Nádia Cristina Da Costa Lopes Nº 47862 Summary This Project Has
Total Page：16
File Type：pdf, Size：1020Kb
Nádia Cristina da Costa Lopes Nº 47862 Summary This project has as its main goal the influence of physical planning in urban morphology, contributing to an analysis of urban form in the municipality of Lisbon. This is achieved resorting to an analysis of cartography produced with McHarg Method in 1:10000 scale and planimetry of the area. It should be noted that through cartographic overlaying we define the Ecological Aptitude for Construction which is thus obtained from a range of physiographic factors like relief, hidrography and solar exposure. Terrain morphology as an indicator of the spatialization of ecological processes in the territory is also implicitly introduced in the definition of Ecological Aptitude for Construction. According to Ian McHarg (1969) the concept of Ecological Aptitude expresses different potentials that certain landscape zones with different ecological behaviour can offer in terms of the implantation of human activities. Territorial aptitude as can be ascertained from human activities occupation criteria allows the operationalization of ecologically-based planning and the rationalization of the land occupation process. In an urban environment, where it is most urgent to preserve the ecological functionality of the landscape, aptitude can make a significant contribution to the task of locating the urban ecological structure and the built areas. The methodology used to define Ecological Aptitude for Construction, as previously said, is based in the McHarg Method applied to the use of built-up land. This method consists in the representation of the study area using thematic cartography and its classification using different colour shadings in terms of the constraints or benefits that natural values represent in terms of building potential. In this way darker tones represent less aptitude caused by the presence of constraints or simply by the lack of any kind of benefits. Through the overlaying of different maps a pattern will emerge where areas represented in lighter shades constitute the ones with greater building aptitude. The use of McHarg Method generally suggests the following steps: identification and inventory – Identification of the main physical and biological processes that originated the morphology of a particular area and that characterize it; compilation and cartography – gather the information related to the main themes (climate, geology, phisiography, Hydrology, soils, vegetation, habitats, land use) and create the necessary cartography; interpretation and classification – analyse the information and classify it according to the Aptitude to each use; summary – a cartographic overlay so as to obtain a synthesis of the Aptitude which will represent possible land uses for each area. Terrain Morphology and Building Aptitude synthesize, in a clear way, some information necessary to the understanding of landscape and planning in harmony with the ecological processes. The first one, representing the global shape of the terrain, is the result of the combining relief with hydrography. This 1 allows the distinction between ecological situations – crest areas, watercourse adjacent areas, slope areas – which represent different concerns regarding the preservation of the ecological functioning of the Landscape and that therefore require evaluation in terms of Aptitude. There should be an emphasis regarding the influence of relief in land use, flow determination and hydraulic and atmospheric accumulation, which causes also some differences in slope microclimates. Crests are constituted by ridge lines and somewhat plain contiguous areas, roughly corresponding to the slope of the hill. In its most reduced form, the crest presents itself just like the ridge. The convex shape of the crests leads to erosion of the soil and to the draining of precipitated water, together with cold air, in the direction of lower contour heights. Therefore Crests constitute extremely sensitive areas, whose degradation produces a deep impact in the ecological balance of the whole hydrographic basin in terms of its hydrological cycle and erosion. Slopes are more or less inclined areas where there is transportation of eroded materials from higher to lower areas; there is also passage of cold air and water to accumulation areas (thalwegs). They represent areas of poor and thin soils that suffer continuous washing by the rain water and so constitute areas susceptible to erosion, a situation that worsens the higher is the gradient and the less is the vegetation cover. The microclimate in the slopes varies with the exposure to geographical quadrants; however, regarding the other ecological situations, the slope represents a temperate area due to the circulation of breezes and the forming of the thermal belt, which constitutes a hot zone in the slope. Watercourse adjacent areas are more or less plain, contiguous to the margins of the streams or waterways and characterized by higher soil humidity, accumulation of materials eroded from higher elevations and of colder air originated from crests and plateaus. They assume a more modest role if associated to the upstream area of hydrographic basins. In this case, soil humidity may not be high but nevertheless significant regarding surrounding areas. Adjacent areas downstream from hydrographic basins roughly match the flood water retention areas. The accumulation of eroded materials from crests and slopes in the watercourse adjacent areas originates the forming of alluvial soils, that is, soils with a high aptitude for the production of biomass. The microclimate of watercourse adjacent areas is characterized by huge diurnal temperature ranges, caused by the accumulation during the night of cold air formed in the crests. The detention basins coincide with areas located upstream of the water courses where, through the confluence of the waters of several affluent sloughs and ravines, occurs the formation of the watercourse bed. In temperate climates and especially in Mediterranean areas, an emphasis should be placed in the equilibrium of the land component of the water cycle, assuring an increased infiltration and diminishing erosion achieved through a smaller torrential runoff, through the planting of protective vegetation or through terracing of the terrain. 2 The geographical orientation of each parcel of terrain determines the amount of solar radiation received by the slopes, a fact that influences greatly the comfort of a construction. Sprawling edification over areas with little aptitude in terms of bioclimatic comfort imply a series of environmental and economic costs that can be considered as incompatible with sustainability. The amount of solar exposure received by a building or by a certain area in the surface of the earth depends, as previously stated, of its position relative to the sun, being therefore a function of the latitude and longitude of the place, of its orientation and slope, of the time of year and solar time, all these factors coming to determine the position of the sun in the horizon. In medium latitudes in the Northern Hemisphere it is generally the slopes facing south that receive the greatest amount of radiation on a yearly basis. In fact, these slopes are the ones that receive more radiation in the under heated period of the year and less in the superheated one, therefore presenting the best thermal comfort conditions, so much so as the gradient increases. This variation according to gradient for the same latitude is caused by the variation of the height of the sun relative to the horizon around the year. In winter, the height of the sun, measured as the angle between the sun rays and the horizon, is smaller, which causes an increase in the solar radiation received by vertical surfaces; in summer, the greater height of the sun causes the more plain surfaces to be the ones that receive a greater amount of radiation. Therefore, a slope with a steep inclination and facing south would be the ideal situation in terms of the thermal comfort that derives from exposure to solar radiation. Slopes facing north, on the other hand, will receive virtually no radiation in the period between Winter Equinox and Winter Solstice, which makes them unsuitable in terms of thermal comfort. Slopes facing east and west can benefit from a positioning regarding the sun that allows them to obtain total exposure values much higher than the ones facing north, but not so great as the ones facing south. Eastern slopes receive radiation during the early hours of the day, while western ones receive it mainly during the afternoon hours. Building invariably means waterproofing great tracts of soil, altering the local energetic balance, altering water natural drainage lines, with a consequent interference in geology and natural slopes and often provoking the destruction of natural heritage sites. In hydrographic basins the waterproofing caused by urban development increases the risk towards people and goods of the occurrence of floods given the diminishing area of soil where water infiltration is possible. This situation is worsened if the flood area, corresponding to the watercourse adjacent area, is obstructed due to construction of buildings or infrastructures, given that it is the only area trough which the waters can flow in case of flooding. In urban environment, these areas are particularly suitable to the creation of green spaces since they could benefit of favourable conditions regarding laying-out and maintenance costs, given that water and organic matter for fertilization would be