Abstract

Abstract: in the future urban renewal research, urban sustainability will continue to be one of the important directions to solve problems arising from urban development. This paper has began with the theoretical basis of sustainable development and urban renewal and then summarized the case of urban renewal in Britain to refine the core of sustainable urban renewal. Subsequently, based on the previous cases and qualitative interviews, this paper has explored the factors influencing the sustainable urban renewal and the target system. According to the results, this paper finally has put forward some suggestions for the realization of sustainable urban renewal.

Aims
The rapid growth of urban economy has promoted the upgrading of urban infrastructure, the adjustment of industrial structure and the spatial reorganization of functional layout, allowing cities to undergo major social economic transformation and spatial expansion (Platon & Constantinescu, 2015). As a consequence, a wide range of urban problems have emerged, such as limited urban development space, insufficient supply of urban green space and service facilities and infrastructure, and decay of inner city (Harata, 2017). How to take advantage of the theory of urban renewal to match the layout of urban spatial structure with urban economy development and then promote the sustainable development of modern cities is the main aim of this study.
Objectives
To clarify the aim to apply the theory of urban renewal to promote the sustainable development of modern cities, three dimensions of research objectives are identified in this study:
Define the concept and historical theory of urban renewal and evaluate the importance and necessity of urban renewal in modern urban sustainable development.
Explore the sustainable urban renewal system in developed countries and regions, and refine the goals to achieve sustainable urban renewal.
Discuss influential factors of the renewal system of sustainable cities and their interaction, and then provide suggestions for sustainable urban renewal
Literature review
The conception and theory of urban renewal
The conception of urban renewal originates in the West and is a series of solutions proposed by Western countries to deal with problems arising in urban development. The essence of urban renewal is to reconstruct the resource carrier of the past and re-realize the function of the city. On the one side, it focuses on re-shaping the declining part, and on the other side it highlights the role of realizing new functions and meet new needs. Urban renewal has become the most influential urban policy in the world and exerted a far-reaching impact on the physical form and social structure of cities.
In the evolutionary process of urban renewal, a wide range of theories have emerged to guide the practices of urban renewal. The first large category of literature was published from the 1940s to the 1960s. Academic research was concentrated on two levels of theoretical studies on urban renewal practices and the discussion of the most popular slum cleanup problem (Johnstone, 1958). In that period, researches of urban renewal were hugely related to the changes in living environment and the improvement of life security after the World War II. The second major categories of documents were published in the 60s to 90s of 20th Century, and most of them put emphases on the diversity of urban functions and social groups. Jacobs (1961) launched a fierce attack on modern urban planning and construction, and put forward some urban planning ideas based on social and economic considerations. Wilson (1987) sharply criticized the loss of urban diversity due to the social transformation of modern urban centers, which led to the harsh lives of vulnerable groups. Hirsch (1983) took Chicago from 1940 to 1960 as an example and criticized the contemporary urban renewal of the legal framework for the loss of social diversity and the expulsion of vulnerable races. These researches of Jacobs, Wilson and Hirsch had a huge impact on the development direction of urban renewal which was no longer confined to the improvement of material environment and turned to pluralistic socialization and function of cities. The third major categories represented the mainstream ideology after the 80s of 20th Century, and was based on ‘Entrepreneurialism’ proposed by David Harvey. Harvey (1989) argued that the most efficient and effective way to govern a city was to manage it like a business, and the government should abandon the long-standing welfare principle and put the dependence on market mechanisms, economic growth, urban competitiveness and attracting foreign investment at the top of the list. Cities were regarded as economies seeking to maximize their economic benefits, and through the introduction of the private sector into the public service sector of the government and the support of private capital and enterprise management, various urban renewal projects can be promoted by means of a market-oriented mode of operation. Since 21th Century, there have emerged different controversies and extensions of ‘entrepreneurialism’. MacLeod (2002) questioned the idea of ‘entrepreneurialism’ negatively from the perspective of the relationship between its inherent contradictions and aggressive growth. Then Hackworth (2007) put forward the conception of ‘Neoliberal City’ and argued that the renewal and development of cities should expand the power of the government and pursue the policy of government intervention. From the conception of ‘entrepreneurialism’ to ”Neoliberal City’, it can be figured out that the city should be a diversified organism, and should not only rely on the market to promote a single economic development and urban renewal should focus on the city’s multiple dimensions. On the basis of this development trend, during the same period, other theories including gentrification in urban renewal, urban creativity has developed to make supplement for the urban renewal system from cultural and political levels. By guiding the renewal area to become the center of cultural economy or stimulating the potential of the renewal area with policies, the urban renewal has taken on the new turn and evolution characteristics of political system and culture (Peck, 2005). These theories like Johnstone’s urban reconstruction of slum cleanup, urban diversity of Jacobs, ‘Entrepreneurialism’ of Harvey are products and guidance for urban renewal and development stages which will be discussed in the following part in the corresponding era. Although they are difficult to explain the mechanism of urban renewal comprehensively, all of them are functioned as organic components of sustainable urban renewal and lay foundation for the theory to become the mainstream. Since 2005, researches on sustainability in urban renewal have gradually risen and have become the mainstream of present urban renewal theories. This kind of theory constructs a more complete and comprehensive urban renewal system.

The development stages of urban renewal practices
Generally speaking, the development process of urban renewal in the west can be roughly divided into two stages. The first stage is the initial period of urban renewal (from the Industrial Revolution to the early stage of World War II), during which the practices of urban renewal are represented by the improvement of urban sanitation of Britain and the United States. The second stage is the practices of urban renewal in the modern sense (from early World War II to nowadays), and it can be divided into four different stages. And in these stages, the term of urban renewal has undergone nearly a century of evolution, which starts from urban reconstruction after the World War II to urban redevelopment, urban renaissance, urban revitalization to urban regeneration. Despite the different English expressions used in urban renewal, it contains the measures of reconstruction, restoration, renovation and conservation to revive the declining regions of the city (Couch, Sykes ; Börstinghaus, 2011). These measures include the improvement of material forms and conditions of use, the continuity and coordination of the social, spatial, cultural, ecological and economic aspects.
Urban renewal and urban sustainable development
From the development of modern urban renewal in Western countries, it can be seen that the goal of urban renewal has changed from the clean-up of urban dilapidated buildings to the emphasis on human settlements, and the renewal features have changed from simple overthrow and reconstruction to the revival of multidimensional communities. The core of urban sustainable development is the harmonious and balanced development of nature, economy and society. In other words, sustainable urban renewal is a mode of urban renewal that has taken social, economic and environmental dimensions into considerations (Williams; Dair, 2007).
Research on the relationship between urban renewal and urban sustainable development is mainly manifested in three aspects. The first is corresponding to a certain level of sustainable urban renewal. Power (2008) discussed the sustainability between building renovation and demolition in urban renewal. Tweed ; Sutherland (2007) surveyed people’s attitudes towards cultural heritage in urban renewal, pointing out that cultural heritage contributes significantly to the sustainability of urban renewal. The second is focused on stakeholders in urban renewal and their participation and pathways to make urban renewal meet all aspects of interests and achieve balance of interests. Brownill & Carpenter (2009) studied the relationship between social, economic, democratic and environmental goals in renewal practice and the new forms of government administration to show the diversified way to guide local residents’ participation. Bagaeen (2006) identified the impact of residents’ participation and patterns on sustainability in the process of rebuilding military sites in three different countries. The third aspect lies in the determination of evaluation indexes and evaluation methods of sustainable urban renewal. Boyko et al (2012) quantified the city’s sustainability assessment, and used different indicators to evaluate the city’s sustainability to make prediction of four different future scenarios of urban development. Turcu (2012) studied three communities from a historical perspective and explored their impact on sustainability from six dimensions of housing and building environment, economy and employment, local communities, resource use, local services and infrastructure.
It can be seen from the research results of the relationship between urban renewal and urban sustainable development that research on urban renewal is not confined to the material renewal of the city itself, but also includes the social, economic, cultural, environmental and other aspects related to urban renewal and then gradually extends to the concern of sustainable urban renewal. Achieving sustainable urban renewal is an important guarantee for healthy urban development. It is foreseeable that in the future urban renewal research, urban sustainability will continue to be one of the important directions.

Methodological approach
In order to achieve the desired research objectives, this study plans to use literature research, case study, qualitative analysis to conduct the research. The reason to choose literature research is that it helps the author to clarify research ideas and research progress of urban renewal. Guided by literature research, the author can collect and consult extensively all kinds of documents and materials related to urban renewal and urban sustainable development, so as to analyze the important position of urban renewal in the sustainable development of modern cities. Generally speaking, there are two ways of research methods including qualitative analysis and quantitative analysis. Quantitative analysis is suitable for finding universal laws, while qualitative analysis emphasizes typicality and uniqueness of the focused targets (Zhao & Wu, 2016). In this paper, the author aims to seek for cases of urban renewal with reference and relatively professional scholar or urban planner to explore the factors affecting sustainable renewal. Therefore, two methods of qualitative analysis including case study and qualitative interview are selected. First of all, case study is more intuitive to help the author to summarize sustainable goals and make comprehensive assessments of typical urban renewal cases. The author will combine the specific cases of urban renewal in Britain to demonstrate the commonness and characteristics of sustainable urban renewal and excavate the essence of sustainable urban renewal from the practical level. Secondly, through interviewing relevant scholars and urban planners, the author will refine the factors influencing urban renewal practice and their interactions.
Impact

Both the practice of urban renewal in the West since the last century and the rise of modern urban renewal in the past twenty or thirty years are closely related to the process of urban development. And sustainable development is a healthy model pursued by human development today. In terms of theoretical impact, the exploration and summary of existing urban renewal experiences in developed countries and regions is of profound significance to the expansion of urban sustainable development theory. In terms of practical impact, research on the theory, method and path of sustainable urban renewal and the factors that affect it will help to fill the shortcomings of urban renewal and guide the government’s decision-making in urban planning.