urbanfloods.PDF

2009

Urban flooding is the accretion of land or property in a built environment, particularly in more densely populated areas, caused by rainfall overwhelming the capacity of drainage systems. A number of major cities and towns in India reported a series of devastating urban floods in the recent decade. Urban flooding is significantly different from rural flooding as urbanization leads to developed catchments, which increases the flood peaks from 1.8 to 8 times and flood volumes by up to 6 times. (NDMA Guidelines). In this paper, challenges of urban flooding have been studied taking instances of three cities of India viz. Srinagar, Gurugram and Chennai, selected for respective rationale. Srinagar is flooded due to unplanned urbanization, Gurugram due to breakage of Wetland linkages and Chennai flooded due to rapid urbanization, topography and siltation. The paper discusses causative factors responsible, the immediate need for flood risk reduction and management strategies.

Flooding is an accumulation of water in an area either by direct rainfall irresistible to the volume of drainage systems or a spill of huge amount of water from water bodies beyond normal limits. It could be localized, impacting a small area or could be vast or massive, impacting very large area. Urban flooding is caused by heavy rainfall overwhelming drainage capacity. It already has large economic and social impacts. These are very likely to increase if no changes are made to the unplanned development of buildings and infrastructure and poor management of urban drainage. Urban floods are a great disturbance of daily life in the city. Urbanization in developing countries doubled from less than 25% in 1970 to more than 50% in 2006. By 2020, seven of the world's ten largest economies will be from Asia. At the same time, Asia in one of the fastest urbanization regions in the world. In 2000, 37% of its population lived in cities and the proportion is projected to reach more than 50% by 2025.Across India, in the recent times, city after city has experienced floods. Through this paper, the author reviews urban flood events within India in recent past. This paper describes why it is important to study urban floods scenarios and what the need for this study is. It highlights the types and causes of the localized flooding as well as its impact and consequences. The study concludes the infrastructure and economic losses due to these urban events.

Flood is one of the significant and frequent disasters in the world. Of these more than 50% of the events occur in Asia. Every year there is loss of human life, animals, houses, goods and property due to the outrage of floods. Urban areas are witnessing drastic population growth resulting in decreasing rainwater infiltration and increase in runoff and flood peak. Severe and frequent flooding events are possibly due to climate change, socioeconomic damage, migration, development practices and political instability, which constantly reshape flood vulnerability. As a part of an integrated urban flood studies at KSNDMC, we are developing a plan for " Urban storm water flood management " –for Bangalore city, which is often subjected to monsoon fury. This paper describes the causes, circumstances and impact of flooding events in Bangalore city. In an urban scenario, like Bangalore, floods occur due to natural phenomenon such as heavy and / or high intensity rainfall, human factors such as blocking of storm water drains, population growth leading to improper land use & unplanned settlements etc. The immediate impact of floods will be mainly on the public transportation because of water submerging the roads, urban settlements in low laying areas due to inundation, chocking of storm water drains inundating the surrounding houses. In the Developing countries, like India, the activities of Flood management are handled by government and are still adopting a reactive approach during floods. This should be changed to proactive action which enhance effectiveness of management and reduce losses. For planning and implementing an effective short and long term flood management plan participation and cooperation between Government, non-governmental, private agencies and public is a prerequisite.

2016

Flood is a temporary overflow of a normally dry area due to overflow of a body of water, unusual buildup, runoff of surface waters, or abnormal erosion or undermining of shoreline. Floods can also be overflow of mud flow caused by buildup of water underground. Increased urbanization has added to the increase of flash floods as well as higher flood levels. Urbanization refers to the modifications made to a natural landscape through paving, lodging and building. How does this affect us? Cement is not capable to soak up water-compared to natural soil-to this excess water is directed to nearby streams, which then overflow, due to the excess amount of water. The urbanization of a catchment area-land whose waters drains into a body of water-dramatically impacts the characteristics of river flooding. There is a correlation between the increase of urbanization, the percentage of the basin paved and the recurrence interval of the flood. (Hollis, 431). We must be aware that our conscious effo...

Flood is a temporary overflow of a normally dry area due to overflow of a body of water, unusual buildup, runoff of surface waters, or abnormal erosion or undermining of shoreline. Floods can also be overflow of mud flow caused by buildup of water underground. Increased urbanization has added to the increase of flash floods as well as higher flood levels. Urbanization refers to the modifications made to a natural landscape through paving, lodging and building. How does this affect us? Cement is not capable to soak up water –compared to natural soil-to this excess water is directed to nearby streams, which then overflow, due to the excess amount of water. The urbanization of a catchment area – land whose waters drains into a body of water-dramatically impacts the characteristics of river flooding. There is a correlation between the increase of urbanization, the percentage of the basin paved and the recurrence interval of the flood. (Hollis, 431). We must be aware that our conscious effort for expansion and living space can actually precipitate a natural hazard. We put ourselves in areas where there is a higher chance for flooding due to the scenic views, the serenity of it all, etc. This paper emphasizes the effect of flood flows in urban environments and its impact in the form of destruction and describe that the occurrence of flood is not a natural calamity.

2011

Urban flooding is an increasingly important issue. Disaster statistics appear to show flood events are becoming more frequent, with medium-scale events increasing fastest. The impact of flooding is driven by a combination of natural and human-induced factors. As recent flood events in Pakistan, Brazil, Sri Lanka and Australia show, floods can occur in widespread locations and can sometimes overwhelm even the best prepared countries and cities. There are known and tested measures for urban flood risk management, typically classified as structural or engineered measures, and non-structural, management techniques. A combination of measures to form an integrated management approach is most likely to be successful in reducing flood risk. In the short term and for developing countries in particular, the factors affecting exposure and vulnerability are increasing at

Irrigation and Drainage, 2006

An increasing proportion of the world's population is living and working in flood-prone areas. There are no indications that this tendency will change. In the rural areas we may observe improvements in agricultural production and an increase in the value of crops, farm buildings, water management facilities and infrastructure. In addition, due to urbanisation, industrialisation and improving standards of living, especially in the emerging countries, the value of property, buildings and infrastructure has significantly increased and will further increase in future. Especially in flood-prone areas in South and East Asia we may observe a very rapid growth of urban areas. In order to cope with this growth of new urban areas reclamation has very often taken place in nearby low-lying areas. From a flood protection and water management point of view this implies removal of storage areas and increase in urban drainage discharges. The paper presents the various developments and their consequences with respect to flood management.

In the recent decades, Indian cit ies are witnessing devastating floods more often due to heavy rainfall, cyclones, etc., Though Tamil Nadu is not under flood risk p rone zone as mapped by meteorological depart ment (New Delh i), within the local body there are few low-lying areas wh ich are susceptible to inundation which also depends mainly on the developments near major drainage systems, encroachment of water bodies, inability of majo r canals to carry heavy rains, overflowing reservoirs. Chennai, one of the fast growing metros is likely affected by the lack o f drainage mainly due to uncontrolled developments of concrete spaces, encroachment of majo r drainage channels, shrinking of marshlands, etc,. Though Urbanizat ion, the vital factor of response for the flood risks is coupled with the climatic variability and ecological imbalances. The paper discusses causative factors responsible for flood risks in Chennai, the immediate need for proper flood risk reduction and management strategies.

IRJET, 2021

Indian cities, where pressures are mounting on land use, are no longer able to ignore the issue of urban floods. Better planning and a disaster response plan that can minimize at least the level of devastation and loss of life. The Intergovernmental Panel on Climate Change has determined that in the future we will see more rainfall in less time and any incident that occurs in urban areas, because of their abundance, will affect a larger population. We urgently need to make our urban center flood-resistant.