Urban Expansion Analysis and Land Use Changes in Rangpur City Corporation Area, Bangladesh, Using Remote Sensing (RS) and Geographic Information System (GIS) Techniques

Rangpur City Corporation (RCC) is the main administrative functional area for both of Rangpur City and Rangpur division and experiencing a rapid change in the field of urban sprawl, cultural and physical landscape, and city growth. These agents of Land use/Land cover (LULC) varieties are responsible for multi-dimensional problems such as traffic congestion, waterlogging, and solid waste disposal, loss of agricultural land. In this regard, this study fulfills LULC changes by using Geographical Information Systems (GIS) and Remote Sensing (RS) as well as field survey was conducted for the measurement of change detection. The sources of data were Landsat 7 ETM and Landsat 8 OLI/TIRS of both C1 levels 1. Then after correcting the data geometrically and radiometrically change detection and combined classification (supervised & unsupervised) were used. The study finds considerable changes for LULC. The findings show that built-up area, water source, agricultural land, bare soil in a change of percentage is 17.23, 2.58, -9.94, -10.19 respectively between 2009 and 2019. Among these changes bare soil is changed to a great extent which indicates the expansion of urban areas is utilizing the land to a proper extent respectively. But these changes also measure the reduction of agricultural land in the context of haphazard urbanization which is risking the term planned urbanization and food security for present and future aspects .


Introduction
Bangladesh is a developing country with the rapid growth of the population. Rangpur is also a fast-growing city in the field of urbanization with having a population of 2.96 million. Because of the fast population growth LULC also changing the emphasizes function of urbanization. The satellite image is carrying many more essentialities for the proper and quick planning of LULC. For this reason, the field surveying method is considered time-consuming and costly which is replacing by RS techniques. Facial (2000) asserted the nature of land-use changes, location of agricultural land losses and for the reason of urbanization, the supply of higher quality of agricultural activities is reducing. Remote sensing satellites are playing a vital role in mapping land use and land cover changes and infrastructural development for several past recent years (Arimoro et al., 2003). But in RCC no such application is implemented for the detection and assessment of these types of operational work (Dewan and Yamaguchi, 2009). Land-use changes arising from agriculture, pasturing, urbanization, bare soil, and deforestation are some of the responsible factors to land cover changes in RCC. These changes in LULC reflect on the growth of population, consumption of land and the local climate. Expansion of RCC has resulted not only in the depletion of natural resources but deterioration of the environment. Agriculturally productive land, forest land, bare land has been transformed into different commercial, residential and other uses. The LULC is the result of the social, economic, environmental phenomenon and their perspective of utilization. The collection of remotely sensed data contributes the synoptic assessments of the function of earth-system, patterning, and change at local, regional and global scales over time (Rajeshwari, 2006). However, the objective of this study is to attempt mapping out the LULC status of RPCC between 2009-2019 with a view of detecting the land consumption rate and the changes that have taken place using RS and GIS techniques; serving as a precursor to the further study on urban induced variations or change in weather pattern of the city. The changes in rapid land use are the cause of the growing population, which is reducing another area of interest like natural vegetation (Nicolson, 1987). The urban centers are increasing in population, but a twofold conversion is undergone for the pre-urban areas; arable and non-arable land both are providing an increasing number of establishments such as commercial, industrial and residential (Heimlich and Anderson, 2001). Kalnay and Cai (2003) assessed that the urban area and its surroundings can be altered by the local climate which is the cause of urban expansion. Instead of using traditional approaches satellite remote sensing is essentially monitoring the change of land use with the facilities of high resolution, which is associated with lower cost (Belal and Moghanm, 2011). Socio-economic factors are influencing human activities for built-up and non-built-up changes even having physical barriers (Long et al. 2007). .Another study shows LULC and its alluvial with risks for soil erosion in the Khlong Kui in 1991, 2005 and 2014 by using GIS techniques and monitored increasing in evergreen forest, rice field, urban areas with decreasing wetlands and deciduous forest (Chaikaew, 2019). In addition the matter of accomplishing GIS data with other data models could have possible solutions. Sing et. al (2018) has shown the changes of LULC for 30 years in the Dhanbad district, Jharkhand, India, which found the possible reasons to reduce dense forest, open scrub, agricultural fallow, river, body of water and mining in 42.63, 60.45, 21.47, 28.80, 50.37 and 19.85% respectively, which could be the harvest of forests for fuel, shelter and agriculture, construction of residential houses on fallow lands, urbanization and sand removal for construction material.

Data and Methods
This study utilizes data for the measurement of LULC changes. Remotely sensed data Landsat 8 and Landsat 7 of both C1 Level 1 were used for the LULC change detection in between the year of 2019 and 2009 (a ten-year time span). Spatial Characteristics of these data having the below approaches ( See Table 1). In addition, these data were collected from earthexplorer.usgs.gov whist path and row were 138 and 042.   Table 3). The distribution of LULC changes rapidly in the sector of the built-up area which is nearly two times higher than in 2019 also the noticeable decreases land is agricultural which is the indication of 10% loss. But it decreased to a great extent of bare soil from 3439 to 145 hectares( Table 2). These changes are defining the urban expansion where agricultural and bare soil is used to urbanized the areas. As city population is increasing the city has been expanded extensively to accommodate the increasing population compared to its early stage the cities spatial expansion is the modification of several constrained physical factors. However the loss of natural resources is the cause of the development.
The LULC pattern changes spatially from 2009 to 2019 (Figures 3 & 4). Earlier in 2009 built-up area was congested at the center where other parts also carried it haphazardly in the northwest, north-south direction. In 2019 the urban area expanded largely northward, westward and southward where the direction of eastward expansion was very low compared with them respectively. The LULC map interpretation in between 2009 and 2019 shows that RCC is expanding in all of the following directions northwest, south-west and southern parts by filling up low lying areas. The major perspective of expanding these areas is the increasing of residential, public and privet structural development. The maximum loss of agricultural land and bare soil provides information about the pressure of urban expansion of it. The study area urbanization is rapidly growing and if it continues it will decrease land cover areas 35.06 percent within the next 20 years which will lead diversified and uneven expansion like present times in 2019. The contributing factors of urban sprawl are increased amount of population, poor land-use policy, low land, unplanned housing and expansion of industrial areas, poverty, absence of multiuse of urban areas which are creating the slums and squatters with decreasing food safety due to the loss of agricultural land. This diversification is negatively affecting both the natural environment and human health as well as for the development of near future perspectives.   Figure 3, 4 makes an evidence of congestion of the city and haphazardly increasing number of built-up area which includes residential, commercial and services, industrial, transportation, roads, mixed urban, and other urban areas within the percentage of 17.53(5670 ha) wherewith the same increasing trend water source also got improvement. The responsible factors for this urban expansion are mainly population growth and haphazard development of residential, industrial as well as public infrastructure. For this reason, the temperature is increasing 20 percent annually where agricultural activities are responsible only for 3 percent (Hasan and Islam, 2015). And the improvement and increased amount of water bodies prove that permanent water sources like river, permanent open water, lakes, ponds, and reservoirs are extended whereas temporal or seasonal water sources like permanent and seasonal wetlands, marshy land, swamps have been decreased. 3208 hectares of agricultural land are negatively increased due to the positive extent of built-up area of 5670 hectares where agricultural land indicates the agents of both cultivated and planted trees like crop fields, fallow lands, vegetable lands, roadside planted trees, mixed forest lands, homestead forest. The bare soil is providing space both for the built-up area and permanent water source and for this reason it is increased negatively of 10.19 percent of 145 hectares of the 10 years span of time. In very recent period bare soil indicates exposed soils, sand fill, landfill sites, and areas of active excavation. This reduction of agricultural land and bare soil is leading the fact of urbanization rapidly.

LULC Change Detection and Analysis
LULC change detection represents the result of Table 3 figure 6) agricultural land carries several responsibilities in Bangladesh agricultural production and 84% of rural people directly or indirectly engaged with agriculture ( Mirza 2015). But it is decreased in RPCC of about 10 percent which is an alarming rate for food safety.

Figure 6: GDP from the sector of Agriculture and Forestry Source: Bangladesh Bureau of Statistics (BBS)
Loss of agricultural land is the reason for the gradual loss of GDP as it is the field of second-largest source of GDP after manufacturing ( 20.17% GDP). As water source is increased by 2.58 percent so that agricultural activity could be benefited from it and also fisheries sector is improving for the reason of available water source (field survey).

Conclusion
This study is an indication of the potential use of GIS and RS techniques for obtaining the objective specific measurement of RCC. The study finds uneven and haphazard increasing of 5670 hectors of land in all directions especially the northern, northwestern, southern and southwestern parts which include settlement, industrial and commercial infrastructure are rapid which is the indication of loss of agricultural land, bare soil with increasing of temperature. In addition the responsible factors for increased urbanization space of bare soil which ensuring temperature rise which is more than 17 percent of agricultural land. But this study also finds that the source of water is increased by 832 hectors of land so this could be the indication of future development of agricultural land as well as urbanization. In addition, other primary economic activities like fishing could be improved. And proper management of urban expansion must be implemented for reduction of agricultural land loss; the separate zonation for the expansion of urban infrastructure could also be conducted with multi structural buildings. Furthermore loss of agricultural land also could be covered through multi structural use of existing agricultural and bare land using the available water source. The extended recommendation proposes a future course of action for the field study to identify the category of several spheres of LULC changes. Agriculture & Forestry GDP