Method For The Forecasting Of Regional Rainstorm-induced Debris Flow

Regional rainstorm-induced debris flow hazard is one of common geology hazards which are of mass occurrence, simultaneity, abruptness, and large-scale thus seriously impedes the economic development of mountainous area. As one of contingent non-engineering cautions against it, the forecast of regional rainstorm-induced debris flow has drawn more and more people's attention. Its research was divided into three parts: analyzing the formation mechanism, the spatial forecast, and the time forecast. But the systemic research was few. And due to the complexity of regional rainstorm-induced debris flow hazard, current researches in this field are far from requirements of guarding against or reducing hazard in mountainous area. Targeted on the limits of forecasting regional rainstorm-induced debris flow, and while based on the researches of predecessors, deeply research in this dissertation are the formation mechanism of rainstorm-induced debris flow, approach to risk degree zoning, forecast and pre,warning models and such system grounded on GIS, some innovative research fruits are achieved in the following aspects.1. According to different dynamic conditions ranging from movement of soil body to formation of rainstorm-induced debris flow, the formation mechanism of both hydrodynamic and soil dynamic kinds of rainstorm-induced debris flow are discussed:â‘ According to variation of rainfall penetration, hydrodynamic kind of rainstorm-induced debris flow is divided into three phases, and characteristic of loose soil of landslides in each period are analyzed, As a result, a theoretical formula of average critical runoff depth when debris flow start is gained.â‘¡The formation process of soil dynamic debris flow are analyzed, it come out with major effect factor of liquefaction and mobile of the soil body: Intensification of soil body disturbance, increase of temperature of soil grain, bring of excess pore water pressure. Thus lays some good theoretic foundation for forecast debris flow.2. Systematic study is conducted on selection, normalization, weight of zoning indexes, and establishment of rainstorm-induced debris flow risk zoning:â‘ Based on rough set theory, a new selection method on zoning indexes is put forward, the issue of representation and comprehensive are settled, which makes zoning indexes selecting more reasonable.â‘¡Based on fuzzy theory, the linear and curve standardized handling method are established, it would be more reasonable and more realistic for the standardized handling.â‘¢Based on rough set theory, the calculating formula of relative significance of the zoning indexes is established, the traditional AHP is improved, which makes the constructed matrix objective and avoids the human factor influence. And the combination weight method is proposed for selecting the value of the favorable coefficient of the subjective and objective weight of the evaluation indexes. The objective and subjective aspects of indexes are taken into account in this method, and a relatively reasonable weight value may be obtained by combining the expert judgment and the objective analysis.â‘£To use extension method to establish risk degree zoning of debris flow of various norms, and provide a universally applicable and workable zoning method.3. With regard to different kind of forecast of rainstorm-induced debris flow, forecast and pre-warning of debris flow is made to combine meteorological products with non-linear theory and probability theory, and establish long, medium and short-term forecast and pre-warning of rainstorm-induced debris flow:â‘ According to residual error correction, residual error correction GM(1,1) forecast model is used to make long-term forecast of region rainstorm-induced debris flow in order to guide the prevention and planning of debris flow.â‘¡Based on fuzzy theory, extension method and Bayes statistics theory, a new medium-term forecast method of regional rainstorm-induced debris is brought out to guide all preparatory work of emergency. This method gives full consideration to general statistical and regional properties of recent dangerous situations of regional rainstorm-induced debris flow. This new method can comprehensively reflect the real situation of regional debris flow.â‘¢To turn abruptness of rainstorm-induced debris flow into question of instability probability of loose soil body under torrential rainfall condition, and proposed is a new method of short-term forecast of regional debris flow so as to help government to strengthen group forecast and prevention of debris flow.4. In light of function and target of forecast and pre-waming system of regional rainstorm-induced debris flow, deeply are discussed debris technological circuit, function and structure design, database design etc. of debris flow forecast and pre-waming system based on GIS, put forward is the technology of establishing database, and some database is created. Visualized is forecast and pre-waming result of debris flow hazard by MapInfo and VB method grounded on OLE, thus provide technological support for information management of debris flow disaster prevention and decrease policy system.