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Urban Spatial Growth Analysis of Khulna City

Md. Rejaur Rahman
Coordinator & Urban Planner
Asian Disaster Preparedness Center (ADPC)
House 531/4, Lane 11, Baridhara DOHS
Dhaka - 1206, Bangladesh
Cell: +8801717 087 089
E-mail: reja.83@gmail.com

Before 60s or 70s, the process of spatial growth of Khulna city was not so complicated because the industries solely, have shaped the spatial development. Now Khulna city has passed its glorious era but till now urban growth and land use change is taking place in a dynamic ways. This study dealt with the major dynamics of urban spatial growth i.e. land elevation, road accessibility, land price, location of important structures etc which were identified as the prevailing factors for urban growth in the City, to have an idea about the future spatial growth of the city. The study tried to find the answer of the question - what will be the shape of this city after 20 or 30 year from right now? This study tried to introduce a model, built by using ArcGIS Model Builder tool which is applicable for the Khulna city in any time if only the spatial factors are used. This model can be a useful tool for decision making for the concerned authorities about the expansion strategy and development control in a sustainable way.

Urbanization and urban spatial growth are the result of combination of natural increase of the urban population and net immigration to urban areas (Firoz, 2004: 27-32). Urbanization can be regarded from demographic point of view, in terms of the proportion of country’s population living in towns and cities. It is observed that urbanization is very closely linked with industrialization, commercialization or the overall economic growth and development; and the process of urbanization exhibits a pattern in which the rate rises steeply as the early stages of industrialization are reached, and tapers off gradually when the proportion urban beings to reach a saturation point. Finally as most of the populations become urbanized, urbanization falls to keep peace with economic development, which is a continuous process.

The urbanization processes in Khulna started in 1836 (Murtaza, 2007). After that the process is going on. After the liberation war of Bangladesh the urbanization rate was reached its higher level high (KDA, 2000: 13) but in 2001 the urban population growth rate was 1.25 (Jahan and Rouf, 2007) which was very low than last four decades. The main cause is the economic decline of the city.

It was not known whether all these different patterns together may lead to an overall pattern - spatial, functional and demographic. The horizontal dimensions of space are certainly a basic determinant of population distribution (Batty et al, 2003: 36). Everyone wants to live pretty close to the city centre. But practically the people are did not do that. The living place are depends on their social, economic and many others factors. So, the people are trying to least distance in where there cost effective and suitable area base on working place distance, house rent, land price, transport accessibility, utility services etc (Masum, 2001: 40-42)

The study tried to identify the influential factors of urban growth. There are mainly two types of urban growth influencing factors. Those are spatial and non-spatial factors.

Table 1: Category of urban growth factors
Spatial Factors Non-spatial Factors
  • Land Price Surface
  • Road Accessibility
  • Land Elevation
  • Private Housing Scheme
  • Demographic factors
  • Social factors
  • Economic factors
  • Political factors

Source: (Hiraskar, 1989: 27-35; Akter, 1996: 19; Sadia, 2000: 35-38)

To identify urban growth influencing factors the study has conducted a pilot survey. Total respondent of pilot survey was 48. The higher percentage represents the higher priority of the influencing factors. Both non-spatial and spatial factors are picked up (table 2).

For GIS analysis, spatial factors have been separated. Others influencing factors such as Migration, Social security, Community services facilities, Economic activities were excluded as the study dealt with only the spatial factors. The short listed spatial factors are:

Influencing Factors Level of influence according to respondent (%)
Land Price 17
Migration 24
Road accessibility 20
Height of Land 18
Social security2
Private Housing 10
Community services facilities 1
Economic activities 8
Source: Field Survey, 2007

For GIS analysis, spatial factors have been separated. Others influencing factors such as Migration, Social security, Community services facilities, Economic activities were excluded as the study dealt with only the spatial factors. The short listed spatial factors are:

. Land Price . Road accessibility
. Land Elevation . Private Housing

Weightage of spatial factors by Analytical Hierarchical Process

For spatial analysis by GIS Model Builder needed the weightage of spatial influencing factors. The Weightage are calculated by Analytic Hierarchy Process (AHP). Weightage has been done by using AHP which considered not only the popular responses but also the relationship and affection between themselves (Alessio, 2004: 9-16; Vishv, 2003: 5).

First, we need to build a raw matrix from the table 3 and survey updates, where only variables considering the second option are selected. From the frequencies averaged value the considerations below are calculated.

If, Variable frequency average > = 0.5, particular raw position matrix value will be 2
Variable frequency average < 0.5, particular raw position matrix value will be 0

Coding the influencing factors

For analysis using AHP needed priority base multiple answers. In this study, 4 is high priority, 3 is medium priority, 2 is normal priority and 1 is low priority. Those priority base data were inputted in MS Excel sheet. Then compare each data with the other to make the raw matrix.

Table 3: Sample Priority base raw data

Table 4: Raw Matrix

The table 4 shows the average value of the 142 samples. If we name the column as i and the row as j and r is the cell value of matrix rij then there will be an equation to be followed to get the judgment matrix.

rij = [(Ki – Kj) / (Kmax - Kmin)] × (bm - 1) + 1 --------------------------(i) when, Ki>=Kj

rij = 1 / {[(Ki- Kj) / (Kmax - Kmin)] × (bm - 1) + 1} ------------------------(ii) when Ki<=Kj bm = Kmax + Kmin

Note: “i” and “j” of rij are the correspondent to the “i” and “j” from Ki and Kj. “i” and “j” respectively represent the coding of row and volume in the judgment matrix in the table 4 Ki and Kj mean the cumulative value of every row of table 4 In this example, Kmax is 7 and Kmin is 1 from the table 4. So we can plot the table 5 from the table 4 as the judgment matrix of the field survey. After summarizing the information, we have got the following 4 by 4 array judgment matrix.

Table 5: Judgment Matrix

This judgment matrix shows the relation in between two pair of criteria. For example, the relation in between Land price and Land price is simply 1 as their values are equal. However, the relation in between Land price and land elevation is 3.33. In the same way, the relation could be found in between other criteria.

Normalized Matrix
To understand the judgment matrix, there need to normalize of the value. This matrix is the final output of the AHP. In this matrix each row represents the influence level of the influencing factors out of 1. [Average values are acceptable]

If we multiply the total value of each criterion, then we will get the total weight of the influencing factors of urban spatial growth of Khulna city, which is equal to 1. So, we can draw the table 6 from this normalized value.

Final Weightage of spatial factors (Using AHP)
Using the AHP process, the spatial factors has given a weightage which tells us about the level of influence of individual factors over the urban growth process. It was seen from the table 6 that the factor rood accessibility have the higher and private housing scheme have the lower level of influence.

Table 6: Level of influence of urban spatial growth
Spatial Factors Level of Influence According AHP (%)
Private Housing Scheme 13
Land Price 19
Land Elevation 31
Road Accessibility 37

Land Price
Land price is an important influencing spatial factor to analyze the growth factor. Land price signifies how housing structures can be easily produced and, thus, should be supplied elastically to the market. Land price of a property is tightly linked with the land, location and the amenities which are associated with the property. Land refers not only to the square footage of the property, but also to intangible attributes (such as the length of the commute to work, quality as a production factor etc.). Location is also an important factor. Generally the price of land near the metropolitan areas is higher than the rural one.

he amenities refer to the different services (e.g. water supply system, gas, electricity etc.), shopping facilities, transportation & communication facilities, educational facilities etc. The land price in the metropolitan areas of Khulna is increasing day by day. Available land is scarce compare to the increasing population rate. So, the primary reason for the increasing of land price is the increased demand. If the supply of land, skilled building workers, materials and so on were perfectly elastic, higher demand would not increase prices. But supply is never perfectly elastic. Land price of an area is also dependent on the local property taxes, operating costs, interest on capital invested in present and future, depreciation allowances for these improvements etc. Demand is exceed too much when people get a suitable land with optimum resources in a minimum price. So, land price is an important factor to evaluate the growth pattern of an area. Figure 1 represents the land price surface. White color represent high price and black color represent lower land price. White and nearly white surface are more potential area for future urban spatial growth.

Road Accessibility
Road accessibility is another important influencing spatial factor to analyze the growth factor. Accessibility is highly linked with the transportation network. Transportation is essentially a service which enables people, firms, and various other entities to carry on activities at sites selected for these purposes in separated locations. Concentrations of people, firms, and other human institutions can be located in an area if the condition of accessibility of that area is excellent. Some supporting activities are needed for any kind of large activity (e.g. industrial, commercial activities etc.) and these human activities can be assured by the higher degree of accessibility. A better design of circulation systems can maximized accessibility for essential movements between linked activities, giving due consideration to safety, comfort, amenity as well as cost. For the further development of an area accessibility is needed to be assured first. So, road accessibility to the potential growth area needed to explore first to see the further growth pattern or development in the Khulna city.

Fig 2: Road Accessibility

Figure 2 represents the road accessibility. White color represents high accessibility and black color represents lower accessibility. White and nearly white surface are more potential area for future urban spatial growth. Fig 2: Road Accessibility

Land Elevation
The spatial growth of Khulna city is explained by its topography. There existing natural levee on either side of the Bhairab-Rupsha River. Height of the levee varies from 7 to 14 feet above MSL and offer excellent opportunities for human settlement development. This levee extends about 0.5 km to 4 km inside from the river on both side. After the construction of Khulna-Jessore road and development of economic activities, the city started to take shape along Khulna-Jessore corridor.

Next to levee follows flood plain, about 4kms inside (western side) from the river, following the river alignment. The height of the plains, on average, is about 4ft. to 5ft. above MSL Beyond the flood plains. Land elevation is an important factor to see the growth pattern in an area. The low land can not stimulate the growth of an area. The water logged area is not suitable for the housing structures. Again the flood plain land stimulates the growth very quickly. Figure 3 represents the land elevation of Khulna city. More suitable elevation for future urban expansion is not less than 5 ft, because the areas having elevation less than 5 ft will be water logged.

Private Housing Developments
Khulna city is strategically located in an important hub so far its development potentialities are concerned. The Khulna Bypass that is under construction has become the main influencing factor of residential development in this area. Khulna University is built up on agricultural land with an area of more than 101 acre. This infrastructure has patronized substantial residential development around the same causing massive land use change.

Fig 4: Private Housing Development and potential zones of future development

However, the main characteristics of the private housing projects of Khulna are as follows: Housing demand is sharply increasing
The market is highly localized
The business is durable but not area specific within the local jurisdiction
Non orderly growth of private housing projects due to the lack of legal bindings
Surrounding area of the private housing is highly potential for future urban expansion of Khulna city (figure 4).

Flow Diagram of Model Builder
All the spatial factors were put down in the model building process to obtain the most potential zones for future development. Slope analysis, gradient analysis and Euclidean Distance analysis were done to reclassify them (figure 5 and 6).

Euclidean Distance and Slope Operation
The Euclidean distance functions describe each cell's relationship to a source or a set of sources. Euclidean used to indentify nearest distance of any feature. For road feature in the analysis used Euclidean distance for identify nearest distance from the roads. Slope identifies the steepest downhill slope for a location on a surface. Slope is calculated for each triangle in TINs and for each cell in rasters. For a TIN, this is the maximum rate of change in elevation across each triangle. For rasters, it is the maximum rate of change in elevation over each cell and its eight neighbors.

Fig 5: Euclidean Distance and Slope Operation in Model builder interface

Reclassify Operation in Model Builder
The reclassification functions reclassify or change cell values to alternative values using a variety of methods. The functions are designed to allow you to easily change many values on an input raster to desired, specified, or alternative values. Reclassify tools used in this analysis for matching the suitability analysis.

Fig 6: Reclassify Operation in Model Builder

Final Output Model
This model can be used at any time for Khulna City to predict the potential areas for future urban growth if these four spatial influencing factors are used (Fig 7).

Fig 7: Spatial factors and weighted overlay map in the model builder

Total model building process was explored in figure 8.

Fig 8: Growth Model in GIS Model Builder

Potential Areas for Future Urban Growth
The figure shows the final potential areas where white and nearly white surface is more potential areas for future urban spatial growth of Khulna city. It is clearly seen that the city will take major shape in the western and north-western side.

Fig 9: Potential Areas for future urban growth of Khulna City

Metropolitan cities of Bangladesh are expanding fast. But until now there have low level urban spatial growth control and management. As a result the spatial growths of cities are uncontrolled and haphazard. It is observed that the city is expanding fast towards the fringe areas, getting the backup strength from the activities in the city periphery. Khulna-jessore by-pass and Khulna University areas are the main attraction point for housing development in the western side of Khulna city. In recent Khulna city Corporation has agreed to extent its boundary. This will leave an impact in further urban growth. Business activities are flourishing in the north and north western part and Rupsha bridge connects the eastern part of Khulna city experiencing frequent urban growth. Zoning and subdivision regulation are most frequently used to prevent or control haphazard growth and sprawl, but it is so difficult to maintain properly because of high urbanization rate, political factors, lack of authorized institutions involvement and rural urban migration is the major cause of population growth which results the haphazard growth and development. There is urgent need to formulate a comprehensive plan for controlled those uneven and unbalanced growth. Otherwise the future management of the city and expansion of the utility service network must be critical.

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