Coherence of a landscape refers to the organization of landscape components; it is the degree of consistency between the components. According to Salingaros (2000) geometrical assembly of elements determines the coherence of an urban environment and connectivity at all scales leads to coherence. He also stresses that coherence is essential for vital urban living environments. Coherence and legibility are strongly related to understanding of a place and feeling of safety. Thus, level of an environment’s coherence affects its legibility by its users. More coherent and legible an environment is, more people make sense of it, and more they feel safe.
Legibility in urban design was introduced by Kevin Lynch in his work "Image of the City" (1960) where he analyzed post-war North American cities’ built environments. Lynch defines legibility as "…the ease with which [a city’s] parts may be recognized and can be organized into a coherent pattern". According to Lynch, legibility is a key basis for sense of place. A sense of place evokes the feeling of "belonging" which makes a place psychologically comfortable. For a designer, it is important to turn empty "space" into a "place "with a meaning to experience. Although place identity is different from sense of place, character and identity of a place are two main aspects of sense of place. Therefore, giving character and identity to a designed place is essential for creating meaningful places for people. Antrop (2005b) states that coherence of particular properties defines identity and changes in coherence causes loss of identity or transforms the identity to a new one. According to Relph (1976) physical setting, activities and the meanings are three basic elements of place identity (in Turner &Turner, 2006). The degree of coherence of the first two components influence the meaning interpreted by the user, and as a result sense of place. Sense of place is unique to both individual and place since it results from the interaction of both. Turner and Turner (2006) identified the components of sense of place as:
• The physical characteristics of the environment,
• The affect and meanings including memories and associations, as well as connotations and denotations;
• The activities afforded by the place,
• The social interactions associated with the place.
Loss of identity and character in modern urban environments is one of the main challenges for designers today. Furthermore it causes loss of community attachment and community identity. Changes in land-use, globalization, decentralization, environmental pollution and changing socioeconomic structure are amongst the reasons for the loss of identity and character. Hence, solutions need to be developed first at planning scale. On the other hand, urban design can help with renewing and creating places with coherence, character and meaning.
As summarized above, the concepts of coherence and legibility are strongly linked to identity, character and sense of place. Therefore coherence and legibility should be adopted as important design principles in urban landscape design in order to create meaningful places which people enjoy to experience. Some key points in enhancing coherence and legibility in urban landscape design are given below;
• Coherence of landscape elements might be visual, functional or ecological. Hence, both natural and cultural landscape elements should be assessed in terms of coherence.
• Both history and cultural values of a place should be considered in attempt to achieve coherence and strengthening identity.
• Local architectural styles and materials should be taken into account in landscape design in order to provide integrity and coherence and preserve local identity.
• Visual quality of a landscape is important for reading and understanding the place. The entrances and exits of a place should be visually clear.
• Placing sculptures or other ornamental features can enhance the visual quality of the environment.
• Human scale is essential in legibility.
• Landscape construction materials should be selected to support or enhance visual coherence overall and between different landscape elements.
• Designed environments should support perceived safety. Open spaces offer people a sense of security since they have a wider perspective of a place to see what is going on around them, however people also needs to find a "niche" for themselves to have some privacy or to hide if they feel insecure.
• Spatial definition also helps people to feel more secure. Knowing boundaries increases confidence. Hence, edges should be clear and visible.
• For ecological coherence, green networks throughout and around the city should be created and connected to each other.
• Time is another variable of coherence. Forms, textures and colors of an urban landscape vary through time. Therefore changes through time and alternatives for the future should be taken into account in design process.
• Coherence between user needs and expectations, and proposed activities should be evaluated. Participation of local people in design process may help to create more coherent design alternatives.
• Diversity is essential for both healthy functional landscapes and creating more appealing environments for people. Diversity of landscape elements without coherence may cause chaos.
• Connectivity between different landscape elements enhances coherence.