The purpose of this research is to apply Remote Sensing and GIS in land use management of Greater Karu Urban Area, Nasarawa State. Specific objectives are to; create land use/cover map of the study area from 1972 to 2012, determine the rate and magnitude of change, determine the suitability of the land for different uses and determine the extent of encroachment into the approved setback areas. Landsat MSS, TM, ETM and Spot-5 satellite imagery of 1972, 1987, 2000 and 2012 were used. A supervised classification approach using ILWIS 3.3 version was also used. Six categories of land use/cover types were generated as follow: built up areas, water bodies, agricultural land, vegetation, rock out crops and bare surfaces. Euclidean distance and weighted overlay from spatial analyst tool of ArcGIS 9.3 software was used for the suitability analysis using Multi-Criteria Decision Analysis and Analytical Hierarchical Process. The guidelines in line with Land Use Act Cap 202 of 1990 and the Nigeria Urban and Regional planning Act of 1990 to monitor and control all developments approved setbacks was adopted. Results from the analysis revealed the Increase in built up area resulted to changes in other land use/cover categories between 1972 and 2012 as follow: natural vegetation has drastically decline from 68.9% to 52.9% between 1972 and 1987. It further decline from 34.3% to 25.4% between 1997 and 2012. Agricultural land witnesses an increase from 8.7% to19.1% between 1972 and 1987. Thereafter, decreases from 25.9% to 15.2% between 1997 and 2012. Bare surfaces witness an increase from 7.8% to 9.1% between 1972 and 1987. Further decrease from 12.2% to 11.6% was observed between 1997 and 2012. Rock outcrops increases from 2.9% to 3.0% between 1972 and 1987. Further increase was experienced from 3.0% to 3.1% between 1997 and 2012 Water bodies covers 10.6% in 1972 and decrease to 6.1% 1987 before increasing to 7.7% in 1997 and subsequent decrease by 5.8% in 2012. The most dramatic increase experienced in built-up area is shown from 1990 to 2012, coinciding with the relocation of the FCT from Lagos to Abuja in 1991. This result to haphazard development and encroachment of built up areas into the approved setback of road network and water bodies are as follow: Highway; 2.5468 Sqkm, local distributors: 1.305 Sqkm, access roads/streets; 1.345 Sqkm rivers, 48Sqkm. It thus recommends the Nasarawa State Government and planners to use the final suitability maps for discussions and decision making in development of the area. At the absent of that, the final suitability map is recommended to guide development in the area.
1.1 BACKGROUND TO THE STUDY
Land is the foundation of all forms of human activity. From it humans obtain the food, shelter and the space to work and relax. Land is amongst man‟s most valuable resources. It is a means of life on which our continued existence and progress depends (Dale, Peter and John, 1988). Land is man‟s most valuable resource. It is the means of life without which he could never have existed and on which his continued and progress depend. Land is a term with many meanings. To the physical geographer it is a landscape produced from natural processes, the product of geological and geomorphologic process. To the economist it is a resource which along with capital and labour is to be exploited in order to achieve economic production and development or conserved to guarantee future biodiversity. To the lawyer land is a volume of space stretching notionally from the centre of the earth to the infinite in the sky, and associated with it are a variety of rights which determine what may be done with it. To many it is simply the space for human activities as reflected in the many different forms of land use.
FAO (1976) defined land as a delineable area of the earth‟s terrestrial surface, involving all attributes of the biosphere immediately above or below this surface, including those of the near-surface climate, the soil, the terrain forms, the surface hydrology (including shallow lakes, rivers, marshes, and swamps) and associated ground water and geo-hydrological reserve, the plant and animal populations, the human settlement pattern and physical results of past and present human activity. Land comprises the physical environment of the earth‟s surface from soils, topography and underlying geology, hydrology, plant and animal population and vegetation, with their influence on potential land use (Harcombe, 2010).
Land is required for various uses in both the urban and rural areas. It is a major factor of production and a vital element in the socio-economic development of any country (Dent and Young, 1981). Studies have emphasized that the quality of land is an important factor for various land uses, thus as nations grow in size and rural areas become urban centers and urban centers become large metropolitan areas, there is always increase in competition and demand of land for different purposes. This requires adequate management to ensure harmonious development and functional efficiency of these uses (Sodeinde, 2002). Human use of land has been proved to alter the structure and functioning of the ecosystem. The most spatially and economically important human use of land globally include cultivation, construction, reserves, protected lands and timber extraction. Recently settlements are becoming large active land use changes especially in the developing regions of the world. This calls for effective land use management (Amos, 1986).
The need for thoughtful and careful stewardship of the land, together with the more intensive use and management of its resources has emerged as a matter of major global concern due to the rapid growth of population that have caused increasing pressure on land, while simultaneously a massive migration of people to cities and towns has led to the uncontrolled growth of urban centers (Dele et al., 1988). Land use management as discussed widely by Mabogunje (1992); Durand-Lasserve (1990) and Kombe (1995) is conceived as processes involving different stakeholders in planning, facilitation and controlling land use and subsequent activities in view of sustainable development.
Land use management entails decision making and the implementation of decisions about land. Land use management involves making fundamental policy decisions about the nature and extent of investment. The scope of land use management involves private and public sectors who develop and make use of land; law which sets out rules and procedures in the management system; agencies which make decisions on how land may be used at various levels of government; plans which inform decisions on how land may be used (Nags and Kudrat, 1998). The content of land use management can be described in terms of three value sets (ecological, social and market values) that must be brought into balance by land planning (Sui, 1992). The analysis of land characteristics in identification of land suitable for development can play an essential part in the planning process. Among the many concerns of urban planners in guiding the spatial arrangement of activities is the optimum utilization of land for the benefit of society (Shuaib, 2005). This involves making choices between available alternatives and as such it requires a procedure for the analysis of available alternatives. Alternatives for development usually start though not necessarily with consideration for buildable land. “i.e. land on which if developments are installed would not have detrimental or adverse effects on the environment”. The process of identifying such land is the assessment of the fitness of tracks of land for development. Land suitability analysis requires integration of several data sets to model land use requirements and the characteristics of the land for the alternatives (Shuaib, 2005).
Almost all African countries have a history of land use management processes dating back to their respective periods of colonial rule. However, formal land use management in Nigeria began in 1863 with the enactment of the Town Improvement Ordinance by the Colonial Government. The ordinance was meant to control development and urban sanitation in Lagos, then the Federal Capital of Nigeria. However, modern land use management could be said to begin in the country in 1946 when the Nigerian Town and Country Ordinance was enacted (Mabogunje, 1992). The general inefficiency associated with majority of the developing countries land policies, the absence of secure tenure, and inadequate land use management capacity have been cited by Bernstein (1994), Hardoy and Satterthwaite (2001) as serious problems precipitating existing land use crises in Nigeria. In recent times, the often-destructive impact of human activity on the land has led to the global need for more careful management of land use and natural resources at sustainable level.
A number of policies that impinge on urban land use management has been articulated and implemented in Nigeria. These include the Land use Act of 1978, Urban Development Policy of 1992, Urban and Regional Planning Act as well as the Housing and Urban Development Policy of 2002. Similarly, land use planning and control measures have been introduced to improve urban land use planning and urban development (Aribigbola, 2008). Despite the existence of these laws and policies, land use management problems still persist in Karu area of Nasarawa State. Consequently, there is the need for a better understanding of the problems and also to articulate how to improve the existing ineffective land use management methods in the area. In evaluation of land use management, suitability plays a fundamental role in regional land-use planning. Its major objective is to evaluate the advantages and disadvantages of development in certain areas, so as to find out places which are most suitable for certain land use development in the future. In the field of suitability assessment for land use management, Geographic Information System, Remote Sensing and numerical modeling techniques have been proved to be efficient tools by recent studies (Ahmed et al., 2000).
GIS is an important tool in land use management. The demands of the different stakeholders is analyzed, visualized and presented to support decision-making. One of the most commonly used methods for land-use decision making is spatial Multi Criteria Decision Analysis (MCDA). This method combines all the spatial factors that are important and results in a map with the best location for a certain type of land-use. Most often with MCDA, the goal is to find the most suitable location for residential, commercial, agricultural and industrial use. In addition, existing Spatial Decision Support Systems (SDSS) which are decision making tools that make use of spatial MCDA often concentrate on a specific type of land-use, for example urban development. When applying land-use suitability on an area, it should contain not only urban development, but also agricultural land-uses. It is against this background that this research is formulated to use remote sensing and GIS that integrates land-use suitability, covering all relevant land-use categories (urban and agriculture) in land use management of Greater Karu Urban Area, Nasarawa State, Nigeria.
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