Research on Visual Interpretation and Spatial Distribution Pattern of the Erosion Gully in Luoyugou Watershed of China

Abstract

There are criss-cross Ravines and gullies in the Loess Plateau, where the erosion gullies grows better. The loess material, which is loose and has the vertical jointing, is easy to suffer from the erosion; the types of erosion in this area mainly include gravitational erosion and the trench erosion. There are typical gulling erosion in Luoyugou watershed of Tianshui northern suburb, located in the interactive region of Longxi Loess plateau hill-gully area and the Longnan mountainous area. Under the support of the SPOT satellite photos in 2008 and field survey, the paper establishes the visual interpretation features of erosion gully, extracting the information of erosion gully, and uses the landscape pattern analytical method, studying the spatial distribution pattern of the erosion gully in the watershed. Finally, the paper draws the following conclusions: 1) The shapes of erosion gullies are strip or arborization, and in the black-white image, the stable erosion gullies appear deep dark color, active erosion gullies present the bright color, and half-active erosion gullies are the shallow dark color; while in color synthesis image, the color of stable erosion gullies mixes garnet, and other erosion gullies are bright green. 2) There are more erosion gullies in the study area where human activities occur frequently, such as the both sides of terraced field, the side of road and the river marshland, the both sides of terraced field have. 3) The erosion gullies in the study watershed are primarily stable ones, whose area accounts for 51.3% of the total erosion gullies, and half-active ones accounts for 18.3%. This phenomenon indicates the progress in the control of the erosion gullies in this basin. 4) From the upstream to the downstream in the research basin, the erosion gully's average shape index has the tendency to reduce gradually, illustrating that the more getting nearly to the downstream, the more the slope of erosion gully to be gentler. The data results match well with the actual terrain feature.