Urban Morphology and Thermal Comfort in the Cities

Romulo Ribeiro and Frederico de HolandaUniversidade de Brasılia, Brazil

rjcribeiro@uol.com.br.

1. Introduction

In the last fifty years cities have grown very fast. In the whole world there was practicallyan inversion between the number of agricultural and urban inhabitants. According tothe last Brazilian demographic census (2000) 81,25% of population lived in urban centers(IBGE, 2001). With such a growth and with little or no planning at all the urban situationin Brazil has become critical, generating several kinds of urban tensions as well an increasein costs of maintenance. Over investment is needed in order to cope with such problems.

Naturally relationships between people and the urban realm intensifies. Featherstone(1996) comments on the transformation of human behavior in relation to spatial trans-formations, and the change of space configuration related to the new structure of society.For example, in 19th Century Paris, people appreciated urban space, using it intensely -as flaneurs. The same holds for Brazilian cities of the time.

The flanuer developed an aesthetic sensibility including involvement and control, care-ful register of what was seen and “random harvest” of streets impressions (Featherstone,1996). With time, the city became progressively a source of tensions. Lack of job oppor-tunity for rural migrants, low qualification of labors force, precarious shelters, are in theorigin of such tensions. Strong schisms between rich and poor cause a state of quasi-civilwar, as the press often reports in Brazilian cities. The city transforms itself in a assem-blage of gated communities which are simultaneously the result and the origin of growingtensions, for the decay of public space that comes together with it. Public space becomesand “automobile desert”. The new flaneur enjoy the new temples of consumption (or theinside space of closed condominiums) indoorwise. No interaction takes place as before butonly the reception of the huge amount of (poor) information offered by the environment.

Lower income strata, the majority from rural origins, appropriate peripheral urbanspace, molding it according to their own needs, often independently of legal regulations.

In Brazilian cities areas occupied by lower income population lack green areas (squares,parks, trees, shrubs), organization, infrastructure and urban facilities. Environment con-ditions are also precarious as far as wind circulation, natural shade, urban hot spots, rainwater drainage (causing severe floods and collapse of parts of hills with poor housing onthem) etc.

Studies have pointed out how difficult it is for poor people to circulate in public spacesin Brasilia (Holanda, 2002). Space is structure basically for vehicular circulation, sidewalksare often inexistent. No trees, benches and other facilities are provided to amelioratenatural conditions imposed by climate, quite uncomfortable in the hottest periods of theyear. Moreover, public transportation if poor; few lines circulate on weekends and themetro system stops completely.

Strong demand of land for housing are related to very few of free areas for leisure withthe exception of a few soccer fields. Other areas become huge deposits for domestic waste,

356 R. Ribeiro and F. de Holanda

Figure 162: Localization of AR XVIII - North Lake and their subdivisions, in the DistritoFederal (CODEPLAN, 1997; IBGE, 2002).

without proper treatment and causing severe health problems.Sociospatial segregation has been analysed by many authors, also as a phenomenon re-

lated to urban configuration (Sposati, 2000, Genovez, 2002, Koga, 2003 and many others).Brazilian urban centers separate clearly socioeconomic classes: higher income classes arein areas with greater availability of infrastructure and services and lower income classesin areas lacking almost the most basic urban services. The first tend to located in thecenter or near to it, the latter in peripheral areas. Governmental action often ignores suchunbalanced situation. (Cintra, 1988).

In the Federal District (henceforth FD, wherein Brasilia locates) demands for hous-ing are very great. It is unattended by public policies and results in illegal occupation ofso far unused land. This is true for lower as well as medium-class social strata, the lat-ter often choosing gated communities alternatives which are covering today a very largepart of the FD indeed. The new areas put the environment balance in severe danger, be-cause of improper deforestation, soil impermeabilization and ill-use of underground waterresources.

Brasilia Pilot Plan, because of its status as a World Heritage Site, has few remaininghousing growth possibilities, resulting in extensive amplification of the satellite cities,both by increments in densities and extension over rural areas. This generates very serioussocio-environmental problems. To start with, atmospheric pollution increases by pollutantgas emissions provided by the great number vehicles in circulation. Data from DomesticTransport Research of 2000, indicate that about 44.92% of FD jobs are located in PilotPlan, and less than 10% of population lives here (CODEPLAN, 2003). Because of thisgreat concentration of jobs in Brasilia and of the great distances between the latter and

Urban Morphology and Thermal Comfort in the Cities 357

Table 14: Distances of Satellite Cities from Brasilia, Source: CODEPLAN, 2003.RA Distance to Brasılia (km)

RA I Brasılia -RA II Gama 30RA III Taguatinga 21RA IV Brazlandia 45RA V Sobradinho 22RA VI Planaltina 38RA VII Paranoa 25RA VIII Nucleo Bandeirante 13RA IX Ceilandia 26RA X Guara 11RA XI Cruzeiro 07RA XII Samambaia 25RA XIII Santa Maria 26RA XIV Sao Sebastiao 26RA XV Recanto das Emas 26RA XVI Lago Sul 08RA XVII Riacho Fundo 18RA XVIII Lago Norte 08RA XIX Candangolandia 11

the satellite cities, vehicle transportation is by far the main way to access jobs, for morethan 90% of population lives far away from them (Table 1).

Most of FD population lives 20km away from their jobs. Vehicles circulation increase airpollution and air temperature. In areas with greater concentration of people and vehicles,like the South Commercial Sector and Taguatinga Centre, the amount of metals in the airare above those allowed by legislation (Bitencourt, 2004; Damaso, 2004). Temperaturesare much higher than those of nearby regions.

2. Urban Climate

Sorre (1934, 1951) defined the urban climate as the usual temporal rhythm of atmosphericstates above places, treated in dynamic form. Three main variables are analysed:

• Temporal rhythm - temporal repetitions of weather variables;

• Atmospheric state - weather attributes such as air mass, winds, temperature, pres-sure etc., that occur in the first atmospheric layer;

• Above places - variation according to the area under study.

In natural systems, i.e. environments not yet touched by human activities, resultsobtained by means of the methodology are reasonably constant in time. In areas underprocess of human transformation, particularly when strong alterations occur in the land-scape, climate modifications tend to be significant. The extreme situation concerns urbanareas, in which the natural landscape has been radically altered.

358 R. Ribeiro and F. de Holanda

Let’s go back to Sorre’s variables, adapted to an urban situation:

• Temporal rhythm - since urban areas are in constant process of change and growth,alterations may occur in the climatic elements because the urban dynamism;

• Atmospheric states - it is important to consider climatic alterations not only abovethe place, but also inside urban areas;

• Above places - relations are studied between urban tissue typology and climaticbehavior above the urban area in case.

Sorre’s (1934, 1951) concepts do not consider the main factor of environmental change,the human being, as well as the consequences, for people, of the modification that theyhave imposed in the natural environment, particularly its climate. As Landsberg (1956)observes, every form, every house, every urban street, causes a new microclimate, and theinteraction between such modifications and the climate must be considered. In irregularsettlements such impact may be greater for often little open space is left in order todrain rain waters and diminish the impact of solar radiation. The importance of massivevegetation is also acknowledged in minimizing building effects (Ross, 1997). Understandingurban climate implies the search of knowledge of interactions between weather variablesand urban morphology variables, and this paper attempts to offer some indications in thisdirection.

3. Case-study

The present area of Administrative Region XVIII - North Lake (henceforth AR XVIII)was created in 1994, including the Lake Mansions Sector (SML), the North IndividualsHousing (SHIN), the Varjao do Torto Village and Center of Activities (CA) (Figure 162).(CODEPLAN, 2003)

According to Domestic Transport Research of 2000 the North Lake has about 1.14%of DF population. Education indicators are: 21.08% have gone only to elementary schooland 35.15% have a university diploma (CODEPLAN, 2003). Such strong contrast happensbecause of the irregular settlement of Varjao do Torto Village and some rural occupation,responsible for 8.49% of people considered as having low family income. In contrast, 73.22%of families are of high income and high levels of education. The latter inhabit the moreexpensive areas in the peninsula and in the sector of the mansions. The AR XVIII presentsfour different urban typologies (Figure 162):

• Low populational density areas, with less than 10 inhabitants per hectare and highincome concentration (North Lake Peninsula and SML areas);

• Uncontrolled growth areas, including commerce, services, low income condomini-ums and kitnets (small living spaces constituted by one single room, bath and asmall space for cooking activities), favoring high population density and high peoplecirculation, in the Center of Activities (CA);

• Small rural properties, to the north of the AR;

• Irregular occupation areas, with low income population, high densities, few or nourban infrastructure and urban facilities (Varjao do Torto Village).

Urban Morphology and Thermal Comfort in the Cities 359

Figure 163: Occupation density in AR XVIII. Lighter tone go for greater densities. Datafrom ASTER sensor image, 24/06/2003.

This situation presents a delicate balance that demands attention concerning socialpolicies which should aim at ameliorating living conditions fo the poor, diminish contrastsand minimize environmental impacts.

One of the main problems of AR XVIII is vehicular circulation. The AR has onlytwo connections to the city at large, one to the Pilot Plan North Wing, the other to theSouth Lake Residential area. In rush hours great traffic jams already occur, increasing theamount of air pollution in the area.

The poor area of Varjao Village occupies a hilly site the vegetation of which has beenremoved. Streets are narrow and steep causing problems of erosion. This also favors, inprinciple, high surface temperatures and altogether affects the quality of life.

4. The analysis

We have attempted to identify whether there were significant correlations between inte-gration measures and some characteristics of the climate. Integration measures for theroad system were generated in the software Ovation 6.5 and the data was transposed toArcGIS 9.0, by which calculation of average census sector integration was calculated. Thelatter was obtained by averaging the integration of all vectors contained within, or crossedby, the borders of census sectors. For the aim of this paper it was considered sufficient tocalculate integration measures of the AR in isolation.

To obtain climatic variations for the area under study, a thermal satellite image ofASTER 08 sensor of 2003/04/26 was considered, in such a way that we could correlatethe Average Integration Index for Census Sector with the thermal image, by using a zonalanalysis though ArcGIS 9.0, in order to get average temperature in each census sector.

Figure 163 shows occupation density in the area. The lighter the grey colour the greaterbuilding density or exposed soil area. This occurs because buildings reflect more light thannatural areas. So the CA subarea presents the highest building density, as well as exposed

360 R. Ribeiro and F. de Holanda

Figure 164: Integration for Census Sectors. Data from 2000’s Demographic Census (IBGE,2002).

soil because of deforested areas to be built in the near future.In Varjao do Torto Village there is also a high building, not as high as the one before.

In the peninsula there is an even density, rather lower than in Varjao, mostly becauseplots of land are much bigger and there is less exposed soil. In the mansions area densityis still lower, with large green areas.

Integration values for census sectors (Figure 164) shows that integration grows towardsthe CA, which constitutes a sort of “local CBD”, with the exception of the Varjao Village,that is quite segregated, because the village has only two connections to the neighboringarea.

In order to compare average integration for census sector with surface temperature ofthe area, we have used the zonal analysis method, and temperatures have been obtainedfrom a satellite thermal image (Figure 165).

Correlation between census sectors integration values and surface temperature was0,31. Such value is not high but This indicate that how much bigger the integration ofthe sector biggest will be the temperature of surface for the same. The Figure 166 clearlyshow the data grouping for Varjao do Torto Village, this being an irregular occupationarea presents low integration, and also presented low temperature of surface, and for theCA, as this is an commercial area and with great constructive growth in last 5 years, thesama presented high integration and temperature values.

5. Final Considerations

For the study area it verified a positive correlation between the integration and the su-perficial temperature data. This possibly occurred had to the fact of that more integratedstreets presenting, normally, bigger circulation of people and vehicles. When analyzingthe figures 164 and 165, it note that in first one the integration grow when more near ofCA and in Plano Piloto direction. In second one verify that the more high temperature

Urban Morphology and Thermal Comfort in the Cities 361

Figure 165: Average superficial temperature for census sectors distribution. Data fromthermal image of ASTER sensor, 24/06/2003.

it located near to main circulation street, as well as in CA area, for being very muchconstructive, commerce and services concentrative area.

In contrast of it waited, the Varjao do Torto Village presented low temperature values.This can have occurred in function of its localization. It is in leans of mount, surrounded,still, for small rural properties, in which the constructive areas still are few.

The present paper points, still that initially, possible thermal comfort problems insidethe study area. The accelerated growth rhythmus of CA, already reflect in environment,increasing the local superficial temperature. Of this form one better planning for thegrowth of this area becomes necessary, as well as for all RA XVIII, once that the same isvery near of Ambiental Protection Area (APA), of National Park, and for if locating tothe edges of the Paranoa lake.

Portas (2000) affirm that, however, the effective planning or of forecast in the longrun translated in rigid parameters for its legal force, in some cases with values of extremeoccupation, and in other insufficient making possible the renewal, as it happens, withfrequency, in the Managing Plans or the Projects of Alignment/Land division, it does notfacilitate the business management of an emptiness perhaps whose probability of entirelyor linked transformation, was not nor could be foreseen. Therefore, adaptative planning(with rules of game instead of parameters) and business management are the two facesof one same and new currency. Assuming, it wants the insufficience of our knowledgeof the functioning of the urban systems, wants the insufficience of public resources toassure its command in all part at the same time. Therefore the new “local state” wouldfinish for frontally adopting the adaptability and the negotiation as integrant processesof the planning, looking for to guide the initiative and the private investment for areasof collective interest, that traditionally would not fit to it to assure, offering in exchangeconstruction guarantees, inspectors and others, that is, enough the average yield so thatthe chance that, for hypothesis, interest to the two parts, is not lost.

The urban planning becomes each more necessary, as Portas (2000) place, without the

362 R. Ribeiro and F. de Holanda

Figure 166: Relation between average integration and average superficial temperature forcensus sectors.

rigidity of the old urbanistic plans, but with a vision flexible integrator and, that canfollow the changes of the urban structure and the society, looking for to take care of tothe social demands for quality housing and ambient, of preservation of the environment.Although to seem utopian, it is possible that an integrated planning can allow the pacificexistence between the urban one and the natural one.

This planning must focus the legal part in such a way, generating housings that affectminimally the environment, as well as the rational use of the natural resources, but, also,it must focus the urban-ambient education, searching the awareness of all the social classesfor the importance, sensitivity and the precariousness of the relation of the city with thenature. This awareness also must affect the public power, so that it manages availablesocial and ambient the resources better.

One becomes necessary more studies on the relation of the urban morphology and thethermal comfort, of form that a multitemporal analysis could give indicative of trendsof sprouting of more critical areas during the local evolution. Thus, this if becomes acontinuous and dynamic work, that can be applied in the several urban areas of theDistrito Federal, a time that the configuration of them differs very much between itself.

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