MScUD 2009-10: Students’ analysis, group 5: urban fabric comparative analysis

The level of interconnectedness, navigability, sun penetration and sky visibility and many other indicators including density, ratio of open space, green space or paved space have been calculated on samples of urban fabrics from Govan and other 3 locations in Glasgow. The comparison makes it clear to what extent various models of city building result in different structures of space.

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Students: Yasmin Jilaihawi, Kirsten O’Hare, Christopher Kelly, Syed Zaidi, Sarah Jane Laverick.

From the Brief:

“General Scope

Why do we propose to conduct comparative studies on different types of urban textures? What do these studies tell us about the quality of urban spaces?

Comparative studies reveal themselves to be very relevant to get a first toolkit to evaluate specific characteristics related to the quality of space. We aim at identifying and quantifying a set of indicators that can help us in describing and comparing the key elements of the urban form. In this work in particular, students are invited to calculate measures of (1) connectivity and accessibility of the urban texture, and (2) solar admittance of a neighbourhood.

A short description of the scopes and objectives of each of the 2 WPs here proposed follows.

WP1. Connectivity and Accessibility of the Urban Texture

Scope

Students will investigate the role of the urban texture in assessing the proper functioning of the city. The urban texture is a combined expression of streets and block design. The design of the site layout and in particular of the urban grid is a powerful tool to control and manage the sustainability of a city. We assume here, that the urban texture intended as a structural property is sufficient alone to explain some characteristics of the city concerning connectivity and accessibility.

The capacity and the arrangement of the street network are key elements in the determination of accessibility. In this work we refer to the arrangement of the network alone, the so named “topological accessibility”, since we are interested in analysing those variables that are directly related and controlled by the work of urban designers.

For instance, both social and environmental aspects are intimately bounded to the design of the urban texture. A permeable urban texture is walkable and gives to people the chance to meet on the public realm. One of the basic urban design rules informs that the more physical connections we have on the street network, the more human connections can consequently be promoted.

Connectivity of the street network

Street connectivity is a key component for a good urban design. High connected street networks perform better in terms of sustainable mobility, encouraging walking and bicycling in urban areas. In fact, grid-like urban structures offer more opportunities for activities and social interactions in general and reduce the travel demand, since everything is reachable in a shorter time.

The apparent contradiction that having numerous connections on the street network would leads to congestion can be denied by correct transportation policies, whereby the car is not considered as the protagonist of travelling and pre-car age models are newly taken into account.

Even if these principles are generally accepted in the urban design community, the question regarding how to establish the connectivity of a place is very open. Numerous indicators have been developed and imported in the urban design practice from very different fields, like biology, physics, geography and sociology. Network analysis and graph analysis collect all this knowledge and represent interdisciplinary research sectors and their applications are useful in very different domains.

The proposed indicators and tools that follow try to delineate a possible practical answer to connectivity measurements for the purpose of increasing walking and cycling in the urban planning design process. These indicators are particularly useful in comparative studies, like for example in cases where we have to analyse a specific condition before and after intervention.

Accessibility of the urban network

Accessibility is defined as the measure of the capacity of a location to be reached by, or to reach different locations. Therefore, the capacity and the arrangement of transport infrastructure are key elements in the determination of accessibility (Rodrigue et al., 2009). A set of structural indicators of connectivity and accessibility is presented in this section.

Objectives

  1. To understand the basic differences between urban fabrics as a result of different street layouts.
  2. To reflect on the historical factors that stay behind the visible manifestations of street layouts.

WP2. Raster cities (environmental analysis with D.E.M.)

Scope

Aim of this work is to introduce students to innovative analytical techniques based on the processing of simple urban raster images, known as Digital Elevation Models (DEMs). Several new algorithms regarding solar accessibility, heat transfer, the urban wind field, visibility analysis and urban morphology were implemented during these years. Together, they aim to constitute a tool for the environmental assessment of cities, thus providing valuable feedback to urban designers and planners. While the investigation of DEMs in non-urbanized areas has been a long-standing research focus in the geosciences and has led to an ample library of functions that are used in most GIS packages, the use of this technique in the urban context remains largely unexplored. Aim of this work it to address this gap.

The investigation of environmental indicators in architecture is not new and there are already several tools that calculate energy performance of buildings very accurately. Nevertheless, these tools are very useful at the micro-scale of architecture (environmental performance software) or at the macro-scale of landscape and regional geography (GIS tools), but the focus on urban texture is mostly lacking. Recently, the increasing attention to environmental policies in urban studies has opened up many questions about how planners should manage those indicators in the design process. In fact, numerous authors and architects are convinced that cities play a leading role in controlling sustainability: strategies for redefining more efficient cities in terms of energy performance and environmental quality were the centre of attention in seminal work by Richard Rogers in defining policies for UK cities (Rogers 1997; Urban Task Force 1999) and supported the debate around the promotion of more compact cities (Jenks et al. 1996, 2000). Anyway, a comprehensive and reliable toolkit for sustainable urban design is lacking among practicing professionals.

Objectives

  1. To use simple tools (sets of scripts) to evaluate the solar accessibility of different urban textures.
  2. To quantify some environmental indicators related to urban form at the scale of the neighborhood.
  3. To conduct a comparative study among 4 different urban sites”.