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 . 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 readily available; vegetation thus plays a very positive role in reducing the impact of possible floods. This means that building activity in hydrographic basin areas should be contained to the maximum; the margins of water lines should be considered strictly non aedificandi areas and in the corresponding

3 adjacent areas there should not be any building construction, but only limited green space and infrastructure occupation. Slopes with gradient under 25%, except those facing north, constitute areas with the best aptitude for urban development, either from the standpoints of comfort conditions, conditions for drainage and laying-out of foundations for building or susceptibility of the existing systems. This ecological situation is the one that comprises a wider scope of aptitudes and where, in peri-urban areas, should be focused any changes from rural use towards edification. Note that in slopes with gradients between 12% and 25% any building activity should be accompanied by protective measures like terracing or alternating with strips of woodland. Slopes greater than 25% should be considered strictly non aedificandi . In crests, the shallowness of soil and consequent proximity of bedrock leads to good draining conditions and good properties for foundation building. However, the comfort provided by these areas is limited due to the steep cooling during the night and the greater exposure to dominant winds. Therefore, crests that are wide enough, assuming the shape of plateaus, are considered apt for edification provided that there is implementation of safeguard measures for protection of the edge of the plateau, which can be achieved through the plantation of strips of protective woodland, while at the same time care is taken to ensure the existence of vegetation inside the inner areas of those crests, which can be achieved through compartmentalization, serving the roles of providing ecological corridors and thermal comfort. It should be noted that plantation of woodland along the edges of plateaus not only ensures that erosion is kept to a minimum and water is infiltrated in the soil, but also guarantees the protection against dominant winds and a reduction of night cooling. The urbanization of a certain area should imply a predominance of suitable gradients, good conditions for setting foundations e good bioclimatic comfort conditions.

The occupation of Lisbon was strongly influenced by its natural conditions, the relief in particular, causing the coincidence of dominant relief lines and the structuring lines of the urban tissue: valleys are lines of traffic whose slopes generally have strong construction density. The relative high altitude of some locations is sometimes expressed in the toponymy: (“high neighbourhood”), Alto do Pina (“heights of Pina”) and if we go further down near the we have name places like Ribeira (“stream”) and Baixa (“downtown”).

In the determination of the Lisbon Building Aptitude we considered, as previously stated, certain factors as indicators of natural or ecological processes, namely relief, hydrography and solar exposure of surfaces. Each one of these factors originates, respectively, slope maps, hydrographic charts and solar exposure maps. The classes of values that are selected for each factor are oriented towards the analysis of the respective influence of a given factor regarding edification. From the overlaying of the slope maps and the Hydrographic charts we obtain the Terrain Morphology.

4 In short, the process of implementation that leads to the definition of Ecological Aptitude for Edification comprehends three stages: the construction of the Digital Terrain Model (DTM), the development of Thematic Charts and the synthesis that derives from the overlaying of all this information. It should be noted that the DTM is a mathematical model that intends to represent, in an approximate form, the topography of a given surface. This model is the basis of all the topographical analysis necessary for the definition of Aptitude for Edification.

The source data for the definition of Ecological Aptitude for Edification can be found on the internet, on the webpage of the course in Urban and Regional Planning (www.civil.ist.utl.pt/~ams/PRUCivil/conteudos.htm ) in digital format with files of type *.shp (ArcMap) and by themes: planimetry, administrative boundaries of the Lisbon Municipality, altimetry, point heights and contour lines spaced 10 meters each.

The construction of the DTM starts with the creation of the Triangular Irregular Network (TIN) which in itself is already a terrain model. The data used in the construction of the TIN is generally the altimetry and the contour values. The resolution of the grid in this project coincides with the smallest parcel of terrain that can be represented as having homogeneous and specific characteristics regarding its neighbouring matrix cells and corresponds to 20 meters.

The hydrographic chart is constituted by the drainage network of rain waters and by the ridge lines or water separation lines, which delimitate the hydrographic basins, and can be obtained automatically from the Digital Terrain Model. In this project the water flow lines and the ridge lines were obtained manually, given their greater similitude to reality, from the height points and from the shape of the contour lines: the water flow lines are obtained from the joining of the lowest height points in the terrain and the ridge lines by uniting the highest height points.

The slope map of the Lisbon Municipality was directly obtained from the DTM and the classes it contains are the following: 0 - 5 %, nearly flat areas; 5 – 12%, building without need of terracing; 12 – 16%, building with terracing; 16 – 25% and >25%, areas with gradient too steep to allow building activity. Note that the separation in two classes (16 – 25% and >25%) of terrains with characteristics considered identical derives from the need to obtain grater detail in visual perception of the study area, given its altimetry.

As previously stated, the terrain morphology is obtained by overlaying the slope map and the hydrographic chart. The result is not automatic since GIS applications available do not possess any function or operation that imposes by itself the set of restrictions necessary for obtaining morphology from slope and hydrographic charts. The morphology of the terrain allows us to demarcate three fundamental ecological areas: crests, slopes and watercourse adjacent areas. Crests and adjacent areas represent the more or less flat

5 areas with a gradient inferior or equal to 5%, contiguous to ridges and to water courses, respectively. The areas between these two types correspond to slope areas.

The solar exposure chart, obtained directly from the DTM, shows the different geographical orientations of each parcel of terrain. According to its orientation, slopes receive a smaller or greater amount of solar radiation which will, in turn, affect the comfort of buildings. The development of the solar exposure chart to be used in the definition of Ecological Aptitude for Edification suggested that we should consider the directions of the four main cardinal points: North, South, East and West. It should be noted that the chart referred to earlier results from the reclassification of the solar exposure chart obtained in an initial phase for the city of Lisbon, in which were considered the above-mentioned directions and also the ones intermediate to them. The reclassification process allows for less complexity in the results gathered and, consequently, a greater ease of interpretation of those same results.

The Ecological Aptitude for Edification, as demonstration of the intrinsic capacity of the territory to support that kind of land use, can be obtained by the overlaying of the above-mentioned charts and allows us to identify the Negative Plan, composed of areas unsuitable for edification or building (non aedificandi ), and the Positive Plan, composed of those areas that are suitable for building activity. The first set can be obtained through the union of areas corresponding to adjacent areas, slopes with northern exposure to the sun and slopes with gradient over 16%; the second set corresponds to crests, slopes with gradient inferior to 16% and with southern, eastern or western exposures. The classification of the areas in the Lisbon Municipality into one of the classes “unsuitable for edification or non aedificandi ”, “moderately suitable for edification” and “highly suitable for edification” assumes that we distinguish between moderately suitable areas and highly suitable areas for building activity. Areas with high aptitude for edification correspond to slopes with gradient inferior to 16% and southern exposure, the rest of the areas belonging to the Positive Plan being considered moderately suitable for edification. It should be noted that these moderately suitable and highly suitable areas to edification are non-restricted to occupation by edification, the first set possessing marginal conditions of suitability to building activity and the second set possessing favourable conditions to that occupation.

The definition of Ecological Aptitude for Edification is preceded by a global and detailed analysis of the City of Lisbon. This analysis is focused on the neighbourhoods that possess distinctive urban morphologies and that located in areas with equally distinctive physiographic characteristics, allowing for a detailed study that can be as comprehensive as possible about the following areas: ; Bairro Alto; Baixa; ; , Bairro da Calçada dos Mestres; Chelas; Costa do Castelo; Encarnação, Bairro da Encarnação.

From the global analysis of Lisbon it can be concluded once again that its occupation was strongly influenced by terrain morphology since the valleys constitute traffic lines and their slopes generally

6 possess high building density. It should be emphasised the existence of slopes with highly variable solar exposures, without a clearly identifiable tendency. The areas with larger building concentration and where most of the traditional commerce and economic activities are located coincide with areas of shallow gradients and small altitude, mainly on the riverbed of the Tagus. In fact, the city grows out from that area. Areas with little building activity coincide with steep inclinations and higher altitudes being, for the most part, used for the location of green spaces of medium to large size. They constitute therefore the ”lung” of this great metropolis. We could mention, among others, the , the Belavista Park and the Madre de Deus Park. Construction is mainly restricted to areas with slopes inferior to 16% since above such value building activity becomes increasingly dangerous, expensive and of uncomfortable pedestrian access. As said earlier, large avenues, railway lines and roadways often coincide with water lines, therefore coinciding with areas of altitude inferior to the surroundings, as a way of facilitating construction and of reducing costs with construction and maintenance. As clear examples of this situation we have Liberdade Av., Fontes Pereira de Melo Av., República Av., Almirante Reis Av., Estados Unidos da América Av., Almirante Gago Coutinho Av., Ceuta Av., the railway stations of Entrecampos, Cais do Sodré and Santa Apolónia. Water courses sometimes represent the boundary that separates areas of town with different functions, such as the water course that coincides with Ceuta Av., constituting the eastern limit of Monsanto Forest Park and separating the green area from the housing area. The ridge lines, possessing altitudes higher than surrounding areas, constitute separation lines between neighbourhoods, especially in the old town. In the newer areas of the city it becomes apparent that construction in areas corresponding to these lines was avoided.

From the detailed analysis of Lisbon it could be concluded that the organization of neighbourhoods and blocks was extremely influenced by the terrain morphology. Areas with rugged terrain show a type of construction generally oriented according to a linear mesh (Campolide, Bairro da Calçada dos Mestres; Costa do Castelo; Encarnação, Bairro da Encarnação). Areas with flatter terrain present a kind of construction generally disposed according to either a regular reticular mesh (Avenidas Novas; Baixa), irregular reticular mesh (Bairro Alto) or a free mesh (Benfica; Chelas). The mesh characteristics of Avenidas Novas suggest blocks comprised, in both directions, on heights which have an average distance of two meters. The Downtown (Baixa) corresponds with a high intervention on the territory. The embankment of the city main watercourses was on the basis of the fragility showed by the territory on the 1755 earthquake, and was also on the basis on the development of the construction on piles after 1755, because constructions from then on, were implanted on one old watercourse or on areas surrounding it. The need to overcome gaps on high heights on the Orient and Occident limits of the downtown (Baixa) led to urban conditions of different degrees of interest. So, at Orient the construction of one big block constitutes a clear architectonic barrier which doesn't connect on an interesting manner the Orient and the Downtown areas. At Occident it's evident a much more sensible relationship between the urban

7 drawing with the initial terrain morphology: the means of implantation of the building of storehouse to establish a relation between the valley/plane of Downtown and the rugged hill, and the Calçada Nova de São Francisco, where the condition of the geometry articulates itself perfectly with the rugged terrain. It shall be pointed out the extraordinary design of this way, which achieves with a curved tracing though with rigorous geometry, the overcoming of a big difference of heights. The Castle front ( Costa do Castelo ) constitutes a tissue strongly marked by the rugged topography of the Castle hill, as the constructions on one territorial non-planned organization were spreading. The blocks have irregular shapes and sizes and the paths present strong inclinations, being often replaced by staircases which overcome great gaps. The urban tissue disposes itself around the road scheme which is coincident with the level curves. The edification conducts itself therefore parallelly to the level curves, creating thus a type of urban morphology quite specific of this area. The Castle front is an organic tissue, where the sediments from different periods overlap themselves on complex juxtaposition. The strata of different languages create a reasoning whose meaning resides fundamentally on its discontinuity. The Calçada dos Mestres neighbourhood, in Campolide, corresponds to a high area where, just as the Castle front, the accommodation of the buildings to the slope changes and elevations is perfectly visible. The constructions are localized between level curves where the ways are drawn with extremely coincidence. On the circulation network tracing of the Bairro da Encarnação, the ways had to adapt to the relief and not the opposite, because that area constitutes an economical houses neighbourhood on which was necessary to spend the less amount of possible money. Indeed, the main alley is not completely linear from the inferior part to the top. The Bairro Alto (translated literally means High Neighbourhood) is composed of dense urbanization, with absence of wide open spaces. The surrounding of the western limit of the neighbourhood is marked by high slopes, which is a factor that reflects a bigger irregularity of the mesh. The urban drawing on areas with slopes superior to 25% articulates admirably with the pre-existent territory trough the construction of Monumental Squares. It shall refered that the “shape” of the level curves of Bairro Alto infuse on the form definition of the Jardim de São Pedro de Alcântara (Jardim means garden). It's on the terrain defined with the construction of one wall of support which allowed that the garden was developed between heights which differ 10m. The disordered growing in Benfica originated leftover spaces between buildings which are occupied by gardened areas. It shall be referred the presence, in areas of higher slopes, of a wide garden with its limit coincident with the slopes interval where it is inserted, considering on the present work of specific and homogeneous characteristics. The Chelas Plan was made accordingly with environmental criteria, in other words, based on the concept of Ecological Aptitude, whereby the built area is situated on zones apt for edification. However, the Valley of Chelas which constitutes the main humid system of the central areas which is being studied, is crossed by an avenue. The ways, located on the valleys, shall be implanted on the line which separates the Adjacent area and the slope, so they not constitute a constrain to the flow of water and the air. Alongside the way, it

8 shall be situated, one of the primary corridors of the green structure, established on the Ecological Structure – environmental component of the PDM (Plano Director Municipal – Municipal Director Plan). The transversal circulation to the valleys shall be assured by viaducts, with sufficient height to not interfere on the air and water streams. Only with manner, all the inherent functions to this ecological situation, are ensured on compatible and sustained means. However, the Bairro do Vale do Fundão (translated literally means Precipice Valley Neighbourhood ) is situated, accordingly with the Aptitude Map, on one area not suitable for edification. Its localization on one gathering basin, local of confluence of watercourses, explain the high humidity on the local.

In terms of the solar exposure, neighbourhoods that enjoy good salubrity and thermal balance and therefore possessing reduced areas with northern exposure are: Bairro Alto; Chelas; Bairro da Encarnação (Encarnação). The Avenidas Novas and Baixa are located in one area considered almost flat, so it hasn't defined solar orientation. The neighbourhoods of Calçada dos Mestres (Campolide) e Costa do Castelo present zones with northern orientation that possess a building density roughly equal to those enjoying other geographical orientations.

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