Although the participation of human activities in landform evolution has had a long history, it is especially active in modern times. With the deepening of the Industrial Revolution, accelerating process of urbanization and constant socio-economic development, the modern landform evolution process is no longer a pure natural process, but a process deeply marked by human activities (Li et al., 1994). Human activity has become the third geomorphologic agent besides the internal and external natural forces (Zhang, 1990). Yan Qinshang, a famous geomorphologist in China, once pointed out that the development of natural landforms is mixed up with factors of human activities, which is an important part in the development and evolution process of natural landforms, either speeding up or slowing down the process (Yan, 1985). The synergistic effect of natural forces and human activities has become a key factor to modern landform evolution and development, which attracts the attention of the geomorphology community to the third geomorphologic agent (Mu, 1990; Diao et al., 2000).

Man-made landform agents mainly refer to the forces that directly or indirectly change natural landform processes in human life and production (Shi, 2009). It is worthy of noting that man-made landform agents are the artificial agents that are imposed to natural landforms on the basis of natural landform agents. This kind of geomorphologic agent varies with the purposes and functions of man-made landform constructions. The geomorphologic agent can be produced by either direct and purposeful human activities, or indirect or unintentional ones. Thus its effect on the whole anthropogenic geomorphological process can be divided into three types: direct, incidental, and unintentional (Nir, 1983). Based on the effect on man-made landform construction, the man-made landform agents can be divided into types of artificial weathering, artificial erosion, artificial transference and artificial accumulation (Hooke, 1994; Yang, 1998). Artificial weathering refers to the further exacerbation of earth surface material compositions weathering rate caused by human socio-economic construction, both physically and chemically. Human activities like tunnel projects, mining and blasting may result in mechanical disintegration or stress-release crack, aggravating the physical weathering process of surface material compositions. And the emission of human “three wastes” may intensify the chemical weathering (Zhou et al., 2013). Artificial erosion includes direct and indirect erosions (Hooke, 1994; Yang, 1998). First, human social and economic constructions directly act on the Earth surface and cause surface erosion. The rate and strength of this kind of erosion are always much greater than those of natural erosion (Chin et al., 2014). Second, the damage of surface environment caused by human activities triggers or increases natural erosion within the area of activities. Artificial transference mainly refers to the transportation and migration of surface materials made by purposeful human activities like infrastructure constructions by means of conveyance (Hooke, 1994; Yang, 1998). Its significant difference from natural transference is that the transportation of materials takes place according to human’s will and needs. Comparatively, the natural transference is generally conducted either from high to low position or from upstream to downstream under the influence of natural forces, and also in this process, the moving capacity is reduced with distance constantly. Artificial accumulation also includes direct and indirect accumulations (Hooke, 1994; Yang, 1998). The former refers to the geomorphologic accumulation made by man’s purposeful, direct transportation, while the latter refers to the geomorphologic accumulation caused by changing natural force conditions due to human activities.

Therefore, man-made landforms are created under the direct or indirect effects of human activities, which include a variety of human actions, such as construction, digging, erosion and deposition (Yang, 1983; Yang and Li, 2001). These actions jointly shape man-made landforms on the Earth surface and constitute the man-made landform agent system.

With the enhancement of human’s ability to reshape nature, the number of types of man-made landforms keeps increasing. According to different research objectives and principles of classification, there are different criteria for man-made landform classification. In accordance with material erosion or accumulation situation, man-made landforms caused by such human activities as urban-rural construction, agricultural production, engineering construction and resource exploitation can be classified into the two types of man-made accumulation landforms and man-made erosion landforms (Yang, 1998). There is not only accumulation or erosion landforms shaped through human activities like building, repairing, digging or dredging in order to satisfy the needs of human production and life, but also waste accumulation landforms created by accumulating industrial and domestic wastes and household garbage and so on. Certainly, the actual man-made landforms are more organic integration of the both. For instance, the Three Gorges Project involves not only excavation and erosion of the bedrock on dam base but also the construction and accumulation for dam rebuilding. The seawall construction in tidal flat includes both the excavation of sediments on tidal flat and the accumulation of soil or stone seawall. In the construction of urban man-made landform, materials like cement, steels, timber, sand and stones create the accumulation landform, namely, the city. Meanwhile, erosion landforms like sand pits, gravel pits and stone pits are formed in surrounding areas through excavation (Zhang, 1990).

Based on the actual needs of human social and economic construction, Ma (2008) classified man-made landforms into types like urban man-made landform, transportation man-made landform, water conservancy man-made landform, farmland man-made landform, mine man-made landform and oilfield man-made landform, etc. She believes that globalization facilitates the homogenization of man-made landforms in different countries, which is the man-made landform construction dominated by rational thinking. The organic integration of various man-made landforms constitutes regional man-made geomorphological landscape (Li and Liu, 1990). Man-made terrains and landforms are of great significance for regional planning and construction, transforming of urban-rural layout, and the development of tourism and so on (Ma, 2008). Based on the principle of morphological classification, we can divide man-made landforms into linear man-made landform, planar man-made landform and three-dimensional man-made landform (Kuang, 1990). Man-made landform possesses environmental function, economic function and value of landscape aesthetics (Chen and Wu, 1993). In accordance with functional morphology, man-made landforms can be classified into nine types, including urban-rural construction morphology and industrial morphology, etc., and the nine types can be further divided into man-made accumulation subtype and man-made excavation subtype based on the causes of formation (Ma, 2008). In fact, this application orientated classification principle does not break the limitation of land use classification.

Urban man-made landform, as a regional type of man-made landform, has three subsystems, including natural landform, man-made landform, and natural and artificial mixed landform. In the 1990s, geographers of the older generation conducted a preliminary study on the classification system of urban man-made landform. They proposed a principle of shape genesis and utility for urban landforms classification (Zhang and Chen, 2000a) and classified urban man-made landforms into two types, the direct and the indirect (Zhang, 1990). Furthermore, they explored the structural relations between constituent parts of the urban landform system (Pan et al., 1989) in order to establish a theoretical foundation for the construction of various classification systems. As man-made landform usually manifests its eco-environmental features due to forming a large amount of impervious surface. Meantime, various individual man-made landforms combine together to constitute diversified regional man-made landforms. Therefore, it is more suitable to adopt a man-made landform classification system based on the classification principle of ecology and morphology (Pan et al., 1989). By referring to the classification method of traditional geomorphology, a three-level classification method of urban man-made landforms based on landform name, morphological feature, and function and utility, respectively, has been adopted, which promotes the research on urban man-made landform classification (Zhou et al., 2007).

Traditional geomorphology believes that geomorphological process includes processes of the internal and external forces of the Earth (Chorley, 1985). With the development of society and economy and the intensified efforts of human to remold the Earth surface, anthropogenic geomorphological process has gradually become an important agent in modern geomorphological process. The anthropogenic geomorphological process significantly influences geomorphological development along with the Earth’s internal and external forces. And the former has even exceeded the latter in influencing regional geomorphological process (Diao, 1990). Although man-made landform has a short history and the earliest one appeared just thousands of years ago, man-made landforms are formed at a fast speed. Their formation may only take several decades, a few years or even several days (Mu and Tan, 1990a). The life span of man-made landforms is affected by multiple factors, including natural, humanistic, economic and political ones (Rózsa, 2007). Man-made landforms are formed on the basis of natural landform’s processes. Therefore, they are deeply influenced by natural environments, such as erosion, denudation, dissolution and earthquake, and, meanwhile, further intervened by human activities themselves.

Anthropogenic geomorphological process is the process of human activities acting on and influencing the geomorphological environment (Zhang, 1990). Since there are direct and indirect impacts of human activities on geomorphological environment, the anthropogenic geomorphological process can also be either direct or indirect (Zhang, 1990). The direct geomorphological process refers to the process, in which human activities directly reshape the Earth surface environment and produce various new geomorphological landscapes. After the formation of man-made landform, the man-made landform itself and human activities, which rely on it still continuously influence the material flow and energy flow in the geomorphological environment, and thus further change the strength and direction of the natural geomorphological process. This process is called the indirect geomorphological process (Zhang, 1990). Direct geomorphological process consists of accumulation process and denudation process. Although the indirect geomorphological process does not act on geomorphic environment directly to produce new landforms, it is a more complicated process and has more extensive effects on geomorphic environment than the direct one.

Anthropogenic geomorphological process, especially the direct one, is irreversible (Mu and Tan, 1990b). The direct geomorphological process usually creates new and relatively independent man-made landforms by processing and reshaping original natural landforms. Such new man-made landforms are jointed with natural landforms in a natural geomorphological system. In anthropogenic geomorphological process, the changes of natural geomorphic environment are irremediable and irreversible. For example, in a project of blasting mountains to build a city, the leveled mountains cannot be restored and the newly built city cannot be moved.

As urban regions are the most active areas of human activities (Cooke et al., 1982). The process of urban human activities influencing geomorphic environment is the urban anthropogenic geomorphological process (Zhang, 1990), and thus the urban anthropogenic geomorphological process is a key part in anthropogenic geomorphological process research (Cooke et al., 1982). The urban geomorphological process also includes the direct and indirect processes (Zhang, 1990; Szabó, 2010). The direct urban geomorphological process can be divided into denudation (damage) process and accumulation (construction) process. Specifically, the denudation process may be further classified into digging, flattening, slope cutting, and excavation processes, and the accumulation process may also be classified into constructing and repairing, stacking, and landfill processes, etc. (Douglas, 1983). The indirect urban geomorphological process is a formation process of urban natural landforms affected by the geomorphologic agents of environmental impact factors after urban transformation (Cooke et al., 1982).

Compared with natural landforms that take a long time for formation and evolution, the development and evolution process of man-made landforms is relatively short. In the early agricultural society, man’s capacity of reshaping natural landforms was quite limited. The man-made landforms were just simple and crude dwellings and cultivated lands, etc. Man-made landforms at that time were very limited no matter in quantity or size, and were abandoned with human migrations (Wang and Pu, 2000). With the advancement of agricultural production technology and the formations of ancient Babylon, Egyptian, Indian and Chinese civilizations, the distribution range of urban and rural settlements and agricultural landforms kept enlarging. And the development of other kinds of man-made landforms like road network was also accelerated continually (Zhang, 1990). It is worthy of mentioning that the research on urban man-made landforms outshines others in the research field of man-made landform evolution.

With the continuous expansion of city size, urban man-made landforms also experience constant formation, expansion and evolution. City, as the region where human activities are most concentrated, is most strongly influenced by human activities. Meanwhile, it is also the largest distribution area of man-made landscapes on the Earth surface. The research on the formation and evolution of urban man-made landforms must be combined with the evolution of urban spatial structure to explore the development pattern and law of man-made landforms in urban areas. Corresponding to urban spatial evolution, the formation and evolution of urban man-made landforms is of an ordered process (Huang and Zhu, 1996), which can be divided into three stages: dilation, renewal and diffusion, and differential renewal and diffusion (Mu and Gao, 1990). In the early formation of a city, man-made landforms such as buildings are arranged in dot distribution in places with convenient transportation and rich resources, then extended outward continuously and developed into landforms of planar distribution. When the city expands to a certain size, influenced by terrain and transportation, urban man-made landforms experience obvious internal renewal like old city reconstruction. Meanwhile, the density and single size of urban man-made landforms keep increasing. After that, blocks with favorable conditions in each region are gradually formed and united together. The spatial distribution range of urban man-made landforms also extends continuously (Cooke et al., 1982). On this basis, by combining the development history of Dalian and the characteristics of its development orientation, Li et al. (2003) divided the evolution of urban man-made landforms in the city area into four periods. They are single-core diffusion period, U-shaped extension period, annular zonary renewal and diffusion period, and multicore radiation-zonary development period. The rapid expansion of the urban space in Dalian directly led to the expansion of urban man-made landforms. From the perspective of horizontal morphological expansion, growth patterns of urban man-made landforms from CDB (central business district) to surrounding areas include concentric sprawl, local fan-shaped expansion, gallery-type radiation, enclave-style growth and agglutinating fill (Liu, 2004). At the same time, urban man-made landforms also show a typical characteristic of vertical growth (Li, 2004). This shows the vertical expansion of man-made landforms in CBD area that presents different time sequence and growth patterns. In addition, the vertical growth of urban man-made landforms has significant periodical characteristics (Chang, 2004). Certainly, the horizontal expansion and vertical growth of urban man-made landforms may exist simultaneously and finally constitute overall urban man-made geomorphological landscape patterns.

Certainly, the evolution of urban man-made landforms includes not only the expansion of landforms, but also their shrinkage and disappearance, such as urban demolition and old city reconstruction. These processes also reflect the renewal and recombination of urban man-made landforms as well as their evolution during urban development. It thus can be seen that the essence of evolution of urban man-made landforms lies in the reconstruction, renewal and optimization of urban geomorphic structures (Zhao, 2007).

Man-made landforms are geomorphic units formed on the basis of natural landforms. Therefore, anthropogenic geomorphological process cannot be separated from natural landform basis. With the increasingly strong needs for reshaping nature and the gradual improvement of social productivity, conscious or unconscious human production practices and activities are heavily influencing the evolution process of modern Earth surface geomorphic system, which prompts researchers to enhance the study on evolution factors of geomorphology. Especially, the role of human activities in modern geomorphological process has caught a great attention (Carol and Harden, 2014). For examples, port site selection needs taking into consideration the coastwise water depth and hinterland conditions (Li and Jiang, 2010); mud flat inning should be conducted in open silting tidal flats (Chen, 2000); and as for city location selection, stable geological structure and relatively flat terrain are necessary (Dong, 2004). However, with the continuous development and effect of human society on environment and intensified degree of environmental reconstruction, the strength and distribution scope of anthropogenic geomorphological process also keep increasing. Science and technology advancements are reducing the influence of natural landform basis on man-made landform construction. Thus, socio-economic factors in human society have become important influencing elements in the anthropogenic geomorphological process. After analyzing the effect intensity of human activities in 37 countries on local geomorphic environment, Nir (1983) believes that population growth, science and technology advancements and the improvement of socio-economic development level are the key factors that affect anthropogenic geomorphological process.

From the emergence of human being to the end of Paleolithic Age, from the Neolithic Age to the period before Industrial Revolution, and from Industrial Revolution to modern times, population growth showed corresponding logarithmic curves. It proves that the three periods of population growth correspond with the three major technical revolutions. There is also an obvious correlation between population growth and socio-economic development (József, 2010). The increasing human demands and continuous improvement of living standard also broaden the range and increase the degree of human activities’ influence on natural geomorphological process constantly. In the Early Holocene Epoch 12,000 years ago, while human lived on a primitive hunting, they started to consciously collect wild wheat for crop cultivation. Their activities altered the surface environment, but the influence on surface environment was limited spatially and temporally. Since the beginning of agricultural society 5000 years ago (József, 2010), the development of irrigation agriculture, the use of metal tools, the spread of plough and wheelbarrow, the construction of road network, and the utilization of wind energy and hydraulic resources have enhanced the spatial and temporal effects of human activities on geomorphic environment. Since the first Industrial Revolution in 1870 and the second in 1950, the use of steam engine, the development of industrialization, the growth of iron and steel industry, the construction of railway network, and the use of electric energy and internal combustion engine have enabled human to exert long-lasting influence on the geomorphic environment in a larger range. The third Industrial Revolution symbolized by the invention and application of atomic energy, electronic computer, space technology and biological engineering since the 1950s has been making the influence of human activities on the Earth’s surface environment permanent and even irreversible. Before Industrial Revolution, the influence of human activities on geomorphic environment grew slowly, which was mainly indirectly resulted from agricultural activities. However, the Industrial Revolution completely changed this pattern of growth. That means, with the exponential increase of population, the total amount of surface material excavated by man shows a sharp rise (József, 2010). Over the past 500 years, the excavated and moved surface materials could be heaped into a mountain with a size of 100 km × 40 km × 4 km. Since the excavating speed is still increasing constantly, the size of the “heaped mountain” is predicted to double in a century (Hooke, 2000). All the facts addressed above demonstrate that socio-economic development and science and technology advancements are the important factors that lead to the acceleration of anthropogenic geomorphological process.

Urban regions are the most typical areas of anthropogenic geomorphological process and geomorphic evolution. Urban man-made landform evolution is an important area in studying anthropogenic geomorphological process and thus is of great significance for exploring anthropogenic geomorphological process (Zhang, 1990; Li et al., 2003). Urban expansion results from integrative action of multiple factors. The factors that dominate urban expansion correspondingly change at different stages of urban development (Li, 2007). Therefore, urban man-made landform evolution is also the result of synergizing multiple factors. The influencing factors of urban man-made landform evolution have received considerable attention since the appearance of the cities (Zhou, 1995).

The basic roles of urban geological and geomorphological conditions, geomorphological processes of different properties and strengths, state policies, urban planning and the level of economic development in the evolution of urban man-made landforms have been widely accepted (Chen and Wu, 1993; Li, 2007). Natural geology and geomorphology are the primary limiting factors for urban man-made landform evolution (Li, 2003). The urban geomorphological process based on natural geological and geomorphological conditions emphasizes the fundamental influence of natural geographical conditions on urban man-made landform development and evolution. The last two factors are human influencing factors that produce a decisive effect on the spatial layout of urban man-made landforms. They embody the characteristics of urban man-made landform construction, such as orderliness, foresight, and continuity (Chen and Wu, 1993; Li, 2007). There is a certain correlation between the speed and scale of urban man-made landform development and urban economic growth (Zhou, 2006). Based on the obvious coupling relationship between urban man-made landform development characterized by a response model of man-made landforms to urbanization and the progress of urbanization, the development law of urban man-made landforms is clarified under the influence of urbanization (Li et al., 2005). The effect of urban population change on urban man-made landform evolution is mainly reflected by the relationships between population growth and construction area and building height. Specifically, with the growth of urban population, the construction area of urban man-made landforms increases correspondingly. However, the relationships between population distribution and construction area in central urban areas and suburbs are inconsistent. Meantime, urban man-made landforms also respond to the population growth through raising the height of buildings (Li, 2003; Zhang and Li, 2007).