Reconnecting River-City: A Visibility and Accessibility Assessment of the Ping River’s View Characters in Chiang Mai City

Abstract

A river’s landmarks have advantages in attracting people to engage with natural/historical settings. However, uncontrolled development can have negative effects on the visual and obstruct people’s access. In this context, researchers have highlighted obstacles to these landmarks and suggested features of the relationship between the visibility and accessibility to these landmarks, aiming to preserve heritage sites. This project evaluated riverscape landmarks to develop a strategic urban design that uses scientific and spatial toolkits to maintain the historic landmark on the riverside in Chiang Mai city. The methodology utilized for GIS included visibility and accessibility assessments as variables for analyzing interconnections and classification utilizing the statistical method of hierarchical clustering analysis (HCA). The findings indicate differences in the accessibility of angular step coverage (ASC) and walking distance coverage (WDC), which have an impact on landmark designation. The city-level landmarks have the highest ASC, while various religious landmarks display the highest visibility. These factors have a unique impact on the HCA results, which are categorized into six groups that are consistent with the historical content and purpose of the landmarks. The clustered groups represent the strategic design of the riverscape, which necessitates policies to enhance the potential for preserving these icons as part of the historic landscape.

1. Introduction

Cultural heritage is a vital resource for sustainable communities and urban development. The beneficial effects of engaging with various types of historic sites on wellbeing have been evidenced in the academic literature. Spending time at heritage sites has been linked to restorative effects, including reducing feelings of anxiety and urban fatigue [1], while experiencing a historic natural environment influences healthy habits (e.g., walking) and improves self-esteem and emotional wellbeing [2], providing higher levels of happiness [3]. Historic sites can also support social cohesion [4] and contribute to the creation of identity and sense of place, which are vital components of heritage conservation [5,6]. Providing the public with opportunities to experience historic settings has tremendous benefits at all levels, ranging from the individual to the social and communal levels [7], and cities should pay attention to these benefits rather than only focusing on the impact that development has on heritage [8]. Urban heritage has been recognized as an important component of improving urban quality of life. The current Sustainable Development Goals (SDGs) emphasize the need to preserve urban heritage and make cities livable for all. Goal 11 seeks to “make cities and human settlements inclusive, safe, resilient and sustainable”, whereas Target 11.4 seeks to “strengthen efforts to protect and safeguard the world’s cultural and natural heritage” [9]. The UNESCO’s Recommendation on the Historic Urban Landscape (2011, page 2) highlights that “Urban heritage, including its tangible and intangible components, constitutes a key resource in enhancing the livability of urban areas, and fosters economic development and social cohesion in a changing global environment. As the future of humanity hinges on the effective planning and management of resources, conservation has become a strategy to achieve a balance between urban growth and quality of life on a sustainable basis”. Efforts should thus be made to ensure that heritage of all types is easily accessible for all individuals in their daily activities [10,11].

Accessibility has become a critical concept in management strategies for engaging people with heritage sites/objects. It refers to the capacity for individuals to access specific places or use specific facilities and services via different modes of transportation [12,13,14]. Barriers that prevent people from accessing heritage can include physical, cultural, and financial constraints [15]. Theoretically, to investigate person–environment interaction, and its application is quantifying the degrees of connectivity to arrival points which can be altered because of the conditions of the spaces in between. Accessibility of a person occurs through physical, perceptual, or a combination the two [13,14]. Accessibility assessment is based on subjective indicators that assess an individual’s perception and/or evaluation, typically through field studies (e.g., questionnaire and interview), and objective indicators which usually use quantitative measurement based on frequency and are external to an individual, so the results of these two measuring approaches do not necessarily have to be the same [16].

Walkability and visibility have recently attracted a lot of attention in quantifying accessibility in historic cities due to the impact of urbanization. Walking and viewing are physical access points that not only enrich the heritage experience [17] but also promote sustainable tourism [18] and historical urban regeneration and conservation [19]. Meanwhile, visibility plays a direct role in historic landscape conservation, acting as a tool capable of linking cultural and natural heritage sites as a whole image and later designating protected/important views. The influence of spatial configurations on walkability and visibility has been discussed by scholars. In recent research, the intensity of these two physical forms of access has been assessed using various methods to identify areas for improvement, thus guiding and facilitating design, particularly with the aim of meeting accessibility and related building and planning regulations. Researchers have pointed out that several aspects have negative effects on visitors’ impressions and their desire to approach historic places by walking, including the street network and route connectivity, which can increase travel time and distance [20,21,22]. According to Yuan et al. (2023), even in identical grid-based roadway networks, walkability is still determined by the quality of the streetscape [23]. Prior studies on the historic cities characterized by mass tourism also agreed with this and suggested that urban designers not only promote connectivity between routes to the sites alone but also take into account the legible landscape by adding more landscape features, such as navigation signs to guide people to specific places [24,25] and facilitate wayfinding [19,26]. Askarizad et al. (2022) also proposed the idea of setting recognizable features, such as urban landmarks and religious buildings, in visible locations, especially in areas with poor spatial legibility due to the spatial configurations of the built environment [27]. Using landmarks as one of the urban features, the urban theory by Kevin Lynch (1972) discusses how to use human perception in time–space to produce urban imageability and effective wayfinding in a city. The arrangement of landmarks in relation to the environment along the edge of a road or river provides a well-recognized image of a city due to their dominant characteristics and symbolic importance. The greater visible landmark from a distance or only in restricted localities aids in providing directions on a different scale [28,29].

In this regard, Viewshed is accepted as an analysis tool that provides significant advantages in determining potential areas for improvement in order to maintain a legible landscape based on the visible areas of important landmarks/features from given viewpoints [30,31], identifying the areas to protect from the visual effects of built environments [32], and understanding the historical/cultural relationship between landmarks [33]. However, a number of studies have confirmed that the visibility of a landmark can be measured in relation to the built environment around it. The surrounding buildings’ height and scale are the key elements decreasing the visibility of historic sites [34]. Sarihan (2021) claimed that additional criteria, such as observer position, distance from the site, dense neighborhoods, and adjacent building forms, should be prioritized while simultaneously advocating for the preservation of open space around the site [35]. According to Liu et al. (2022), the site’s prominence in architectural design and its height in comparison to its surroundings can attract visitors’ attention [36].

These elements present a number of challenges. In addition, landmarks along historic rivers require further investigation. However, previous studies have focused on determining the effect of landscape features on visual quality perception regarding the urban waterscape [37,38]. In waterfront areas, spatial characteristics influence their use for recreational activities [39], while the built environment also affects the vitality of the waterfront in historic urban areas [40]. Thus, the study of historic rivers emphasizes the crucial role of the surrounding infrastructure and architectural forms in improving the urban visitor experience and reconnecting people and water [40,41]. Historic rivers around the world are currently under threat from urbanization, particularly those located in urban areas. The riverbank area, which has rich historical and cultural heritage, can potentially be harmed by development projects, and the built environment may create a barrier between people and the river if regulated planning and development do not take cultural and natural heritage conservation into account [42]. As a result, the edge of a river should allow visual or motion penetration to increase connections with the rest of the city structure, which can be accomplished by boosting accessibility or recreational use [28]. To date, there has not been as much interest in investigating urban historic rivers.

In the absence of previous riverscape and landmark evaluations, the objective of this study is to analyze the visibility and accessibility of riverscape landmarks using spatial analysis to identify features based on these landmarks. The method was used to determine the need for alternative urban plans based on visibility and accessibility characteristics. This study provides a procedural technique that combines spatial and statistical analyses to assess cultural resources and to identify potential areas for improvement to further aid in historic riverscape conservation and design guidelines to enhance the heritage experience in cities.

2. Materials and Methods

2.1. Case Study: The Ping River in Chiang Mai

Chiang Mai is a city in northern Thailand. It was the ancient capital of the Lanna Kingdom. The city of Chiang Mai previously had another name, “Noppaburi Sri Nakhon Ping Chiang Mai”, which refers to a city on the banks of the Ping River. The historic walled city of Chiang Mai has an almost square shape and was built according to the royal command of King Mengrai, whose exceptional city planning led to the construction of a city on flat terrain at the foot of Suthep Mountain, with the Ping River serving as a lower basin to the east. In addition to offering fertile ground suitable for habitation and cultivation, this physical geography also indicates that this location is capable of draining water from higher to lower levels, preventing flooding in the ancient city area. For generations, the Ping River has been home to people with diverse cultural backgrounds. Local settlements, including Mueang Sad, Wat Ket, and Fa Harm, thrived on both banks of the river. According to Easum (2023), the Ping River area has been recognized as one of the city centers of Chiang Mai, developing alongside the old walled city, which was home to royal palaces for the highest-ranking local royal elites, important markets, temples, and sacred spaces [43]. The Ping riverbank was also inhabited by outsider groups, especially American missionaries; British diplomats; British subjects from Burma, India, or the Shan State; Chinese merchants; and Siamese officials. The Ping River traditionally played a significant role in the local economy and Lanna culture because it served as the main corridor for trade with other communities and kingdoms, including traders from India, Myanmar, and Yunnan, among others [44]. It was also used as an important cultural corridor for Chiang Mai inhabitants. It was a year-round gathering place for Lanna rituals and culture that were centered around the Ping River.

Currently, the role of the Ping River has shifted. However, it continues to provide water for agriculture and urban consumption. Even though people are less dependent on the river for transportation and trading activities, the riverside area is still used for recreational and tourism activities. People can see the riverscape atmosphere by taking a scorpion-tailed riverboat cruise, which was once employed as a mode of transportation on an occasional basis. Furthermore, different city celebrations like the Songkran Festival (water splashing) and the Loy Krathong Festival (floating water lanterns) are held there. As a result, numerous restaurants and hotels have sprouted up along the river. Currently, it appears that the historic landscape of Chiang Mai’s city is being affected by large-scale projects and intrusive buildings as a result of rapid urbanization and unregulated building control and urban planning, notably prior to 2012 [45]. This situation brings adverse effects on the city’s visual integrity and significant values. The walled city as well as the area near the river are full of inappropriate built environments.

In the case of Chiang Mai, city planning and regulations appear to lack appropriate measures to mitigate the adverse impacts of development with an optimal or reasonable intensity of control and to safeguard the interlinkage between cultural and natural heritage. Land use policies represent a planning instrument that can encourage growth. They also play a major role in accelerating changes in the urban fabric and landscape. For example, zoning the city into specific land uses, such as business zones or industrial zones, will influence patterns of use and bring about a greater volume of larger buildings in certain areas. Regulatory systems should aim to cultivate sustainable development in historic cities by balancing the historic and development dimensions. The City Comprehensive Plan (fourth revision, 2021) sets forth the gathering of public opinions [46]. The land use of Chiang Mai is categorized into 15 zones, according to which the heights of buildings, the ground area coverage (GAC), and the floor area ratio (FAR) are determined. In response to the specified purposes, maximum building heights are calculated from the construction surface to the ceiling, excluding the roof area. However, this regulation does not apply to utility structures like electric poles and transmission poles. Buildings with a height of 12 m are often allowed in most land uses, with the lowest height restriction (9 m) only being applied to the conservation residential zone, while other regions adjacent to the conservation area along the river have no height restrictions, with only GAC and/or FAR regulations being issued. Several historical and natural areas appear to have insufficient protection, particularly the area between the walled city and the Ping River, which has no height restrictions but strict GAC and FAR regulations. Due to the current predicament, the city’s historic landscape and the interlinkage of the river and the people are threatened.

2.2. Study Area

This study’s investigation area included both banks of the Ping River, which serve as the city wall’s perimeter. Because this study attempted to assess the visibility and walkability of the historic sites located on the riverside, the area was determined by a buffer radius of 500 m from the river, which is a common value set for measuring visibility in urban areas [47,48]. Similarly, the walking service distance was determined as the distance that people are willing to walk to reach nearby parks or local public transport stops within 4–6 min, as guided by prior studies [49,50].

The study area consisted of 19 historic sites differing in type and height (Figure 1 and Figure 2). These included museums, public figures’ residences with 2- or 3-story buildings, religious places (i.e., Buddhist temples, Chinese temples, Sikh temples, Muslim mosques, and Christian churches), and monuments. There are also river-crossing bridges, namely Nakornping Bridge, Chansom Memorial Bridge (or Khuakhaek), Nawarat Bridge, and Iron Bridge. For details of the 19 historic landmarks, the historic content is provided as part of the research narrative in this study as primary support for the riverscape design strategies. Therefore, a brief history of the landmarks is described below.

(1)

The Chiang Mai Philatelic Museum was originally the Payap (Northern) Provincial Courthouse, established during the modernization of Siam, and is a one-story brick-and-mortar building. Later, this building was used as the first post and telegraph office in Chiang Mai Province, officially opening on 1 April 1910. Subsequently, in 1990, the Communications Authority of Thailand renovated the building and established it as a postage stamp museum [51].

(2)

The Northern Telephone Museum was established by TOT Public Company Limited to preserve the original telephone exchange building, established in 1950, which is considered the location of the first telephone exchange in the region. It is an old building that serves as a source of historical learning. The museum is a two-story building [52].

(3)

Chedi Khao may not be a pagoda in a temple or ancient site. However, this landmark is located on the banks of the Ping River, in the middle of the intersection of Wichianon Road and Wang Sing Kham Road, near the Chiang Mai Municipality Office and Nakornping Bridge. Since the white pagoda does not have the same shape and height as other pagodas, which are religious objects, some people think that the pagoda may be a stupa containing the ashes of a legendary Burmese ruler or an influential person who ruled Chiang Mai from 1558 to 1774 [53].

(4)

The Residence of the Chief Justice was related to the landmark in Item (1) during the modernization of Siam (Thailand). The central government introduced the justice court administration into major provinces as a court of justice in 1895. Consequently, a special commissioner was appointed to supervise the provincial courts. That was when the provincial headquarters was established in Chiang Mai. The administration of the Payap Province Court began in 1898. Therefore, the commissioners required the residence near the justice court to facilitate administration in the area [54].

(5)

Nhong Kham temple is named after a marsh that is assumed to have been created by digging up soil to make bricks and then burning them to build the outer city wall of Chiang Mai. It appears in the archive in 1902. In fact, local history scholars confirmed from their investigations that this is a temple that the Pa-O or Tong Su people, an ethnic minority in Burma, worked together to maintain [55].

(6)

San Pa Khoi temple is estimated to have been built in 1881. This temple was initially located on the eastern bank of the Ping River and was called Wat Nang Liao. The area where the temple is located was flooded, so it was moved to its current location. The temple was named after the sub-district. This temple is about a hundred years old, based on evidence that the pagoda of this temple was built during the reign of King Kawirorot Suriyawong, the ruler of Chiang Mai at the time [56,57].

(7)

Tha Satoi temple was located on the eastern bank of the Ping River, with a small Chiang Mai-Lamphun cutting through it. When the temple was eroded and damaged by water, it was moved to its current location. It was originally called Wat Si Sroi Sai Mun. Around 1817, King Kawila, the king who restored the independence of Lanna, brought his army to establish a stronghold in this area, Wat Tha Satoi. In the area where Tha Satoi village was located in the past, the villagers made a living by making wooden sticks to pound large wood to beat bees and catch other animals. The villagers regularly traveled by boat between Tha Satoi in the east and Wat Chaimongkol in the west [56,57].

(8)

Sanjao Pung Tao Gong has an interesting history. Since ancient trade evolved to navigate along waterways, some Chinese merchants sailed over to live and do business in Wat Ket Karam, an old port in the market area on Chang Moi Road. The presence of Chinese merchants has brought dynamics to this area until the modern days. As more Chinese people began to live there, the first shrine in Chiang Mai was built based on the faith of the Chinese people, which is the Pung Tao Kong Shrine. This name is in Teochew and means “original community”. It is located on the banks of the Ping River, representing a boat trade area. It is believed to be more than 140 years old, because the number 2416 (1873) can be found on the roof’s structure [58].

(9)

The first church of Chiang Mai (Chiang Mai Community Church: CMCC) was founded during the early days of Christian evangelism. Rev. Daniel McGilvary and Rev. Jonathan Wilson established the church on 18 April 1868. It is called the First Presbyterian Church of Chiang Mai in English. It was also the first church in the north of Thailand. In the same year, King Kawilorot donated a piece of land on the east bank of the Ping River to be the location of the mission compound, which is now the location of the First Church of Chiang Mai and the First Church Region [56,57].

(10)

The Governor’s Residence was established at the same time as the City Hall. The provincial justice court separates the governor’s residence and workplace, which is different from the residences of vassal states, rulers, and city governors, which are usually in the same place or in overlapping areas. The Chiang Mai Governor’s Residence is an old building that has played a role in Chiang Mai for a long time. It was opened as a tourist attraction and an English language school for students in mid-2012 by the former governor, M.L. Panadda Diskul. In the past few decades, there has been a trend of moving government offices out of the city, such as the City Hall and the prison, allowing for greater expansion compared to the cramped space in the city, similar to Chiang Mai Province, where the current policy for using such areas is still unclear [59,60].

(11)

Uppakhut Temple was named after Phra Uppakhut or Phra Buakhem, a monk during the reign of King Ashoka the Great. Wat Uppakhut was established in 1757 and received royal permission for its boundary markers in 1913. Wat Uppakhut has an important tradition, which is the tradition of giving alms to Phra Uppakhut. Northerners believe that if there is a full moon of any month that falls on a Wednesday, or what is known as Peng Put, Phra Uppakhut will disguise himself as a novice and come to collect alms at midnight. Therefore, there is a tradition of giving alms at midnight [61].

(12)

Wat Saen Fang was built during the reign of King Saen Phu, the third king of the Mangrai Dynasty, around 1576. In the name of the temple, the word “Saen” comes from King Saen Phu’s name, while the word “Fang” comes from the royal faith of his ancestors. At that time, King Saen Phu intended to entrust his wealth to Buddhism. It is also an empty piece of land near a small river, a short distance from the Raming River (Ping River) [62].

(13)

Wat Sri Don Chai is located in the outer wall of Chiang Mai. The history of this temple’s construction is unclear, but it has been said that Wat Sri Don Chai was originally called Wat Pa Kluai and was an abandoned temple. Later, Phra Phothi Rangsi Marachisa, the provincial abbot of Chiang Mai at that time, gathered people of Buddhist faith to renovate and restore Wat Sri Don Chai [63].

(14)

Attaqwa Mosque, also known as San Pa Khoi Mosque, is located on the east bank of the Ping River in Chiang Mai Province. It is one of the seven Chinese mosques in Chiang Mai Province. This mosque was first built in 1967 and completed in 1969 by a group of both Chinese and non-Chinese Muslims. It is considered the first Islamic school in Chiang Mai Province, preserving Islamic culture and education in a manner similar to that in Kunming, Yunnan Province, China [64].

(15)

Ban Ho Mosque: In 1915, Chinese Muslims who immigrated to settle down in Chiang Mai Province agreed to donate money to buy land and to construct a mosque on the west side of Ping River. The mosque, made of bricks and mortar, cost approximately 3000 rupees at the time (approximately THB 2400). This is considered the first mosque building of Yunnanese Muslims who immigrated to Thailand in Chiang Mai Province. The community is generally known as “Baan Ho Islamic Mosque” [65].

(16)

Chiang Mai Religion Practice Center is a place for the religious activities of Buddhist organizations on important Buddhist days and for cultural and traditional activities for people in Chiang Mai Province. It was originally part of Uppakhut Temple. It was established as the Chiang Mai Buddhist Center Foundation on 15 January 1958, with the objective of spreading the principles of Buddhism through lectures, sermons, Dhammasakajja, Q&As, and other appropriate methods, spreading other knowledge and being a place for Buddhist activities and other activities in the city. Currently, in addition to important Buddhist activities, it is also used as a place for joint activities of the five religious groups of Chiang Mai Province [66].

(17)

Gurudwara Chiang Mai (Wat Sikh) is a religious site or temple (Gurdwara) for the Sikh community in Chiang Mai. It was originally a one-story wooden house with a large courtyard for religious ceremonies. It was built by a Sikh family, including the family of Mr. Esher Singh (the first Sikh to travel to Chiang Mai in 1905), Mr. Rattan Singh, Mr. Gian Singh, Mr. Wariaam Singh, and Mr. Amarathas Singh. In 1975, it was renovated again as a permanent building [56,57]

(18)

The church at Chiang Mai Christian College was established in 1968, when Protestantism in Chiang Mai Province was widespread and generally accepted, with an increasing number of believers. Therefore, the First Chiang Mai Christian Missionary Group discussed and built a new church. To accommodate religious activities and the increasing number of members, this church was discontinued, and the ownership was transferred to “Chiang Mai Christian School” to be used as a place to provide training on Christian ethics to students and as a symbol of the school until today [67].

(19)

Ket Karam Temple is assumed to have been built in 1971 B.E. (1428 CE). The original name was Wat Saket. It was built by Phraya Sam Fang Kaen, the father of Phraya Lokaraj (the ruler of Chiang Mai from 1442 to 1487 CE), who worked with Phraya Mueang, Phraya Kham, and Phraya Lue, along with 2000 followers, in the construction of Wat Ket. The chedi or pagoda at Wat Ket Karam is a replica of Phra Kesa Kaew Chulamani in Daowadungsa heaven. It is the annual pagoda for those born in the year of the dog who must come to pay homage once in their lives for good fortune. The replica pagoda has a slightly tilted tip because it is believed that the tip must not point directly up to Phra Kesa Kaew Chulamani in heaven [68].

2.3. Procedural Framework

The analysis method for this research included assessments of the visibility, walking distance, and angular step segments. This study assumed that the sites visible from most areas and that are more easily accessible by walking have the potential for improvement to promote people’s interactions with the river. The analysis was conducted in three stages. Firstly, the proportion of the visible area of the landmarks along the river was assessed through Viewshed, a tool used to determine the visibility of features from a specified location. Secondly, the walkability of the target sites was examined via GIS, considering accessibility to be determined as the site being easily reached within a few turns using angular steps and a walking distance within a radius of 500 m. Finally, the hierarchical clustering analysis employed statistics to determine the classification of groups, represented as view characters, depending on the features of the groups according to descriptive statistics and mapping (Figure 3).

2.3.1. Visibility Analysis

This stage aimed to assess the visual potential of the historic buildings located along the riverfront. We applied Viewshed in ArcGIS pro 3.3 (ESRI Inc.) to assess the visible areas of the historic places from the surrounding locations. Viewshed was suitable for this study because it provides a raster-based analysis of topographic wide vistas with different terrain heights. This tool creates outputs representing visible and invisible surface areas, indicated with values of 1 and 0, respectively. Given that the total viewshed was concerned with the visibility of the site’s location, a 1.6 m surface offset was added to account for the position of the average eye level of an adult. The viewshed was generated based on the buildings’ heights and input in the form of a feature offset. The height was determined by the highest building on the site. For example, Buddhist temples are sites that consist of many buildings, but their pagodas were used because they are the tallest buildings in the area. The viewshed was assessed in a buffer area with a 500 m radius around the site to focus on the visual service radius of the given places. The analysis required spatial data, such as elevation surface and buildings, to be input into the parameters for the analysis. In this study, we used a digital elevation model (DEM) with a resolution of 5 m × 5 m. However, the original DEM data did not include building data such as heights or locations. So, the researchers generated the surface map by adding the building data to the ground elevation. The building dataset was created based on actual heights and locations in the study area.

2.3.2. Angular Step Coverage

The angular step coverage (ASC) process aimed to evaluate the approach to a historic landmark. As a component of space syntax theory, angular segment analysis concentrates on the angular shift in direction inside the street segment rather than the axial line, which focuses on the link. The interpretation of angular change is important for assessing how city dwellers navigate and orient themselves [69,70]. It represents the shortest angular (fewest turns) paths that people may choose to reach their destination as opposed to shorter paths with more turns [71,72]. It relates to the local memory of navigation, which is appropriate for the approach employed by this study in terms of landmark coverage [72,73]. In Turner’s 2000 study, it was discovered that a tourist will take the shortest angular path rather than the shortest path measured by the Euclidean distance. The purpose of this study was to employ this potential in the process of approaching a landmark (the origin) as the input for an angular segment analysis that focused on changes in direction (turns).

Using the landmark as the origin and evaluating the angle change in the urban network system, this method calculated the near approach to the landmark. Initially, the GIS-based urban network system comprised an angle segment network for the depthMap X software version 0.8 created by UCL. The angular segment analysis prescribed the angular step for each landmark based on its origin. As the subject memory for selecting appropriate angles, the angular step employed 90-degree angles as the turning angles [74,75]. All direction changes were weighed in relation to their angular direction changes based on the finding that one turn in the angular segment analysis equals 90 degrees. For instance, in Figure 4, the angular step from origin a to b is 0.5 turns, while that of a–d is 2 turns, since a–b only has a 45-degree direction shift and a–d has a 180-degree total change from 90 degrees for a–c and c–d, respectively. Based on this assessment, this study limited the turning to two turns or 180 degrees as a measure of the primary accessibility to the landmark. The total length of the two turn segments was then measured without restriction. The segment’s length was taken into consideration in hierarchical clustering so that the grouping of landmarks could be discussed in more detail.

2.3.3. Walking Distance Coverage

The approach to determine the walking distance coverage (WDC) was identical to that for the angular step distance. The WDC used the landmark as the origin, just like the angular step, but it was not weighed. Rather, it used the segment length as a direct distance in all directions, with a radius of 500 m from the origin. According to the general comfortable walking distance, a 500 m radius was calculated [76,77]. The overall length of segments was then summarized and shown as the landmark’s walking distance coverage. Figure 4 illustrates alternative approaches to summarizing the total length from the origin. The WDC collected all lengths (l) within a 500 m radius of the origin regardless of weight. For instance, it gathered a, b, c, d, and e without exception; however, if a, b, and e exceeded 500 m, the extension was terminated at that point. The WDC served as the foundation for the landmark’s service radius and reach. The WDC and angular step were evaluated using a statistical method to classify the group with other input parameters.

2.3.4. Hierarchical Clustering Analysis

This stage involved evaluating the possibility of employing a hierarchical clustering analysis to classify the properties of landmarks based on similarity. The group assessment conducted using this statistical method provided insights into view characters, potentially leading to recommendations for the riverscape design strategy.

In this study, unsupervised clustering of the hierarchical clustering analysis (HCA) was employed. The input material produced by GIS included the following: the service radius of 500 m as the walking distance coverage (WDC), the distance from the river (DR), the viewshed of the landmark (VS), and the angular step coverage (ASC). Using Orange Canvas, an application for data mining, assessment, and visualization, the statistical method was performed and calculated [78]. All input materials in the hierarchical clustering analysis were used to generate linkage groups based on similarities. The HCA result and the optimal grouping step that best described the clustering were then determined by analyzing the distance matrix and dendrogram produced by the tool. The clustering group determination functioned as an additional attribute of the historic landmark and reverted to the landmark group map in order to yield a more coherent outcome. In conjunction with the input table (DR, VS, AS, and SR), the grouping map was explored to characterize each group’s view characters. The discussion was included in the riverscape design concept as a recommendation based on its view characters.

3. Results and Discussion

The importance of experiencing cultural heritage is evident in the physical and psychological benefits it provides to individuals and its promotion of social cohesion, sustainable tourism, and historical urban regeneration and conservation [1,2,3,4,5,6]. Hence, the emphasis on design solutions and interventions in this historic river city, which considers the benefits to wellbeing provided by heritage, highlights the need for accessibility assessment through a combination of walkability, accessibility, and visibility analysis methods via WDC, ASC, and Viewshed assessments. The research can be carried out holistically with the surrounding landscape.

3.1. Results Regarding the Viewshed, ASC, and WDC

In this research, the visible areas of the landmarks that can be seen from certain locations were measured.

Table 1. Statistical assessment results of visibility and accessibility.

No.	Name	Height (m)	Distance from River (m)	Viewshed (sq.km)	Walking Distance Coverage (m)	Angular Step Coverage (m)
1	Chiang Mai Philatelic Museum	6	104	0.17	5516	9758
2	Northern Telecoms of Thailand Museum	6	53	0.23	6385	9078
3	Chedi Khao	8	20	0.13	4721	5793
4	Residence of the Chief Justice 5	8	31	0.29	5355	11,061
5	Nhong Kham Temple	8	463	0.05	3812	6488
6	San Pa Khoi Temple	8	295	0.09	5588	5220
7	Tha Satoi Temple	8	211	0.08	2035	1229
8	Sanjao Pung Tao Gong	9	55	0.25	6393	8973
9	The First Church of Chiang Mai	9	75	0.28	5608	5419
10	Governor’s Residence	9	92	0.25	4053	10,827
11	Uppakhut Temple	10	313	0.21	6432	7909
12	Saen Fang Temple	10	472	0.09	4600	9914
13	Sri Don Chai Temple	10	434	0.06	2254	5868
14	Attaqwa Mosque	12	436	0.13	4749	3318
15	Ban Ho Mosque	12	243	0.25	4711	4708
16	Chiang Mai Religion Practice Center	12	223	0.27	5203	12,115
17	Gurudwara Chiang Mai	14	108	0.33	6201	5268
18	The Church at Chiang Mai Christian College	15	29	0.37	5921	7041
19	Ket Karam Temple	18	102	0.41	3649	5597

shows the detailed results for each site from the viewshed analysis of 19 landmarks located within a 500 m radius of the Ping River. As expected, the highest visibility is observed for the tallest sites in this study, namely Ket Karam Temple (18 m high), the church at Chiang Mai Christian College (15 m high), and Gurudwara Chiang Mai (14 m-high), with visible areas of 0.41, 0.37, and 0.33 sq.km, respectively. Meanwhile, the lowest visibility was observed for the sites considered to be low-rise buildings located further from the river, namely Nhong Kham Temple (8 m high), followed by Sri Don Chai Temple (10 m high) and Tha Satoi Temple (8 m high), at 0.05, 0.06, and 0.08 sq.km, respectively. Interestingly, the Residence of the Chief Justice, the First Church of Chiang Mai, Sanjao Pung Tao Gong, and the Governor’s Residence have high visibility, with visible areas of approximately 0.25–0.29 sq.km despite being low-rise buildings with a height of about 8–9 m. Similarly, Ban Ho Mosque and Chiang Mai Religion Practice Center (12 m high), which are located a little bit further from the river but are near a main road, have visible areas of 0.25 and 0.27 sq.km, respectively (see Figure 5). According to these findings, we can validate previous research’s conclusions [27,35], which state that the locations of taller features and more surrounding open spaces can affect landmark visibility.

The results of the walking distance coverage (WDC) and angular step coverage (ASC) (

Table 2. Summarized descriptive statistics of the assessment results.

Variable (n = 19, in Meter)	Mean	SD	Min	Median	Max
Distance from River (DR)	197.81	160.79	20	108	472
Viewshed (VS) (sq.km.)	0.21	0.11	0.05	0.23	0.41
Walking Distance Coverage (WDC)	4904.53	1291.53	2035	5203	6432
Angular Step Coverage (ASC)	7136	2865.87	1229	6488	12,115

) revealed another aspect of walkability. When a distance of 500 m was used in the analysis, it was possible to define the street network and connectivity in terms of the function and location of the landmarks. The results for the WDC differed from those for the ASC. The standard deviation is 1665.4 m, the average value is 4904 m, and the range is 2254 to 6432 m. The WDC has a much lower standard deviation than the ASC, indicating that each landmark’s coverage range is less distributed and differentiated in length than in the ASC. Upon initial examination, the WDC appears to be incapable of differentiating between the characteristics’ lowest and highest values. The longest group mostly includes semipublic institutions that serve communities, such as temples, shrines, churches, and museums (Uppakhut Temple, Sanjao Pung Tao Gong, Telecom Museum, Gurudwara, and Chiang Mai Christian College Church, for instance). These sites are situated on either side of the river, and they are all notably related to the everyday activities of the local community. For example, Sanjao Pung Tao Gong is the primary shrine dedicated to commerce; Uppakhut Temple is a community temple established for customs and beliefs; and the primary function of Chiang Mai Christian Church is that of a school. They permeate the local urban network, as represented by the WDC value. However, city-level functions of landmarks such as the Governor’s Residence, the Chief Justice’s Residence, and the Chiang Mai Religious Practice Center have modest permeability. The lowest WDC level also features interesting characteristics, most of which are local religious sites. Their roles are reflected in their WDC permeability; for example, Ket Karam Temple, Sri Don Chai Temple, and Tha Satoi Temple, with WDCs of 3649, 2254, and 2035 m, respectively, primarily serve their communities’ networks (see Figure 5). The WDCs in this study’s material were very responsive to and dependent on their local networks rather than the city-level networks; still, the WDCs demonstrated the connections between them and the possibility for riverscape walking streets alongside rivers and/or the growth of tourist attractions with landmarks.

According to the methodology, the angular step coverage (ASC) represents the approach as a from–to distance relating to the angular changes while turning. Its range is between 1229 and 12,115 m, with an average of 7136 m and a standard deviation of 2865.87 m, indicating a larger difference in value than for the WSC. Significant findings from the ASC show that the iconic properties with the highest angular segment lengths are those next to main streets and the Nawarat Bridge. For example, the Chiang Mai Religion Practice Center, the Residence of the Chief Justice, and the Governor’s Residence are landmarks that are close to one another and located next to the Nawarat Bridge, which connects the main street of Chiang Mai to these landmarks. At 12,115, 11,061, and 10,827 m, respectively, they have the highest ASC.

On the contrary, the collection of landmarks that represent local community centers, such as Tha Satoi Temple, Attaqwa Mosque, and Ban Ho Mosque, had the lowest angular segment coverage at 1229, 3318, and 4708 m, respectively. Evidently, the high-ASC landmarks and the low-ASC landmarks have comparable character traits. The high-angular-length group’s institutional properties were established in Chiang Mai during the modernizing era. Since the governor’s and justice court’s offices have been moved to the outskirts of Chiang Mai, these properties are either mostly empty or have a reduced purpose. Conversely, features that function as the hub of local communities were highlighted by the low-angular-length group. These are situated in quiet, peaceful residential areas in the middle of secluded areas, where discretion is required. The urban network underpinning these distinct groups of sites demonstrates the public need for urban connectivity. This angular segment analysis reveals the underlying logic of landmark locations and provides a partial recommendation for public space rehabilitation in the near future.

Interestingly, the overall results regarding the viewshed, WDC, and ASC reveal that the river can be reached by viewing and walking from Chiang Mai Philatelic Museum, Northern Telecoms of Thailand Museum, Chedi Khao, the Residence of the Chief Justice, Sanjao Pung Tao Gong, the Governor’s Residence, Gurudwara, and the Church at Chiang Mai Christian College, which are all close to the riverfront, except for the Chiang Mai Religion Practice Center, which is situated a little farther away but still on a main road (see Figure 5).

3.2. Results of the HCA

The primary statistical method used to aggregate all the assessment data and map them into clustering groups as specified in the conceptual framework was hierarchical clustering analysis (HCA) and mapping. The distance matrix’s gradual color display indicates both the dissimilarity groups and the clustering’s similarity (Figure 6). It clearly reveals two comparable groups (upper left; dark color) from Uppakhut Temple to Gurudwara and from San Pa Khoi Temple to Sri Don Chai Temple (bottom right; dark color), with Tha Sa Toi Temple standing out as an anomaly unrelated to any landmark (bright color). The distance matrix is able to identify feature similarities and provide a detailed relationship between the locations. For example, San Jao Pun Tao Kong is closely related to the Telecom Museum, the First Church of Chiang Mai, and Gurudwara; these can also be reflected as a dendrogram, as seen in this manuscript. For grouping purposes, this dendrogram will be converted into a hierarchical structure.

In the hierarchical clustering analysis, there were six unique clustering groupings. The characteristics of the landmarks are strongly reflected in these six HCA groups. With a notable dissimilarity compared with any other landmark, Tha Satoi Temple (C5) is eliminated from all groups based on the grouping selection (Figure 7) based on the distance matrix. Despite this, the dendrogram of C5 is combined with that of C6 (Saen Fang Temple, Nhong Kham Temple, and Sri Don Chai Temple) in greater depth. Additionally, this group of six is able to identify character traits that are comparable based on their roles, locations, and accessibility within urban networks. Six groups of landmarks are identified based on their variables from a statistical perspective using the distance matrix and HCA. Each group displays unique characteristics that serve as representations of the view characters.

3.3. View Character Map

The view character map, generated by HCA, provides detailed information about each view character in the group, as well as their positions (Figure 8). The following are the view characters based on the HCA classification. The C1 group includes Ket Karam Temple, Christian College Church, Chiang Mai’s First Church, and Gurudwara Chiang Mai. This group depicts the diversity of riverscape landmarks and represents holy spaces in the communities, with the highest VS value and a moderate DR (29–109 m). The C2 group includes the Chiang Mai Religion Practice Center, the Residence of the Chief Justice, and the Governor’s Residence. The landmarks in this group are located next to the Nawarat Bridge. They represent the function of space at the city level and have the highest ASC. Since these sites symbolize the modern era of Chiang Mai City, their placement makes them highly promising for development as integrated green/urban spaces, such as city historical parks. The C3 group includes Chedi Khao, the Philatelic Museum, the Telecom Museum, and Sanjao Pung Tao Gong. This group represents the landmarks on the west bank of the river. They share a street with the market, which has moderate values regarding the VS, WDC, and ASC. They are also quite close to the river (DR). These sites can serve as prominent elements on the river’s west side and connect as a tourist route. The C4 group includes San Pa Khoi Temple, Attaqwa Mosque, Uppakhut Temple, and Ban Ho Mosque. This group serves as the hub of the local community’s religious activities. The low VS (between 0.09 and 0.25 sq. km) and the greater distance from the river (DR) (between 243 and 436 m) set this group apart from C1. However, these sites are located in local communities isolated from the main street. With VS = 0.08, WDC = 2035, and ASC = 1229, the C5 group is extremely special, comprising the Tha Satoi Temple alone. With only a local street connecting it, this temple is situated in a remote area on the east side of the river, giving it the lowest accessibility score in relation to the WDC and ASC. It actually represents the local community’s most highly secluded landmark (Tha Satoi). The C6 group consists of the Saen Fang, Nhong Kham, and Sri Don Chai temples. This group comprises landmarks located far from the river. The DR in this group is the highest among the groups (472, 463, and 434 m, respectively). Some of the landmarks in this group are not visible from the river, but they have the potential to connect to the river route or serve as points of interest.

The riverscape of Chiang Mai can be categorized through the use of a statistical assessment and spatial analysis, as they combine multiple historical centers and layers. They display the linked landmarks of interest and the possibility of joining these landmarks with the existing and expanding urban network. This study’s assessment of the view characters is consistent with the local history. According to the view characters, C1 and C2 serve as key city and local nodes for the Chiang Mai riverscape, while C3 comprises a chain of landmarks that links the area on the west side of the river. C4 and C5, on the other hand, are undiscovered gems that serve as hubs for the neighborhood and are in more secluded regions, requiring less of a visual magnet. C6 comprises landmarks that extend further from the river than others and serves as a link connecting the river and the city.

4. Conclusions

The purpose of this study was to demonstrate and categorize the riverscape by utilizing landmarks as a key node for maintaining visual integrity. This study employed a combination of statistical methods and geographical analysis to explain the features of the landmarks along the Ping River in Chiang Mai, Thailand. The outcomes can be classified into landmark groups based on their distinguishing characteristics. The classification categories determined the difference in location, possibility for development, and unique riverscape design strategies. In the case of prior studies, accessibility was determined according to the legibility and the connectivity of the street [23,24,25,26,27,28,29]. This study adds that landmarks should be visually open and provide physical access by walking. It also suggests maintaining open spaces around the sites, especially around the low-rise landmarks located near the river, while regulating height and design control in association with historical landmarks to make a unique contribution to the townscape’s character.

The findings of this study also highlight how crucial accessibility is a factor in understanding a landmark and how it interacts with urban networks. The combination of visibility and accessibility allows landmarks to consider not just the landmark and its surroundings but also the relationships between landmark-landmark, landmark-community, and landmark-city. This study suggests focusing on the riverscape as a whole and then creating detailed designs based on its classification group in order to establish a riverscape design strategy that responds to these results. For instance, the city-level landmarks (C1) ought to be preserved as historically significant and iconic city landmarks, while the public space along the river might be expanded by utilizing the C2 group as the core and connecting it to historic/green spaces.

This methodology’s toolkit includes historical information on landmarks, statistical methods, and spatial analysis. It has been demonstrated that using these methods together increases comprehension of the riverscape landmark. The visual conditions and geographical attributes of landmarks that reflect local preferences and urban network permeability are revealed by the visibility and accessibility tools in spatial analysis. The statistical method that refers to the spatial result and can categorize it as a group can be used in conjunction with the spatial analysis tool to present the detailed attributes of each landmark. Finally, the design idea is conveyed by classifying view characters into different groups. Using view character as a medium, the procedural toolset in this research aims to transform the academic results or geographical analysis of riverscapes into practical applications. The spatial analysis and statistical methods then narrate historical elements in a coherent manner. This outcome may provide the groundwork for future improvements to the study area’s riverscape and validate the historic community’s preferred visual esthetic as determined by scientific data.

For further research, expanding the riverscape factor variables is necessary. Community preferences and usage should be taken into consideration. The viewpoint of the riverscape as a tourist destination may be expanded by including user experiences from locals and visitors. Furthermore, in response to appropriate city planning, further studies can be conducted through scenario testing. The evaluation tool can also be broadened; for example, it may require a specific set of tools, such as a network analyst or a 3D analyst, to examine the focal point corresponding to a landmark in the riverscape from a certain perspective. These studies, however, will concentrate on scope area visual and accessibility assessments. This suggests that the riverscape study should be evaluated using a number of tools to offer insights into design options based on the scientific approach of classification.