By. Abdul Wahid Hasyim
Recently the temperature is getting increasingly higher especially during the afternoon. Many are of the opinion that Malang is not as cool as it was several years ago. Workers begin dreaming of having air conditioners in their rooms. The average temperature of Malang in 2000 ranges from 260C to 280C (Agriculture Dept, UNIBRAW, 2000). An observation in 2001 at Klojen sub district, the e busiest district, revealed that in the afternoon the temperature ranged from 340C – 380C. A difference of temperature by 3C – 4C was noted, which affected the temperature of Malang city.
Ten years ago the city’s average temperature ranged from 23C – 26C. The air was cool, birds were seen to fly from trees in many areas. The city activities were not as high as they are now. But open spaces gradually disappeared as they were occupied by houses, offices, commercial districts, street facilities, parking spaces and the like. This change of land use results in the degrading of the environment, for example, the increasing temperature of the city.
The increasing temperature adds more burden to the city as it demands more supply of electricity, fuel and clean water which are needed in the cooling process and to prevent dehydration. That means uneconomical uses of energy.
The management of city land use in a research is considered as factors that affect city temperature. This is achieved through two steps (1) Factor Analysis, to obtain information on original variables on a small composition of new factors (2) All regression and Best Subset Regression/BREG). The final outcome will be the variables that determine the change of temperature in Malang on the basis of land use management.
1. Urban climate-general issues
1.1. Historical background
The ancient Indian architectural manual “silpasastra” (translated by Acharya, 1979) laid out rules for the sitting of villages, towns, and fort, based on prevailing wind direction and solar orientation. Vitruvius (75-25 BC) Book I of the “Ten Books on Architecture” (Trans, 1960) also considered city layout in relation to local environmental conditions. Ezra Stiles in the 1750s noted that the air of town were warmer than that of the countryside (meyer, 1991). Charles Caldwell (1798 ) opined that Philadelphia possessed a summer temperature superior by three to four degrees, to that of the country. William Currie (1792) attributed the narrowness an irregular form of house and crowded building habits as causes for New York’s high temperatures in the summer. For the shake of street-level thermal comfort. Palladio recommended that in cold place the street should be “ample and board” while in hot place streets be “narrow with high houses” (Bosselman, et al, 1995). Caldwell (1833:367) suggested “city houses (be made of) thick wall, small windows and spacious apartments surrounded by trees of sufficient elevation to shade them. For the hot, humid city of New Orleans, Caldwell (1836:634) opined narrow streets and overhead balconies would suffice. Luke Howard (1833) is credited to have carried out the first systematic study of inadvertent urban climate modification (Landsberg, 1981). He compared the temperature record of a city weather station (London) with that of a (then) rural station (Kew Gardens) and found that the city station was warmer. The warmth of cities in contrast to their rural surrounding is now called the “urban heat island” UHI, a term probably coined by Gordon Manley in 1958 (Landsberg, 1981)
1.2. Urban Heat Island in Tropical City
As Bridgman, Warner, and Dodson in their book “Urban Biophysical Environments” (1995) state, there is a temperature difference between the city and its surrounding villages. This is caused by (see Figure 1):
a. The shortwave radiation from the sun enters the earth, divided into direct components and diffused components.
b. The fragment of shortwave being reflected back to the atmosphere, known as ALBEDO.
c. Long wave radiation takes off the earth into the atmosphere, depending on the earth’s surface temperature.
d. Long wave radiation from the atmosphere onto the earth’s surface, depending on the atmosphere temperature.
e. The remaining radiation: the excess of incoming energy components and the outgoing energy components.
The shrinking of the green areas due to the badly-planned land use management causes the sun rays and its reflections to bounce back completely to the atmosphere without being absorbed by the now smooth earths’ surface. It is the sun reflection which causes the temperature to get higher as it moves from one smooth surface to the other before it gets reflected back to the atmosphere.
The increasing temperature of Malang City puts more burdens on the city. A good management of land use is necessary in order to depress and lower the temperature, which in turn will lead to comfortable and healthy environment. The objectives of the study are:
1. Identifying the other influential factor of land use,
2. Determining the weight and effect of the city land use on the city’s temperature.
3. Establishing the city’s land use in an effective and efficient manner.
2.1. Research questions
The common phenomena in big cities such as Bandung, Jakarta, and Surabaya should not occur again and again. Big cities in Indonesia typically give top priority to physical developments oriented to economic growth without serious consideration on the environmental balance. News is full with reports of floods, water shortage, increasing temperatures and many others. The study is aimed to answer the following problems:
• How to control the sun reflection so that it can be absorbed by the land surface cover before getting back to the atmosphere?
• How to arrange high temperature areas in land use planning?
• How to improve the quality of environment thorough the land use planning that constitutes the fundamental basis of city ecosystem?
The main challenge and important duty of a planner is to design an efficient and focused environment in cities with a view to achieving a continuous development. Multidisciplinary approach from various scientific perspectives will be of much help in attaining the goal above. In carrying out the study, the writer makes some approaches to the covers of city land surfaces that comprise the foundation of the city’s ecosystem.
2.2. Land covers units and types in Malang
The rapid growth of Malang has manifested in varied physical developments. There is a change in the land use from agriculture to non-agriculture. Malang consists of 5 sub districts, namely, Blimbing, Lowokwaru, Klojen, Sukun, and Kedungkandang, each of which has its own characteristics of physical development. Being the center of the city, Klojen sub district has the most rapid development.
The map of Klojen shows types of land covers that have been predominantly converted into commercial uses, houses, industries, education, and offices. The amount of green open areas is markedly decreasing as more and more of these areas are turned into economic-oriented sites. Land surface covers is the result of the land use function and the development that are planned for the interests of the people in the past, the present and in the future. The diversity of the physical developments on the covers and the accompanying activities will determine the social diversity and environment qualities on the city system. For example, the interconnectedness of city land surface cover and temperature (Henry and Dicks, 1987). Energy, substance and information move laterally in a city system depending on the land use type and activities (see Figure 2).
The first step of Principal Component Factor Analysis using Varimax rotation yields 3 common factors that account for 74.3% The F1/factor 1 (open space/ 30.1%) is dominated by gardens, houses, and education; F2 (distance to the workplace/ 23.3%) is dominated by houses, and offices, while F3 (the availability of facilities/ 20.6%) is dominated by houses.
The second step uses All Regression and BREG. The former indicates that house width has a strong effect on Seq-SS (5.3708), office width (2.0311), and commercial width that has a weak effect (0.0153) on temperature. Afterwards, through the best regression groups 6 variables are obtained with C-p of 6.2, namely, house width, commercial width, industry width, education width, facilities width and offices width that have effects on temperature.
3. Case study
With its complete facilities, Malang attracts urban people. Around 900.000 people living in Malang; its annual population growth is 2%. Klojen is the most popular sub district due to the facilities it offers that cater for human basic needs. The sub district lies on the center of the city, bordered by four others sub districts: Blimbing, Lowokwaru, Kedungkandang, and Sukun.
The urge to meet the human basic needs result in unregulated land use. This manifests in the building of houses near the city center, business space, road network, low-priced public transportation, and other supporting facilities that compound the city’s problems. It is easy to spot a change of protective function. The change of Taman Indrokilo into luxury housing complex is one example; other examples is the building of houses along the bank of Brantas River, the conversion of open spaces into hardened surfaces used for parking. All of these result in environment degradation due to the excessive burden on land supporting capacity, which manifests in the increasing temperature of the city.
The change of land use oftentimes is the result of need for space. Lots of discussions on the uncontrollable rate of this change have been going on everywhere, including in developing countries. Economic development is often the main cause of environmental change. This is worsened by the weakening power of City Plan as a control device, which often gets manipulated by certain parties with their own interests.
Klojen Subdistrict consists of 11 villages/kelurahan, namely Penanggungan, Samaan, Rampal Celaket, Gading Kasri, Oro-oro Dowo, Klojen, Kauman, Bareng, Kidul Dalem, Kasin, and Sukoharjo. Penanggungan, Oro-oro Dowo and Kasin have the largest Green Open Space, namely 11.62 hectares, 10.91 hectares, and 10.98 hectares, while the one with the highest occupied land is Oro-oro Dowo (147.44 hectares), which is understandable due to its largest area (160.70 hectares) and its central location among the other villages. This location allows it to serve as a link between one village and the other (see Figure 1). Taken as a whole, these villages have highly intense activities due to their central locations; what marks them off from each other is the proportion of the activities.
Strategic locations have uncontrolled prices. Businessmen compete in every possible way to obtain them, ignoring the regulations on the city plan and on building. Eager to obtain as much profit as possible, they change the function of houses, drainage system and green open space, turning them into commercial centers, such as shop house, offices, educational centers, and industrial places. The mismanagement of the city layout plan gives birth to informal groups of people, who clutter the space in Klojen and disrupt Malang citizens especially during the rainy season and drought. In the rainy season, Malang, located 800 meters above the sea level, gets flooded because the water cannot gets easily absorbed into the ground and the drainage system is messed up. During the drought, there is shortage of water as the water storage in the ground diminishes; the high temperature makes a stuffy and stifling atmosphere as a result of the lessening green areas and the rapid emergence of concrete buildings.
The temperature of Klojen sub district is very much influenced by land surface covers which are brought about by the change of land use and activities. The Factor Analysis, All Regression and BREG reveal that the uses of housing, office and commercial land dominate the surface covers. The three types of uses share the same characteristics, namely, they are focused on the provision of city facilities that are centered in the hub of the city. Physical developments and activities that are centered on the city will reduce open lands; consequently the parks in CBD areas are diminishing.
The high temperature can be keenly felt in some locations that have intense activities, especially in the center of the city. Of 7 variables tested there are 3 variables which have significant effects on the temperature change, namely, houses, offices, and education.
5. Recommendation for Malang urban heat island
Klojen sub district is mainly characterized by high population and great number of buildings with private gardens. This will rapidly reduce the amount of land and raise the density. For the planning, it is necessary to manage housing land use on the basis of vertical growth for several families who have only one garden.
The above technique will prevent the waste of land, and will promote more green covers for the land surface because the land use function has wider green areas. Eventually, this will create more healthy and comfortable environment for the city dwellers.
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(Had been presented at *Kungliga Tekniska högskolan [KTH] – Royal Institute of Technology, Sweden, November 2002, **Senvar IV- International Seminar Trisakti University, Jakarta, 2003)