Visual Impact Assessment Method for Cultural Heritage: West Lake Cultural Landscape in Hangzhou, China

Abstract

Visual Impact Assessment (VIA) is a critical tool in managing cultural heritage, evaluating the impacts of development and construction projects on the visual aspects of heritage values. However, VIA is often constrained by subjectivity, low public participation, and a lack of generalizability. This study aims to develop a methodological framework for a more objective and comprehensive assessment of visual impacts on cultural heritage. The study establishes criteria for indicators based on the value attributes of cultural heritage, develops an assessment indicator system, and integrates visual sensitivity assessment through multi-factor calculations with visual perception assessment using the AHP method and questionnaire surveys. This constructs an assessment framework that combines both objectivity and subjectivity. The Shangri-La Hotel East Building project at the World Heritage site of the West Lake Cultural Landscape of Hangzhou, China, is employed as a case study to empirically demonstrate the framework’s practicality and effectiveness. The results indicate that the Shangri-La East Building significantly impacts the attributes of the West Lake. The conclusion demonstrates that the indicator system, grounded in the attributes of cultural heritage, enhances the framework’s applicability across different contexts. The integrated assessment framework, which includes both a quantitative assessment of visual sensitivity and a public-participation-based assessment of visual perception, is shown to be effective in predicting the visual impacts of proposed projects on heritage values. The study also underscores the importance of Heritage Impact Assessment as a preliminary evaluation.

1. Introduction

Heritage Impact Assessment (HIA) seeks to identify and assess the impacts of construction projects on cultural heritage and provide mitigation measures to achieve a balance between heritage conservation and sustainable development [1]. Visual Impact Assessments (VIAs) of cultural heritage sites are a key component of HIA that focus on assessing the potential impacts of construction projects on the visual landscape of a heritage site [2,3,4]. This includes direct interference with sight lines and disruptions of the site’s original landscape background [5].

As evidenced in UNESCO’s State of Conservation (SOC) reports for World Heritage sites, construction and development have emerged as a prominent concern regarding cultural heritage, ranking second only to management and institutional factors from 1979 to 2013 [6]. Notable examples include the Jahan-Nama tower in Isfahan, Iran, the Ohkta Center skyscraper near the historic center of St. Petersburg, Russia, Waldschlösschen Bridge in the Elbe Valley of Dresden, Germany, and the new high-rise buildings of the Maritime Mall in Liverpool, United Kingdom. These cases illustrate how urban development has resulted in the destruction of the visual landscape of cultural heritage sites and caused irreversible damage to heritage values. Consequently, Elbe Valley in Dresden, Germany, and the Maritime Mall in Liverpool, United Kingdom, were removed from the World Heritage List [7,8]. These cases underscore the complex challenges involved in protecting cultural heritage in an era of globalization and emphasize the crucial role of visual landscapes in cultural heritage protection.

In 2009, UNESCO and ICOMOS published the Guidelines for the Impact Assessment of World Heritage Properties, providing guidance on HIAs [5]. These guidelines have been continuously updated with the latest insights and practices [9], and in 2022, the Guidelines and Toolkit for Impact Assessment in the Context of World Heritage Properties was released [2]. However, these international documents aim to facilitate the unified management of World Heritage properties. They focus on procedural steps, processes, generic content, and requirements, but do not propose specific technical approaches to assessment. UNESCO also advocates that States Parties conduct in-depth research and practices tailored to the actual situation of heritage sites.

Most methods and theories of VIAs originate from disciplines such as urban planning, landscape architecture, and geography, given their extensive focus on visual impact [10,11,12]. While visualization and quantification methods are widely used, traditional indicators often focus on visibility and distance, neglecting other dimensions of visual impact. In the context of cultural heritage, assessment indicators should prioritize heritage value, but the diversity of cultural heritage forms presents challenges in developing universal metrics. Moreover, the nature of the public interest in cultural heritage mandates public participation in the assessment process. The increasing impact of urban regeneration and development on cultural heritage sites underscores the need for innovative assessment techniques to effectively evaluate potential impacts on heritage values.

This study aims to develop a more objective and comprehensive method for assessing the visual impact of cultural heritage. It proposes an assessment framework with an indicator system based on the value attributes of cultural heritage, integrating the methods of visual sensitivity assessment and visual perception assessment. A case study of the Shangri-La Hotel East Building at the World Heritage site of the West Lake Cultural Landscape of Hangzhou, China, demonstrates the framework’s effectiveness in predicting visual impacts and informing mitigation measures. The results indicate the significant visual impact of the building on the West Lake’s valued features. Proposed mitigation measures, including reducing the building’s height and modifying the roof design, align with actual implementation. The conclusion highlights that the emphasis on attributes in heritage management enhances the applicability of the indicator system. Integrating visual sensitivity and visual perception assessments strengthens the assessment framework’s relevance for cultural landscapes. Additionally, assessing potential risks and devising appropriate mitigation strategies are crucial for the effective conservation of heritage and the promotion of sustainable development. This study provides a scientific approach to predicting the visual impact of development on heritage values, facilitating proactive mitigation measures.

2. Literature Review

Visual Impact Assessment (VIA) has evolved into an autonomous assessment apparatus that employs a plethora of methodologies and instruments to evaluate the prospective visual consequences of construction operations on cultural heritage sites. Notable among these are the BLM Contrast Rating Method, the Landscape and Visual Impact Assessment (LVIA), and the Queensland Scenic Facilities Compilation Method.

The BLM Contrast Rating Method was developed by the U.S. Bureau of Land Management (BLM) [13] in conjunction with the Forest Service (FS) [14] under the aegis of the National Environmental Policy Act of the 1960s [15]. The method utilizes a Visual Resource Management (VRM) system to generate a series of visual resource inventories, categorizing visual resources and associated conservation objectives. The assessment process is based on an array of elements, including landform, vegetation, water bodies, color, and adjacent landscapes. These elements are used to rate the scenic quality management area as high, medium, or low, ensuring the rational utilization and protection of landscape resources through scientific assessment. The Berkeley Contrast Rating System, developed in the late 1970s by the BLM, FS, and the University of California, Berkeley (UC) [16,17], is a derivative of the BLM method [18]. It refines the quantitative analysis of Visual Impact Assessment, particularly in the assessment of visual elements at key viewpoints. The Prototype Visual Impact Assessment Manual (PVIM) standardizes the VIA process by using contrast ratings to quantify the severity of scenic visual impacts against the visual elements of proposed projects [19]. However, this method relies on subjective viewpoint selection and lacks a public participation mechanism, thereby neglecting the public’s perception and needs regarding landscape changes.

The Landscape and Visual Impact Assessment (LVIA) system, developed in the UK since the 1950s, regulates and protects landscape resources by assessing both “landscape receptors” and “visual receptors” in parallel [20,21,22,23]. The methodology is founded upon a dual classification of landscape resources and visual amenities [24]. It considers both the people and the landscape in a reciprocal manner [25], which is particularly applicable to cultural landscape heritage. However, although the LVIA system incorporates public participation in the assessment process, its sensitivity assessment is primarily based on qualitative descriptions and is somewhat subjective. Furthermore, there is no explicit provision for public participation, which may impact the fairness and comprehensiveness of the assessment.

The Queensland Scenic Amenity Methodology (QSAM) originated from Australia’s national planning policy for coastal environmental protection and has been extended to include Visual Impact Assessment (VIA) for development projects in coastal areas. This methodology comprises the two following principal elements: a baseline public landscape preference survey and landscape change assessment. It defines four “visual domains” (bush, rural, urban, and coast) and several “visual elements” to reflect the general public preferences regarding different landscape types. For any development project, the three most heavily utilized and affected public viewpoints, located no more than five kilometers from the project site, are selected for impact assessment by simulating the measurement of visual areas and elements [26]. While this methodology aims for objectivity, its results still depend on the assessor’s perspectives.

The practice of conducting landscape visual sensitivity assessments originated in the 1960s in high-income countries in the Western world. In the 1980s, with the refinement of legislation, regulatory frameworks, and management systems pertaining to the conservation of landscape resources, the fundamental techniques of landscape visual sensitivity assessment were formalized. The initial focus of visual sensitivity studies was on establishing the theoretical and conceptual basis for assessment. This included analysis of the perceived value of the landscape [27]. Beginning in the 1990s, assessment methods introduced a variety of factors, such as slope, distance, visual probability, and salience, to quantify the visual sensitivity of landscapes. This approach has continued to the present day [28,29,30]. To analyze sensitivity in a more comprehensive manner, some of these introduced methods consider visual absorption ability, activities, and number of viewers [31]. The benefit of the visual sensitivity assessment approach is that it is frequently employed in conjunction with Geographic Information Systems (GISs) for the processing of geographic information, including Digital Elevation Models (DEMs) of landscapes [31]. Through the application of quantitative analytical techniques, the susceptibility of diverse visual environments to visual alterations can be ascertained.

While current Visual Impact Assessment methods are distinctive in their application, they typically encounter three significant challenges. First, there is a tendency towards subjectivity in the selection of viewpoints and in the overall assessment. Although LVIA introduces the concept of sensitivity to assess the visual prominence of landscapes, its specific assessment often relies on qualitative descriptions [32] due to the absence of quantitative factors such as viewpoint distance, slope, and visual chance, potentially leading to subjective bias that affects the accuracy and reproducibility of the assessment. Secondly, public involvement is limited. While public participation is permitted in the perception assessments of most methods, fully considering public opinion is challenging due to the specialized nature of the assessment content and the lack of clear regulations. Third, the universal applicability of assessment indicators is weak. The indicators of current methods are closely tied to specific landscape features and require customization across regions, limiting their broader applicability in diverse geographic and cultural settings. Additionally, the selection of indicators, often dependent on professional researchers, restricts their flexible application to varied landscapes, hindering the assessment’s objectivity and comprehensiveness. The complexity of cultural heritage necessitates a robust methodology for evaluating the visual effects of development projects. This methodology should be capable of accurately predicting visual impacts and enabling timely interventions to mitigate these impacts.

3. Methodology

3.1. Assessment Framework

This study proposes an assessment framework integrating qualitative and quantitative methods, employing a more objective, universally applicable, and inclusive approach to address the assessment needs of various cultural landscapes.

The study establishes a criterion for selecting assessment indicators based on the attributes of cultural heritage. The term “attributes” is a specialized concept in the field of World Heritage conservation. It refers to the elements that embody and convey the Outstanding Universal Value (OUV) of a heritage site. These elements can be tangible entities or intangible forms, such as natural processes and cultural practices. This criterion enables the selection of assessment indicators that reflect the distinctive characteristics of heritage sites. It entails identifying heritage landscapes that align with the heritage values in question. Furthermore, the correspondence between the attributes, the value elements, and the indicators at various levels render them applicable across heritage sites. This enhances the efficiency of the selection process and increases the general applicability of these assessment indicators.

This framework builds upon and enhances the integration of sensitivity and perception assessments within the domain of Landscape and Visual Impact Assessment (LVIA). To advance the objectivity of the sensitivity assessment, the framework introduces a methodology for evaluating the visual sensitivity of landscapes that entails the quantitative computation of numerous influencing factors, thereby transforming the visual sensitivity, which was originally based on qualitative descriptions, into quantifiable indicators.

In accordance with LVIA, this study develops an enhanced system for determining weights and scoring impacts to reinforce the public participation mechanism. In this system, the responsibility for determining the weights of visual perception factors is assigned to experts, while the public is tasked with scoring the impacts of these factors. This ensures that the assessment results synthesize the opinions of experts and the public.

The VIA framework for cultural heritage constructed in this study (as Figure 1) comprises the four following principal steps: data collection, assessment indicators, assessment calculation models, and assessment results and mitigation measures.

• Data Collection: As the initial phase of the assessment process, this encompasses the gathering of diverse data types pertaining to the site and the proposed project. Heritage managers need to furnish topographic and structure modeling data to guarantee that the information accurately reflects the site’s characteristics. The project owner submits details on the siting, massing, form, and materials to enable an accurate assessment of the visual impact of the project on the cultural heritage site.
• Assessment Indicators: Indicators are developed based on the cultural heritage site’s attributes, beginning with the identification of attributes, value elements, and visual perception objects. Subsequently, an assessment indicator system for the heritage site is constructed according to established criteria. Finally, a viewshed analysis of the proposed project is conducted to screen out the affected indicators.
• Assessment calculation models: This comprises a twofold assessment of visual sensitivity and perception. The visual sensitivity of the heritage site is determined by quantitatively calculating the four following influencing factors: relative slope, relative distance, visibility probability, and landscape conspicuousness. In contrast, the visual perception of the proposed project is based on the visual perception factors and obtained through the comprehensive weighting scores of experts and the public. In determining the visual perceptibility of the proposed project, these perception factors are considered, along with the comprehensive weighting scores of experts and the public.
• Assessment Results and Mitigation Measures: The results of this Visual Impact Assessment, together with the associated mitigation and enhancement measures, are presented. These results are derived from visual perceptibility and visual sensitivity through a matrix approach, and corresponding mitigation measures are proposed based on a detailed description of the impacts on the character-defining elements of the heritage site values.

3.2. Assessment Indicators

This study establishes a hierarchical VIA indicator system, based on the attributes of cultural heritage. This system comprises three level indicators (α, β, and γ) and visual perception factors (δ) for mapping and assessing the value, attributes, and elements of cultural landscape heritage sites in a hierarchical manner.

• Indicator α: This indicator is based on the type of sightline analysis and divides the heritage value into the two following categories: “General Layout of Landscape” and “Significant Landscapes and Viewpoints”. The “General Layout of Landscape” encompasses both surface and linear elements, and visual impacts are evaluated through visual surface analysis. In contrast, the “Significant Landscapes and Viewpoints” category focuses on point elements, and visual impacts are determined through view corridor analysis.
• Indicator β: In cases where the cultural heritage sire in question exhibits clearly defined attributes, this indicator (β) is directly composed of these elements. In the absence of clearly defined attributes that collectively constitute the character-defining value of a given cultural heritage site, this indicator is constructed by identifying the morphological characteristics of the landscape elements and the heritage values they express.
• Indicator γ: The attributes are further subdivided into specific heritage value elements. The indicator γ under “α1 General Layout of Landscape” comprises direct visual elements, whereas the indicator γ under “α2 Significant Landscapes and Viewpoints” encompasses classic viewpoints and renowned scenic locations.
• Visual Perception Factor δ: In accordance with indicator γ, the elements of value features are decomposed from the perspectives of history, ecology, aesthetics, culture, and so forth, according to the requirements of visual perception assessment. This allows the value elements belonging to the same indicator β to share the same visual perception factor δ.

In light of the aforementioned criteria, a comprehensive indicator system for cultural heritage can be devised, with the template presented in

Table 1. Template for the Visual Impact Assessment Indicator System.

α: Types of Heritage Value	β: Attributes	γ: Value Elements	δ: Visual Perception Factors
α1 General Layout of Landscape	β(A) XXX	γ(A-1) XXX	δ1 XXX ……
		γ(A-2) XXX
		……
	……	γ(B-1) XXX	δ1 XXX ……
		γ(B-2) XXX
		……
α2 Significant Landscapes and Viewpoints	β(M) XXX	γ(M-1) XXX	δ1 XXX ……
		γ(M-2) XXX
		……
	……	γ(N-1) XXX	δ1 XXX ……
		γ(N-2) XXX
		……

This table serves as the template for the assessment indicator system that is constructed as part of this study. The indicator α is fixed; the remaining indexes must be completed with data specific to the cultural heritage in question. This entails entering the corresponding β, γ, and δ as appropriate for the specific attributes, value elements, and visual perception factors of the heritage site being assessed.

serving as a foundation. Through a viewshed analysis of the proposed project within the designated heritage area and the overlaying of visually affected regions with the distribution space of heritage attributes, the value elements potentially affected by visual impacts can be identified and the actual indicators to be assessed can be discerned.

3.3. Assessment Calculation Models

Assessment calculation models comprise the two following principal components: visual sensitivity assessment and visual perception assessment. These are combined through the use of both quantitative and qualitative analyses, thus ensuring a comprehensive assessment. The geographic distribution of each heritage value element (corresponding to each indicator γ) is analyzed to identify the viewpoints that provide a direct view of the proposed project. At these locations, images of the viewpoints are captured through panoramic photography, and virtual images of the proposed project are incorporated to simulate its potential visual impacts on the existing landscape.

The visual sensitivity assessment was conducted using ArcGIS software, whereby the precise geographic information of the viewpoints and heritage sites was processed to quantify the relevant factors affecting visual sensitivity. The visual perception assessment was implemented through the methods of the Analytical Hierarchy Process (AHP) and questionnaire surveys, which were combined with the images of the viewpoints to collect and synthesize the opinions from various parties and to qualitatively analyze the subjective perceptions of visual impacts by different stakeholders.

The final visual impact level was obtained by combining the levels of visual perceptibility and visual sensitivity, as shown in

Table 2. VIA judgment matrix.

Visual Impact Level		Visual Perceptibility
		High	Medium	Low
Visual sensitivity	High	High	High	Medium
	Medium	High	Medium	Low
	Low	Medium	Low	Low

.

3.3.1. Visual Sensitivity Assessment

Visual sensitivity reflects the ability of a heritage landscape to adapt to the visual changes that may be brought about by a proposed project. This is assessed by identifying and defining the elements or points of view that will potentially be affected by these changes (visual receptors). In the context of cultural heritage, visual receptors can be classified into elements of heritage value and evaluated in terms of the primary viewpoints from which visitors are drawn.

In alignment with the principles of landscape sensitivity assessment analysis, the factors affecting visual sensitivity are classified into the four following main categories: relative slope, relative distance, visibility probability, and conspicuousness [28,29,30]. The visual sensitivity (S) of a heritage site is a function of its sensitivity components, which are assessed based on each single factor.

$$\mathrm{S}=\mathrm{f}\left({\mathrm{S}}_{\mathsf{\phi }},{\mathrm{S}}_{\mathrm{d}},{\mathrm{S}}_{\mathrm{t}},{\mathrm{S}}_{\mathrm{c}}\right)=\mathrm{m}\mathrm{a}\mathrm{x}\left[\mathrm{m}\mathrm{i}\mathrm{n}\left({\mathrm{S}}_{\mathsf{\phi }},{\mathrm{S}}_{\mathrm{d}},{\mathrm{S}}_{\mathrm{t}}\right),{\mathrm{S}}_{\mathrm{c}}\right]$$

(1)

where S_φ is the sensitivity component obtained based on the slope of the landscape surface relative to the viewer, S_d is the sensitivity component based on the relative distance between the landscape and the viewpoint, S_t is the sensitivity component based on the chances of the landscape appearing in the visual field of the viewpoint, and S_c is the sensitivity component based on the landscape conspicuousness.

• Relative slope (φ) is the slope of the landscape surface relative to the viewpoint. As the relative slope increases, the area of the landscape that can be observed within the human visual field expands, enhancing the likelihood of detection and raising the level of visual sensitivity. The relative slope (φ) is calculated from the slope angle α, slope direction γ, and sight direction β of the landscape surface (see

  Table 3. Sensitivity component corresponding to relative slope.

  Relative Slope (φ) Calculation Equation	Data Processing Methods	Corresponding Sensitivity Component (Sφ)
  $\mathsf{\phi }={\sin }^{-1}\left({\displaystyle \frac{\tan \mathsf{\alpha }}{\sqrt{1+{\left(\tan \mathsf{\alpha }\right)}^2}\sqrt{1+{\left[\tan \left(\mathsf{\gamma }-\mathsf{\beta }\right)\right]}^2}}}\right)$	Natural Breaks	High
  		Medium
  		Low

  Where φ (0° ≤ φ ≤ 90°) is the relative slope; α (0° ≤ α ≤ 90°) is slope angle of the landscape surface; β (0° ≤ β < 360°) is the angle between the sightline and due north; and γ (0° ≤ γ < 360°) is the landscape slope direction.

  ). It is then divided into the three categories of high, medium, and low by the Natural Breaks method, which yields the sensitivity component corresponding to the relative slope (S_φ). The natural breakpoint method is selected for its capacity to reduce classification error by minimizing within-group variance and maximizing between-group differences, thereby unifying the disparate components of the data to facilitate composite visual sensitivity.

• Relative distance (d) is the distance between the landscape and the viewpoint. As the distance between the observer and the landscape decreases, the visual presentation of the landscape becomes increasingly clear, stimulating the observer to a greater extent, and enhancing visual sensitivity. In the case of extensive landscape areas, such as those comprising cultural heritage sites, the external modulus theory posits the use of 1000 m and 4000 m as boundaries, which are then subdivided into high, medium, and low levels (see

  Table 4. Sensitivity component corresponding to relative distance.

  Relative Distance (d)	Visual Experience	Corresponding Sensitivity Component (Sd)
  <1000 m	The color, material, and outline of the structure can be recognized	High
  1000 m~4000 m	The outline of the building can only be roughly discerned	Medium
  >4000 m	Inability to see buildings and other structures	Low

  ). These levels collectively constitute the sensitivity component corresponding to the relative visual distance (S_d).

• Visibility probability (t) is the chance of a landscape appearing in the viewer’s visual field. The higher the visual probability of a landscape, the greater the number of potential stimuli in an observer’s field of view, increasing the likelihood of its observation. The visibility probability of a landscape within the context of cultural heritage is expressed as the probability that the landscape appears within the visual corridor or visual focal point corresponding to the visual field of view (see

  Table 5. Sensitivity component corresponding to visibility probability.

  Visibility Probability (t) Calculation Equation	Data Processing Methods	Corresponding Sensitivity Component (St)
  $\mathrm{t}={\displaystyle \frac{\mathrm{n}}{\mathrm{m}}}$	Natural Breaks	High
  		Medium
  		Low

  Where t is the visibility probability of a landscape point; n is the number of visual corridors and visual foci where the point occurs; and m is the total number of visual corridors and visual focal points.

  ). The visibility probability is categorized into high, medium, and low by the Natural Breaks method to obtain the corresponded sensitivity component (S_t).

• The conspicuousness (c) of landscape reflects its attraction to human vision, which is mainly determined by the contrast between the landscape and the environment, including the contrast between form, line, color, texture, and motion. Therefore, landscape demarcation lines, such as the skyline, mountains, and water boundaries, and areas with distinctive shapes and landforms should be classified as high-visual-sensitivity zones in accordance with the prevailing circumstances (see

  Table 6. Sensitivity component corresponding to conspicuousness.

  Landscape Type to Which the Landscape Surface Belongs	Corresponding Sensitivity Component (Sc)
  Important visual skylines	High
  Significant boundaries of different landscape elements	High
  Peculiarly shaped landforms	High
  Other areas of high contrast	High
  The rest areas	Low

  ).

3.3.2. Visual Perception Assessment

Visual perception assessment aims to qualitatively assess the subjective perceptions of visual impacts by different stakeholders. The assessment is centered on the visual perception factor (δ), employing a comprehensive analysis through the dual perspectives of experts and the public (see Figure 2). The visual perception of a proposed project, as determined by the assessment, is categorized into the three following levels: high, medium, and low.

The relative importance of each visual perception factor is evaluated and determined by experts. Given the transparent structure of the indicator system employed and the straightforward interconnection between the various indicators, this study employs the AHP (Analytic Hierarchy Process) method, which is utilized by cultural heritage managers and researchers to assess the relative importance of different perceived factors within the same heritage value element based on the visual landscape of a heritage site. The weight (W) of each visual perception factor relative to the value element to which it belongs is calculated using the nine-level scale method.

Public assessment involves conducting a qualitative analysis of the general public’s subjective perception of visual impacts on heritage value elements. Accordingly, a comprehensive questionnaire is developed, comprising a series of images from different viewpoints, which are created using virtual images of the proposed project. The questionnaire commences with perception factors such as “natural landscape integrity” and “water continuity”, employing straightforward inquiries to ascertain the respondents’ perspectives. It utilizes a rating scale of 1–5 to quantify the impact of each visual perception factor, which is denoted as public rating (V).

Subsequently, the weights of the perception factors are multiplied by the public ratings and added together (the formula is as follows), resulting in a weight score Q, which is converted into a visual perceptibility level based on the grey clustering method.

$${\mathrm{Q}}_{\mathrm{x}}=\sum _{\mathrm{k}=1}^{\mathrm{n}}{\mathrm{W}}_{\mathrm{k}}{\mathrm{V}}_{\mathrm{k}}$$

(2)

where Q_x is the weight score of the visual impact on the xth heritage value element and W_k and V_k are the weight and impact scores of the kth visual perception factor under that value element, respectively.

4. Case Study

4.1. West Lake Cultural Landscape of Hangzhou

The West Lake Cultural Landscape of Hangzhou is a World Heritage Site, globally renowned for its natural beauty of lakes and mountains, its deep historical relics, and its rich cultural and historical sites. As an outstanding spiritual habitat in China’s history, it is known as the “lake with cultural meanings, the most recognized spiritual home in Chinese history” and “Heaven on Earth” [33].

The West Lake is located on the western side of the city center of Hangzhou, China, covering an area of 4235.76 hectares. Its cultural heritage value is reflected in the six following attributes: the beautiful natural landscape, the spatial characteristics of the city and the lake with “three sides of clouds and mountains and one side of the city”, the unique landscape layout with the “two causeways and three isles”, “Ten Poetically Named Scenic Places of West Lake”, which are the most original and representative serial poetically named scenic places, the various historic monuments and sites relating to mainstream Chinese cultures such as Confucianism, Buddhism, and Taoism, and the distinctive flora of both historic and cultural values such as “the flowers for the four seasons”, the “alternatively planted peaches and willows”, and the Longjing Tea Plantation. The Heritage Area of West Lake covers the distribution area of these attributes, including the entire visual space of the core landscape units such as the “Ten Poetically Named Scenic Places of West Lake” (see Figure 3).

On the basis of the selection criteria mentioned above, this study constructs a set of indicators for the Visual Impact Assessment of the West Lake (see

Table 7. West Lake cultural landscape Visual Impact Assessment indicators.

α: Types of Heritage Value	β: Attributes	γ: Value Elements	δ: Visual Perception Factors
α1 General Layout of Landscape	β(A) Natural waters and hills	γ(A-1) Waters	δ1 Natural landscape integrity δ2 Hydrological texture continuity δ3 Landform feature hierarchicalness
		γ(A-2) Northern hills
		γ(A-3) Southern hills
	β(B) Spatial feature between the Lake and the City	γ(B-1) City outline of east shore	δ1 Architectural contour coordination δ2 Natural skyline integrity
		γ(B-2) Skyline of hills around the lake
	β(C) Landscape layout of causeways and isles	γ(C-1) Su Causeway	δ1 Causeway–isle visual correlation δ2 Causeway–isle landscape coordination δ3 Causeway–isle Visual Visibility
		γ(C-2) Bai Causeway
		γ(C-3) Lesser Yingzhou Isle
	β(D) Characteristic flora landscape	γ(D-1) Intercropping Peaches and Willows	δ1 Seasonal landscape visibility δ2 Plant landscape coordination
		γ(D-2) Special flowers landscape of four seasons
		γ(D-3) Longjing Tea Plantation landscape
α2 Significant Landscapes and Viewpoints	β(E) Ten Poetically Named Scenic Places	γ(E-1) Su Causeway in the Morning of Spring	δ1 Natural landscape integrity δ2 Historical style continuity δ3 Landscape corridor visual accessibility δ4 Garden mood integrity δ5 Landmark visual conspicuousness
		γ(E-2) Breeze-ruffled Lotus at Winding Garden
		γ(E-3) Autumn Moon Over the Calm Lake
		γ(E-4) Lingering Snow on Broken Bridge
		γ(E-5) Viewing Fish at Flowery Pond
		γ(E-6) Orioles Singing in the Willows
		γ(E-7) Three Pools Mirroring the Moon
		γ(E-8) Twin Peaks Piercing the Cloud
		γ(E-9) Leifeng Pagoda in Evening Glow
		γ(E-10) Evening Bell Ringing at Nanping Hill
	β(F) Historic monuments and sites	γ(F-1) Baochu Pagoda	δ1 Natural landscape integrity δ2 Historical style continuity δ3 Landscape corridor visual accessibility δ4 Landmark visual conspicuousness
		γ(F-2) The site of Leifeng pagoda
		γ(F-3) Liuhe Pagoda
		γ(F-4) Jingci Temple
		γ(F-5) Feilaifeng Peak
		γ(F-6) Lingyin Temple
		γ(F-7) Yue Fei’s Tomb
		γ(F-8) Wenlan Pavilion
		γ(F-9) Baopu Monastery
		γ(F-10) Site of Qiantang Gate
		γ(F-11) Site of Temporary Palaces of Qing Dynasty
		γ(F-12) Stele of Wu-He-Fu Lin Bu’s Tomb
		γ(F-13) Building Complex of Xiling Engravers Society
		γ(F-14) Longjing
		γ(F-15) Other monuments and sites

).

According to the World Heritage Committee’s SOC Report, the main factors affecting the West Lake cultural landscape include the encroachment of neighboring buildings on the skyline, the impact of tourism on the carrying capacity of the scenic area, and land transfer [36]. Since the 1950s, buildings around West Lake, such as the Shangri-La Hotel [37], Wanghu Hotel [38], and Kerry Centre [39], have been controversial because of their planned or constructed heights; historic buildings such as Lingyin Temple and Hangzhou Buddhist Academy within the scenic area have undergone specific Heritage Impact Assessments due to expansion needs; and areas such as Wangjiang New City within the main urban area have adjusted the upper limits of their building heights to protect the views of the West Lake landscape [40].

The Shangri-La Hotel East Building project was selected for this study to assess its visual impact on West Lake. The East Building was seven stories high when it was built in 1962, located in the heritage core area on the north shore of West Lake (Figure 4a). However, its negative visual impact on the landscape of West Lake is controversial among relevant scholars and local people [41]. When West Lake was nominated as a World Heritage Site in 2011, the Hangzhou Municipal People’s Government made a commitment to UNESCO to downgrade the East Building and implement environmental improvement measures after the lease expired. After extensive consultation, the West Lake Scenic and Historic Interest Area Management Committee decided to demolish and lower the East Building by two stories by 2019 (see Figure 4) [36]. In this study, the original seven-story East Building is used as the proposed project for simulation to assess its visual impacts on the West Lake landscape.

4.2. Assessing the Visual Impact of West Lake

4.2.1. Viewshed Analysis and Screening of Assessment Indicators

Firstly, a detailed digital model of the proposed project and the surrounding heritage site environment is created using the ArcGIS CityEngine software and open data. This model incorporates the topography, buildings, and roads of the West Lake heritage site. A visual field analysis is then conducted using the roof of the East Building before and after the floor lowering as a viewpoint. The resulting view areas are overlaid with the heritage site boundaries (see Figure 5), screening the key value elements visually influenced by the building. These elements form the basis for the indicators to be further assessed (see

Table 8. VIA Indicators for Shangri-La East Building.

α: Types of Heritage Value	β: Attributes	γ: Value Elements	Viewpoint
α1 General Layout of Landscape	β(A) Natural waters and hills	γ1(A-1) Waters	1
		γ2(A-2) Northern hills	2
	β(B) Spatial feature between the Lake and the City	γ3(B-2) Skyline of hills around the lake	3
	β(C) Landscape layout of causeways and isles	γ4(C-2) Bai Causeway	4
		γ5(C-3) Lesser Yingzhou Isle	5
α2 Significant Landscapes and Viewpoints	β(E) Ten Poetically Named Scenic Places	γ6(E-4) Lingering Snow on Broken Bridge	6
		γ7(E-7) Three Pools Mirroring the Moon	7
		γ8(E-9) Leifeng Pagoda in Evening Glow	8
	β(F) Historic monuments and sites	γ9(F-12) Stele of Wu-He-Fu Lin Bu’s Tomb	9
		γ10(F-13) Building Complex of Xiling Engravers Society	10

). Subsequently, field research identifies the locations of corresponding viewpoints, and the images of the proposed project are incorporated into these viewpoints (see Figure 6).

4.2.2. Assessment Data and Calculations

• Visual sensitivity assessment

According to the visual sensitivity assessment calculation model, this study integrates the raster data of the heritage landscape, the coordinates of viewpoints, and the information of visual corridors through the ArcGIS software. On this basis, the four influencing factors of relative slope, relative distance, visibility probability, and conspicuousness are each calculated, and the visual sensitivity of the heritage landscape of the East Building for each viewpoint is obtained through comprehensive analysis (see

Table 9. Visual sensitivity analysis.

Value Elements (γ)	Viewpoint	Factors Affecting Visual Sensitivity				Visual Sensitivity
		Relative Slope	Relative Distance	Visibility Probability	Conspicuousness
γ1(A-1) Waters	1	High	High	Medium	Medium	Medium
γ2(A-2) Northern hills	2	Medium	High	Low	Low	Low
γ3(B-2) Skyline of hills around the lake	3	High	High	Medium	Low	Medium
γ4(C-2) Bai Causeway	4	Low	Medium	Medium	Low	Medium
γ5(C-3) Lesser Yingzhou Isle	5	Medium	Medium	High	High	High
γ6(E-4) Lingering Snow on Broken Bridge	6	Low	Medium	Low	Medium	Medium
γ7(E-7) Three Pools Mirroring the Moon	7	Medium	Medium	High	High	High
γ8(E-9) Leifeng Pagoda in Evening Glow	8	Medium	Medium	Medium	Medium	Medium
γ9(F-12) Stele of Wu-He-Fu Lin Bu’s Tomb	9	Medium	High	Medium	High	High
γ10(F-13) Building Complex of Xiling Engravers Society	10	Medium	High	Medium	Medium	Medium

).

• Visual perception assessment

A questionnaire incorporating images of all the viewpoints was designed based on the visual perception factor. Distributed online from February to April 2024, it yielded 107 valid responses. The YAAHP software facilitated the determination of factor weights through importance comparison and data calculation. A panel of three experts in heritage management and landscape planning conducted the importance comparison, assessing the significance of each visual perception factor relative to the heritage value elements. The visual perception scores of the East Building from each viewpoint were then calculated using the grey evaluation method, integrating the questionnaire data with the determined weights (see

Table 10. Visual perception evaluation computing.

Value Elements (γ)	Viewpoint	Visual Perception Factors (δ)	Factor Weight (W)	Impact Score (V)	Impact Weighted Scores (Q)	Visual Perceptibility (P)
γ1(A-1) Waters	1	δ01 Natural landscape integrity	0.7028	1	0.9326	Medium
		δ01 Hydrological texture continuity	0.1822	0
		δ01 Landform feature hierarchicalness	0.1149	2
γ2(A-2) Northern hills	2	δ02 Natural landscape integrity	0.5813	2	2.0902	Medium
		δ02 Hydrological texture continuity	0.1096	0
		δ02 Landform feature hierarchicalness	0.3092	3
γ3(B-2) Skyline of hills around the lake	3	δ03 Architectural contour coordination	0.1429	2	3.7142	High
		δ03 Natural skyline integrity	0.8571	4
γ4(C-2) Bai Causeway	4	δ04 Causeway–isle visual correlation	0.1226	0	0.3202	Low
		δ04 Causeway–isle landscape coordination	0.3202	1
		δ04 Causeway–isle Visual Visibility	0.5271	0
γ5(C-3) Lesser Yingzhou Isle	5	δ05 Causeway–isle visual correlation	0.3338	3	1.4262	Medium
		δ05 Causeway–isle landscape coordination	0.1416	3
		δ05 Causeway–isle Visual Visibility	0.5247	0
γ6(E-4) Lingering Snow on Broken Bridge	6	δ06 Natural landscape integrity	0.1399	1	0.4202	Low
		δ06 Historical style continuity	0.2803	1
		δ06 Landscape corridor visual accessibility	0.0457	0
		δ06 Garden mood integrity	0.0951	0
		δ06 Landmark visual conspicuousness	0.4391	0
γ7(E-7) Three Pools Mirroring the Moon	7	δ07 Natural landscape integrity	0.3503	2	1.6317	Medium
		δ07 Historical style continuity	0.0666	0
		δ07 Landscape corridor visual accessibility	0.0467	0
		δ07 Garden mood integrity	0.3392	1
		δ07 Landmark visual conspicuousness	0.1973	3
γ8(E-9) Leifeng Pagoda in Evening Glow	8	δ08 Natural landscape integrity	0.3357	2	2.0441	Medium
		δ08 Historical style continuity	0.2801	3
		δ08 Landscape corridor visual accessibility	0.0735	0
		δ08 Garden mood integrity	0.2662	2
		δ08 Landmark visual conspicuousness	0.0445	0
γ9(F-12) Stele of Wu-He-Fu Lin Bu’s Tomb	9	δ09 Natural landscape integrity	0.6324	4	2.7122	Medium
		δ09 Historical style continuity	0.1826	1
		δ09 Landscape corridor visual accessibility	0.0775	0
		δ09 Landmark visual conspicuousness	0.1075	0
γ10(F-13) Building Complex of Xiling Engravers Society	10	δ10 Natural landscape integrity	0.6133	4	2.6924	Medium
		δ10 Historical style continuity	0.1196	2
		δ10 Landscape corridor visual accessibility	0.1703	0
		δ10 Landmark visual conspicuousness	0.0968	0

).

4.3. Assessment Results

4.3.1. Visual Impact Assessment Results

Visual sensitivity and visual perception were matched by the judgment matrix (e.g., Table 2) for “high–medium–low” to obtain the levels of visual impact (e.g.,

Table 11. Visual impact levels of East Building.

Attributes (β)	Affected Elements (γ)	Visual Perceptibility	Visual Sensitivity	Visual Impact Level
Natural waters and hills	γ1(A-1) Waters	Medium	Medium	Medium
	γ2(A-2) Northern hills	Medium	Low	Low
Spatial feature between the Lake and the City	γ3(B-2) Skyline of hills around the lake	High	Medium	High
Landscape layout of causeways and isles	γ4(C-2) Bai Causeway	Low	Medium	Low
	γ5(C-3) Lesser Yingzhou Isle	Medium	High	High
Characteristic flora landscape	/	/	/	Negligible
Ten Poetically Named Scenic Places	γ6(E-4) Lingering Snow on Broken Bridge	Low	Medium	Low
	γ7(E-7) Three Pools Mirroring the Moon	Medium	High	High
	γ8(E-9) Leifeng Pagoda in Evening Glow	Medium	Medium	Medium
Historic monuments and sites	γ9(F-12) Stele of Wu-He-Fu Lin Bu’s Tomb	Medium	High	High
	γ10(F-13) Building Complex of Xiling Engravers Society	Medium	Medium	Medium

).

According to the assessment results and viewpoint images, the specific impacts on each attribute of West Lake are listed as follows:

• Natural waters and hills

The value elements affected are “Waters” and “Northern Hills”.

The level of visual impact on the waters of West Lake is assessed as medium. Particularly on the boat route in the northwest waters of West Lake, the East Building, with its large volume, has a significant impact on visitors’ perception of the hierarchy of landforms in the peaks and the integrity of the natural landscape, which is mainly reflected in the architectural form and color.

The northern hills are subject to a low level of visual impact. The East Building is faintly visible in the shade of sycamore trees on Beishan Street and Xiling Bridge at the southern foot of Jewel Hill. The screening effect of the vegetation adequately mitigates the impact of the East Wing on the natural landscape integrity of the North Hill Peak Range; however, its impact is still of concern.

• Spatial features between the lake and the city

The value element affected is “Skyline of hills around the lake”.

There is a high level of visual impact on the skyline of the hills surrounding the lake. The seven-story massing of the East Building stands out significantly at the northern foot of Lone Mountain, even directly blocking part of the skyline and significantly affecting the overall visual impact of the city–lake landscape.

• Landscape layout of causeways and isles

The value elements affected are “Bai Causeway” and “Lesser Yingzhou Isle”.

Bai Causeway is subject to a low level of visual impact. Although the silhouette of the East Building appears distinct and prominent against the natural skyline to the northwest of the Bai Causeway, the impact of the East Building is relatively low, but not negligible, due to the numerous visual focal points on the Bai Causeway, including the lake, the islands in the lake, the peaks of Nanshan Mountain and Jewel Mountain, and the Baochu Pagoda to the northeast.

Lesser Yingzhou Isle is subject to a high degree of visual impact. On the north side of Yingzhou Island, the East Building is extremely prominent along the cruise route, seriously affecting the visibility and coordination of the “two causeways and three isles” landscape layout.

• Landscape layout of causeways and isles

This was subject to a negligible visual impact.

• Ten Poetically Named Scenic Places

The affected value elements are “Lingering Snow on Broken Bridge”, “Three Pools Mirroring the Moon”, and “Leifeng Pagoda in Evening Glow”.

“Lingering Snow on Broken Bridge” is subject to a lower level of visual impact. At the Broken Bridge viewpoint on the east side of the Bai Causeway, the East Building forms the end of the natural skyline, and despite the impact of its rigid silhouette on the natural smoothness of the skyline, the visual impact of the East Building can be mitigated, to some extent, by the rich visual landscape surrounding the Broken Bridge.

“Three Pools Mirroring the Moon” is affected to a higher level. The “Lesser Yingzhou” pavilion on Yingzhou Island is an important vantage point for viewing West Lake, and the top of the East Building becomes the visual focus here, weakening the viewer’s perception of Baochu Pagoda and Jewel Mountain and seriously affecting the completeness and coordination of the landscape.

The level of visual impact on “Leifeng Pagoda in Evening Glow” is medium. The observation deck on the top floor of Leifeng Pagoda is an important viewpoint looking north to West Lake, and the form of the East Building is particularly abrupt at this viewpoint; although the viewpoint is rich in landscape content, the influence of the East Building still cannot be ignored.

• Historic monuments and sites

The value elements affected are “Stele of Wu-He-Fu Lin Bu’s Tomb” and “Building Complex of Xiling Engravers Society”.

“Stele of Wu-He-Fu Lin Bu’s Tomb” is subject to a high level of visual impact. Standing at the northeast side of Lone Mountain Island in front of the Stele of Wu-He-Fu, the East Building becomes a significant visual focus on the west side of the viewpoint, seriously affecting the viewer’s visual perception of the natural landscape pattern of Beili Lake–Jewel Mountain.

The level of visual impact on “Building Complex of Xiling Engravers Society” is medium. The form, color, and detailing of the East Building are clearly visible at the entrance to the rear hill of the Engravers Society, and although this entrance is not the main access point, the presence of the East Building still has a medium level of visual impact on the visual landscape.

4.3.2. Mitigation and Enhancement Measures

To mitigate the visual impact of the East Building of the Shangri-La Hotel on West Lake, this study suggests the following desirable mitigation measures: first, it is recommended that the building height be reduced to at least five stories; for optimal results, it could be further reduced to three or four stories. To balance the building massing, the footprint of the west side of the building can be increased accordingly. Second, it is recommended that the roof design of the building be adjusted to adopt a warm- or dark-colored pitched roof to better fit with the overall landscape character of West Lake.

Given the spatial features between the lake and the city, the volume, shape, and color of the East Building affect people’s experience of viewing Jewel Mountain north of West Lake (e.g., Figure 7, Viewpoint 3). To minimize interference with the skyline of the hills surrounding the lake, it is recommended that the East Building be reduced by at least two stories to ensure that no more than 80% of the height of Jewel Mountain is obscured from the viewpoint, thus ensuring the integrity of the skyline view. The design of the roof should also be adjusted to better blend in with the surroundings.

At the viewpoints of “Three Pools Mirroring the Moon” and “Lesser Yingzhou Isle”, the East Building has a significant impact on the visual amenity of the heritage. From the viewpoints of “Lesser Yingzhou Isle” (Figure 7, viewpoints 5 and 7), it is recommended that the East Building be lowered to at least five stories in order to significantly minimize its visual impact so that its exposed portion does not exceed the height of one story, and that it be lowered to at least four stories to ensure that it is not visible at all from the viewpoints, eliminating its visual impact completely.

Regarding the viewpoints of “Stele of Wu-He-Fu Lin Bu’s Tomb” and “Building Complex of Xiling Engravers Society” (Figure 7, viewpoints 9 and 10), the height of the East Building also needs to be adjusted to minimize disturbance to the natural skyline. To prevent the building from protruding too much along the western skyline, it is recommended to lower the building by two to four stories and improve the roof shape to make it less visually prominent.

5. Discussion

5.1. Overall Evaluation for West Lake Visual Impact Assessment

The seven-story Shangri-La East Building has a considerable visual impact on the four following attributes of West Lake: spatial features between the lake and the city; landscape layout of causeways and isles; Ten Poetically Named Scenic Places; and historic monuments and sites. The proposed mitigation measure is to reduce the height of the building to five floors, which is in accordance with the redevelopment project implemented by the Hangzhou Municipal Government and aligns with the experts’ opinions.

To fully mitigate the negative visual impact of the East Building on the West Lake landscape, an optimal strategy would be to reduce its height to three or four stories. This approach would effectively neutralize its detrimental effect on viewpoints 5 and 7 while simultaneously curbing its impact on viewpoints 9 and 10. Nevertheless, this option would necessitate substantial modifications to the structure and configuration of the edifice to attain a harmonious equilibrium in terms of its volumetric proportions.

As a structure with a history of over 60 years, the decision to lower the East Building was made by the local government following extensive consultation with contractors, experts, and academics to reduce its impact on the West Lake landscape. In light of the financial implications and the investment of resources, the option of lowering the building to five stories was a compromise reached after a comprehensive assessment of the various aspects involved. A comprehensive heritage impact assessment should have been conducted prior to its construction. This would have allowed for design adjustments, ensuring its height and style are more harmonious with the surrounding environment. Moreover, this proactive approach can reduce the additional costs associated with later modifications, thereby ensuring both economic and cultural benefits for the project.

5.2. Analysis of the Methodology for Selecting Assessment Indicators

The assessment indicator selection method proposed in this study is directly related to the attributes of heritage sites, and this process simplification is universal for all kinds of cultural heritage assessments. For cultural landscape heritage sites with clear attributes, the assessment indicator system can be constructed quickly, which is convenient for heritage managers. For any proposed project, the indicators to be assessed can be efficiently selected through simple modeling, visual field analysis, and field visits (Table 6).

The advantage of this approach is that it does not reconstruct the indicator system based on information from a single project; rather, it selects the applicable indicators from a set of unified and validated indicator libraries. Consequently, this approach enhances the efficiency of the assessment process, while ensuring the reliability and consistency of the assessment results.

The assessment of the Shangri-La East Building enables the establishment of a set of assessment index systems applicable to the West Lake cultural landscape. It is incumbent upon managers to adjust the model information in accordance with the particulars of the proposed project and to ensure the regular updating of the total model of the heritage site, guaranteeing the accuracy and timeliness of the assessment.

When this methodology is extended to other cultural heritage sites, the assessment implementer must identify and categorize the value attributes and value elements of the heritage site in question, construct the corresponding assessment indicator system, and carry out simple numerical modeling. This will allow for the integration of many subsequent proposed projects into the heritage site model for comprehensive and accurate assessments.

5.3. Analysis of Assessment Methods for the Trade-Off between Objective Sensitivity and Subjective Perception

The assessment methodology employs a matrix approach to integrate the visual sensitivity of a heritage site and the potential visual perception impacts of a proposed project.

The visual perception assessment employs expert assessment to determine the relative importance of factors and combines them with the public’s impact ratings to provide a comprehensive analysis. This assessment method considers both the expert’s assessment of the significance of perception factors and the public’s intuitive evaluation of visual viewpoints. As illustrated in Table 10, to attain a high impact score (>2.5) for any viewpoint, it is imperative that perceptual factors with higher weights therein obtain high impact scores. This is particularly evident regarding viewpoints 3, 9, and 10. Among these viewpoints, the perception factors of “natural skyline integrity” and “natural landscape integrity” were identified by experts as being the most crucial for the viewpoint landscapes. Meanwhile, the public assessment indicated that the East Building had a significant visual impact on these two factors.

In the assessment of visual sensitivity, landscape conspicuousness serves as a crucial modifier of relative slope, relative distance, and visibility probability. These three factors must be quantified to ascertain the level of sensitivity. Only when all three factors have a significant impact on sensitivity will a “high sensitivity” assessment result be obtained. The concept of conspicuousness is introduced by considering landscape contrast, which encompasses specific landscape types that may have been overlooked in traditional visual factors. This was assigned a ‘high’ sensitivity rating at viewpoints 5, 7, and 9. In the case of heritage sites comprising complex natural and human landscapes, such as cultural landscapes, this approach to sensitivity assessment can provide a more comprehensive perspective.

6. Conclusions

This study proposes a comprehensive framework for assessing the visual impact of cultural heritage. The case study of the Shangri-La Hotel East Building in Hangzhou’s West Lake World Heritage Site demonstrates the framework’s effectiveness in predicting visual impacts and informing mitigation measures.

The approach of establishing an assessment indicator system based on the attributes of a heritage site has a high degree of universal applicability. The term “attributes” describes essential qualities that are commonly assessed and identified as contributing to the Outstanding Universal Value of a cultural heritage site. In the process of World Heritage nomination, it is typically required to prepare a comprehensive document that outlines the attributes of the site in question [42]. In 2019, ICOMOS further established the criteria for identifying and assessing the attributes of cultural heritage projects being considered for nomination [43]. Furthermore, the current management of World Heritage in China requires the supplementation and improvement of the attributes of all properties. Accordingly, the establishment of an indicator system centered on value attributes facilitates the applicability of the assessment method. This approach to constructing an assessment indicator system can provide a comprehensive reflection of the multifaceted values of cultural heritage, facilitating effective comparisons and analyses across diverse cultural and historical contexts.

The integration of quantitative sensitivity assessment and qualitative perception assessment serves to enhance the accuracy of assessment results. Visual perception assessment, which includes questionnaire research on public perceptions and hierarchical analysis to determine weights, takes into account the opinions of experts and the public, yielding the weight score of visual perception. Visual sensitivity assessment involves the quantitative calculation of the function of each influencing factor and the establishment of the correction mechanism, such as conspicuousness, resulting in the visual sensitivity of a heritage landscape. Visual sensitivity and visual perceptibility are matched by a matrix of “high, medium, and low” to determine the levels of visual impact. The combination of visual sensitivity and perception represents a methodology that is applicable to the assessment of cultural landscape heritage. As cultural landscapes result from human–nature interactions [41], this approach allows for an examination of both the tangible and intangible elements, as well as the emotional and experiential aspects, inherent to these environments.

The application of the assessment framework to evaluate the visual impacts on the cultural heritage value of West Lake resulting from the Shangri-La East Building project yielded consistent results with the implementation of the lowering project through expert verification. This outcome substantiates the efficacy of the methodology employed. The optimal mitigation strategy would entail the demolition and lowering of additional floors. However, this is challenging to implement in practice due to the high costs and economic losses associated with such an approach. Although the lowering of two stories has demonstrated positive mitigation effects, it is evident that this measure represents a realistic compromise when considered in the context of a comprehensive trade-off. This also underscores the significance of undertaking an assessment of the visual impact of heritage at the earliest stages of project decision making, rather than conducting an evaluation after it has already occurred. Assessing potential risks and devising appropriate mitigation strategies are crucial for the effective conservation of heritage and the promotion of sustainable development.

A key challenge in this research was the tendency for questionnaire-based Visual Impact Assessments to underestimate actual impacts. Traditional 2D photographs cannot fully capture the 3D spatial characteristics of heritage landscapes. Adopting digital reality technologies like virtual reality (VR) and augmented reality (AR) would provide more accurate simulations. Additionally, the GIS system faced computational limitations, hindering the assessment efficiency. Optimizing GIS code is crucial for improving computational performance and ensuring accurate assessments.