Geomorphy

Connotation of geomorphic information, characteristics and analysis method of geomorphic system

Geomorphology is a three-dimensional surface form formed by the interaction of internal and external forces in the crustal surface to a certain stage of development. It is a function of internal and external forces, media properties and time. It can be expressed as follows：

*M* is the geomorphological morphology. F is the effect of internal and external forces on the surface.x, y, z is the space coordinates. F:sub:`i` is the internal force. F:sub:`e` is the external force. m is the medium nature of the geomorphology, including lithology and tectonics. t is the action time。

Different combinations of types, intensity, mode of action, properties of medium, acting time of internal and external forces directly affect the surface morphological characteristics. That is to say, geomorphological information contains characteristic geomorphological information belonging to different internal and external forces and different stages of development. With this information source, we can extract all kinds of characteristic parameters needed for composite analysis, and get the comprehensive evaluation results of different topics。

Geomorphological system is an open dynamic system, which is a complex composed of various types and elements of geomorphological morphology. It not only transfers and transforms material, energy and information flow among the internal subsystems, but also exchanges material, energy and information flow between the system and the external environment, so it generates the transfer network of complex material, energy and information. Geomorphological system is always in the dynamic process of input-conversion-output, that is, there are often energy sources flowing through the system to the dissipation area, which leads to the orderly entropy reduction process of the system, thus having certain structure and corresponding entropy bits, storage capacity and self-regulation ability. The development, occurrence and evolution of geomorphology is essentially a complex material flow and transportation process in which the surface material, which constitutes the geomorphological elements, undergoes deformation, displacement (uplift, fault, etc.) separation and combination (erosion, transportation, accumulation, etc.) under the action of the internal and external forces of the external environmental energy flow of the geomorphological system. Because of the similarity between geomorphic material transport process and thermodynamic conduction, many geomorphic evolution models, such as slope evolution models, are in the form of heat conduction equations：

Among them, *H=H(x,y,t)* is the elevation of the earth’s surface。

Because the actual regional geomorphological system is too complex and huge, the precise explanation in mathematical sense can not be obtained in metrological research. For example, the above evolutionary models are often directed at a certain external force process, which is limited to extremely simple and ideal initial conditions without considering the spatial differences of the medium, while the forces inside and outside the actual area are diversified, the medium is not uniform, even the initial elevation H:sub:`0` can not be expressed as definite functional formulas. Therefore, the approximate solution can only be obtained by appropriately discretizing the infinite to the finite。

Specifically, the idea of finite element method and finite difference method is introduced to decompose the whole regional landform into many ‘tiny’ units (let alone terrain, its top surface is termed landform), as shown in Figure 14-12. In a small regional space, a variety of more universal analysis models are established to calculate various spatial geomorphic parameters and study complex geomorphic processes. The discretization is the premise and characteristic of quantitative analysis of regional geomorphic information system。

Figure 14-12: Discrete analysis of regional geomorphology

Geomorphology is a function of structure, process and time. Quantitative indicators of existing geomorphological forms and their material composition reflect the sum of previous internal and external forces in the geomorphological system. The analysis method of geomorphic information system is to extract the characteristic parameters of different sides of the geomorphic system, and to acquire the overall understanding of the development law of regional geomorphology by using the comprehensive analysis method of the system. With the development of geographic information system (GIS), it is possible to establish geomorphological information system (GIS) for quantitative analysis and processing of huge and complex geomorphological spatial data, and for information compounding and comprehensive evaluation。

Geomorphological Information System

Geomorphological information system is developed based on GIS tools, which integrates the general functions of GIS and includes the following modules of geomorphological analysis：

1. Geomorphological morphology analysis: It is used to extract the geomorphological characteristic parameters reflected by the surface morphology, including DEM and various geomorphological parameters based on DEM: slope, slope direction, fluctuation, river network density, valley parameters and so on。

2. Geomorphological Information Composition: It includs composite model of geomorphic parameters and composite model of geomorphic information/thematic iInformation. The former combines the geomorphic parameters to find the regularity and obtains the comprehensive analysis results. The latter combines the geomorphic information with the information of geology, hydrology and meteorology, considering that the geomorphic pattern is also influenced by the external dynamic geology。

3. Geomorphological Regional Assessment: Based on the analysis of single or multiple landform characteristics, the impact of landform environment on agriculture, construction, engineering, tourism, living conditions and the impact of landform conditions on the occurrence, development and prevention of various natural disasters are evaluated。

4. Analysis of Geomorphological Causes include: Internal dynamics genesis analysis model: Internal dynamics is the force generated by the energy in the crust, which determines the pattern and framework of the landform. It can be analyzed from two aspects: geometric effect and mechanical mechanism. Finite element method is an effective method to study the dynamic mechanism of the landform。

5. Geomorphological prediction: Two models can be used for geomorphological prediction, they are theoretical geomorphological prediction model and statistical geomorphological prediction model. The former is based on genetic analysis and uses mathematical and physical models to simulate macro and micro geomorphological development, while the latter is based on historical data of geomorphological development and uses the method of “black box” or “grey box” to carry out statistical analysis and predict geomorphological development trend。