Assessing and Optimizing Rural Settlement Suitability in Important Ecological Function Areas: A Case Study of Shiyan City, the Core Water Source Area of China’s South-to-North Water Diversion Project

Abstract

China’s rural revitalization strategy has entered a new stage of development, in which optimizing the layout of rural settlements constitutes both a critical component and an urgent task for promoting integrated urban–rural development. Important ecological function areas play a vital role in maintaining ecological security; however, research focusing on the evaluation and optimization of rural settlement suitability within these regions remains limited, thereby constraining their sustainable development. Accordingly, this paper selects Shiyan City, situated within the core water source area of China’s South-to-North Water Diversion Project, as a case study. From an ecological perspective, a suitability evaluation system for rural settlements is developed, specifically tailored to important ecological function areas. This system integrates ecological factors including geological hazards, vegetation coverage, soil and water conservation, and soil erosion. Utilizing GIS spatial analysis and the minimum cumulative resistance model, the study assesses the suitability of rural settlements within these important ecological function areas. Furthermore, it proposes corresponding optimization types and strategies for rural settlements in such areas. The findings indicate the following: (1) The rural settlements in the study area demonstrate a “large dispersed settlements and small clustered settlements” distribution pattern, exhibiting an overall high-density agglomeration, though their internal layout remains fragmented and disordered due to geographical and ecological constraints. (2) The spatial comprehensive resistance values in the study area exhibit significant heterogeneity, with a general pattern of lower values in the north and higher values in the south. The region was categorized into five suitability levels: high yield, highly suitable, generally suitable, less suitable and unsuitable. The highly suitable areas, despite their limited spatial extent, support the highest density of rural settlements. In contrast, unsuitable areas occupy a substantially larger proportion of the territory, reaching 46.83%. These areas are strongly constrained by topographic and ecological factors, limiting their potential for development, and the spatial layout of villages requires further optimization, with emphasis placed on ecological conservation and adaptive sustainability. (3) Rural settlements are categorized into four optimized types: Urban–rural integration settlements, primarily located in high yield areas, are incorporated into urban development plans after optimization. Adjusted and improved settlements, mainly in highly suitable areas, enhance service quality and stimulate economic vitality post-optimization. Relocation and renovation settlements, including those in generally suitable and less suitable areas, achieve concentrated living and improved ecological livability after optimization. Restricted development settlements, predominantly in unsuitable areas, focus on ecological conservation and regional ecological security post-optimization. This study integrates ecological function protection factors with spatial optimization zoning for rural settlements in the study area, providing scientific reference for enhancing residential safety and ecological security for rural residents in important ecological function areas.

1. Introduction

Rural settlements constitute the fundamental unit of rural production and livelihood, serving as a key indicators of the dynamic interplay between human activities and the geographical environment [1]; As integral components of rural spatial structures, they support agricultural production, sustain livelihoods, and contribute to ecosystem preservation [2]. World Bank data indicate that the proportion of the global urban population increased markedly from 43% in 2000 to 56% in 2020. Reflecting a pronounced trend of rural-to-urban migration, which leading to significant challenges such as the “hollowing out” of rural areas and spatial fragmentation of rural settlements. Additionally, inefficient utilization of rural construction land threatens fragile ecological environments, posing a significant challenge to regional sustainability [3]. In the context of comprehensive rural revitalization, it is imperative to integrate spatial planning strategies that balance resource conservation with environmental protection, promote sustainable rural development, safeguard national ecological security, and foster a livable, productive, and esthetically appealing rural environment [4,5]. Currently, 577 million people reside in China’s 2.449 million natural villages, making rural settlements the predominant mode of rural residency. Therefore, revitalizing rural settlements and optimizing land use patterns are critical challenges that must be addressed as part of China’s rural revitalization strategy [6].

The spatial enhancement and layout optimization of rural settlements have long been key research areas in geography, sociology, and management. Scholars worldwide have conducted extensive research on this topic. International studies have primarily focused on the rationality of site selection [7], spatial layout [8], formation and evolutionary processes [9], and influencing factors of rural settlements [10], with a discernible shift in research paradigms from spatial analysis toward social science approaches. In contrast, domestic research has placed greater emphasis on spatial distribution characteristics [11], spatiotemporal evolution patterns [12], and layout optimization of settlements [13], resulting in a substantial body of findings. In the realm of suitability evaluation, studies generally follow two main directions: one focuses on suitability evaluations based on multi-factor and multi-dimensional analysis [14,15,16], while the other examines specific suitability indicators [17,18,19]. Nevertheless, the research content remains fragmented, and evaluation criteria lack standardization. Research on the evaluation factors of rural settlement suitability generally falls into three main categories. The first is social factors, which include rural population dynamics and local economic conditions. Among these, population loss has been identified as a major driver of changes in rural land use [20], a phenomenon fundamentally rooted in the contradiction between the growing public aspiration for improved living standards and persistent imbalances in urban–rural development and the insufficient development within rural regions. The second is natural factors, as the physical environment provides the foundation for settlement formation and development. Geographic conditions play a direct role in determining settlement layout, with a favorable natural environment being essential for optimal spatial planning [21]. The third category is locational factors, which significantly influence settlement distribution and land use changes. Proximity to major rivers, roads, and towns is a key determinant shaping rural settlement patterns [22,23]. In recent years, growing concerns over environment security have brought increased attention to factors such as ecological function, environmental sensitivity, and natural disasters. Researchers have gradually emphasized the need for a more comprehensive perspective that balances rural settlement development with ecological conservation. As a result, integrating environmental protection considerations into settlement suitability evaluations has become a key focus in this field.

Ecologically significant functional zones possess considerable ecological value, and their protection and ecological security have garnered increasing attention from researchers. Existing studies have primarily evaluated these zones based on dimensions such as ecosystem service functions, ecological vulnerability, ecological carrying capacity, and ecological security patterns [24,25,26,27], thereby establishing a theoretical foundation for understanding their ecological baseline and conservation requirements. Against this backdrop, the relationship between the evolution of rural settlements and environmental protection has emerged as a key research focus [28], with investigations into the impact of human settlement activities on ecosystems and their adaptation mechanisms becoming central topics. Notably, typical ecological functional zones—such as the nature reserves surrounding Wudang Mountain—preserve some of China’s most intact subtropical forest ecosystems [29]. These ecosystems serve as crucial habitats for rare species, such as the Sichuan snub-nosed monkey and the rhesus macaque. The survival status of these species serves as a direct indicator of regional ecosystem health, yet they face threats such as habitat fragmentation resulting from increased human activity [30]. Moreover, although they serve as vital ecological barriers for their respective regions, these zones are constrained by unique natural environments and ecological resources. They often face practical challenges, such as inadequate infrastructure development and relatively low socioeconomic development, which result in significant disparities compared to non-essential ecological functional zones. Although considerable progress has been made in evaluating and optimizing the suitability of rural settlements in non-protected areas, research specifically targeting ecologically significant functional zones remains insufficient and requires urgent attention. Conducting suitability evaluations and optimization for rural settlements in such zones holds multiple practical implications: Firstly, scientifically guiding settlement layout can effectively protect and restore the ecological environment, mitigating human impacts on fragile ecosystems [31]; Secondly, as these zones often harbor abundant natural resources, optimizing settlements can promote rational resource allocation and sustainable utilization [32].

Shiyan, as the core water source area of China’s South-to-North Water Diversion Project, holds the title of the “Ecological City of the Hanjiang River Basin”, and occupies an irreplaceable strategic position in ecological conservation [33]. Therefore this study takes Shiyan as a case example. By employing kernel density analysis and Voronoi diagrams, we constructed a comprehensive assessment framework encompassing topography, location, socio-economics, and ecology. Additionally, we applied the Minimum Cumulative Resistance (MCR) model to evaluate the suitability of rural settlements, identify optimization types, and propose spatial layout improvement strategies. Our findings aim to provide insights for the integrated development of urban and rural areas, as well as ecological conservation in Shiyan City. Furthermore, this study serves as a reference for rural settlement planning in other ecologically significant regions.

2. Materials and Methods

2.1. Materials

The South-to-North Water Diversion Project is one of China’s major infrastructure projects, alleviating the long-standing conflict between water supply and demand in the northern region, while at the same time facing problematic considerations of ecological quality and disaster prevention and mitigation. In order to ensure the long-term sustainability of the South–North Water Diversion Project and the safety of the ecological environment, many settlements close to the reservoirs and the main water protection zones have been required to be relocated or rebuilt in order to not only improve the environmental quality of the surrounding area, but also to provide a healthier living environment for the people living in the area [34]. As the core water source of the South-to-North Water Diversion Project, Shiyan City has an irreplaceable strategic position in terms of ecology, and assumes the role of alleviating the contradiction between the people’s growing material needs and unbalanced and insufficient development [34]. Located in the northwestern part of Hubei Province, Shiyan lies in the eastern part of the Qinba Mountainous Region, within the middle and upper reaches of the Hanjiang River. The city shares borders with Chongqing, Shanxi, and Henan Provinces to the west and north, and with Xiangyang City and Shennongjia of Hubei Province to the east and south, respectively. Spanning 23,669 km², the city’s terrain is predominantly hilly and mountainous, with elevations highest in the north and south, sloping downwards towards the center from the southwest to the northeast. Shiyan includes the counties of Yunxi, Zhushan, Fang, and Zhuxi, as well as Danjiangkou City, and the districts of Maojian, Zhangwan, and Yunyang [35], with a total population of 3,153,200 (Figure 1). Unlike rural settlements in plains or suburban areas, mountainous settlements face long-term constraints imposed by topography and geomorphology, along with a high frequency of natural disasters. These areas are also characterized by the interweaving of ecological space, agricultural production space, and rural settlement space, leading to greater spatial disturbances. Additionally, these regions experience more significant external environmental pressures. Shiyan City thus serves as a representative and typical case for studying the sustainable development of rural settlements in ecologically important areas, where the landscape is constrained by steep topography, high disaster risk, and stringent ecological protection measures.

2.2. Data Sources

The primary source of Shiyan City’s land use data is the 2020 Landsat 8 OLI multispectral data. Land use types were determined through manual visual interpretation using the ArcGIS 10.3 software platform. Subsequently, basic geographic data such as rural settlements, cultivated land, water bodies, and roads were extracted from the land use data. Statistical data, including population and GDP figures, were sourced from the Shiyan Statistical Yearbook, Hubei Statistical Yearbook, and relevant government reports. Digital Elevation Model (DEM) data were obtained from the United States Geological Survey (USGS) (http://glovis.usgs.gov/), while NDVI (Normalized Difference Vegetation Index), geological hazard information, and other environmental data were retrieved from the Center for Resource and Environmental Science and Data of the Chinese Academy of Sciences (https://www.resdc.cn/). Additionally, data on soil erosion sensitivity and water conservation function importance were acquired from the Geo-Remote Sensing Ecological Network Platform (http://www.gisrs.cn/).

3. Methods

First, the spatial aggregation characteristics of rural settlements in the study area were analyzed using kernel density estimation. Next, the complexity and dispersion of the settlements were further examined through Voronoi diagram analysis. An evaluation system for rural settlement indicators was then established, structured around four dimensions: “location, nature, society, and ecology.” The weights of each indicator were determined through the Analytic Hierarchy Process (AHP), leading to the generation of suitability evaluation results. Based on these results, the types of rural settlement layout optimization were identified, and targeted optimization strategies were proposed for each settlement type.

3.1. Kernel Density

Kernel density estimation quantifies settlement density within a defined spatial extent, where the kernel density value reflects the degree of spatial aggregation [36]. The formula for its calculation is as follows:

$$f_n\left(X\right)={\displaystyle \frac{1}{nh}}\sum _{i=1}^{1}k{\displaystyle \frac{x-x_i}{h}}$$

(1)

$f_n\left(X\right)$ is the target computed kernel density value, $nh$ the number of points in the threshold range; $x$ and $x_i$ are the study element points; $h$ is the search radius; $k$ is the kernel density function; $x-x_i$ is the distance between two element points [37].

3.2. Voronoi Diagram

Voronoi diagram, known as Tyson polygon, is a spatial segmentation method for identifying the influence and radius of a village, which has obvious advantages in spatial analysis and optimization with the formula:

$$T_i=x:d\left(x,p_i\right)<d\left(x,p_j\right)p_i,p_jϵS,p_i\ne p_j$$

(2)

$d$ is the Euclidean distance, $x$ denotes an element in the set $T_i$, which is a convex polygon. In any Voronoi polygon, the distance from any interior point to the occurrence $p_i$ of that convex polygon is less than the distance from that point to any other occurrence $p_j$, which are also called the center of mass or the occurrence element of the Voronoi diagram [38].

$C_V$ is the ratio of the standard deviation of the area of the Voronoi polygon to the mean, which is calculated by the formula:

$$C_V=\mathrm{Standard}\mathrm{deviation}/\mathrm{mean}\times 100\%$$

(3)

The $C_V$ values mainly reflect changes in the area of Tyson polygons, which in turn reflect the distributional characteristics of rural settlements, thus guiding the formulation of rural development policies and planning measure [39]. In this study, we plan the direction of resettlement of rural settlements based on the influence sphere of influence of weighted Voronoi diagram, so as to optimize the spatial layout of rural settlements to the maximum extent.

3.3. Minimum Cumulative Resistance (MCR) Model

The Minimum Cumulative Resistance (MCR) model, initially proposed by Knaapen [40], describes the movement of a species or entity from its source to a destination while encountering various resistance factors. This model has been widely applied in studies on species dispersal and ecological landscape pattern formation [41]. In recent years, it has been increasingly used to evaluate the spatial expansion of rural settlements, simulating their growth and diffusion from a source site to surrounding areas. Regions with lower resistance values are considered more suitable for rural settlement expansion, whereas areas with higher resistance values are less conducive to development [42,43]. Its calculation formula is as follows:

$$MCR=f_{min}{\sum }_{j=n}^{i=m}\left(D_{ij}\ast R_i\right)$$

(4)

MCR denotes the minimum cumulative resistance value, $f$ is a positive function, and min means that the resistance takes the minimum value; $D_{ij}$ denotes the distance from source $j$ to a point through the landscape substrate $i$. $R_i$ denotes the resistance of landscape $i$ to the movement of a species [44].

3.3.1. Determination of Sources

In the Minimum Cumulative Resistance (MCR) model, the “source area” represents the initial of expansion for each element. Including all settlements within this source area may result in an undue competitive edge, potentially hindering the agglomeration and coordinated development of rural settlements. Therefore, to effectively evaluate zoning suitability in response to the continuous expansion of typical rural settlements over a specific period, it is essential to select settlements that exhibit high suitability levels and regional representativeness.

In this study, populated point of origin were selected based on multiple criteria encompassing natural geography, location, economy, and ecology, specifically as follows: ① Settlements with more than 20 households in mountainous areas are classified as medium-sized villages, meeting the criteria for settlement agglomeration. Consequently, rural settlement patches were selected with an area exceeding 0.5 hm², approximately corresponding to 4000–6000 square meters. ② The study area was categorized based on slope and elevation. Settlements were prioritized at elevations below 500 m with slopes less than 8°, particularly those with a maximum slope of 5° or less and elevations below 300 m. ③ Roads play a crucial role in sustaining residents’ daily activities and economic production. Proximity to major transportation routes significantly enhances accessibility; thus, settlements within 1000 m of major roads were selected, considering the topographical constraints of mountainous regions. ④ The ecological environment is fundamental to human activities and livelihoods, especially in ecologically functional zones. Therefore, settlements were required to meet ecological safety standards, avoiding areas prone to geological hazards and adhering to ecological protection regulations. Additionally, settlements needed to maintain a minimum distance of 300 m from water sources while ensuring access to potable water [45,46]. Populated point of origin shown in Figure 1.

3.3.2. Resistance System Construction

Shiyan City, characterized by hilly terrain with significant elevation changes and slopes, is rich in woodland resources and features numerous rivers, contributing to its ecological diversity. The study identified key factors shaping rural settlement distribution and development, considering the area’s specific geographical and environmental characteristics. These factors include land use type, proximity to water sources, distance to townships, accessibility to major roads, distance to arable land, elevation, slope, terrain variation, population size, and per capita income. Additionally, geological hazards, vegetation cover, and the significance of soil and water conservation functions were incorporated to construct the resistance index system (

Table 1. Comprehensive impact measurement indicator system.

First Indexes	Second Index	Drag Coefficient					Weights
		5	4	3	2	1
terrain	Elevation	>1500	1000–1500	700–1000	300–700	≤300	0.1274
	Slope	>35°	25–35°	15–25°	8–15°	≤8°	0.1274
	terrain variation	>502	362–502	260–363	157–260	≤157	0.1274
location	Distance to main traffic arteries	>5000 m	3500–5000 m	2500–3500 m	1000–2500 m	≤1000 m	0.1763
	Distance to town	>15,000 m	10,000–15,000 m	7000–10,000 m	3000–7000 m	≤3000 m	0.0236
	Distance to water source	≤500 m	>3500 m	2500–3500 m	1500–2500 m	500–1500 m	0.0911
	Distance to arable land	>2800 m	1800–2800 m	1000–1800 m	500–1000 m	≤500 m	0.0911
social economy	population density	≤50	50–100	100–150	150–250	>250	0.0596
	GDP per capita	≤5	15–20	15–20	15–20	>20	0.0542
ecology	Land type	Ecological land, special land	Other sites	Agricultural land	Transportation land, industrial and mining land	Village construction land	0.0165
	Geologic hazards	>24	16–23	9–15	4–8	≤3	0.0335
	NDVI	≤0.2	0.2–0.4	0.4–0.6	0.6–0.8	>0.8	0.0192
	Desertification sensitivity	Extremely	Highly	Moderately	Mildly	Not	0.0096
	Erosion sensitivity	Extremely	Highly	Moderately	Mildly	Not	0.0099
	Importance of soil and water conservation functions	Extremely	Highly	Moderately	Mildly	Low	0.0121
	Importance of water-holding functions	Extremely	Highly	Moderately	Mildly	Low	0.0211

).

Elevation, slope, and terrain variation play a crucial role in settlement design, infrastructure development, and agricultural resource utilization. Low-altitude and low-slope areas generally exhibit higher living standards and population densities, facilitating the establishment of rural settlements. In contrast, as elevation and slope increase, construction costs and complexity rise, resulting in scattered settlement patterns that impact rural livelihoods [47,48].

Location factors, such as proximity to transportation networks, arable land, urban centers, and water sources, significantly influence settlement sustainability. As a national core water source with stringent water quality requirements, Shiyan City places a high demand on water resources. Transportation infrastructure plays a pivotal role in regional development, while agricultural land serves as an economic foundation. Generally, closer proximity to roads, towns, farmlands, and water sources enhances settlement viability, reducing resistance to rural settlement. Conversely, greater distances exacerbate production challenges and living conditions [49,50].

Socio-economic factors, notably population density and economic development, are also critical determinants. A growing population fosters settlement expansion and economic activity, providing both labor and market demand. Economic development serves as a driving force, attracting more residents to densely populated, economically vibrant regions, thereby reinforcing settlement clustering. Conversely, sparsely populated and economically underdeveloped regions tend to experience depopulation and stagnation [51].

Land use types directly shape the industrial structure, production methods, and living conditions of rural settlements. In important ecological function areas, land use is restricted to protect ecological integrity, while construction land must be developed and managed with sustainability principles. Shiyan City is prone to geological hazards, further limiting rural settlement expansion. Vegetation cover plays a critical role in maintaining ecological balance, regulating climate, preventing natural disasters, and enhancing human well-being; however, dense vegetation may also constrain settlement development. The significance of soil and water conservation functions, sensitivity to rock desertification, and soil erosion are key indicators of ecosystem health and vulnerability. Protecting these ecological functions is essential for ensuring regional sustainability and ecological security, thereby contributing to broader global environmental stability and fostering harmonious human-nature coexistence. Consequently, land use type, geological hazard frequency, vegetation cover, soil and water conservation importance, and sensitivity to rock desertification and soil erosion were selected as ecological resistance factors in this study [52,53,54].

The Analytic Hierarchy Process (AHP) combined with expert scoring was employed to determine indicator weights [55]. Resistance factor values were classified into five resistance values: 1, 2, 3, 4 and 5. Lower values indicate lower resistance and higher settlement suitability. Resistance scores for each influencing factor were spatially visualized using ArcGIS tools including Euclidean Distance, Raster Calculator, and Reclassify, as shown in Figure S1.

4. Results

4.1. Spatial Characteristics and Evaluation of the Suitability of Rural Settlements

Kernel density analysis (Figure 2a) indicates that rural settlements exhibit a pattern characterized by “large dispersed settlements and small clustered settlements.” On average, there are approximately 7 patches per square kilometer, ranging from 4 patches in sparsely populated zones to 42 patches in high-density regions. Significant variability exists across different regions. High-density areas are primarily concentrated in the northwestern and north-central parts of Shiyan City, forming three main core zones with kernel density values ranging from 20 to 42 patches/km², demonstrating significant settlement clustering. Conversely, low-density areas gradually extend outward from these core zones, resulting in several sub-core areas with kernel density values between 4 and 20 patches/km², reflecting a broader pattern of contiguous distribution. In contrast, other regions display sparse settlement distribution, with most areas exhibiting below-average kernel density values.

The Voronoi diagrams characterize the spatial dispersion of rural settlements. Related scholars [56] have proposed that when ${\mathrm{C}}_{\mathrm{V}}$ > 64%, the point set state is a “cluster” distribution. The total area of rural settlements in Shiyan City is 31,206.10 hm², comprising 172,893 individual settlements, and its rural settlement ${\mathrm{C}}_{\mathrm{V}}$ value averages 233.88%, which is much higher than 64%, and the distribution is more dense, belonging to the cluster distribution type (Figure 2b). A more granular analysis at the township scale shows that 80% of townships have a coefficient of ${\mathrm{C}}_{\mathrm{V}}$ values falling within the range of 92.24% to 233.88%, reflecting a pronounced clustered distribution of rural settlements. However, scattered and irregular settlement patterns persist due to region-specific geographical and ecological constraints.

In summary, settlements within the study area exhibit a dispersed spatial distribution and significant regional variations in their land use density. It is imperative to conduct a comprehensive suitability assessment and develop optimization strategies tailored to the study area.

Based on the resistance factor weights outlined in Table 1, each resistance factor was assigned a weight and integrated to calculate the first-level index for the spatial layout of rural settlements in Shiyan City (Figure 3). In terms of topographic resistance, the northwestern and southern regions of Shiyan City demonstrate greater resistance levels, whereas the central and northern areas exhibit relatively lower resistance values. Locational resistance follows the spatial distribution of transportation corridors and water bodies, with lower resistance levels observed in the northern and northwestern zones. Socio-economic resistance demonstrates a trend where regions with concentrated populations exhibit lower resistance values. Ecological resistance tends to be lower in the north and higher elsewhere.

These resistance values were combined to generate a comprehensive resistance surface. The resistance baseline is predominantly influenced by topographic and ecological resistance, with values ranging from 1.0 to 4.8. Overall, the northeastern part of the study area demonstrates more advantageous topographic conditions and greater economic vitality. Ecological resources exhibit a pronounced north–south disparity, with the northern regions offering substantially higher livability than their southern counterparts. The cost distance module was applied to calculate the minimum cumulative resistance cost from the source location of the rural settlements to the resistance base surface [57]. The suitability evaluation results were derived by dividing all raster cells into five grades. The results show that the minimum cumulative resistance value of rural residential areas in Shiyan ranged from 0 to 132,464.38. According to the Cell-Statistics method, Shiyan was divided based on the minimum cumulative distance values into high yield areas (0–2593), highly suitable area (2593–6753), generally suitable area (6753–12,986), less suitable area (12,986–27,012), and unsuitable area (21,012–13,2464.38).

Statistical comparative analysis (Figure 4) indicates that Shiyan City contains a relatively limited extent of high yield area; however, rural settlements within these areas account for the largest proportion of settlements, comprising 46.09% of the total settlement distribution. The areas classified as generally suitable and more suitable comprise 44.86% of the total area, with rural settlements constituting 48.37% and the number of rural settlement patches reaching 59.62%. In contrast, the area designated as unsuitable accounts for 46.83% of the total, with rural settlements occupying only 5.54% and comprising 8.22% of the total number of patches. This phenomenon arises from the steep topography, richer forest land resources, limited arable land, and inconvenient transportation in these regions. Furthermore, as a significant ecological function area, Shiyan City has implemented ecological restoration measures, enhanced environmental monitoring, and promoted ecological civilization in recent years. This has resulted in the protection of ecological resources, leading to sparsely populated areas that are ecologically sound and unsuitable for development and construction.

4.2. Optimization of the Layout of Rural Settlements

The suitability zoning results were superimposed with rural settlements, and based on the current characteristics of rural settlements in Shiyan City, the settlements were classified into four optimization types (Figure 5), in accordance with technical regulations for village planning and related research [51,58].

Urban–Rural Integration: This category encompasses mainly high-suitability areas where rural settlements are in closely proximity to towns and cities, promoting strong urban–rural integration. These settlements are primarily concentrated in the north-central and south-central parts of the city, covering approximately 32.27% of the total area for rural settlements. The favorable geographical location and well-developed transportation infrastructure make them focal points for fostering urban–rural connectivity. To optimize development in these areas, settlements should capitalize on their proximity to urban centers by improving transportation networks, enhancing public services, and upgrading infrastructure. Integrating these areas into urban development planning will further facilitate industrial transformation, modernizing local economies and diversifying industrial structures to ensure sustainable, high-quality growth.

Adjustment and Improvement Type: Settlements in this category are primarily located in high suitability areas, surrounding towns and cities, and benefiting from strong foundational infrastructure and promising development potential. These areas, mainly in the northern part of the study region, account for 38.63% of the total area for rural settlements and are adjacent to urban–rural integration zones. Given the favorable natural environment and solid production base, optimization efforts should prioritize improving basic infrastructure and public services according to each settlement’s specific development needs. Increased investment in fixed assets is recommended to maximize locational advantages, promote cross-industry linkages, and strengthen regional industrial integration. Encouraging intensive and large-scale industrial development in these areas will help stimulate regional economic vitality.

Relocation Type: This category consists of settlements in generally suitable to lower-suitability areas, mainly distributed in the northwestern and central parts of the study region, comprising generally suitable and less suitable areas, covering 24.00% of the total area for rural settlements. These settlements are relatively scattered but are situated in areas with a favorable ecological environment. However, high-altitude terrain and poor transportation accessibility significantly hinder urban integration and economic development. Relocation and centralized resettlement are the most viable strategies for optimizing these settlements. Efforts should be directed toward preventing disorganized land expansion through public awareness campaigns and policy incentives. Additionally, underutilized land resources should be activated by encouraging villagers to redevelop abandoned homesteads and repurpose unused land, improving land use efficiency. Enhancing rural living conditions in these areas will also contribute to ecological sustainability and rural revitalization.

Restricted Development Type: This category includes areas deemed unsuitable for settlement due to their strong ecological functions, dense vegetation cover, limited transportation access, and scarce resources. These areas, primarily located in the northwestern and southern regions of the study area, account for 5.10% of the total area for rural settlements. Steep terrain, high altitudes, and environmental risks—such as mine pollution and geological hazards—further constrain long-term development prospects. For these settlements, ecological conservation and regional environmental security should take precedence. Support should be provided for integrating isolated, under-resourced settlements into better conditions while ensuring the quality of life for relocated residents. Moreover, effective remediation of hollow villages should be implemented, alongside reuse strategies for residual homesteads. Reclamation and ecological restoration efforts should convert suitable land into agricultural and forestry areas while processing land unsuitable for reclamation ecologically. These measures will contribute to more efficient land resource utilization while maintaining ecological balance.

5. Discussion

5.1. Spatial Distribution Characteristics and Multidimensional Influencing Factors

This study reveals that rural settlements exhibit an uneven distribution pattern, characterized by “agglomeration near urban peripheries and diffusion in outlying areas.” This finding is consistent with the research of Li Jing et al. [36] on village-scale settlements in Jilin Province, which similarly indicates that urbanization is the primary driver of spatial structure. However, this study further identifies the significant synergistic influence of natural and infrastructural factors—including topography, transportation networks, and water availability—on settlement distribution. Crucially, ecological constraints—such as the frequency of geological hazards, the importance of soil and water conservation, and susceptibility to rock desertification—substantially restrict rural settlement development within ecological functional zones, thereby exacerbating spatial imbalance. This multidimensional mechanism compensates for the overemphasis on socioeconomic factors in previous studies [59] and aligns with contemporary research trends emphasizing the coupling of human, land, and ecosystem systems.

5.2. Suitability Evaluation and Planning Applications Under Ecological Constraints

This study develops an integrated evaluation system that combines geological safety with ecological function importance, thereby enhancing traditional socio-economic conditions and natural dominated assessment frameworks [60]. The results indicate that in important ecological function areas, topography and ecological conditions collectively constrain the distribution of rural settlements. This finding is consistent with the research of Ma Libang [3] on topographic constraints; however, the present study further underscores the moderating role of ecological function assessment. The evaluation further indicates that areas characterized by low geological hazard risks, high soil and water conservation significance, limited water source protection importance, low sensitivity to rock desertification, and minimal susceptibility to soil erosion are more suitable for settlement development. This conclusion provides empirical support for the findings of Yin Jingbo and Liu Yang [53,61]. thereby offering a scientific basis for national territorial spatial planning and policy formulation. From the perspective of land cover management and ecological conservation, the evaluation system provides guidance for improving the precision of territorial spatial management, optimizing the spatial allocation of governance resources, enhancing the targeting and effectiveness of ecological conservation measures, and facilitating preventive rather than remedial spatial governance strategies. This approach is consistent with current ecological conservation policy orientations.

5.3. Optimized Classification and Differentiated Development Strategies from an Ecological Perspective

This study proposes four optimized settlement categories and provides tailored strategies and recommendations for planning layout, infrastructure development, industrial growth, and ecological conservation, based on the characteristics of each category. In comparison with the five-category classification proposed by Zou Yafeng [51], this study does not establish a distinct “specialized conservation” category. Instead, it recommends incorporating villages with historical and cultural heritage into either the urban–rural integration or relocation–reconstruction categories for management, emphasizing planning feasibility. Furthermore, for hilly areas within important ecological function areas and disaster-prone regions, the study introduces an innovative “Restricted Development” category, recommending ecological resettlement and restricting development to protect ecosystems—a proposal consistent with successful ecological relocation and ecological conservation practices [5]. However, it should be acknowledged that this classification system primarily relies on the authors’ subjective assessment of local conditions. Future research should incorporate the participation of both the public and planners to enhance the universality and applicability of the classification. Additionally, while some less suitable rural settlements have experienced localized development, factors such as high altitude and poor accessibility, particularly inadequate road infrastructure, hinder their effective integration with the urban system, thereby underscoring the necessity of relocation strategies. The study further indicates that, compared with other regions, urban development in the study area remains highly concentrated and constrained, resulting in substantial disparities in settlement distribution and development levels. To address these issues, in addition to urban–rural integration, the “adjustment and optimization” category is proposed. This enables rural settlement planning to adopt more precise and effective implementation pathways, necessitating differentiated strategies to simultaneously enhance ecological conservation and the quality of human settlements.

6. Conclusions

This study selects Shiyan City, a core water source area for China’s South-to-North Water Diversion Project, as a case. A comprehensive suitability evaluation system was developed from an ecological perspective. The MCR model and GIS spatial analysis were utilized to assess rural settlement suitability. Based on the assessment results, distinct optimization categories were identified, and corresponding planning strategies were proposed. The primary conclusions of this study are as follows:

(1)

The distribution of rural settlements in the study area demonstrates marked agglomeration around towns, with the highest concentrations observed in the northwest and central-northern regions, while many settlements remain widely dispersed and spatially unorganized. The comprehensive resistance values generally exhibit a spatial gradient, decreasing in the north and increasing in the south. In terms of settlement suitability, the study classifies areas into five categories: high yield area, highly suitable area, generally suitable area, less suitable area, and unsuitable area. The high yield areas occupy the smallest proportion of land area yet contain the highest concentration of rural settlements. By contrast, the unsuitable areas cover a relatively large area, strongly shaped by topographic and ecological factors, thereby underscoring the need for optimizing the spatial distribution of rural settlements.

(2)

The rural settlements in the study area are classified into four distinct categories: Urban–rural integration, Adjusted and improved, Relocation and transformation, and Restricted development. The Urban–rural integration type primarily encompasses settlements located in high yield zones adjacent to towns. Optimization measures should be integrated into urban development master plans, designating these areas as strategic reserves for future urban expansion. The Adjusted and improved type primarily covers settlements in generally suitable zones, with a focus on optimizing industrial structures to foster new rural residential areas characterized by rational spatial layouts, strong potential for rapid economic development, adequate infrastructure, and an improved living environment. The Relocation and transformation type is concentrated in the northwest and central regions of the study area, encompassing settlements situated in generally suitable and less suitable zones. These areas are designated for implementing external controls while enhancing internal land use efficiency, thereby guiding residents toward more concentrated and organized living arrangements. The Restricted Development type primarily covers settlements in unsuitable areas, where rural settlement expansion is strictly limited, abandoned homesteads are reclaimed, and ecological conservation is prioritized.

This study develops a systematic ecological evaluation framework for assessing the suitability of rural settlements in important ecological function areas. The framework integrates ecological factors, including geologic hazards, NDVI, desertification sensitivity, importance of soil and water conservation functions, into the assessment process, thereby broadening the scope of traditional settlement suitability evaluations. Based on this framework, differentiated revitalization strategies are proposed for distinct categories of rural settlements, enriching the theoretical framework for rural sustainable development through spatial planning and multi-objective coordination in ecologically sensitive regions. It provides a novel paradigm for understanding the synergistic mechanisms within complex “human-land-ecology” systems. The findings offer a scientific basis for constructing beautiful and harmonious countryside, and hold significant practical value for promoting governance and green sustainable development in comparable ecological functional zones.

The evaluation and optimization of rural settlement layouts span multiple disciplines, contributing to enhancing rural livability and supporting policies for a more harmonious and sustainable countryside. However, this study has several limitations. Firstly, regarding the selection of influencing factors, although an evaluation system for the suitability of rural settlements in ecological functional zones was constructed, limitations persist in indicator selection and data acquisition. These include the absence of official data on ecological protection redlines and potential conflicts between biodiversity conservation and settlement expansion. Furthermore, constraints in data availability and resolution resulted in insufficient spatiotemporal accuracy for certain ecological elements. Future research should integrate multi-source remote sensing data and field surveys to validate and optimize the model, with particular emphasis on identifying spatial trade-offs between settlement patterns and highly ecologically sensitive areas.