Simulation Of The Loess Gully Development Based On Cellular Automata Model

Loess Plateau is famous for its typical and unique loess gully landforms in the world. Nowadays, more and more researchers are engaged in exploring the fundamental principles that what morphological characteristics the loess gully system presents and how the gully will develop with the time going. Comparing with the other landforms, the loess gully system and their catchment areas have developed in a relatively shorter period while it is still a process of ten thousand years or even longer. Hence, through the physical and numerical simulations, it is of great importance and value to reveal the basic principles of the loess gully evolution, using GIS spatial analysis methods.This paper has adopted a cellular automata model based on the bottom-up approach to attempt modeling the evolution process of the loess gully system. The highly accurate DEM data of small watersheds in multi-period, simulated through the indoor artificial rainfall, support this attempt. With the cellular automata model, the relationship between the loess gully development and erosion variation is analyzed.1. A loess gully development based on CA model is given.The paper tried to make an expansion of CA transition rule from qualitative classification to quantitative regression. Through divided elevation variation into three types, including the reducing, increasing and the invariant, it can conduct the regression between each elevation variation and variable. Select reasonably spatial factors as variables, and mine the transition rules of elevation variation’s type by applying Decision-making tree algorithm. Build the regression estimate model to calculate the elevation variation, so the gully development based on CA model is achieved. This method can express the gully development by the gully morphology and elevation variation.2. The dynamic process simulation of the loess gully development is achieved.This paper simulates separately the single-period and multi-period loess gully development processes by utilizing the constructed loess gully development model based on CA model, and verifies the model from the level gully morphology and the vertical elevation respectively. The simulation results show that the transition rules of category about elevation difference have different dependence degrees on different space factors, and dependence degree on the distance factor is the largest. The simulation precision of the level gully morphology is73.7%, which also get better effects in positive and negative terrain distribution of multi-period simulated small watershed. The simulation results of vertical elevation variation show that although there are local errors, it is basically a correct simulated trend of loess gully elevation.3. Analysis the dynamic relationship between gully development and erosion by simulating the elevation variation. It’s shown that the erosion progress of gully head is the heaviest with greatest elevation variation, followed by gully edge, and then by gully bottom, with the minimal elevation variation.The combination of numerical simulation with physics simulation is considered to be help in this research to explore the progress and mechanism of loess landform development.