LAND CAPABILITY INDEX MAPPING OF ENUGU AREA AND ENVIRONS, SOUTH EASTERN NIGERIA

 

 ABSTRACT

 

It has been projected that the population of Enugu area will grow at approximately 300%. This information is further strengthened by the projected, 237,298, 2006 population figure of Enugu area. By the year 2010, this implies that there is the expectation of over population of the area in future. Problems of housing, unemployment, waste disposals and the general lowering of standard of living are always associated with over population. It has therefore become necessary to map out areas of residential industrial and waste disposal land use for future utilization.

Land capability index mapping using geographic International system (GIS) is one of the appropriate tools for solving these impending problems. Land capability index mapping of Enugu area and environs has been undertaken using Arc View 3.2a. academic, Excel statistical software and auto card software   of GIS. A total of 12 Land use determinants have been selected as the thematic data layers, and the basic factors influencing the choice of waste, residential and industrial land use. These theme which are in map forms are slope, water table, surface and subsurface water conditions, elevation, geology, soil, drainage and geostructural  stability (fault, erosion, land slide and flooding). These maps have been scanned, georeferenced digitized and polygonized using authocard drawing capabilities to convert them to vector formats and later exported to arc view software environment for analysis. The thematic layers were weighted using the criteria obtained from field work, laboratory and literature surveys. The thematic layers were subjected to overlay using the arc view software overlay model builder. The operation yields layers showing areas of preferred waste disposal, residential and industrial land use options in a map form. Three different maps of the land use options were produced. Areas of varying suit abilities were isolated; 3 for waste, 3 for residence and 3 for industry. They represent suitable, low suitability and unsuitable areas respectively. The three land use maps were superimposed to obtain a single one appropriate for purposes of urban and environmental planning.

CHAPTER ONE

 

        1.1       INTRODUCTION

Land capability index mapping is the aspect of land use planning which ensures the maximum and safe utilization of land. Land use planning is a process which involves the determination of the suitability of a particular piece of land for a particular use. The purpose of land use planning is to make the best, most sensible, practical, safe and efficient use of each parcel of land. (Dutra and  Hober 1998).

Land capability is the interpretative groupings of land units with similar potentials, limitations or hazards, (Fisher and David 1990). It is important to know the limitations of the land and the uses it is capable of supporting, how susceptible a soil is to such factors as erosion and contamination influences, and what land use it is suitable for. The location of land is a vital factor in deciding its uses. Pearce and Turner (1990) observed that irresponsible development has resulted in severe environmental damage and declining quality of life for many people. Geological problems arise due to hazards from ground displacement, earthquake , landslide and soil which expand on wetting. Dimitri and Krynine (2003), observed that the development of any land area both for industrial, residential and waste disposals requires detailed geological and engineering studies so as to ascertain   the capability of the land for the purpose. For example, septic tanks will not be permitted in land slide areas because they will aggravate sliding problems by introducing water into the ground (Davis and Rogers 1975) .

Until the population stabilizes, growth pressure will force man into relatively underdeveloped environment, such invasion involves tampering with the landscape and disturbing the habitats of the flora and fauna. The growing population will be introducing problems of water supply, waste disposal,

water / air  pollution  and  housing. Proper  planning for development and land                      allocation for particular uses are two of the most critical problems facing modern urban centers. Land use planning constitutes an instrument for such planning and allocation of resources. The process is accomplished through the use of a variety of factors. These factors can be divided into four categories; (Chapin 1965): physical (geology and topography) economic, social and political factors. Geologic factors include hydrology, hydrogeology, and geostructural stability, while topography includes slope and elevation. Economic and social factors include problems of land ownership. Land capability index mapping is the basic tool for planning and allocation of resources. In the third

world countries, development is impeded by two common factors – environmental hazards and   increased cost of development. Enugu and its environs inherit these two problems. The city originated in a coal miners camp in 1915, and gradually developed into an administrative capital with an area of over 200km². This development went without any consideration for   land use processes. The main economic activities in the area include commerce, large and small scale manufacturing, transportation and agriculture. The study is necessitated by the increasing report of degradation of the environment, loss of lives and property as a result of structural failures, odour problems and obnoxious gas emissions. The result of this study is expected to provide information towards the development of a sustainable use of land in Enugu area and environs with the hope of minimizing natural hazards and making life more meaningful.

 

1.1       LANDUSE DETERMINANTS

According to Arthur and Irwin (1982), the land use determinants include topography, climate, geology, soils, drainage, hydrology and hydrogeology. Others are population and economics, government interest and zoning. These factors are described below:

Topography: This includes slope, elevation and relief.

Climate: The elements of climate are rainfall, temperature, wind and air quality.

Geology: These include rocks and structures, aquifers, landslide, faults and seismic hazards.

Soils: The parameters of soil include soil depth, water holding capacity, permeability, shrink and swell behaviour (expansive soils) and septic tank suitability.

Drainage: Drainage involves flooding, erosion and sedimentation.

 

Hydrology: This aspect involves existing surface water supply, existing sewage disposal, and its effect on water supplies and stream flow.

Hydrogeology: This involves groundwater potential, water table, subsidence due to ground water withdrawal, and water quality.

Land Use: The components of land use are for residential, commercial, agricultural, recreational and other uses.

Population and Economics: Consideration under population factor includes population size, characteristics, projections, and housing, while the economic aspects include economic gains.

Government Interest: These are classified under government agencies, local government, state, country and city. Government allocates land for any purpose.

Zoning: Land areas are zoned based on basic needs. It should be noted that the environment at any one time reflects the impact of these land use determinants. As the original environment is altered, it may lead to the modification of the original determinants. It should also be remembered that the determinants themselves change with changing values and technology (Arthur and Irwin, 1982).

Economic determinant emphasizes why present land use patterns are as we find them. Theories emphasize that location decision are based on optimal economic returns, e.g. a factory is sited based on their needs. Again social determinants are concerned with social values and behaviour. Social scientists advance reasons for change in population location and values. Political determinants express public interest.

Political decisions will determine how the physical environment is to be altered. Of importance in the physical environment is the geologic environment and how it conditions and responds to human activities. From the land use planning point of view, there are two basic ways of categorizing the geologic environment. These are considered as hazards as well as resources. Soil may be a resources or a hazard. According to Smith and Krisjanason 1989 some soils shrink and swell, while others slide or creep down hill causing various degrees of damage. Landslide is often a resource that can be converted into a park or left as an open space. Mountains and beaches are attractive for recreational purposes.

 

1.2      GEOGRAPHIC INFORMATION SYSTEM(GIS)

With the growing constraints and growing number of factors to be  considered in industrial, waste and residential land use selection today, there is an urgent need to adopt modern technology like Geographic Information Systems (GIS) for the analysis and suggestion of best locations (Verbyla and Chang 1997). Presently, the world is experiencing social, scientific and educational revolutions that are technologically driven. GIS is a central component in the world’s environmental information culture (Agrawal, 2000). The application of GIS has been widely acclaimed to facilitate efficient decision making and planning. GIS consists of a set of computerized tools and procedures that can be used to effectively store, retrieve, overlay, correlate, manipulate, analyze, query, display (both graphically and numerically)  and disseminate land related information (Kang 2002). Today developed and developing countries are applying GIS technology to upgrade their earth resource information system and in some cases to obtain for the first time information on some aspects of their environment. The need for earth resources information and mapping in the developing world particularly Nigeria calls for attention. This will offer valuable source of information that can be used for the development of agriculture, land  resources, water  resources and  ecosystem.

 

GIS is effectively used in the selection of the proper area for residential, industrial and waste disposal site locations. In the process spatial data is stored as different thematic layers and manipulated to derive new usable information using the existing ones in GIS. (Verbyla and Chang 1997).

 

1.4 LOCATION, EXTENT AND ACCESSIBILITY

The study area is located between the Latitudes 6⁰ 16 N to 6⁰ 31N and between Longitudes 7⁰ 20E to 7⁰ 41E. It covers an area of about 200 Sqkm. The area is accessible from Aba, Onitsha, Makurdi and Abakaliki. It is also accessible by air and rail. The railway extends from Port Harcourt to Northern Nigeria via Enugu. The topographic map of the study area is represented in Fig. 1a, while the map showing the road network is shown in (Fig 1b).

 

 

 

 

   

 

 

 

 

 

 

 

 

Fig. 1b: Road Network Map of Enugu and Environs 

      Source: Topographic Map Sheet FSN 72, Enugu Area 1:250,000

 

 

1.5 JUSTIFICATION

Enugu originated as coal miner’s camp in 1915 and gradually developed into an administrative capital. Over the years, since it assumed the administrative seat of Eastern Nigeria, Enugu has grown both in population and economic activities. It has been estimated that by the year 2010, the population would be about 12279000 at 4% growth rate or 16718960 at 5% growth rate. There is thus the need to plan for waste disposal, build industries and erect more residential buildings. Also over the years, the city has grown industrially from a coal mining activity to other manufacturing outfits e.g. Beer Brewing, soft drink bottling, pharmaceuticals, food processing and petroleum related industrial activities. These industries need to be located on safe geotechnically sound terrain, with good road network. Such industries should not constitute hazards to the people. The need for residential accommodation has been and continues to be of high concern. Current overcrowding conditions are severe, and future requirements for new dwelling units would soon be a serious problem. There is therefore the need to map out areas that are both technically, and geotechnically safe and economically rewarding. The result of this is expected to provide information towards the development of sustainable use of the land for Enugu area and its environs as a means of minimizing natural hazards and making life more meaningful. This work should therefore provide a map showing suitable areas for industrial, residential and waste disposal site locations.

 

1.6 AIM AND OBJECTIVES

The aim of this study is to minimize the occurrence of environmental hazards and hence raise the quality of life of the greater number of Enugu residents in the most cost effective manner possible. To achieve this, field study, literature survey, and laboratory investigations were undertaken using the GIS facilities as analytic tools.

 

The objectives of the study are as follow:

1. To carry out an environmental base line survey of Enugu area as the basis for land use/suitability for various uses.
2. To locate areas that are relatively more suitable for residential, industrial and waste disposal land use options.
3. To compare the land capability against the existing land use with the intention of identifying the problems arising from any non

compatibility.

 

1.7 SCOPE

The scope involves a desktop compilation of base line data in relation to land use planning. Considering and examining the appropriate environmental factors of land use determinants would help to produce or develop land capability index map for the area.

 

LAND CAPABILITY INDEX MAPPING OF ENUGU AREA AND ENVIRONS, SOUTH EASTERN NIGERIA

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