city being standing in the hilly terrain urban flood is the consequence of high stages of water in low lying areas and drainage channels in towns or cities as a result of heavy torrential shorter rainfall, drainage congestion, accumulation of water in flood plains, breaches in drainage embankments or tidal surges and many more. The history of urban planning in Bhubaneswar has started after 2000 due to the rapid urbanization. The city has a history of receiving heavy rainfall due the effects of various cyclonic storms and deep depressions in Bay of Bengal. After the year 2000 the city has faced many heavy rainfall due to various climatic factors and the increasing urbanization causin increase in surface runoff is causing urban flooding in various parts of the city. The effects of urban flooding is leading to the damage in various public and private properties. The thesis aims to study the effects and propose mitigation strategies of urban flooding in Bhubaneswar. The main objectives of the thesis is to identify the vulnerable locations prone to urban flooding by analysing various methods in GIS and also to identify the location prone to urban flooding along with estimation of watershed regions. Another objective of the thesis is to estimate the surface runoff coefficient so as estimate required drainage of storm water and finally propose recommendations to upgrade the systems for urban flooding in Bhubaneswar.