= A A a Toe = : - T —— 5 Eee er EEE e A ui RE 
  
ROUGH AREA SOIL EROSION MAPPING VIA GIS MODELING 
Yu Jiang 
Department of Geography 
Indiana State University 
Terre Haute, IN 47809 
USA 
Chengcang Shi and Genong Yu 
Chengdu Remote Sensing Subcenter for Agriculture 
Chengdu, Sichuan 610066 
P.R. China 
KEY WORDS: 
1. INTRODUCTION 
Soil conservation is an important aspect of 
environmental protection, especially in China 
which has over one billion people who rely on 
limited land resources to develop agriculture. 
Since the 1980's, due to a fast growing population 
and excessive land utilization, soil erosion has 
become a serious issue in China. In the middle 
1980's, a national soil erosion survey (1:500,000) 
was undertaken using MSS imagery through 
visual interpretation. However, as environmental 
pressure increased, soil erosion mapping with a 
larger scale and higher quality was more desirable 
than before. In 1987, The European Commission 
provided 1.5 million European Currency Unit 
(ECU) to support the soil conservation research in 
the Upper Yangtze River. In this program, a 
significant part of funds were for soil erosion 
mapping using remote sensing and GIS 
technologies. 
1.1 Soil Erosion Mapping Status in China 
Soil erosion mapping is a challenging topic which 
not only requires both remotely and ground-based 
data, but also requires the knowledge of soil 
erosion mechanisms. Soil erosion mechanisms, 
which are complicated, were generalized into six 
factors in the Universal Soil Loss Equation 
(USLE) developed in the 1940's in the United 
Soil Erosion, Mapping, GIS, Modeling 
States. Since then, the USLE was widely used in 
the world. However, despite the popularity of 
USLE, it was found hard to apply in China 
because 1)The rainfall index needs many 
experimentation to set; and 2) A slope factor is 
hard to establish when the slope is greater than 15 
degrees. The new Revised Universal Soil Loss 
Equation (RUSLE) which is starting to be 
implemented in the United States is uncited to 
address the concerns identified in this research. 
The experiments required to set factor values are 
expensive and time consuming, so the China 
national soil erosion survey did not adopt USLE 
in the 1980's. Instead, the approach of visual 
interpretation and assessment was used. However, 
visual interpretation and assessment is strongly 
dependent on the personal knowledge and skills, 
which led to quality differences from map to map. 
1.2 Overview of the Research 
The research was aimed at providing a dependable 
approach to soil erosion mapping, at scale 
1:100,000, which should be applicable in high 
relief mountains and in areas with a complicated 
geological background. The mapping technique 
should be simple and inexpensive to implement, 
with a mapping quality should satisfy the 
requirements at the county level government. 
Therefore, remote sensing and GIS was adopted to 
achieve this goal. 
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