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Article

Ecological Health Assessment of an Urban River: The Case Study of Zhengzhou City, China

by
Jie Li
1,
Lintong Huang
2 and
Kai Zhu
3,*
1
School of Art, North China University of Water Resources and Electric Power, Zhengzhou 450045, China
2
College of Water Resources, North China University of Water Resources and Electric Power, Zhengzhou 450045, China
3
School of Intelligent Manufacturing, Henan Polytechnic, Zhengzhou 450018, China
*
Author to whom correspondence should be addressed.
Sustainability 2023, 15(10), 8288; https://doi.org/10.3390/su15108288
Submission received: 7 April 2023 / Revised: 11 May 2023 / Accepted: 16 May 2023 / Published: 19 May 2023
(This article belongs to the Special Issue Integrated Water Resources Management Promoting Achievement of Multiple Sustainable Development Goals (SDGs))
Browse Figures
Figure 1
<p>Geographical location and river reach distribution of Zhengzhou City. Note: For convenience of expression, the name of the river and the Arabic numeral label of the river section are used to represent each river section. For example, Jin1 represents the Jinshui River–Hanghai road section.</p> "> Figure 2
<p>Indicator function division. Note: Ⅰ is the social function, Ⅱ is the habitat and channel function, Ⅲ is the water ecological function, Ⅳ is the water landscape function, and Ⅴ is the space enclosure function.</p> "> Figure 3
<p>Ecological health score of river landscape corridors in Zhengzhou.</p> "> Figure 4
<p>Proportion of each secondary indicator’s score value.</p> "> Figure 5
<p>Indicator difference test.</p> "> Figure 6
<p>Descriptive statistics for indicators.</p> "> Figure 7
<p>Ecological health of different river landscape corridors.</p> ">
Versions Notes

Abstract

:
Urban river ecological health assessment is an effective means to manage urban rivers, and combining principles of landscape ecology can provide new help for the ecological restoration of urban rivers and improving their ecosystem service value. From the perspective of important functions of ecosystems, based on typical sample site investigations of different river sections, questionnaire surveys, and remote sensing technology, a fuzzy comprehensive evaluation model based on the factor analysis method was used to construct an indicator system that can quantitatively reflect the ecological health of urban rivers. This comprehensive evaluation index system includes five major functions: social function, habitat and corridor function, water ecological function, water landscape function, and spatial enclosure function. The study identified key areas, key rivers, key river sections, and main indicator projects for the ecological restoration of the urban river landscape corridors in Zhengzhou. The study results also showed that the urban river landscape corridors in Zhengzhou have prominent problems in social function, water ecological function, and habitat and corridor function, and 62.1% of the river sections are currently in a sub-healthy state. The flood control function, eutrophication of water body, naturalization rate of revetment, and five other indicators in the old city district are significantly lower than those in the new city district, and the old city district should be the focus of the ecological restoration of urban river corridors. From the evaluation of the ecological health status of typical river sections, the Jinshui River and Xionger River have a larger number of river sections that urgently need restoration. This study provides a reference for the ecological restoration of urban rivers in Zhengzhou, a rapidly urbanizing region, and has reference significance for the construction of water landscapes in small and medium-sized cities with low levels of urbanization.

1. Introduction

River corridors play an important role in purifying pollution, improving the quality of biological habitats, maintaining biodiversity, and enhancing landscape quality [1]. Based on the principles of ecological corridors, a river corridor includes the water body of the river itself and the vegetation zone along the river that is different from the surrounding matrix [2]. The landscape ecological service functions of the corridor mainly rely on the continuous spatial experience and perception of the riverbank vegetation [3]. With the rapid development of urbanization, human economic activities have extensively transformed the spatial structure of riverbank vegetation, largely damaging the ecological functional structure of landscape corridors and natural ecological cycles, such as through encroachment on riverbank green spaces, neglecting the three-dimensional planting of riverbank spaces, homogenization of landscape green spaces, and fragmentation of landscape corridors [4]. As a result, the ecological systems of some sections of vegetation have rapidly degraded, and the quality of ecological services is poor. As the urban water environment deteriorates and the waterfront landscape becomes increasingly important in terms of urban ecological services, a landscape corridor evaluation system that incorporates river ecological health will help regional decision makers carry out river ecological restoration work.
The urban river is an important component of the urban ecosystem, and it serves as a carrier of vital environmental elements and a characteristic landscape that affects urban regulation and cultural services [5]. Therefore, the healthy ecological environment of the river corridor is related to the survival and development of the city. Countries and regions such as the United States, the United Kingdom, Australia, and South Africa have successively carried out corresponding river health assessments based on their national and regional environmental characteristics, using a series of methods such as the Index of Stream Condition and Urban River Survey [6,7,8,9,10]. However, there are significant differences in river health assessment indicators and evaluation standards across different countries and regions. These evaluation methods include the problem of incorrect indicator selection, which can lead to inaccurate evaluation results. Nevertheless, this kind of comprehensive and systematic approach to establishing indicators has played a significant role in the assessment of urban rivers that are currently heavily affected by human activities [11]. Overall, river health is primarily based on the construction of indicator systems from four aspects: hydrology, water quality, habitat, and biology [12,13]. Although there is currently no unified standard or method for river health, it has become an important means of river management to ensure that it meets the needs of human production and life while achieving sustainable development of the river ecosystem.
Since Forman proposed the concept of using landscape corridors to provide migration channels for river biological populations, the principles of river ecological corridors that include landscape ecology have gradually taken shape [14,15]. River landscape corridors are based on maintaining the health of the river, and further include landscape patterns to better provide ecosystem services for human society [16]. Compared with the evaluation of natural river health, the evaluation of urban river landscape corridor health factors is influenced by numerous anthropogenic factors, exhibits distinct regional environmental differences, and requires consideration of the functional role of waterfront landscapes, among a series of issues [17].
Based on its location advantage as a railway transportation hub, Zhengzhou has developed rapidly and become one of the representative cities of China’s urbanization, with a urbanization rate of 68% in 2021 [11]. It boasts the largest marshalling yard in Asia and the largest railway container freight center in China, as well as being the crossroad of China’s ordinary and high-speed railways. However, in recent years, ecological problems such as deteriorating water quality, a prolonged dry season, and natural landscape degradation have seriously impacted the ecosystem service value of its urban rivers. Therefore, this paper takes the section of Zhengzhou city as an example to explore a method that can comprehensively reflect the ecological and landscape health status of urban river landscape corridors.
Based on the results of a literature review, this study establishes an index system to evaluate the ecological health of urban river landscape corridors in Zhengzhou. The ecological health of river landscape corridors is summarized in terms of water ecology, spatial morphology, vegetation and its structure, land use characteristics, and other factors [9,12,15]. The comprehensive evaluation of the health characteristics of river landscape corridors can provide a decision making reference for the planning, management, and protection of urban rivers.

2. Materials and Methods

2.1. Study Area

Zhengzhou is located in the central–northern region of Henan Province, China (Figure 1). The average temperature in Zhengzhou is 14.2 °C, with the lowest temperature in January and the highest in July. As Zhengzhou is located in the central plain and is adjacent to the Yellow River corridor to the north, there are often strong winds during the autumn and winter seasons, with high evaporation rates, while the summer is hot and rainy [11]. Precipitation during autumn and winter is significantly less than during other seasons. Within the urban area of Zhengzhou, there are a total of 124 rivers of varying sizes, with 29 rivers having a catchment area exceeding 100 km2. Of the 9 rivers in the main urban area of Zhengzhou, the Kuhai River belongs to the Yellow River basin, while the remaining 8 rivers belong to the Jialu River system, including the main stream of the Jialu River and its first-order tributaries, such as the Suoxu River, Dongfengqu River, Jinshui River, and Xionger River [18]. The urban rivers in Zhengzhou are all seasonal rivers with a small natural base flow. Due to the impact of urbanization, the ecological health and landscape pattern of these rivers have deteriorated to varying degrees in recent years [18]. The main urban area of Zhengzhou is composed of five districts, namely Zhongyuan District, Jinshui District, Guancheng District, Erqi District, and Huiji District.

2.2. Data Preparation

The current indicators of plant communities, shoreline width, water transparency, and eutrophication status were observed and recorded on-site. GIS tools and Baidu Maps were used to compare and distinguish differences between river sections, and high-resolution satellite remote sensing data were incorporated to aid in this effort. Data collection for the land use characteristics surrounding the river sections and the heterogeneity of the river landscape corridor was conducted through on-site surveys. Based on the survey results, it was found that the landscape layout and vegetation communities on both sides of the urban river landscape corridor are mostly approximately symmetrical. Therefore, survey sampling points were selected on one side of the river section. During the survey process, questionnaires were distributed, with 10 questionnaires being distributed for each sampling point selected in each river section. A total of 380 questionnaires were distributed, with 362 valid questionnaires being collected, resulting in a response rate of 95.3%. The collected data will provide evaluation results for the cultural and landscape functions of the waterfront and the satisfaction levels with the landscape facilities. The content of the questionnaire is provided in the Supplementary Materials.

2.3. Principles for Selecting River Corridor and River Section Sampling Sites

Four representative rivers in Zhengzhou’s main urban area, namely the Jinshui River, Jialu River, Xionger River, and Dongfengqu River, were selected according to the different regions through which the rivers flow. Zhengzhou city was divided into the new city area and old city area according to the urban planning and construction development time. To ensure the clear vegetation spatial features of the river landscape corridor and the accuracy of the obtained data results, the Jialu River was taken as an example. Based on the average rainfall and average runoff at the Jialu River hydrological station during July, August, and September, which are the months with high water volume and relatively stable flow, the selected months are more conducive to judging water ecological indicators related to the river.

2.4. Methods

2.4.1. One-Way ANOVA (Analysis of Variance)

One-way ANOVA is a method used to test whether two or more samples are significantly different under the influence of a single factor [19]. By using analysis of variance, the impact of different factors on the health of urban rivers can be determined. Therefore, the overall health status of rivers in the new and old urban areas was used as the response variable, and the evaluation indicators of different rivers were used as the explanatory variables. These variables were standardized and input into SPSS software (International Business Machines Corporation, New York, NY, USA) for analysis of variance.

2.4.2. Factor Analysis

Factor analysis is a technique for simplifying multiple variables. Assuming the removal of multicollinearity between variables, factor analysis groups variables with strong correlations into a category to ensure low correlation between different categories and to fully reflect the overall information of the original variables. Its basic principle is to assume m variables, such as x 1 , x 2 , … , x m , and construct an n × m -order matrix [20].
X = ( x 11 x 12 ⋯ x 1 m x 21 x 22 ⋯ x 2 m ⋮ ⋮ ⋮ ⋮ x n 1 x n 2 ⋯ x n m )
Then, variables are standardized to eliminate the influence of dimensions, and the standardized variable is z 1 , z 2 , ⋯ , z m . These m standardized variables can be expressed linearly by factors F1, F2, …, Fm [21]:
z j = a j 1 F 1 + a j 2 F 2 + ⋯ + a j m F m
where a i j ( i , j = 1 , 2 , ⋯ , m ) constitutes the factor load matrix, j = 1 , 2 , ⋯ , m . By arranging the m factors in Equation (1) in descending order of their contributions to variance, it is customary to select p factors with larger contributions (cumulative contribution rate exceeding 60%). Using factor analysis to extract potential indicators influencing the ecological health of urban river corridors as secondary indicators of the evaluation system, not only can a reasonable and hierarchical indicator system be formed, but it can also help effectively address the adverse effects of the multicollinearity of various influencing factors on urban decision makers in formulating planning programs.

2.4.3. Evaluation Indicator Range

After classifying and organizing the retrieved literature, it was found that the evaluation index system mainly involves various aspects such as river hydrological function, landscape and recreational function, flood control function, cultural and educational function, and river ecological function [22,23,24,25]. However, these indicator layers do not fully comply with the actual situation in Zhengzhou, and it is necessary to re-select the indicators in a targeted manner in combination with the specific problems of the city. Through field investigations of river landscape corridors and the opinions of experts in related fields such as landscape architecture, water conservancy engineering, and ecology, and considering the practical problems such as difficult data collection and quantification of some rivers in Zhengzhou, similar indicators were combined. For example, river animals and aquatic organisms have a close relationship with the water quality and structural conditions of the river, so their survival environment was merged with the preservation degree of deep pools and shallow shoals in the river. Regarding the navigation function, considering the seasonal water shortage in northern cities, rivers have the characteristics of low water flow, low water level, and seasonal water imbalance, so this factor was excluded. The obtained data results of the evaluation of waterfront landscape cultural function and landscape facility satisfaction were normalized and subjected to one-way analysis of variance along with the observed values of other indicators. Data processing was carried out using SPSS 22.0 software. Based on the above analysis and preliminary screening of indicators, combined with the actual situation of Zhengzhou’s river landscape corridor, 26 evaluation indicators have been preliminarily determined. These 26 factors were used for factor analysis.

2.4.4. River Landscape Corridor Indicator System of Zhengzhou City

The 26 evaluation items were screened through an expert questionnaire survey. The measurement of the evaluation was conducted using a five-point Likert scale, which was divided into five standards: very important, important, average, unimportant, and very unimportant, with corresponding scores of 6, 3, 0, −3, and −6, respectively. Factor analysis was applied to evaluate the preliminary 26 indicators. Common factors with eigenvalues greater than 1.0 and cumulative contribution rates of variance exceeding 60% were selected to ensure that the common factors can better reflect the overall characteristics of the original data. Therefore, the first five principal components cumulatively explained 63.724% of the variance (Table 1), indicating that 16 indicators (Table 2) can accurately reflect the information contained in the original 26 indicators. For the convenience of later discussion, the 16 indicators were replaced by numbers 1–16.
The rotated component matrix is shown in Figure 2, where the 16 factors are grouped into 5 clusters, each containing a certain number of indicators. Based on the actual meanings of these indicators, the river landscape was divided into five functions: social function (1–4), habitat and corridor function (5–7), water ecological function (8–11), water landscape function (12–14), and spatial enclosure function (15–16).

2.4.5. Health Assessment of Urban River Landscape Corridor

The health evaluation of urban river corridors is conducted on three scales: the urban scale, river section scale, and cross-section scale. The river section scale refers to the different characteristics and river environments of different river sections. Considering that some indicators can only reflect the ecological health status of the river corridor in continuous river sections, the length range of the river section is selected as 0.6–1 km. The cross-section scale refers to the typical characteristics of the river corridor in the river section. The evaluation criteria for the health of urban river corridors are divided into five levels: very good, good, fair, poor, and very poor. A five-level scoring system is used to assign scores ranging from 1 to 5 points. The higher the score, the better the health status of the river corridor; the lower the score, the worse the ecological health of the river corridor. The detailed calculation method and corresponding score descriptions are shown in Table 3.
At the same time, in order to make the comparison between the scores more carefully and accurately reflect the differences between the scores, the score index is converted to the percentile system when evaluating the comprehensive scores of the five functions and the ecological health status of different river landscape corridors. The maximum score in the five-point system is set to 100. The specific conversion formula is as follows [3]:
x i ′ = x i x max × 100
where x ′ i is the score of the percentile system, x i is the score of the five-point system, and x max is the maximum value of the five-point system.

3. Results

3.1. Ecological Health Assessment of River Landscape Corridors

Four rivers, the Xionger River, Jinshui River, Jialu River, and Dongfengqu River, were assessed for their ecological health. According to the principle of river section selection, 12 sections of the Dongfengqu River were selected, which are represented by Dong 1–12. Xiong 1–9 were chosen as the nine sections of Xionger River, and the other river sections are shown in Figure 3. There are no sections of the river landscape corridor that have been rated as “very good”, indicating that there are currently no highly healthy river landscape corridors in Zhengzhou. In total, 62.1% of the river landscape corridors are in an unhealthy or sub-healthy state, while only 37.9% of the sections are in relatively good condition. The study found that green belts on both sides of the rivers were extremely narrow or completely occupied by the city’s main roads, and there were sewage inlets near some sections of the rivers. In addition, some sections were blocked by walls and the embankments were hardened, while the river channels were severely encroached upon by hydraulic facilities, buildings, and roads, which were the main reasons for the lower scores of the river landscape corridors.

3.2. Ecological Function Assessment of River Landscape Corridors

The score ratios of different indicators are shown in Figure 4. The ranking of the five comprehensive functional scores of the river corridors in Zhengzhou City from high to low is as follows: habitat and corridor function (70.53 points) > spatial enclosure function (68.95 points) > water landscape function (64.34 points) > water ecological function (58.55 points) > social function (53.03 points). Among them, the scores of social function (indicators 1–4) and water ecological function (indicators 8–11) were the lowest, while the scores of habitat and corridor function (indicators 5–7) were the highest. This indicates that water ecological function and social function are the key points for river ecological restoration in river corridors. In terms of water ecological function, 23 river sections, or 58.55%, were generally below average. In terms of the social function of river landscape corridors, the proportion of river sections with a score of less than 4 was 73.68%, which was due to the insufficient water flow in some river sections, resulting in poor overall service effectiveness of social function and low social recognition.
The sixteen secondary indicators were evaluated separately, and the proportion of indicators with a score below 3 was ranked from largest to smallest as follows: landscape cultural function (84.2%) > retention of shallow shoals and deep pools (78.9%) > moving distance of floating objects (70%) > landscape facility satisfaction (65.8%) = near-natural degree of revetment (65.8%) > canopy closure (60.5%) > fish diversity index (55.3%) = number of vegetation patches (55.3%) > ratio of riparian width to river width (52.7%). This indicates that the construction of landscape and cultural function indicators needs to be strengthened urgently in the river landscape corridors in Zhengzhou City.

3.3. Indicator Difference Analysis

The differences between indicators of the new and old urban areas were compared (Figure 5). The results of the analysis of variance (ANOVA) reveal significant differences between the groups. When the Sig value of an indicator is less than 0.1, it can be considered as having significant differences between groups. Based on the magnitude of the differences between indicators, the significance of five indicators (i.e., riverbank width, retention of shallow and deep pools, fish diversity index, ratio of water surface width to river channel width, and ratio of building height to distance from building to water body) are all zero, indicating significant differences between the five evaluation indicators in the new and old urban areas. Indicators 7 and 9 reflect the water ecological function of the river, indicating that the water ecological quality of the river in the old urban area is far inferior to that in the new urban area. Indicator 6 indicates that there is a significant difference in the river width between the new and old urban areas, reflecting the limited space in the old urban area for riverbank expansion due to spatial constraints in the process of urbanization. Indicator 13 reflects the quality and effectiveness of urban waterfront landscapes, indicating that the water in the new urban area can meet the needs of waterfront landscape viewing and water activities, which is related to the flow of multiple rivers passing through the new urban area. At the same time, in order to expand the landscape water surface, water conservancy dams were constructed downstream in the construction of the new urban area, ensuring relatively sufficient water volume in the river channel of the new urban area. However, this also resulted in poor water mobility and reduced connectivity between river and lake systems. Indicator 16 indicates that the new urban area has better conditions for implementing waterfront green space expansion, and the visual effect of the river landscape corridor space is relatively good, with a wide field of view.
Figure 6 shows the differences in the descriptive statistics of various indicators between the old and new urban areas. These are the average values of different indicators in the corresponding river sections of the new urban area and the old urban area. Compared to the new urban area, the old urban area performs better in indicators 2 (landscape cultural function), 3 (river curvature), 5 (canopy closure), and 12 (number of vegetation patches). Regarding the landscape cultural function, the mean score in the old urban area is 2.18, while in the new urban area, it is 2. Although the old urban area has a slightly higher score, both areas have low scores, indicating the lack of landscape cultural function of the waterfront spaces of Zhengzhou city. The canopy closure in the old urban area is higher than that in the new urban area by 0.13, which is because the vegetation in the old urban area has been there for a longer time, resulting in a higher canopy closure than the new urban area.
The near-natural degree of revetment in the old urban area is 1.82, indicating a relatively poor condition, while in the new urban area, it is 3.19, indicating that the new urban area has paid more attention to incorporating ecological concepts in river construction. In addition, a comprehensive evaluation of the 16 indicators in Zhengzhou city revealed that eight indicators scored below 3, accounting for 50% of the entire evaluation indicator system. This suggests that future river ecological restoration in Zhengzhou city should focus on improving the satisfaction of waterfront facilities, creating river landscape cultural corridors according to regions and river sections, setting up water-friendly spaces and paths for residents to increase their opportunities for water activities, enhancing the flood prevention capability of river corridors, carrying out near-naturalization transformations of revetments in river landscape corridors, and creating diverse habitats for aquatic plants and animals.

3.4. Analysis of the Difference in River Ecological Health

The Jinshui River and Xionger River had the smallest difference in scores for their ecological landscape corridors, indicating that their health status is relatively poor. This is because most of the river sections of the Jinshui and Xionger rivers pass through the old city area, where the river corridors are generally narrow and the water ecological environment is affected by factors such as high-density population, impermeable surfaces, and limited space for river landscape corridors, leading to poor river health status.
The comprehensive scores for different river sections of the four rivers are shown in Figure 7. The ecological health status of different river sections of the same river varies greatly. Among the different river sections of the Jinshui River, the optimal ecological condition was found in the Jin9 section, while the worst was found in the Jin4 section. Among the different river sections of the Xionger River, the optimal ecological condition was found in the Xiong8 section, while the worst was found in the Xiong6 section. The optimal ecological condition of the Jialu River was found in the Jia2 section, while the worst was found in the Jia1 section. The optimal ecological condition of the Dongfengqu River was found in the Dong7 section, while the ecological condition of the Dong2 section was the worst. The river sections with poor ecological health status for the four rivers mentioned above are all located in the old city area, while the ecological health status of the river landscape corridors in the new city area is generally better than that in the old city area. Therefore, the key areas for the ecological restoration of urban river landscape corridors are in the old city area, where efforts should be made to improve various evaluation indicators, while also paying attention to coordinating the restoration of the water ecological function of the rivers in both the old and new city areas.

4. Discussion

Against the background of urbanization, the natural ecological condition of river landscape corridors has been greatly disturbed [11]. However, due to the fixed land use types on both sides of the river corridor, it is difficult to achieve natural recovery of river landscape corridor ecological health in the short term [26,27]. Therefore, targeted river ecological restoration measures need to be implemented by regional decision makers to improve the ecological health of urban river landscape corridors. Decision makers can use different ecological restoration techniques according to the heterogenous requirements of different river sections [28]. Zhao et al. used landscape pattern models and hydrological models to obtain ecological health indicators of urban rivers and found that urbanization processes have led to changes in landscape structure and expanded regional differences in the Yangmei River Basin [29]. In semi-arid regions, a scientific regulatory model and new financing channels for water conservancy construction can assist in embankment construction, river regulation, multi-level rubber dam water storage, ecological restoration, artificial lakes, and riverfront landscape construction [30]. Additionally, water landscape characteristics vary significantly between rivers of different scales, and karst topography can significantly improve the water landscape quality of major rivers [31]. The construction of river landscape corridors not only needs to focus on the health of the ecosystem, but also needs to consider the social and cultural service value, that is, the enhancement of human aesthetics. Therefore, implementing spatial zoning, segmentation, and classification management of riverbank sections is an important method for creating green ecological corridors along rivers and lakes. The river channel morphology should be based on hydrological, hydraulic, or sediment characteristics before canalization. The reference material of the pre-disturbed river channel morphology can be obtained through the collection of historical water conservancy data, satellite cloud image records of river morphology in different years, etc., as a reference for the restoration of the river channel morphological structure. Different problems and environments may be encountered during the restoration of different river segments, and differentiated strategies should be adopted accordingly. At the same time, in the old urban areas of Zhengzhou city, the riverside space of the river sections is limited, the flood control section is narrow, the landscape facilities on the embankment are simple, and the riverside habitat is lacking [32]. Therefore, the focus of restoration should be on optimizing the functional structure of river embankments, the deepening and natural ecological transformation of embankments and riverbeds, and restoring river shallow shoals and deep pools.

5. Conclusions

This study established a total of 16 indicators and conducted an empirical study of the Zhengzhou section using a fuzzy comprehensive evaluation model based on factor analysis. This study provides a quantitative evaluation of the health status of urban river sections on the landscape scale. Currently, only 37.9% of the rivers have a relatively good ecological health status in their landscape corridors, while the others are in unhealthy or sub-healthy conditions. The established comprehensive evaluation index system not only focuses on the biological health of the rivers but also emphasizes the structure and function of the rivers. The system takes into account the harmonious coexistence between human beings and nature, and further extends the functions to serve human society. The results showed that the current ecological health status of the river landscape corridor is not optimistic, and urgent ecological restoration is needed to improve the urban water ecological function and water landscape security in Zhengzhou. Significant differences in ten indicators, such as water eutrophication, riverbank width, and flood control function, were found between the new and old urban areas. The health status of river landscape corridors in the new urban area is relatively better than that in the old urban area, and the river sections with poor ecological health are generally located in the old urban area, indicating that the focus of river landscape corridor ecological restoration should be on the old urban area. The study also revealed the specific ecological health scores of rivers in Zhengzhou, in descending order: Jialu River (71.92 points), Dongfengqu River (64.17 points), Jinshui River (52.92 points), and Xionger River (51.69 points). The correlation between river landscape and human interference in urbanized areas is closely related. Understanding and grasping this correlation is the basis for protecting and restoring the scientific construction of riverbank zones. It has important reference value for proposing key plant types and targeted riverbank land adjustment strategies based on local conditions.
Nonetheless, the present study primarily focuses on constructing the evaluation system and discussing the strategies for ecological restoration. Further in-depth discussion on the effectiveness of ecological restoration needs to be combined with other cases. However, as the process and effects of restoration may not be immediately apparent, the next step is to evaluate the effects of restoration through specific projects. Moreover, in-depth analysis at the micro-technical level and further utilization of landscape ecological principles can provide assistance in addressing urban water environmental issues.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/su15108288/s1, Table S1: Construction of Evaluation Index System for Urban River Landscape Corridor Health.

Author Contributions

Conceptualization, J.L.; methodology, J.L.; software, L.H.; validation, K.Z., J.L. and L.H.; formal analysis, J.L.; investigation, J.L.; resources, K.Z.; data curation, L.H. and K.Z.; writing—original draft preparation, J.L.; writing—review and editing, L.H. and J.L; visualization, K.Z.; supervision, K.Z.; funding acquisition, K.Z. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the Scientific and technological key project of Henan Province in 2023, grant number 232102230110.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Not applicable.

Acknowledgments

We would like to express our sincere gratitude to the editors and reviewers who have put considerable time and effort into their comments on this paper.

Conflicts of Interest

The authors declare no conflict of interest.

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Figure 1. Geographical location and river reach distribution of Zhengzhou City. Note: For convenience of expression, the name of the river and the Arabic numeral label of the river section are used to represent each river section. For example, Jin1 represents the Jinshui River–Hanghai road section.
Figure 1. Geographical location and river reach distribution of Zhengzhou City. Note: For convenience of expression, the name of the river and the Arabic numeral label of the river section are used to represent each river section. For example, Jin1 represents the Jinshui River–Hanghai road section.
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Figure 2. Indicator function division. Note: Ⅰ is the social function, Ⅱ is the habitat and channel function, Ⅲ is the water ecological function, Ⅳ is the water landscape function, and Ⅴ is the space enclosure function.
Figure 2. Indicator function division. Note: Ⅰ is the social function, Ⅱ is the habitat and channel function, Ⅲ is the water ecological function, Ⅳ is the water landscape function, and Ⅴ is the space enclosure function.
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Figure 3. Ecological health score of river landscape corridors in Zhengzhou.
Figure 3. Ecological health score of river landscape corridors in Zhengzhou.
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Figure 4. Proportion of each secondary indicator’s score value.
Figure 4. Proportion of each secondary indicator’s score value.
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Figure 5. Indicator difference test.
Figure 5. Indicator difference test.
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Figure 6. Descriptive statistics for indicators.
Figure 6. Descriptive statistics for indicators.
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Figure 7. Ecological health of different river landscape corridors.
Figure 7. Ecological health of different river landscape corridors.
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Table
Table 1. Explanation of total variance.
Table 1. Explanation of total variance.
Extract the Sum of Loads SquaredSquares Sum of Rotating Loads
SumPercentage of VarianceAccumulation %SumPercentage of VarianceAccumulation %
8.15031.34831.3483.59013.80713.807
2.76710.64341.9912.98111.46425.271
2.3789.14551.1362.84410.93936.211
1.7476.72057.8562.3489.03145.242
1.5265.86863.7242.2638.70353.945
Table
Table 2. Specific components of river landscape corridor indicator system in Zhengzhou city.
Table 2. Specific components of river landscape corridor indicator system in Zhengzhou city.
Serial NumberIndicatorSerial NumberIndicatorSerial NumberIndicatorSerial NumberIndicator
1Landscape facility satisfaction5Canopy closure9Fish diversity index13Ratio of water surface width to river channel width
2Landscape cultural function6Riverbank width10Near-natural degree of revetment14Water surface transparency
3River curvature7Retention of shallow shoals and deep pools11Moving distance of floating objects (velocity)15Ratio of riparian width to river width
4Flood control function8Eutrophication of water12Number of vegetation patches16Ratio of building height to distance from building to water body
Table
Table 3. Health assessment methods of urban river landscape corridors and their descriptions.
Table 3. Health assessment methods of urban river landscape corridors and their descriptions.
IndicatorEvaluation ScaleEvaluation MethodologyHealth Assessment Status Description
1River sectionQuestionnaireThe environmental and ecological status of the river landscape corridor is minimally disturbed, and the five functions of the river landscape corridor are normal (5 points).
2River sectionField investigation
3River sectionGIS spatial analysisThe ecological environment of river landscape corridor is less disturbed by urbanization, and one or two functions of the river landscape corridor are degraded to a certain extent (4 points).
4Cross-sectionFlood protection standard
5Cross-sectionGIS spatial analysis
6River sectionGIS spatial analysisThe ecological function of the river landscape corridor iss disturbed to some extent, the water body is polluted, and the riparian vegetation zone is destroyed (3 points).
7River sectionField investigation, Baidu Maps
8River sectionField investigation
9River sectionField investigationThe ecological environment of the river landscape corridor is strongly disturbed by urbanization, the structure and function of the water body and the river are seriously disturbed, and the vegetation along the river landscape corridor is greatly disturbed (2 points).
10River sectionField investigation
11Cross-sectionField investigation
12Cross-sectionField investigation
13River sectionField investigationThe river landscape corridor is severely disturbed by urbanization, the water body dries up, the water pollution is serious, the vegetation belt is destroyed or occupied by roads and buildings, and the natural characteristics of the river landscape corridor disappear (1 point).
14Cross-sectionField investigation
15Cross-sectionField investigation
16Cross-sectionField investigation
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Li, J.; Huang, L.; Zhu, K. Ecological Health Assessment of an Urban River: The Case Study of Zhengzhou City, China. Sustainability 2023, 15, 8288. https://doi.org/10.3390/su15108288

AMA Style

Li J, Huang L, Zhu K. Ecological Health Assessment of an Urban River: The Case Study of Zhengzhou City, China. Sustainability. 2023; 15(10):8288. https://doi.org/10.3390/su15108288

Chicago/Turabian Style

Li, Jie, Lintong Huang, and Kai Zhu. 2023. "Ecological Health Assessment of an Urban River: The Case Study of Zhengzhou City, China" Sustainability 15, no. 10: 8288. https://doi.org/10.3390/su15108288

APA Style

Li, J., Huang, L., & Zhu, K. (2023). Ecological Health Assessment of an Urban River: The Case Study of Zhengzhou City, China. Sustainability, 15(10), 8288. https://doi.org/10.3390/su15108288

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