1. Introduction
Explosive population growth, urbanization, and extreme rainfall are causing urban flooding more frequently, with many countries suffering severe damage [
1,
2]. Especially in China, critical damage to people’s life and property by urban flooding occurred in a number of cities [
2]. For instance, a rare rainstorm in Zhengzhou, Henan province, in July 2021 cost 302 lives and inestimable property losses [
3]. A similar incident happened in Xi’an on 24 July 2016 [
4]. The risk of urban flooding generated innovative approaches to storm water management [
5,
6].
First, in 1972, the United States developed BMPs (Best Management Practices). The initial goal was to control non-point source pollution and was gradually extended to water quality and stormwater management [
7]. In the 1990s, the WUSD (Water-Sensitive urban Design) [
8], NDS (Natural Drainage System) [
9], SUDS (Sustainable Urban Drainage System) [
10] and LID (Low-Impact Development) [
11] concepts were put forward by Australia, Germany, Britain and the United States, respectively. In China, the Sponge City Program (SCP) was proposed in 2012, combined with the current nature-based approaches of constructing urban drainage facilities through natural storage, natural infiltration and natural purification, to simulate natural ecology and optimize the urban environment and urban flood management [
12]. Now, numerous sponge facilities and evaluation systems have been proposed and used by researchers. For example, bioretention and permeable pavements were employed in Xi’an and Zhengzhou to effectively reduce the rate of urban flooding [
13]. In addition, models such as SWMM [
14], BIM [
15] and SUSTAIN [
10] are wildly used in Sponge City for evaluation and urban flood warning. Various models or technical indicators are commonly used to evaluate the function of sponge facilities, but the actual experience and feelings of residents are generally neglected [
15,
16]. The perspective of residents should be considered to further promote the development of Sponge City to find the deficiencies in Sponge City planning and awareness development [
17,
18].
Meanwhile, considering the SCP related to the renewal of old communities and infrastructure, the residents’ participation was also needed to maintain sponge facilities [
7,
9]. Hence, the building of Sponge City was also affected by the complexity of the residents’ attitudes. However, lacking of residents’ participation and preliminary in-depth investigation may cause some of the residents to oppose the approach, causing potential conflicts in program implementation [
7,
18]. Consequently, some policy-makers and researchers devoted themselves to improving awareness of Sponge City among residents and tried to explore the feasibility and applicability of encouraging residents to engage in decision-making [
19]. For instance, the guidance of “pay attention to raising the public awareness in the importance of Sponge City construction, encourage residents participate in city construction” was put forward by the provincial government of Jiangsu and Zhejiang [
20,
21]. In addition, the mode of “residents’ participation” was considered to apply in the sponge-style renewal of old communities in several pilot cities [
22].
Today, great progress has been achieved in building Sponge City [
23]. However, the study of Sponge City has focused on t storm water management and urban flood reduction in the long term [
24,
25]. There is little research concentrating on the subjective assessment of the effects of and changes made by Sponge City from the perspective of the residents [
26,
27]. In previous studies, investigation of satisfaction among residents for specific sponge measures and facilities was conducted by several researchers, such as the citizens’ preferences and attitudes towards urban waterfront spaces in Hangzhou and the residents’ satisfaction with sponge-style renewal of an old community in Zhenjiang [
7,
15]. However, the social effect of building Sponge City has been neglected [
28]. Few studies compare the satisfaction among residents between Sponge City and traditional communities [
29]. Therefore, more practices are needed to assess the performance of Sponge City and evaluate their social impact by investigating the satisfaction of residents [
27,
29].
Therefore, it is essential to understand the residents’ awareness perspective, and know the real feelings and attitudes related to the implementation of sponge infrastructure for promoting the building of Sponge City [
30,
31,
32]. To understand the clear changes of citizens’ awareness under the different living environment, we chose the adjacent Xixian New District and Xi’an for the comparison of Sponge City to a traditional city. This choice was intended to reduce the biases related to climate, culture or economic differences. Moreover, Xi’an is much older than the Xixian New District, providing a significant contrast. Three objectives were included to compare Sponge City to a traditional city: (1) the demographic and individual characters of respondents in different communities; (2) the realization of the residents’ attitude and perception towards Sponge City and local government; and (3) the practical social significance during Sponge City’s construction. Field investigation and observation in two communities located in Xi’an and Xixian New District revealed differences among residents with various of ages and educational backgrounds. The study presented here contributes to the field of urban planning and flood control – by assessing perspectives of affected community members and developing technical guidance to improve urban planning in the future.
4. Analysis of Demographics and Sociology
The sections above describe the evaluation for respondents’ conceptions, awareness of Sponge City and satisfaction level with living comfort and government. However, how were respondents with different ages or education backgrounds shown in this investigation? How did the respondents with the same characteristics above but living in different cities evaluate their homes? This will be discussed next.
Figure 7 shows the distinctions in the assessments among respondents in different areas and groups towards their cities (the
X axis: Sc—Sponge City; Pp—Permeable pavement; B—Bioretention; Rg—Rainwater garden; Uf—Urban flood; Gr—Green rate; Lc—Living comfort; T—Travel; Gs—Government support; P—policy; the
Y axis represents the value of
). Four figures, a–d, were established to illustrate the comparative assessment of respondents with different ages and educational backgrounds from Baihualinjian and Tongdejiayuan. Moreover, we calculated the average, Pearson’s r and the F-value to more carefully explain the existing phenomenon. Pearson’s r indicates the similarity level of the trends, and the F-value indicates the significance of the difference.
First, in
Figure 8, we can easily observe that the average
value of each aged group of Baihualinjian (53.87 for younger and 52.99 for older) were greatly lower than Tongdejiayuan (72.63 for younger and 68.68 for older). Then, in
Figure 8, we found that the average
value of residents living in Tongdejiayuan with master’s, bachelor’s or high school degrees were 76.88, 62.15 and 68.68, respectively, while in Baihualinjian these values were 62.07, 50.18 and 50.78, respectively.
In comparing the residents with different ages or educational backgrounds who live in the same area, we found the performance was more similar across age groups in Xi’an, with the better curve-fitting degree in
Figure 7, and Pearson’s r was 0.91 compared with 0.81 in Xixian New District. Furthermore, at the 95% confidence level, there were no significant differences in the evaluations of different age groups in either Baihualinjian or Tongdejiayuan, F
Baihualinjian = 0.036 < F
Tongdejiayuan = 2.01 < F
0.05 (1,18) = 4.41.
For residents in Baihualinjian with different educational backgrounds, the fitting degrees of residents with master’s educations and with bachelor’s or high school degrees were similar; the Pearson’s r were 0.54 and 0.60, respectively, and both of them were much lower than the 0.92 of those with high school education and bachelor’s degrees. The difference between the residents with graduate degrees and those with bachelor’s or high school degrees was significant, Fmaster/bachelor = 7.42 > Fmaster/high school degree = 6.10 > F0.05 (1,18) = 4.41. However, there is no significant difference between the people with high school education and those with bachelor’s degrees, Fbachelor/high school degree = 0.15.
Similarly, the curve fitting between the postgraduate education group and other groups was also worse in Tongdejiayuan: the Pearson’s r was 0.61 and 0.64, respectively, as shown in
Table 5. A better fitting degree was shown in the groups with bachelor’s degrees and high school degrees or below, for which the Pearson’s r was 0.80. The significant difference was shown in residents with master’s degrees and others, and even an extreme difference occurred in the master’s degrees and high school degrees or below groups, F
master/high school degree = 13.42 > F
0.01 (1,18) = 8.29 > F
master/bachelor = 7.06 > F
0.05 (1,18) = 4.41. However, there was no significant difference between those with bachelor’s degrees and high school degrees or below, F
bachelor/high school degree = 1.10 < F
0.05 (1,18) = 4.41.
Based on the data above, the young people in both areas have shown a better awareness and support level towards Sponge City than older people. In addition, with the improvement in education level, residents have a better understanding of Sponge City and exhibit greater government satisfaction. However, on the whole, the difference in scores of residents with different education levels was significantly larger than that between different ages, and the performance of residents with master’s education was most prominent.
Then, we compared the differences among people with the same ages or educational backgrounds but living in different types of cities in this survey. It is found that the higher the education level and the younger the age, the worse the curves fit and the more significant the differences were. In
Table 6, the Pearson’s r
(19–35) = 0.59 < Pearson’s r
(36–60) = 0.94, while F
19–35 = 24.68 > F
36–60 = 16.17 > F
0.01 (1,18) = 8.29. This indicates that the changes in the evaluation of various indicators in this survey were more similar among the older residents, but there was a much more significant difference in the younger group of residents between the two places. Continuously, Pearson’s r
high school degree = 0.92 > Pearson’s r
bachelor = 0.86 > Pearson’s r
master = 0.44, while F
Master degree = 18.46 > F
bachelor = 17.06 > F
0.01 (1,18) = 8.29 > F
high school degree = 7.71 > F
0.05 (1,18) = 4.41. This means that residents with graduate degrees in Sponge City and the traditional city have extremely significant differences in the performance of the survey and have different trends in the evaluation of various indicators.
In summary, the higher evaluation for Sponge City appeared in those who were younger and with better educational backgrounds. However, among the residents with the same ages and educational backgrounds, those from Sponge City performed better. What is worth noting is that the differences in region are much larger than those in age or educational background. Therefore, based on the results of this survey, we can conclude that the construction of Sponge City has greatly improved residents’ awareness, quality of life and support for the local government.
5. Discussion
A social field investigation and index evaluation were used to compare the differences in awareness and satisfaction among residents living in Sponge City or a traditional city. The empirical results suggest that residents living in Sponge City were more aware of and more satisfied with the urban construction and policies. In the analysis of groups with different ages and educational backgrounds, we found that the proportion of residents with better education or who were younger was much higher in Sponge City than the traditional city. Meanwhile, the younger and more well-educated people exhibited better understanding of Sponge City. Thus, we conclude that a stronger a preference for Sponge City building is demonstrated from the perspective of demographic and social characteristics.
In addition, this study was expected to fill the deficiency in investigating residents’ awareness and feelings in Sponge City construction, which is a long-term, incremental, and explorative process. Making full use of the media to disseminate the concept of Sponge City and creating relevant lessons to educate people would be helpful. Moreover, the survey results suggest several policy measures to ensure that the perspectives of residents are known by decision makers. For instance, some polices could be released to establish a definite and supervised feedback system between the government and residents to coordinate interests and ensure the equal power of all parties in the process of participation. Thus, policies could be designed more precisely and in a timely manner. Consequently, the government should pay attention to improving the level of awareness and acceptance of Sponge City among residents, especially in traditional cities. Encouraging residents to participate in the construction of Sponge City can help to strengthen the relationship between the government and citizens, change the negative attitudes of some people and improve the public’s awareness of Sponge City. Thus, the mode of resident participation in city building could be attempted, and some policy support should be given by the government to encourage residents to engage.
Although the factors that affected the preferences of residents in choosing which community they wanted to live in varied with different aspects, the urban aesthetic, travel convenience on rainy days and urban flood rate cannot be ignored. Based on the survey results, the residents from Xixian New District showed greatly satisfied with their living conditions, due to the travel convenient, highly green rate and the great urban flood management. Therefore, the advantages of Sponge City should be fully used by local governments for making polices to help with employment and urban planning. For instance, a higher subsidy for house purchases towards young and well-educated people would attract those people. For the city itself, young people, especially those with excellent education, are needed for sustainable development. Competitiveness can be continuously enhanced, and the investment in building Sponge City can be returned in other aspects by introducing talents. In addition, the construction of Sponge City will create jobs and attract a large number of related workers such as engineers and building workers, which further promote the development of the city.
Overall, this research is expected to enrich the study of awareness and satisfaction among residents of Sponge City. First, this research can help to examine the outcome of Sponge City and reflect the improving life quality taken by Sponge City from the perspective of residents. Second, this research can inform government to help them understand the satisfaction among residents in different cities and to make targeted measures throughout the process of Sponge City construction. Moreover, this study suggests that it is important to understand the awareness and satisfaction of Sponge City programs among residents using field investigations. There are also a few limitations in this investigation. We were limited by the number and space of the sample, and a deeper analysis of demographic and social characteristics could not be implemented, such as occupational classification. Further research should be more widely and carefully considered in the specific sponge facilities and put emphasis on comparative investigations in different areas.