Journal of Space Technology, Volume V, No.1, July 2015 Landuse Changes and their Impacts on Natural Drainage System of Malir River Basin Sumaira Zafar, Arjumand Zaidi Department of Remote Sensing and Geo-information Science Institute of Space Technology, Karachi, Pakistan [email protected] [email protected] disasters. Rapid urbanization of a city may alter its natural Abstract— Karachi, a metropolitan city, is facing rapid hydrology giving rise to blockage and frequent flooding of the population growth causing environmental, social and economic drains. stresses and challenges. Beside planned development, unplanned urbanization, urban slums, illegal and informal settlements, and Till to date, it was believed that urbanization is one of the encroachments on natural drains have radically changed landuse causes behind climate change but now it is being observed that and drainage pattern of Karachi. One of the biggest challenges this change is badly affecting the urban centers by making that Karachi is facing now-a-days is localized floods after heavy them more vulnerable to natural hazards [2]. The extreme rain episodes due to increased surface overflow rates coupled weather events like heavy rainfall in short period of time may with the blockages of natural drains. In Karachi there are two main rivers, Lyari and Malir, which play a major role in cause flash floods that can impair transportation, transmission draining storm water of the city. At present, these rivers are lines and other infrastructure besides public health. With the severely affected by urbanization and bad management that increase of urbanized and developed areas, land areas become caused blockages at many locations. This paper investigates the paved and hard which restrict the percolation of water into the changes in landuse and their impacts on natural drainage pattern ground. In rural areas most of the rain water infiltrates or of Malir River basin over the past 16 years (2000-2015). percolates into the ground which minimizes the surface runoff Geospatial techniques are used to analyze landuse and landcover and raises the ground water table. In urban areas the situation changes of upper Malir River basin. Satellite derived Digital is quite opposite where impervious land surface promotes Elevation Model (DEM) and topographic sheets (1950s) are used runoff that may turn into flash floods and destroy everything to delineate natural drainage pattern of Malir district. Landuse/landcover and river drainage maps are overlaid to which comes in its way [3]. After flash floods, water stands in identify critical areas where natural river bed has been the surrounding area for extended period of time. This encroached. Most part of the Malir River basin has been stagnant water becomes the production site of mosquitos and occupied by agricultural fields and urban settlements which other harmful bacteria which cause dengue, malaria and other caused narrowing of the river and complete blockage at some diseases in the area. Pakistan being a developing country is locations. The blockages shown on the output maps can be more vulnerable to these hazards. In a growing city like utilized for the revival of natural drainage network of Malir Karachi, with a current population over 20 million, the need River basin. The beneficiaries of this study may include, but not for additional urban lands cannot be disregarded. Although, limited to, the urban planners, Sindh development authorities the allocation of urban zones with better watershed and flood mitigation and management agencies. management can largely reduce the above mentioned Index Terms— Flood, Geospatial techniques, Natural drainage, problems [4]. Satellite data, Urbanization II. JUSTIFICATION Water always flows through its natural path where it finds a I. INTRODUCTION gradient. If there is any obstruction in its path, it tries to he world is experiencing the largest urban growth in remove it and moves forward. Most of the waterways in T history with more than half of the world’s population Karachi have been obstructed by encroachments of urban living in towns and cities. By 2030 this number will swell to settlements, roads, crop field and other structures [5]. When almost 5 billion, with urban growth concentrated in Africa and water hits a blocked area, it causes damages in terms of lives Asia [1]. Rapid urbanization of mega cities in developing and assets. Malir River basin is one of the examples of these countries has been responsible for not only alterations in the blocked waterways where width of the river at many locations natural phenomena but has posed serious health challenges is less than 10 meter and at one location it is completely due to insufficient water and sanitation infrastructures, blocked by an agriculture field. Revival of natural drainage inappropriate waste treatment and disposal facilities and network would allow flood water to follow its natural path substandard living conditions. Less privileged communities thus minimizing the damages caused by floods and torrential that migrate to big cities are not only victims of several types rainfalls. Sindh Irrigation and Drainage Authority (SIDA) has of communal diseases but are more vulnerable to natural put a considerable effort in identification and revival of natural 77 Journal of Space Technology, Volume V, No.1, July 2015 drainage network in few districts of Sindh [6]. SIDA has relied natural features of an area are disturbed and this situation mostly on field work for this purpose. Although SIAD’s usually causes serious damages to the society. There are some efforts are praiseworthy but the method adopted by SIDA is very generic problems associated with the growing urban quite cumbersome that involved intensive budget. Ground data centers like need for drinking water, sewerage and sanitation, collection is always an expensive and time consuming transportation, disaster management, health facilities, solid technique. On the other hand, the use of geospatial techniques, waste management, industrial waste dumping sites and many as proposed in this paper, are more precise and time and cost others. Urbanization is also responsible for climate change due effective. to anthropogenic activities. Climate change also impacts urban areas due to unusual extreme weather events like tornados, A. Statement of the Problem dust storm and heavy rainfall in a short period of time. In the Malir River basin of Karachi is encroached by crop fields, history of Karachi, a number of floods due to rainfall caused illegal embankment and urban areas and, therefore, flood destruction in the city. Table 1 shows a list of some significant water cannot drain properly causing destruction in the floods in Karachi [11]. The highest intensity rainstorm was neighborhood. These blockages slow down the drainage of recorded in 1977. flood water and cause ponding in the surrounding areas. This Table 1: List of Floods in Karachi situation may adversely affect daily life and health of the Flood Date Rainy Rainfall People inhabitants. S.N. (day-month-year) hours (mm) killed 1 07-08-1953 24 278.1 -- B. Objectives 2 01-07-1977 24 207.0 248 i. To develop landuse/Landcover maps of Karachi for years 3 na-na-2003 48 284.5 --- 2000 and 2015 4 17-08-2006 -- 77.0 13 5 21 to 26-06-2007 -- 110.2 228 ii. To identify landuse/Landcover changes from 2000 to 6 09 to 11-08-2007 -- 191.0 21 2015 7 22-08-2007 -- 80.0 --- iii. To classify major landuse/Landcovers that may cause 8 18-07-2009 4 245.0 20 blockages 9 31-08-2009 -- 147.0 --- iv. To identify and map the blocked water ways 10 13-09-2011 -- 145.0 --- 11 na-na-2013 -- 150.0 50 na = not available III. STUDY AREA Karachi is the largest metropolitan city of Pakistan with more IV. MALIR RIVER SYSTEM than 20 million people and population density of 10,000 people per square kilometer. It is the world’s largest city by Malir River basin has total catchment area of about 1,850 population and 7th largest urban agglomeration [7]. Located on square kilometer around south eastern boundary of Karachi the coast of Arabian Sea, as shown in Figure 1, Karachi is one (Figure 2). Malir River system consists of two major streams, of the oldest city of Pakistan and has great strategic and Mol and Khaddeji, and three tributaries named Konkar, economic importance due to the presence of a harbor. It is the Thaddo and Sukkan. River flows southwards and westwards financial and commercial hub of Pakistan that contributes through Gizri Creek and discharges finally into the Arabian around 25 percent in the Gross Domestic Product (GDP) of Sea. The central part of the river basin is made-up of sediment the country. People from all over Pakistan come here for deposits comprising coarse conglomerate, sand stone, clay- business and other livelihoods. A substantial increase in the stone and limestone, whereas, the lower plain is composed of urban area of Karachi during last 30 years has been observed alluvial deposits. In the lower plain, the river is wider and due to these reasons. The city is growing towards north and shallower and gets braided. The catchment has a rugged west directions. terrain and comprise of rocky waste land covered with sandy soil. Common vegetation in the river basin includes shrub Urbanization is the process of concentrating peoples in a trees and bushes. The lower part of the basin has good grass relatively small area. During the process of urbanization, cover full of orchards and vegetable patches which gradually reduces southwards. Slums are located on both sides of the river with some industrial units. Malir River overflows during the monsoon rainfalls. Storm water stays in the surrounding area for extended period of time due to insufficient drainage which damages the infrastructure and property [5].Disposal of untreated industrial and municipal effluent has also severely contaminated the water of Malir River.