Surface Water Drainage and Flooding in Karachi City S. AKHTAR AND
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Sindh Univ. Res. Jour. (Sci. Ser.) Vol.44 (1) 59-70 (2012) SINDH UNIVERSITY RESEARCH JOURNAL (SCIENCE SERIES) Surface Water Drainage and Flooding in Karachi City S. AKHTAR AND M.R. DHANANI* Department of Geography, University of Karachi, Karachi, Pakistan *Corresponding author. M. R. Dhanani, E-mail: [email protected] Cell, No.03453541162 Received 13th November 2011and Revised 2nd January 2012 Abstract: Urban flooding is natural phenomenon. It has become a serious problem of cities of both Developed and Under- developed region. The rapid population and areal growth of cities and intensive urban development have intensified this problem. Cities are generally flooded when excessive precipitation takes place beyond the capacity of surface drainage. Urban sprawl and urban encroachment intensify this problem in form of reducing rainwater infiltration and increasing surface runoff. Lack of planning about rainwater and sewerage discharge and population growth aggravate this problem. Like other major cities of the world problem of urban flooding has been intensifying in Karachi City which is the largest city and financial hub of Pakistan. The monsoon rain creates a serious problem for city dwellers and urban planners. In view of the significance of the problem the present study is an attempt to examine the problem of urban flooding in historical perspective and evaluate the surface drainage problem in context of urban growth and urban planning. Keywords: Urban flooding, Urban sprawl, Flash flood, Torrential rainfall 1. INTRODUCTION of the area. This problem is serious in arid and semi- Urban flooding is a phenomenon which arid areas where drainage is ephemeral and dry beds occurs as a result of rainfall overwhelmed by provide open land for urban development. drainage capacity (APWA, 1981). There are various Construction of rain drain channels and sewerage factors which are linked with this problem. The most channels should be constructed to ensure the future important factors are as follows: population growth. i) the meteorological factors in which iv) in the less Developed regions of the world occurrence of heavy rainfall within a short duration the cities are facing challenges of haphazard growth and long spell of rainfall in which soil infiltration and unplanned urban structures. Problem of low – capacity reaches at the saturation level and surface income urban housing which enhance growth of runoff increases. squatter settlements and lack of governance on the implementation of land utilization and building by- ii) Urban sprawl is strongly linked with urban laws intensify the problem of urban flooding flooding. Cities are expanding with alarming rate. cause loss of life, property and urban infrastructure. Growth of urban built up area particularly construction works in the beds of water ways and in Urban flooding is a significant problem in the flood plains and reduction of unlined surface cities of both developed and less developed regions which eventually cause increase in surface runoff of the world (Balmer, 1984). In September 2008 considered one of the main reason of this problem. severe flood occurred in the coastal city of Houston, USA as a result of torrential rain and iii) Urban planning and management has a key hurricane. The urban life had been collapsed for a role in intensifying and managing urban flooding week. Urban flooding has become a common problem. Urban planners should frame development phenomenon in many mega cities of the world plans like new housing schemes, industrial areas, like Mumbai, Chennai, Kolkata, Dhaka etc. It causes highways, airports etc to ensure the natural drainage catastrophic damages of life and economy. In *Department of Geography, University of Sindh, Jamshoro, Pakistan S. AKHTAR AND M.R. DHANANI 60 Pakistan the problem of urban flooding has been e) Satellite imageries were used to locate urban intensifying in large cities like Karachi, Lahore development over surface drainage and rivers’ and Rawalpindi. During the Monsoon season from beds of Malir, Lyari and other small channels. July to September risk of urban flooding is very high. In August 2004, 600 mm rainfall was recorded 3. RESULTS AND DISCUSSION in the twin cities of Rawalpindi and Islamabad. As a Population and Physical Growth of Karachi City result flood damaged squatters, roads, and bridges. At least 10 people died 50 injured and more than Karachi started its growth as a walled city in 100 cattle died. The problem of urban flooding is 1729 with a population of 1000 and an area of 0.12 quite significant in Karachi which is the industrial sq km. The British occupied Karachi in 1839 and it and business hub of Pakistan. Karachi had was annexed as a part of Sindh in British Indian experienced severe floods which occurred 1843. In1853, Karachi Municipality was established periodically. In 1977 severe flood occurred in the and a marked expansion and development of the flood plains of the Malir River and the Lyari River town took place. The city was no more a fortified killed 267 people, more than 30,000 were homeless settlement. In 1923, Karachi Municipality and 100,000 were temporarily dislocated. Houses approved Miram’s Development Plan for the were destroyed and roads were damaged. The total planning and development of Karachi. Under that loss was estimated about 5 billion rupees (KDA, plan Bunder Road (M. A Jinnah Road) was extended 1981). The present study deals with urban flooding up to the Central Prison. In 1941 the population of which has now become a serious problem all over Karachi city increased to 386655 and its area the world, affecting urban life, infrastructure, expanded to 115 sq. kms. (KDA, 1984). mobility of people and economy of the city. In this context Karachi has been selected for study which is Pakistan came into existence in 1947 and the largest city of Pakistan. Karachi was made its capital. It retained its status as capital till 1960 when the capital of Pakistan was 2. MATERIALS AND METHODS shifted to Islamabad. Soon after the creation of The objectives of the present study are following: Pakistan large scale migration from India took place. Apart from this influx, a large number of people a) to study topography and surface drainage of the also migrated to Karachi from different parts of City Pakistan . As a result the population of Karachi b) to analyse the historical records of flooding in increased rapidly. In 1951 Karachi with a population Karachi City. of 1.6 million became the largest city of Pakistan. c) to compute relationship of rainfall and surface Many new urban housing schemes were developed runoff as well as quantify flood frequency in the after the creation of Pakistan As a result the area of Malir River. Karachi city expanded to 368 sq kms in 1961 and d) to identify flood prone areas in the City. population increased to 1912598. In 1971, separation e) to identify causes of urban flooding in Karachi of East Pakistan (now Bangladesh) took place. About City. 0.175 million people came from Bangladesh to f) to evaluate methods of flood control and flood Karachi. The population of Karachi increased to management in the City. 3,498,614 in 1972 while the area expanded to 640 sq kms. The population and areal growth of Karachi city To study the above objectives following continued. Its population increased from 5,153,000 methods were used: in 1981 to 9,280,000 in 1998. It is estimated that in 2010 population of Karachi increased to 15 million. a) Collected precipitation data of the last 80 years Its area extended to about 1800 sq. kms. Urban of Karachi City from Meteorological office. sprawl is big challenge for city planners which has b) Obtained historical data of surface runoff in the increased built up land, population pressure and Malir River which is the main river in the City encroached settlements. As a result problem of from WAPDA. flooding in the city has been intensifying year by c) Conducted a reconnaissance survey of surface year. geology and surface drainage of Karachi. Topography and Surface Geology d) Field surveys were conducted to identify the sewerage system and problem of urban The topography of Karachi is comprised of encroachment in the City plains, river valleys and hilly ranges. The main areas Surface water drainage and flooding in Karachi City 61 of Karachi City have been developed in between the coast. The coast of Karachi is dominated by cliffs, interfluves of the Lyari River and the Malir River. sea stacks, sandy beaches, sand bars and sand spits, The City is bounded by hilly ranges located in the swamps, mudflats and salt marshes. Due to hill west, north and north-east. The hilly ranges of torrents at the slope of hills alluvial fans and bajada Manghopir are located in the north-west. It starts features form depositional surface while the low from the Hub River Dam area run north to south angle piedmont slopes represent the erosional than turn toward west with the name of Orangi surface. Weathering and mass wasting are two hills and Gorakh Lakki hills. These hills finally dip at dominant geomorphic processes in the area. The Cape Monze at the coast of Karachi. One of the outcrops in Karachi comprise different epochs of important coastal ranges is known as Jhill hills. At tertiary period and quaternary surface deposits. It the eastern coast of Karachi the topography is comprises from Eocene to Pliocene rocks. The dominated by an eroded hilly range known as outcrops are exposed in different areas of the Ibrahim Hyderi hills. The north-eastern part of the City belong to Pliocene locally called Manchhar Malir River is also occupied by hilly ranges. In formation, Miocene locally called Gaj formation and between the Lyari and the Malir River remnants of Oligocene locally called Nari formation.