长江上游泥石流危险度区划的步骤

SOME STEPS OF THE REGIONALIZATION OF DEBRIS FLOW DANGER DEGREE IN THE UPPER REACHES OF CHANGJIANG RlVER

本区划分为四个步骤：１．单指标分级、分区，并编制成图；２．复合指标分级、分区，并编图；３．专项指标分级、分区，并作图；４．泥石流危险度指标分级、分区，并作成“长江上游泥石流危险度分区图”（见刊前）．

The statistical unit, occupied latitude 10'and longitude 15’,is adoped as a basic unit, in order to analyze and contrast the data of landform and geology.The area of the statistical unit is 486 to419 km￣2 from south to north and the average arca is 444km￣2. The error rate is ±5.6%.The steps of the regionalization are as follows:1.Classification of single index and its mapping The landform indexes are classified into 5 classes by relative height; geologic indexes by theproduct of the weathering coefficient of stratum and the length of fault; temperature indexes bythe comprehensive value of its elements; and precipitation indexes by comprehensive value of itselements. The regionallzations of the 4 indexes are worked out based on the classification,andthen the division malps may be mapped as FIg.1 4 according to these regionaliztions.2. Classification of compound indexes and their mapping Compound indexes including comprehensive indexes of geology and landform(consisting ofgeologic indexes and landform indexes)and climatic indexes(consisting of temperature indexesand precipitation indexes),are classified into 5 classes. The regionalization of them are worked outbased on the classification and the division maps are mapped as Fig;5-6 according to theregionalizations. 3. Classification of special indexes and their mapping.Special indexes,including the indexes of natural danger degree of debris flow consisting ofcompehensive indexes of geology and landform and climatic indexes, and the indexes of economicdevelopmental level ,are classified into 5 classes. The regionalization of them are worked out basedon the classification and the division maps are mapped as Fig.7-8 according to theregionalizations.4.Classification of the indexes of debris flow danger degree and its mapping The indexes of debris flow danger degree consisting of the indexes of natural danger degreeof debris flow and the indexes of economic developmental level is classified into 5 classes too, Theregionalization is worked out based on the classifieation and “Division map of debris flow dangerdegree in the upper reaches of Changjiang River”is mapped as the figure on the head of the publi-cation according to the regionalizations.