The ubiquitous sameness of urban greenways prompts questions on generative design grammar and syntax, whether creative, critical rethinking at that level might be lacking. However the design syntax of urban greenways is not explicitly discussed thus leaving a critical gap in knowledge. This paper begins tackling the larger question by acting on the fundamental subset of it, by operationalizing the design syntax of urban greenways. This is done through mathematics-based graph studies to analyze patterns and shapes, photography based thermal, material and morphology studies, and section analyses to make imagery-derived deductions on the design syntax. Recommendation on approaches to diversify and enrich the design syntax includes a more direct reference from ecosystem science theories such for siting and planning the urban greenways at macro- to meso-scale, a mixed-method approach, combining mathematics, photography and drawings based frames for analyses at meso-, to micro-scale, and a turtle view scale for designing at meso- to micro-scale, with an emphasis on latter.
Design thinking ; Syntax ; Greenway ; Urban ; Planning ; Landscape ; STEM integrated design ; Inter-disciplinary
Greenways, also referred to as linear landscapes and landscape corridors in popular discourse, acquired a distinct body of knowledge developed through key contributions of Little (1990, 1995), Fábos (1995) , Fábos and Ahern (1996) , Flink et al. (2001) , Jongman and Pungetti (2004) , Fábos (2004) and Hellmund and Smith (2006) , over time. Little (1990, 1995) explained the idea of a greenway as a combination of greenbelt and parkway, to quote “…if you take a syllable from each of these terms – green from greenbelt and way from parkway , the general idea of greenway emerges: a natural, green way based on protected linear corridors which will improve environmental quality and provide for outdoor recreation (Little, 1995: 4).” The President’s Commission on Americans Outdoors (1987) envisioned “a Living Network of Greenways… to provide people with access to open spaces close to where they live, and to link together the rural and urban spaces in the American landscape… threading through cities and countrysides like a great circulating system.” Fábos, 1995 ; Fábos, 2004 emphasized that “greenways are ecologically significant corridors, recreational greenways and, or greenways with historical and cultural values” and thus advocated for greenway planning as a comprehensive multipurpose, multi-objective effort. Ndubisi et al. (1995) observed, that “environmentally sensitive areas when interconnected could serve as greenway corridors.” Ahern (1995) explained, “(that) greenways do not attempt to transform or control the entire landscape—but by focusing on riparian corridors and other environmentally sensitive areas, greenways are more modest in their ambitions, while exploiting selected linear elements in a strategic and synergistic manner.” My own research concurs with Ahern’s idea and defines greenways as “synergistic landscapes that create harmony amongst the urban system with broader biophysical system” (Sharma, 2010 ).
Many offshoots of the greenway concept have simultaneously emerged and thus led to confusion about the identity of greenways. In addressing this identity crisis, the comprehensive greenway nomenclature by Hellmund and Smith (2006: 2) is reviewed and reinterpreted here to highlight the following definitive and distinctive features:
The current perception of or design attitude toward greenways, especially urban greenways, is that they are physical connectors between places with green cover. Lindsey et al. (2008) described greenways as linear open spaces or parks along rivers, streams, ridgelines, or historical infrastructure corridors, such as canals or railroads, with the potential to shape the urban form and connect people to places (53). Within this view of urban greenways, the paper investigates the varieties of design approaches and language, currently being generated.
A critique of greenway design projects and proposals forms the foundation of this study, which synthesizes the urban greenway design syntax by using the basic principles of design, such as form, shape, material, and texture. A contemporary research method of graph analysis is then applied to the greenway design at the macro-scale to derive an understanding of patterns. Photographic appraisal is undertaken to extricate morphological details at the meso-scale, and analysis of section drawings is conducted to view the design details of urban greenways at the micro-scale. This study presents only one view on design, which is physical form oriented, but design can be discussed across multiple frames, such as sociology, philosophy, and economics, to mention a few. This investigation on design syntax does not present the breadth of discourse in this field because this is not the purpose of the current study. Instead, the investigation should be read as a complement to the broad contemporary discourse on the topic. The integration of science, mathematics and design is presented in terms of an experimental method.
Syntax is mostly used in linguistics, but Hillier and Leaman (1974) reintroduced the concept to architecture and urban design through space syntax. Conceptualization of space syntax originated from questioning of critical thinking in design and most prevalently used to map and understand physical connectivity (Hillier and Leaman, 1974 ; Baran et al ., 2008 ). Lynch (1960) offers a matrix for reading and assessing form. The matrix alludes to clarity in terms of figure background, contrast, and dominance; visible form or geometry, visual scope, and joints or nodes; and continuity, directionality, and motion awareness. This matrix serves as a structure for organizing forms, patterns and spaces to design a city (1960) and Alexander’s (1977) too for designing and retrofitting places, however, not a direct framework for design and planning of an urban greenway. The inquiry into design syntax, presented in this paper, considers previous studies on connectivity and syntactic investigations of Alexander (1977) and Lynch (1960) , but focuses exclusively on understanding the design syntax of urban greenways. The paper uses the term “design syntax” to imply the composites of urban greenway with reference to the resultant spatial form. The intention is not to compare the design syntax with linguistics syntax as in this paper since that should follow this investigation in collaboration with a linguistic syntax expert, but to derive an operational understanding of design syntax first. Urban greenways, would be referred to as those designed primarily for humans; approaches that aim to reconcile the design for humans and other biodiversity are beyond the scope of this paper but are discussed in forthcoming text by Sharma (in press) .
This section presents a review of urban greenway proposals and projects along the Appalachia to examine the current design syntax. Knoxville City in Tennessee claims to have 65.53 miles of paved and unpaved greenways in aggregation (City of Knoxville, 2012 ). The current plan is said to have coevolved with the Knoxville bike plan proposed in 1975 (Knoxville Regional Transportation Planning Organization, 2012 ) and has emerged in the Knoxville Greenways and Community Trails Commission Report, 1992; the Knox County Greenways Plan, 1994; the Knox County Park and Recreation Facility Plan, 1998; and the Knoxville Parks, Greenways, and Open Space Resource Inventory, 1999. The Knoxville–Knox County Greenways Plan aims to embrace the ethos of sustainability and green infrastructure through the integration of energy-saving and water-conserving technologies, open space systems, riparian greenways, forest preserves and natural areas, and natural drainage systems, such as bioswales and pervious paving. The main intent of this plan is to develop the park and open space system as the foundation for community development while facilitating the preservation of important natural resources (Knoxville Metropolitan Planning Commission, 2009: 7, 10, 20 ). Economic revitalization is a concurrent goal of the Knoxville–Knox County Greenways Plan. Therefore, planning for sports fields is well emphasized. Green trails are to be designed for multipurpose use, with a conscious effort to enhance the natural beauty and property value of the area. The recommendation is to establish parks or greenways within a quarter-mile walk for residents in urban areas and within half a mile in lower-density suburban areas.
The greenway vision for Charlotte City in Mecklenburg County, North Carolina aims to address the goals of floodplain protection, stormwater management, and recreational opportunities (Haden and Stanziale, 1999: 31) . A provision for physically walkable or bikeable connections for close-to-home and close-to-work recreation opportunities is thus central to the greenway planning vision. The city of Raleigh, North Carolina followed suit by instituting and executing the plan for the Capital Area Greenway System for the twofold purpose of avoiding flooding and providing an avenue for people to connect with nature (City of Raleigh, 2012 ).The retirement town of Morgantown, spread over five square miles, is hoping to re-attract its customer base by further enhancing the beauty and walkability of the town through greenways (City of Morganton, 2012 ). Resource preservation is integral to retaining the attraction value of the town.
The “Louisville Loop is an estimated 100-mile trail system that will encircle the city and link existing and new parks and neighborhoods to civic attractions, transportation alternative and recreation opportunities (Fischer and Louisville Metro Council, 2013 ). The 26-mile love system was built from the early 1890s through the 1930s, Creating large community parks on disparate sites that each displayed unique qualities of Louisville’s varied landscapes, and connecting them to the neighborhoods of Louisville with the ‘ribbons of green’ that became the parkways (‘ways to the park’), was the fascinating, visionary, and enduring concept brought about by the wisdom and will of Frederick Law Olmsted, Sr.” (Fischer and Louisville Metro Council, 2013 ). The Floyds Fork Greenway is a two-mile segment of the Louisville Loop. The Floyds Fork Greenway Master Plan established the design direction for more than 4000 acres of new parkland at the edge of the metro region of Louisville, Kentucky (City of Louisville, 2010 ; Wallace et al., 2010 ). The plan was developed to conserve land and bring in tourism from the Louisville metro region into the town to support retail development and the local economy.
The greenway master plan for Anne Arundel County, Maryland is an offshoot of the Maryland Department of Natural Resources’ plan “to identify large, contiguous blocks of ecologically significant natural areas (hubs) and to link them with natural corridors to create an interconnected network of natural resource lands across the state” (Anne Arundel County, 2002 ). As a result, the Maryland Atlas of Greenways, Water Trails, and Green Infrastructure was published in 2000, and it served as a precursor to Anne Arundel County’s Greenway Master Plan ( Maryland Greenways Commission, 2012 ). The plan emphasized on biodiversity conservation and used the habitat suitability index to maintain or provide biodiversity corridor connections.
The design decisions of most greenway proposals for naturalistic setting are more in the spirit of form following topography and thus result in very delicate looking and natural low-impact greenway designs with compacted earth or gravel paths, well-composed tree canopy, and beautifully framed views of nature (Sharma, 2010: 351–352 ). However, in urbanized setting, greenway proposals and executed designs have a sturdy looking, multi-traffic oriented design with the integration of concrete or asphalt pavements, street fixtures, and a tree canopy that bear the look of a controlled mechanical assembly.
Most reading and perceiving of ambient surroundings occur at the visual scale of far, near or in-between. For the purpose of this paper, I will use macro-scale to refer to far view or a few hundred feet of bird’s-eye view; micro-scale, for near view or view up to 20 feet and meso-scale, as a reference to in-between view of up to100 feet. This also establishes the visual scale as basis of reading design syntax.
For reading design syntax of urban greenways, I begin with graph studies for pattern recognition since it is one of the basic tools available for morphological understanding of the design syntax at the macro-scale, even in contexts where Geographic Information Systems technology may not be readily available. The methods of section drawings and photograph-analysis, have been popularly used to explain greenway design in seminal texts such as by Flink et al. (2001) and Hellmund and Smith (2006) , besides contemporary research by Nordh (2012, 2010) . I will use the section analyses of drawings for abstracting design details at the micro-scale, and Picasa-treated photographic analyses for an insight into material and morphology at meso-scale. Ranging from a macro/regional/bird׳s-eye view scale to a micro/local/pedestrian/turtle view scale, the methods of graph analysis, morphological as well as thermal studies through photographs and section analyses presented in this article offers a mixed-method approach for the objective reading, assessing, and designing of urban greenways.
Graph theory is at the heart of space syntax theory (Hillier and Leaman, 1974 ; Baran et al ., 2008 ), with a focus on movement patterns of the users. The abstraction of greenway pattern through graph drawing in this paper is focused on understanding the pattern of greenway design as a component of design syntax and starts with mapping of the most proximate, possible patterns that facilitate essential functions of connection and conduit. This experimental approach of integrating mathematical perspective, through graph-based drawings in design of urban greenways, was shared by Sharma in 2013 (528–532), in anticipation of engaging mathematicians in greenway design and planning issues, thus, creating conditions for transdisciplinary design thinking. This adapted language blending maths and design, resulted in engaging attention of transportation engineers and planners at Morgan State University, and a collaborative research on “Impacts of Urban Street Patterns and contextual Land Uses on Environmental Sustainability and Safety in the Mid-Atlantic Cities” is underway (Shin et al., 2014 ).
The factors that influence decisions on locating urban greenways (Figure 1 ), which in turn affect the spatial layout pattern of greenways, are as follows: (1) conservation, protection, or preservation needs of natural resources; (2) proximity of natural resources and residential or publicly accessible areas; (3) distance between residential areas and natural resources or other civic amenities; (4) view sheds; and (5) economic valuation of land that should be acquired for urban greenways and is adjacent to the proposed greenways.
Urban greenways: reading pattern through graph overlays.
Graph-based extrapolations are also intended as means to trigger design thinking from mathematical frames of equations and relevant postulates. For example, mathematicians can start answering questions, such as, if a greenway design is a function of sum/product of variables of landscape systems and location of greenway routes, than what is the correlation or covariance amongst each unit of investigation. To enunciate, landscape systems – subsurface geology and hydrology are the common contexts in which greenways occur, are constants – a steady factor, given their relative static nature and surface transportation routes or locations of greenways and design elements of greenways – dimension, shape, form, material, and texture, are variables – changing factors, than a calculation of covariance between both the variables would make an informative study for greenway designers.
The semiotics of landscape based on the types of design elements, compositions, locations, and morphologies involved were extensively discussed by Lynch (1960) and Jorgensen (1998) , amongst others, and were supported by analyses of photographic views of landscape. An established practice in the spatial design and geography disciplines, photographic analysis helps gain insights into the qualitative aspects of design, spatial distribution, and trends (McCullagh and Davis, 1972 ; Nordh, 2012 ; Nordh et al ., 2010 ). Inspired by photographic appraisal approaches (Nordh, 2012 ), this study adapts and applies such method to further understand the design of urban greenways at the micro-scale. Please see Table 1 for a reading of the morphology of urban greenways through digital photography modifications.
A review of the built and proposed greenways, drawn as representative sample from a region, in Figure 1 ; Figure 2 shows that the design and morphology of greenways have not changed much. Table 1 presents the photographic study of morphology. With Google’s Picasa software, the “invert colors” effect was applied to the original greenway photographs, as shown in column 2 of Table 1 , followed by the “heat diagrams” and “pixelate” effects, the results of which are shown in column 3 of Table 1 ; any technology similar to Picasa could be used. The application of the “invert colors” effect results in lost morphological details, such as material, texture, and form. The application of the “heat diagrams” effect reveals the corresponding heat patterns of the materials, whereas that of the “pixelate” effect enables a quick reading of the percentage distribution of the materials. Picasa’s “heat diagrams” effect shows the colors in inverse, that is, blue is the hottest, and red is the coolest. The colors were not further digitally altered to avoid any error or loss of information that may occur because of the author’s lack of understanding of the actual software code. This simple two-step process shows the materials that generate high heat (indicated by the color blue in Picasa’s “heat diagrams”) without having to crunch the albedo indexes of the materials; these materials could then be replaced with other material choices that do not generate high heat (as indicated by the red color and shades of yellow and green in Picasa’s “heat diagrams”). The morphology of the design elements is experienced at the level of “personal” view or perspective and is represented through sections, as discussed below.
(a) Section analysis for design syntax based on seminal drawings. (b) Section analysis for design syntax based on built and proposed examples. Key used: T: tree+other plant material, PW: Pedestrian pathway, BW: Bikway, CW: automobile or carway, SW: predominant stormwater management interventions requiring grading.
Views, perspectives, and sections are integral means of understanding space and analyzing design (Lynch, 1960 ; Alexander, 1977 ). Forsyth and Krizek (2011) again shed light on the issue of scale and speed at which we experience urban spaces. This section of the article focuses on viewing landscape at walking speed by working through section drawings because sections highlight the form, material, and textural design qualities that are lost in large-scale drawings and top-view plans. The contemporary design of urban greenways formed at the human experiential scale in sections is inventoried in Figure 2 a and b
The study of urban greenways is synthesized, and the generic diagrams of plans and sections are abstracted from urban greenways illustrations and photographs, similar to those presented in Figures 1 , 2 a, b and Table 1 , are presented in Figure 3 .
Urban greenways: design: typical plan and section studies for design syntax and form
The representation of greenways through sections is emphasized but not celebrated for its unique contribution to critical design thinking in relation to greenways. Compared with Forman’s diagrams, which show a bird’s-eye view of greenway corridors, and Flink’s greenway guidelines, which discuss greenway planning from the perspective of the human view cone and human experience (Forman, 1995 ; Flink et al ., 2001 ), the greenway section drawings by landscape architects essentially (need to) bring out not only the surface but also the subsurface view of the greenways because land design involves a holistic understanding of the total land. The amphibious vision of super- and sub-landscape, is therefore essential. It is also acceptable to digress from the transportation planning based idea of taking people from point A to point B in the fastest time possible in designing urban greenways. A designer should influence people to shift from hare like speedy walk to a turtle like walk by slowing them down when they view esthetically pleasing, psychologically calming, and stress-relieving landscape designs. The unique qualities of section drawings, which are very critical to a designer of land and ecosystems, need to be identified and celebrated with their own unique signifier at the “turtle view” scale. This means that the designer should consider the land both from the top of the ground line and under. This turtle view scale is poetically reflected in the 2002 photomontage by Weller and Griffiths (Weller, 2001: 11 ), referring to art Masterpieces, showing a figure peeling off the top layer of landscape as a sheet, in an act of un-covering or revealing what is underneath.
The design syntax of urban greenways as abstracted in Table 1 and Figures 2 a, b and 3 show the core or genotypic structure of urban greenways; the thesis on the core and peripheral elements of Greenways is presented in forthcoming article on “Decoding the Genotype of Greenway design and planning: Stedmanian frame as a tool for understanding, explaining and progressing design thinking” (Sharma, in press ). The malleable physical form is open to new thinking and redesigning to address emergent issues. The typical or genotypic design syntax of contemporary greenways shown in Figure 1 ; Figure 2 a, b and 3 , comprises of shape, form, material, and texture, with further details outlined as below:
usually mixed because of the multimedia template of the surface material(s) of greenways, which are mostly synthetic, and plant materials that could range from fine-leafed/textured trees, shrubs, and grasses to fine- to broad-leafed or coarse-textured plant materials
Alexander advocates paths made of brick and paving stones over asphalt and concrete, which, he says, are only easy to wash but do nothing for humans or plants (Alexander, 1977 ). I tend to agree with Alexander for reasons of aesthetic appeal and earthiness yet, it is a subjective viewpoint and the design decision should be run through an objective analytical framework. Using ecological footprint analyses (including land, water, carbon, nitrogen, and methane footprints) as guide in making decisions on material selection will be a step in the direction of objective, environmentally conscious, and scientifically informed, objective decision making. Ecological footprint based on microclimatic conditions, low land, and carbon footprint might be given a premium in a microclimate receiving good rainfall, whereas water footprint may be the highest priority for localities with insufficient rain. This study recommends the integration of sustainable technologies to enrich the greenway typology while positively promoting sustainable development. The range of sustainable technologies or land practices that could be integrated in mainstream greenway design practice comprises constructed wetlands, bioswales, composting, porous pavements, rain gardens, green roofs, and living walls, with technologies, such as hydroponics, aeroponics, and permaculture. To elaborate on eco-footprint analyses, let us shift our view from the macro-scale of a city landscape to the micro-scale of a green patch outside a house. At this micro-scale, the material template of a green patch could be a combination of materials used for greenway surfacing and planting. Depending on the purpose of the greenway, the material for greenway surfacing may be compacted earth, gravel, brick, timber, concrete, and asphalt. An educated inference can be made even without complex computation. The green patches that favor synthetic materials requiring many levels of industrial processing or even naturalistic material resources from remote locations – thus involving long transportation, high fuel consumption, and associated pollution emissions – will have a larger eco-footprint than green segments using locally resourced and minimally processed surfacing materials. Therefore, the latter green network will have a lower eco-footprint than the former.
The proposed framework aims to bring specificity in terms of applying the concept to greenway planning. The framework supports the idea of consciously designing urban landscape and greenways as a green switch or work gates (as explained in Odum’s well-known energy flow diagrams) to control and direct contextual energy flows (Sharma, 2006 ; Ahern, 1995 ).
The working structure of the design syntax – pattern/shape, form, material, texture, outlined in Section 4.1 , serves as a useful tool to understand the design language used to construct urban greenways. However, more clarity is rendered by further synthesis and refinement of the design syntax corresponding to the idea of composite alphabets, conjunctions and meanings as presented in Figure 4 .
Operational design syntax of urban greenways.
The structure of design syntax as presented in Figure 4 is simply to arrive at a basic operational structure with a scope of creativity, innovation and experimentation in generating different forms/meanings though play with design assemblies. Each composite of the operational design syntax can be further investigated in detail for various descriptors of each design composite/alphabet. For example, the form for T when it is deciduous tree would be different than form for T where it is three storied canopy of vegetation. However, the currently articulated design syntax provides a parent operational syntax for further studies and critiques. Basic design components/ alphabets, design assemblies/conjunctions and spatial forms/meaning are co-related and change in one affects the other.
The layout pattern is the spatial organizational context in which the design syntax of urban greenways is read. The positioning of urban greenways with regards to a comfortable walking distance of about 10–20 min from residential areas serves as the locational criteria. This is in sync with the concept of “promenade catch basin” presented by Alexander (1977: 171, 173) , and should be integrated and sustained as one of the urban greenway siting principles. Additionally, science offers knowledgebase to draw from. Hellmund and Smith (2006: 65, 191) mention Island biogeography and network theories as a potential reference in process of greenway planning. The ecological hierarchy proposed by Odum and Barrett (1971) , explains the composition of ecosystem, in incremental scale and complexity, at the levels of: organism, population, community, ecosystem, landscape, biome, and biosphere. Hargens et al. (2009: 95) simplified the hierarchy as follows: atom, cells, organism, ecosystem, biosphere, and universe. These levels of ecosystem can be used as a guide for spatial layout of greenways; see Table 2 for a beginning interpretation corresponding to urban greenways.
|Organism||A greenway segment within a city or county|
|Population||A group of greenway segments or a connected greenway network|
|Community||A group of greenway networks in a region|
Such an ecosystem science informed organizational approach directs us to view visible and invisible associations with the broader biophysical systems to be viewed at a nested scale of hierarchy from organism to community. Doing so enables a conscious designing of urban greenways as a metacommunity or a metasystem with composite subcommunities or subsystems; such a design grants a chance to urban greenways to function as a dynamic, resilient system similar to natural ecosystems.
Urban greenways have been incorporated in cities for the purposes of stormwater management, recreation, tourism and alternative transportation. Even with emphasis on one of these objectives, most greenways automatically serve other goals in varying degrees. Simply put, they are designed for multi-functionality. While some cities, such as Knoxville, approach greenways as an environment-friendly alternative transportation mode because they help reduce fuel consumption and pollution generation, others, such as Raleigh and Charlotte in North Carolina, plan greenways to address urban environmental issues, such as stormwater management, seasonal flooding, and heat island effect. Only a few areas, such as the city of Louisville and the county of Anne Arundel, push the boundaries further and consider environmental succession patterns in designing greenways. The greenway design sections, material template, and thus syntax do not vary remarkably. The procedural method to plan most urban greenways is very real-world based, depending on land availability, open space networks, conservation easements and zoning codes, closely followed by site conditions and contextual needs.
As an observation on critical design thinking on urban greenways, it is important to note following points. Firstly, currently, morphological studies are predominantly undertaken at two scales of bird’s eye view and the human view scale, as seen in seminal greenway guidebooks such as those by Flink et al. (2001) and Hellmund and Smith (2006) . This study extends the scalar approach to greenway design by adding the third scale of “turtle view”.
Additionally, this article reinforces interdisciplinary design frameworks through an experiment in integration of science, mathematics and design. The integration is achieved through the combination of mathematics-based graph analysis, photography, and pattern- and section reading-based morphological analyses, in addition to ecosystem science theories of hierarchy and network and island biogeography, in design analyses, which are eventually used in decision making on design. Next question to ask, along this line, would be on technology; the level and role of it in enriching the design syntax of an urban greenway.
Lastly, the study articulates the design syntax for urban greenways which despite in nascent stage, offers a fundamental design grammar or framework to greenway professionals, for conceptualization of urban greenway designs and section drawings that push the frontiers of design thinking, through addition, subtraction, modification or complete alteration to the proposed design syntax, and address the wicked design problem of ubiquitous sameness.