Over the past 40 years, China has witnessed the largest urbanization process unprecedented in the world and realized the huge transformation from “rural China” to “urban China”. In such a short period of time, China, compared to other countries, faced more complex and prominent challenges, including natural resource and environmental damage, security risks and cultural degradation against the backdrop of resource shortage, frequent natural disasters and rich cultural heritage. In recent years, the United Nations Human Settlements Program has paid great attention to sustainable urbanization, urban security and resilience and cultural diversity. For China, how to balance between protection and development, and security and development and achieve spatial security and sustainable development under complex conditions is an urgent and worldwide challenge.

As an indispensable management approach and technical method of spatial governance in a large country, regional Footnote 1 spatial planning research and practice plays an irreplaceable role in leading regional development, adhering to ecological and security bottom lines, coordinating regional spatial resource allocation, guiding urban development and improving people’s living environment. Wu Liangyong, a famous Chinese urban planner and architect, proposed that “to actively carry out regional planning and create pleasant human settlements in regional planning and implementation is an inevitable choice” (Wu, 2005). Therefore, it is of great significance to carry out innovative research on the theories and methods of regional spatial planning and explore the path to sustainable urbanization in China, and to enlighten urban development worldwide with China’s experience (The Editorial Department, 2019).

China has a vast territory consisting of highly diverse and disparate regional spaces. In addition, due to climate change, the characteristics and problems of regional spaces are constantly changing, thus bringing great uncertainty. It calls for a method that fits China’s realities and responds to dynamic changes, so as to realize the vision of “creating a good living environment”. However, most of the previous studies and practices centered on economic competitiveness, and failed to pay due attention to natural environment, security risk and cultural characteristics. Thus, they were unable to solve regional development problems under China’s realities. To realize the goal of pursuing secure and sustainable development of regdevelopm,entional space and in view of national conditions, this paper proposes the “national spatial planning theory” which centers on the “precise adaptation” of urban development to natural and cultural conditions. It constructs a regional spatial optimization methodology and technical system of precise analysis, adaptive distribution and dynamic evaluation, which has been applied in regional planning practices on multiple scales in the past 20 years.

1 Research Background and progress

1.1 Regional spatial characteristics in China

1.1.1 Disparity

Spatial disparities among regions in China are manifest in geographical conditions such as climate, elevation, topography, and hydrology, and regional cultures including ethnicity, language, customs and architecture, as well as economy, population, and urban development in economic and social aspects.

In terms of China’s natural and geographical conditions, the land is high in the west and descends to the east. It comprises three parts with different altitudes, including the Qinghai-Tibet Plateau with an average elevation of over 4,000 m, major plateaus of 1,000–2,000 m and plains mostly below 500 m. According to the climate impact on architectural design, the Uniform Standards for Civil Architecture Design (GB50352- 2019) divides China into seven climate zones.

In terms of regional culture, as the world’s only continuous civilization, China has been a multi-ethnic and multi-cultural country since ancient times. Various regional cultures derived from Yan, Qi, Lu, Jin, Wu, Yue, Chu, Ba and Shu States during the Spring and Autumn and Warring States period (Wu, 2005). And they continued to evolve throughout history, resulting in the coexistence and flourishing of diverse and disparate regional cultures today.

In terms of economic and social development, there are great disparities among regions due to natural resources, location, policy, history, culture and other factors. Areas to the east of the Hu Huanyong Line Footnote 2 are densely populated and economically developed. They account for 43% of the total territory, 93% of the arable land nationwide, 94% of the population and 95% of the GDP. Population and businesses are highly concentrated in city clusters and metropolitan areas around mega cities. In 2020, residents in major city clusters including the Beijing-Tianjin-Hebei region, the Yangtze River Delta, the Guangdong-Hong Kong-Macao area, and the Chengdu-Chongqing region reached 553 million, accounting for 40% of the populationFootnote 3.

Regional spatial disparities provide diverse contexts and conditions for the development of human settlements, thus requiring a regional spatial research method and technology to suit local conditions.

1.1.2 Dynamics

China’s regional space is characterized by dynamic changes in natural and geographical conditions, regional cultural characteristics, and socio-economic development.

First, natural and geographical conditions are constantly changing due to climate change. The global average temperature in 2020 is 1.2℃ higher than the pre-industrial level (the average temperature between 1850 and 1900) Footnote 4 China’s annual average surface temperature increased by an average of 0.26 °C per decade from 1951 to 2021. During the same period, the northwest, north, and northeast parts, and the Qinghai-Tibet Plateau experienced the fastest temperate increase Footnote 5. From 1961 to 2018, the distribution of precipitation changed significantly in major basins across China. From 2001 to 2019, the average annual precipitation in river basins in northwest China increased by 9.2% compared to 1956—2000, while that in the Liao River, Hai River, Yellow River and Huai River basins decreased slightly (Zhang, 2022).

Second, China’s diverse cultures also changed over time. Especially in the past four decades, with massive population movements in the rapid process of urbanization, cultural elements among regions also experienced integration, renovation, and evolution.

In addition, economic and social factors such as the economy, population and urbanization have been changing continuously and dynamically. For example, in the urbanization process over the past 40 years, a large number of surplus rural workers migrated to the southeast coast in the first 30 years, while in the past 10 years, population inflow slowed down in the east part but became faster in the mid-west part, while the northeast saw a considerable increase in outflow (Wang et al., 2020).

Regional spatial dynamics lead to the dynamic adjustments of internal and external environments, problems, and intended needs, thus requiring a regional spatial research method and technology that adapts to the changing realities.

1.2 Current problems of regional spatial research in China

A large number of regional spatial studies and related practices in China were conducted against the backdrop of rapid industrialization and urbanization, with the aim of improving regional economic growth and competitiveness. Drawing upon international theories and approaches, they seek to develop technical methods on the basis of central place theory and growth pole theory (Fang & Chen, 2007). Those studies played a critical role in developing the urban system layout and channelling economic activities to the urban space. However, given resource and environmental damage, frequent natural disasters, cultural degradation and spatial dynamics and disparities among regions, such studies can hardly play their due role in guiding the sound urban development, protecting natural and cultural resources effectively, preventing and managing security risks and building a beautiful living environment.

1.2.1 Limited technical methods and homogeneous results

Regional spatial studies and related practices that prioritize economic development mainly focus on creating regional urban system structures by identifying development axes, central cities, and functional zones (Gu & Zhang, 1997; Liu & Lu 2005; Lu 1987; Peng 1988; Song & Gu, 1988; Yang, 2003). They put less attention on regional disparities and dynamics in natural environment and cultural characteristics. In addition, they do not adapt the layout of urban areas to natural and cultural conditions, thus leading to the problem of homogeneous research results. For example, the spatial structure pattern that combines city clusters, metropolitan areas and cities of different sizes is applied to various regional spaces, without considering their specific realities. Take Hebei Province for example. There are many medium-sized cities that are mostly located in the center of the region. It should focus more on the development of medium-sized cities and explore the model of combining the development of small- and medium-sized cities and rural towns (Wu, 2005). In contrast, in those areas with disadvantageous natural conditions, such as the northeast China, the Qinghai-Tibet Plateau, and the South China Sea, their urban development model should be greatly different from that in other regions. A one-size-fits-all model is absolutely not recommended.

1.2.2 Lack of response to uncertainty and dynamics

In the context of uncertain external environments and dynamic regional space, regional spatial research and practice should be moderately flexible to meet multiple objectives and adapt to different plans. However, a large number of studies and practices mostly focus on drawing the ultimate development blueprint rather than simulating various scenarios to cope with uncertainty and changes. As a result, when the external environment and internal elements of the regions change unexpectedly, the “blueprint” would “fail”, and regional development and urban development would be mired in trouble and even face severe risks and challenges. For instance, a flash flood ravaged Zhengzhou on July 20th, 2021, when the maximum daily rainfall reached 624.1 mm, 3.1 times of the 199 mm 24-h flood prevention standard designed to withhold a 50-year flood. And the maximum hourly rainfall reached 201.9 mm, breaking the historical record observed by China’s meteorological authority Footnote 6. During the event, inadequate prediction and response to complex climate events in urban planning and development resulted in significant casualties and economic losses. In addition, most of these studies and practices focus on plan preparation but lack dynamic monitoring, evaluation and optimization, thus failing to form a closed loop and unable to cope with the changes in regional space and especially the exacerbating climate change in recent years.

1.3 Theoretical approach and practical experience of regional spatial research in other countries

The study of theories and methods related to regional space originated in the West. Modern urban planning has included the idea of region since its conception. Patrick Geddes said that “each true design, each valid scheme should and must embody the full utilization of its local and regional conditions and be the expression of local and of regional personality ”(Geddes P., 2012). Around the twentieth century, under rapid industrialization, the central place theory, the growth pole theory, ther core and periphery model and related research methods were the mainstream theories. They aim to pursue economic growth and centered around the laws of economic activities. In the late twentieth century, as the conflict among resources, environment and rapid development became increasingly prominent, the concept of sustainable development gradually received attention in the field of regional spatial research. The concept and method of analyzing various regional resources as the main premise for development received more and more attention. By analyzing some recent studies and related practices of regional spatial in other countries, this paper concludes that there are two main points to learn from in terms of technical methods as follows:

First, precise analysis and monitoring of important issues in key regions should be conducted to help improve spatial optimization programs. The “Paris Region’s Development Master Plan” (SDRIF, Le Schéma directeur de la régionl Île-de-France 2030) contains an in-depth analysis of the main priorities for biodiversity conservation and restoration to support planning decisions, including the scope of ecological origins and corridors, water resources conservation areas prioritized for restoration, and key areas to maintain ecological coherence Paris Region Governmen (2012). The “Upper Mississippi River and Basin Restoration and Protection Strategies” (UMRPS) proposes the strategies to balance security and development of the river. It is based on the detection and analysis of ecological problems and security risks facing each subsystem by monitoring the land use of the basin, and changes in the river’s ecosystem and geological conditions (Minnesota Pollution Control Agency, 2017). The “America 2050: A Prospectus” proposes the strategies for disaster prevention and control, transportation, and infrastructure planning in mega-metropolitan areas by analyzing population density, commuting data, ecological zoning, and housing affordability (Regional Plan Association, 2006).

Second, multi-scenario simulation for spatial optimization should be adopted to support forward-looking modeling. “ET2050: Territorial Scenarios and Visions for Europe” decomposes models including MULTIPOLES (demographics), MASST3 (economy), MOSAIC (transportation), METRONAMICA (land use), and SASI (integrated spatial development), as well as more comprehensive cross-industry metamodels (TV + and PASH +). It examines the possible developments and changes in social, economic and territorial cohesion in the EU in 2010 towards 2030 and 2050 under different scenarios and assumptions in order to better cope with future uncertainties. As the report points out, “the way to present and explain model’s results is never completely free from personal subjectivity, moreover, but it is precisely in order to highlight and contrast one’s prejudices and expectations, away from wishful thinking, that it is indispensable to use quantitative data and apply sound forecast models” (ESPON, 2013).

To sum up, in recent years, regional spatial research and related practices in other countries have begun to conduct more precise analysis of specific areas and problems, propose adaptive spatial strategies and carry out multi-scenario simulation with the help of models. Considering that regional spaces in China are diverse and disparate and the problems faced by China are quite different from those of other countries, we can take international experiences as a reference but not copy them blindly. Instead, we need to create a complete set of regional spatial research theories and methods that fits China’s realities.

2 Essence of “National spatial planning theory”

2.1 Background of the National Spatial Planning Theory

Around 2000, as economic globalization and regional integration went deeper, the spatial development of urban areas at national and regional levels became a hot topic in the theory and practice of urban and regional planning in many countries. National and regional spatial planning has increasingly become an important means and measure for improving the comprehensive competitiveness of countries and regions. Its status and role in the sustainable development of countries and regions have attracted attention from all sectors of society, forming an essential part of the public policies of governments.

During this period, with the establishment of China’s socialist market economy, national and regional spatial planning, as a policy tool for the country’s coordinated socio-economic development, was given more attention by the government and academia. However, at that time, most of China’s regional spatial research and planning aimed at fostering economic development. In addition, related theories were built on Western ones, such as the central place theory and the growth pole theory. Therefore, it is difficult to address complex issues under China’s specific conditions, including ecological and environmental damages, prominent risks and hidden dangers, and cultural degradation. The root cause of these issues is that the layout of urban areas puts economic development before nature and culture and does not match the natural endowment and cultural characteristics of different regions. Therefore, instead of focusing solely on economic development, regional spatial research and planning should pay more attention to creating a better living environment and balancing protection and development as well as security and development. As a result, its theoretical approach should also be adjusted accordingly.

Against this background, and in view of China’s diverse and significant geological differences among regions, the following are important issues that need to be addressed in China’s spatial research and planning: how to coordinate between conservation and development and between security and development; and how to adapt urban development to local natural and cultural conditions. “The National Spatial Planning Theory” is a spatial planning theory that focuses on these issues and aims to create a sound living environment and the sustainable development of the country and its various regions.

2.2 Theoretical connotation of “National Spatial Planning Theory”

The national spatial planning theory is a theoretical approach to urban spatial planning at national and regional levels based on the science of human settlements created by Wu Liangyong. The science of human settlements is “a new discipline system centered on environment and human production and life. It focuses on buildings and the protection and development of artificial and natural environment in urban areas ”(Wu, 1995). The “national spatial planning theory” adheres to the concept of adopting the science of human settlements in regional spatial planning advocated by Wu Liangyong. It proposes the theoretical approach of spatial planning with the “precise adaptation” of cities and towns to nature and culture as the core and tailored to suit the disparate and dynamic regional spaces in China. The “precise adaptation” refers to coordinating urban areas (the core vehicle for economy and society) with natural and cultural conditions at national and regional levels. It aims at the accurate, rational and adaptive alignment of the urban layout with facilities and differentiated and dynamic natural environments, cultural characteristics, and socio-economic development in different regions. It mainly includes the following connotations:

First, the “national spatial planning theory” is the first theory that proposes to develop the national urban spatial layout based on the analysis of ecological environment. It divides national and regional spatial resources into ecological security layer, infrastructure layer and human settlement layer. The ecological security layer refers to the spatial resources based on natural and ecological elements, which is the foundation of human settlements; the infrastructure layer is the infrastructure network with transportation as the core, which is the skeleton of the space; and the human settlement layer includes the varying types of human settlements at different levels, which is the core of human life. The “national spatial planning theory” elaborates on the spatial elements of the three layers from the perspective of a pleasant living environment. That is, it takes the ecological security layer as the core of spatial resource analysis and the basis of urban layout, evaluates the carrying capacity of regional spatial resources by quantitative analysis and the analysis of population mobility, and identifies the development trend of urban areas, so as to create an urban spatial layout and infrastructure network compatible with the natural environment (Wang, 2010), realizing the adaptation of urban layout to natural environment.

Second, in view of the diverse and disparate regional spaces in China and the uncertainty brought by the intensification of global climate change, an effective means to ensure the spatial security and sustainable development of the national territory is to figure out the resource inventories in different regions, create an adaptive urban spatial layout and continue to monitor, evaluate, and optimize the dynamic changes in space. Therefore, the “national spatial planning theory” further proposes a full-cycle regional spatial research method and framework of “precise analysis, adaptive distribution and dynamic evaluation”. To be specific, it means creating urban areas that are compatible with disparate and dynamic natural environments in different regions by laying a solid foundation, making development plans and optimizing the momentum, so as to provide vital support for the sustainable development of urban areas.

2.3 Expansion of “National Spatial Planning Theory”

The “national spatial planning theory” was first put forward at the beginning of the twenty-first century, while the connotations of the theory have been constantly expanded from creating pleasant living environments to prioritizing safety risks and cultural characteristics in the context of China’s further urbanization, exacerbating global climate change and evolving problems in regional and urban development.

During China’s urbanization process over the past 40 years, the first 30 years saw a rapid development of cities and towns. In the face of tightening resource and environmental constraints, severe environmental damage, outstanding land supply and demand conflicts, and resource depletion, the core issue at this stage was to balance the need for rapid development and the goal of sustainable development. Therefore, during this period, the “national spatial planning theory” centered on regional spatial resource analysis based on natural and ecological elements to create adaptative urban spatial layouts focusing on ecological concerns.

In the past decade, as urbanization slowed down and global climate change intensified, the problems that accumulated in the first 30 years under the high-density and high-intensity development models have burst out, exposing the inadequate abilities of regions and cities in addressing disasters and posing severe challenges for the security of human settlements. Therefore, the “national spatial planning theory” has shifted the focus to security issues and strived to adapt urban spatial layouts to cope with natural disasters in different regions by analyzing regional security risks and identifying their types and risk levels.

In addition, on top of the natural and environmental elements such as ecology and security, cultural characteristics such as landscape features and local cultures are an indispensable part of a beautiful living environment and the high-quality development of national space. Therefore, combined with real-life projects, the “national spatial planning theory” proposes to analyze the cultural resources in regional space and create an urban spatial layout and cultural space system adapted to the cultural characteristics in different regions.

At this point, with the “precise adaptation” of urban areas to natural and cultural conditions as the core, the “national spatial planning theory” has developed a full-cycle theoretical framework of “precise analysis, adaptive distribution and dynamic evaluation.” It consists of two layers, namely ecologically sound and safe natural environment and cultural characteristics, which lay a theoretical foundation for building the technical system of regional spatial optimization (Fig. 1).

Fig. 1
figure 1

Theoretical understanding of “National Spatial Planning Theory”. Source: Illustrated by the project team

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3 Methodology and technical system of “precise analysis, adaptive distribution and dynamic evaluation”

Based on the understanding of the “national spatial planning theory”, a full-cycle regional spatial optimization technical system comprising three technologies (precise analysis, adaptive distribution, and dynamic evaluation) is created (Fig. 2). It combines various tools and methods, promotes the efficient integration of big data, information technology and planning technology and creates a more comprehensive deductive model for spatial analysis and optimization. It also provides new tools for regional spatial optimization.

Fig. 2
figure 2

Technical Map of Regional Spatial Research. Source: Illustrated by the project team

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“Precise analysis” means to carry out precise analysis of various factors, including ecological, security and cultural factors, in regional space in a differentiated and targeted way. It includes static analysis of the current status of regional space, and dynamic analysis and prediction of historical changes and possible future scenarios. “Adaptive distribution” means to create an urban spatial layout and infrastructure network that is adapted to nature, culture, and socio-economic development by analyzing the population and industrial development. Instead of a development blueprint under the ultimate goal, spatial planning is about multi-solution simulation based on various target scenarios. “Dynamic evaluation” means to monitor and evaluate and optimize the development of regional space in a timely manner, so that the urban space continues to adapt to natural and cultural conditions.

3.1 Precise analysis technology

A model that comprises evaluation indicators in ecological, security and cultural aspects is created for larger regional spaces. It is designed to evaluate if the space is eligible for human settlements in terms of environment, security, and characteristics and identify the “livable” and “non-livable”, “secure” and “insecure” areas in the country. The results of precise analysis include two aspects: first, “spatial identification”, that is, to evaluate the space’s eligibility for human settlements and to identify spaces suitable for development activities; second, “feature identification”, that is, to precisely identify regional features in terms of natural and ecological conditions, disaster types, and cultural characteristics, so as to figure out the basic conditions and requirements for planning and development. When considering the eligibility for human settlements, factors related to land conditions (such as elevation, terrain, landform, and land use), climate conditions (such as average annual precipitation, accumulative days above 10 ℃, temperature and humidity index), ecological environment measurements (such as the importance and vulnerability of ecosystem function), and geological disaster security bottom line factors (such as earthquake, landslide, cave-in, mudslide and subsidence) are adopted to create an evaluation model. Data values Footnote 7 of each factor are classified into different levels according to the land’s adaptivity for development and construction. For example, in the case of terrain factors, a slope map showing different angles (≤ 3°, 3–8°, 8–15°, 15–25°, and > 25°) is created by DEM. By taking into account the evaluation result of multiple factors and examining the carrying capacity of water resources and the bottom line of environmental and food security in different expansion scenarios via dynamic spatial expansion models, including the minimum resistance model, this paper divides China’s national space into five levels according to the adaptivity for construction and identifies “livable” and “non-livable” space.

For human settlement security evaluation, nine common natural disasters in China, including heavy rainfall, flood, earthquake, landslide, mudslide, typhoon, hail, snowstorm, and extreme high-temperature and low-temperature events, are evaluated in two dimensions: hazard Footnote 8 and vulnerability Footnote 9 to get the evaluation result of each disaster Footnote 10 Through probability, those disasters are divided into three disaster chains: heavy rainfall-earthquake-mudslide, typhoon-heavy rainfall-flood, and snowstorm-low temperature-high temperature. For comprehensive risk evaluation, the scores are summed up to precisely identify “secure” and “insecure” spaces in the country. Based on that, through spatial cluster analysis of the types of disasters, China’s national space is divided into nine disaster-specific zones in three parts. They are the eastern part affected by typhoon, heavy rainfall, and flood, the western and northeastern part affected by low temperature, snowstorm and hail, and the northeaster and southeastern part affected by earthquake, thunderstorm and landslide.

For human settlement feature evaluation, factors of cultural and natural features (such as world cultural heritage sites, cities, towns, villages and neighborhoods of historical and cultural importance, and traditional villages) and local culture (ethnicity, dialect, customs and architecture) are used to build a comprehensive evaluation index model, based on the distribution of cultural resources and influence within regions. It aims to measure the features of regional spaces, precisely identify culturally distinct spaces in the country that require protection and management, and summarize the regional cultural characteristics.

3.2 Adaptive distribution technology

The adaptive distribution technology consists of the technology based on “spatial identification” and “feature identification”, corresponding to the results of precise analysis in the same aspects.

The technology based on “spatial identification” is to identify the space suitable for development activities and determine “where to build the city” based on the forecasts of urbanization rate and population movements. It utilizes economic and social analysis technologies, such as web-based city centrality evaluation, so as to support the siting of new cities and districts, the determination of areas for urban construction and the creation of central city systems.

The technology based on “feature identification” is to identify natural and ecological features, disaster types and cultural characteristics of the region based on precise analysis. It is also used to delineate urbanization zones at national and regional levels according to the prediction of population movements and population distribution, propose urban development models that suit the natural, cultural, economic and social realities in different zones and determine “how to build the city”. For instance, for hilly areas prone to geological disasters, such as earthquakes, landslides and mudslides, a large-scale centralized development model should not be adopted, and the spatial layout should adapt to their terrain and geological conditions.

Furthermore, although this paper focuses on spatial planning methods and technologies at the regional level, the approach of “precise analysis and adaptive distribution” can play a vital role at different scales, including urban areas Footnote 11, neighborhoods, buildings, and engineering facilities, as well as in technical methods of other disciplines, including planning, architecture, structure, transportation, water conservation, and energy. For instance, by identifying regional natural and ecological characteristics, we can determine the organization of urban open space, the layout of building clusters, human comfort in buildings and energy-efficient construction technology. By detecting regional disaster types, we can determine the density and intensity of urban development and the construction standards and technical requirements for infrastructure projects and architectural structures. Ultimately, we can develop the knowledge map of adaptive technology (Fig. 3) that corresponds to the disparate development models of different regions based on years of research and planning practices. The map integrates planning and construction technologies from a macro perspective and across multiple scales and disciplines. It should be noted that, with the expansion of the spatial scales of adaptive distribution, the accuracy of precise analysis should also be continuously improved.

Fig. 3
figure 3

Knowledge map of adaptive technology. Source: Drawn by the project team based on the practices of several projects

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As to the working method, based on development policies, environmental protection objectives, multi-scenario disaster risk prediction, socio-economic development, scientific progress and changes in the ways of production and lives in different countries and regions, the multi-target and multi-scenario solution simulation model is built to simulate, compare, and select spatial solutions under different scenarios. The simulation and optimization model includes three subsystems concerning solution simulation, evaluation and optimization. The final result is to generate a scientific and proper optimization solution after a repeated cycle of “solution generation, evaluation and iterative optimization”. Generally speaking, under the ideal scenario and preset rules, the final solution worked out by the model is optimal. However, given the limited objectives that can be considered by the model and related constraints, the model cannot fully meet all the real-world conditions and requirements, so there are many planning objectives that cannot be considered or quantified. Therefore, artificial intelligence should be combined with manual planning techniques to determine the final solution.

3.3 Dynamic evaluation technology

The dynamic nature of regional space requires that regional spatial research should solely focus on the planning process. Establishing a monitoring, evaluation, and optimization system capable of real-time monitoring, regular evaluation, dynamic maintenance, and timely adjustment and optimization is an effective means to cope with dynamic changes and uncertainty (Shi et al., 2019).

To be specific, a multi-factor monitoring, dynamic evaluation technology that covers both the regional and urban levels should be developed. In practice, the implementation of regional planning consists two levels: “direct” implementation by transforming the planning into policy tools and construction activities at the regional level, and “indirect” implementation by transferring them from the regional level to the urban level. Therefore, region-level monitoring and evaluation should cover both the regional and urban levels. The region-level monitoring and evaluation includes the evaluation of individual factors, such as regional resources, environment, and infrastructure (Zhang & Pan, 2021), as well as the benefits, such as spatial intensive performance and coordination. Different regions can carry out evaluations specific to their own characteristics. City-level monitoring and evaluation includes the monitoring of general features, including the density of population, buildings, and facilities, as well as the evaluation specific to a city’s characteristics. For instance, during the COVID-19 epidemic, the specific evaluation on a city’s density, facilities, and ecological spaces at the city, block, and community levels was conducted to analyze the weak points in COVID prevention and control.

A working method that coordinates “monitoring, diagnosis, early warning and optimization” is explored. In the monitoring process, a database of the buildings, roads, greenery, water bodies and transportation is built based on remote sensing data and third-party big data to outline the environmental background of human settlement with an accuracy of 100 m. In the diagnostic process, at the regional level, the spatial intensive performance evaluation model and coordination evaluation model are built to analyze the features and efficiency aggregated factors, such as land use, population, and economy, as well as their coordination with the environment, so as to figure out the weakness in regional development. At the city level, with the help of analytical technology driven by big data and AI, diagnostic methods are adopted, including indicator-based spatial correlation analysis, diagnosis-based multi-dimensional aggregation, and effective coverage analysis based on supply–demand matching, to find out the weaknesses in urban planning and development. In the early warning process, real-time evaluation of types and levels of security risks that may take place in regions and cities is carried out and a coordination mechanism for early warning and emergency response is established. In the optimization process, local optimization of regional space is conducted in a timely manner. Once external conditions change significantly or face serious risks, a new round of regional precise analysis and adaptative spatial planning would begin to optimize the regional space holistically and systemically, forming a closed loop of the full-cycle spatial optimization technology.

4 Application on different regional spatial scales

The regional planning practices led by the authors, including the national urban system planning, the Beijing-Tianjin-Hebei region’s urban and rural planning and Zhouqu post-disaster reconstruction plan of Gansu Province, are used as examples to illustrate the applications of the “national spatial planning theory” in regional planning. It should be noted that the method has been developed and improved in practice. Along with the continuous progress of urbanization, the evolution of problems and needs and the improvement of big data, IT and other technical tools, the method has gone through a process from initial conceptualization with simple technical tools to continuous expansion and improvement of theoretical understanding and technical methods.

4.1 Practical application on the national scale

The National Urban System Plan (2006) proposed the approach to urban planning based on “precise adaptation” that prioritized ecological environment. The first national suitability evaluation of human settlements was carried out. It used the factors of landform, climate and water resources, and precisely identified the “livable” and “non-livable” spaces in the country. It concluded that 8.55% of China’s land resources were suitable for urban development (excluding arable lands), which provided an important scientific basis for the path of intensive, compact, and sustainable development path (Wang, 2006).

Based on the key R&D programs under the 12th Five-Year Plan, the national security evaluation of human settlements was carried out from the perspectives of disaster risk and vulnerability with district and county as the basic unit. It identified “secure” and “insecure” spaces and provided the prerequisite for the proper siting and spatial planning of various cities. In addition, it also identified the disaster types in different regions and analyzed the correlation between various types of disaster risks and diversified urbanization models, which provided a scientific basis for different regions to adopt urban development models that suit their disaster types (Wang et al., 2019).

Based on the spatial resources identified by the precise analysis, the predictions of population movements, and the analysis of industrial development and the requirements of national development strategy, a “diversified, multi-polar and web-based” national urban space structure that adapts to the natural environment and facilities balanced development was created. A basic urban development plan for nearly 10 years featuring diversified urban development modes, a multi-layer system of core cities, and connected infrastructure was formulated. In the context of natural and ecological features and disaster types in different regions, as well as the predictions of population movements and population distribution, the national space was divided into multiple urbanization zones to guide such regions to adopt adaptive urban development models that suit their realities.

After the completion of the plan, based on the long-term tracking of the dynamic national spatial development, nationwide monitoring and evaluation were carried out. Over 70 types of spatial data were integrated to establish a new urbanization monitoring platform and an indicator system of multiple scales and dimensions to monitor and evaluate the speed and quality of the urbanization process, the spatial structures of urban areas, the quality of urban development, the living standards in communities and the quality of roads and continuously track the performance, coordination and resilience of the national spatial structure.

4.2 Beijing-Tianjin-Hebei urban and rural plan

To cope with the sprawl of construction land, water shortage, severe air pollution and land subsidence caused by groundwater overdraft in the Beijing-Tianjin-Hebei region, the “Beijing-Tianjin-Hebei Urban and Rural Plan” proposed for the first time the precise analysis of ecological resources, including geological conditions, water resources, ecological environment and atmospheric wind field and other factors. The precise analysis identified the space suitable for construction. It concluded that less than 3% of the total land resources in the region were suitable for additional urban developments, excluding the current urban land and ecological corridors, which provided a scientific basis to control the disorderly growth in the areas around Beijing.

According to the “precise adaptation” idea and the “precise analysis and adaptive distribution” approach, the principle (i.e. determine the population size based on water resources, determine the location based on geological conditions, and determine the form based on meteorological conditions) and the technical roadmap were proposed. And the urban layout with centralized structures as the mainstay and supplemented by decentralized arrangements to suit the natural environment, including geological conditions and atmospheric wind field, was established. It informed the decision-making on the siting of areas for non-capital functions, the spatial organization of Beijing-Tianjin-Hebei region, and the deployment of major regional infrastructure.

In addition, located on the territory of ancient Yan and Zhao states, the Beijing-Tianjin-Hebei region is known for its long history and abundant cultural resources. It is home to nearly a quarter of China’s key cultural relics protection units, seven historical and cultural cities, and six world cultural heritage sites. Thus, the project analyzed the region’s cultural resources and characteristics, and identified and integrated important cultural resources. It proposed to build a regional cultural network system of “one core, four belts, multiple zones and multiple points” and developed cultural heritage landscape corridors, such as the Canal Waterway Cultural Corridor and the Great Wall Historical Corridor. It also implemented cultural projects, such as the national spirit monument, the watershed ecological and cultural conservation area and modern culture functional zoning and promoted the cultural projects,such as the Grand Canal Cultural Belt.

Based on the key R&D programs under the 12th Five-Year Plan, regional monitoring and evaluation were conducted in 13 typical city clusters, including the Beijing-Tianjin-Hebei city cluster. Their development quality was measured against the evaluation of five indicators, namely economic performance, land use and ecosystem, public services, infrastructure, and public security. The results were integrated with the entropy weight method, the principal component analysis and the Delphi method. Such results indicated that the Beijing-Tianjin-Hebei city cluster lagged behind in environmental quality, such as water environment, atmosphere, and industrial effluent discharge, and then the optimization and improvement strategy was proposed.

4.3 Zhouqu post-disaster reconstruction plan

In the “Zhouqu Post-Disaster Reconstruction Plan”, given the local geographical conditions, narrow land space and prominent disaster risks, the project analyzed the geological conditions and disaster risks to help choose the site of new areas for post-disaster settlement and development. Evaluation factors, such as the slope and elevation, were selected to identify the sites of less than 25° and contiguous areas larger than 10hm2 (Fig. 4, L). Two seismically active faults and the analysis of potential population growth were taken into consideration when choosing the location and scope of the new area. Landslides, mudslides and other hazards within the area were further classified and evaluated (Fig. 4, R) to determine the site of new areas for post-disaster settlement and development.

Fig. 4
figure 4

Evaluation of natural geographical conditions and geological disaster risk in Zhouqu. Source: Zhouqu Post-Disaster Reconstruction Plan

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When planning the new area, based on the precise analysis of landslide and mudslide risks, the county planned to build six mudslide ditches for areas of medium vulnerability and reconstruct the east bank of Bailong River and the south side of the new area. After analyzing flood risks, the plan proposed raising the flood risk management standards in order to withstand a 50-year flood. Besides, after examining the local cultures of multiple ethnic groups in Zhouqu, the plan proposed to create the spatial forms and architectural styles of typical Han and Tibetan features to combine with local customs and features of the times.

In addition, based on the results of precise analysis, the “Zhouqu Post-Disaster Reconstruction Plan” set out measures to increase the security and resilience of the existing urban areas. They are opening the evacuation routes to facilitate external connections, reserving some space on both sides of major trenches to build drainage channels, and building a disaster memorial park and greenspace on both sides of the drainage channels for emergency evacuation.

In ten years since the plan’s implementation, Zhouqu has successfully withstood many heavy rainfall events. Currently, the project team is still tracking and monitoring the reconstruction project and carrying out diagnosis and development evaluation in due course, to identify security risks and problems and formulate response strategies, so as to ensure long-term security.

5 Conclusion and prospect

In order to address the problems of resource and environmental damages, complex and prominent security risks and cultural degradation in China’s rapid urbanization process, the regional spatial research should shift the focus from improving economic competitiveness to balancing conservation and development, and security and development. Therefore, the theoretical understanding and technical approach should be adjusted accordingly. On this basis, the authors propose the “national spatial planning theory” featuring the “precise adaptation” of urban development to natural and cultural conditions and the technical approach of “precise analysis, adaptive distribution and dynamic evaluation” that suits the spatial dynamics and disparities among regions. The theoretical connotations and technical approach have continued to expand and improve based on the practices in the past 20 years. At the same time, the urbanization process continues to advance and the problems keep evolving. China has entered a new phase of urbanization characterized by structural adjustment in the context of exacerbating climate change and growing challenges for national and regional development. There is still a long way to go to improve the theory and approach of regional spatial research and to develop a more widely applicable technology.