Land-unit Based Flow Network Model in Small Catchment with GIS Support
基于GIS的小流域地块单元划分与汇流网络计算

Land unit is the basic unit in soil erosion management and ecological environment construction. To understand the roles of water and sand movement among the land units is significant in spatial management of small basins. The land unit is defined as a piece of land with homogeneous geographic characteristics. Within a land unit, the elevation, slope, aspect, soil type or soil texture, landuse or landcover are same or similar. It is now becoming much important in land planning and land management. This paper described the characters and functions of land unit. Based on geographic information system, the methods for land unit dividing, parameters organization, and attribute extraction were expatiated. To meet with the needs of soil erosion model, land productive model and socio economic model, which are main models developed for soil and water conservation measures, a mathematical model for calculating flow network among land units in small catchment was developed. The data set used in the model was grid format elevation data and land unit data layer. The model result was a relation table which shows flow structure of water and sand movement among land units. The flow network relation table then was connected with the erosion model to give out the flow sequence of erosion process.