Study On The Risk Assessment Of Debris Flow In Mountain

Prevention and reduction of geological disasters are the key points of risk management.Geological disaster risk assessment is the basis of geological disaster risk management. Thethesis depended on the project―Geological disaster risk assessment in important towns ofshaanxi province‖in China Geological Survey, took the debris flows around urban area inshanyang county, shangluo city, shaanxi province as the researching objects and used3dterrain scanning, high resolution remote sensing survey, engineering geological mapping andhidden danger point exploration as the main means. It analysed the debris flow formation ofthe regional geological environmental conditions, carried out the debris flow disasters earlyrecognition and field investigation, and found out the debris flow development features anddistribution. Based on the domestic and foreign risk assessment theories and technologies, weintroduced the concept of intensity, analyzed the debris flow risk under different rainfallconditions and explored the debris flow disaster risk assessment methods. The conclusionswere displayed as follows:1. It summarized the domestic and foreign risk assessment methods and put forward anew risk analysis method based on the identification of debris flow, investigation data in theflied, qualitative analysis and quantitative evaluation. The risk analysis of debris flows aroundurban area in shanyang county confirmed the applicability of this new method. The resultindicates that this method can evaluate debris flow risk accurately and be applied widely.2. It showed the effects of geological environment characteristics on development anddistribution of debris flows, suggesting that the urban area in shanyang county had threeessential factors triggering debris flows: The terrain boundary of middle mountain areas, lowmountain areas and river areas is relatively obvious, which is beneficial to catchment anddrainage. There were many cracked rocks formed by Niu Erchuan—Yin Hua deep faults.Concentrated rainfall and spatial characteristics of rainfall led to adequate water source.3. It summarized the characteristics of debris flows around the urban in shanyang county:potential debris flows mainly located in the southern urban areas, belonged tomountain-valleys-heavy rains-low frequency ones and were in the development of debrisflow. 4. It evaluated the risk of Hongchun gully in shanyang county under different rainfallconditions. The qualitative analysis results showed that the level of hazard was C, the level ofconsequence was Ⅱ and the level of risk was high. The quantitative evaluation resultsshowed that the risk lied in acceptable zone when rainfall occurred once every5years, therisk lied in tolerable zone when rainfall occurred once every10or20years, the risk lied inunacceptable zone when rainfall occurred once every50or100or200years.5. It analyzed the risk of debris flow located in the southern urban area on the premise ofrainfall happened once20years. Qualitative risk analysis results revealed that the risk ofgullies around the urban areas in shanyang county was middle-low, the risk of local area (forexample Hongchun gully) was high. Quantitative results showed that all gullies risk lied intolerable zone. All the above results suggested the risk of debris flow in shanyang county waslow and there was no need to engineering management, revealing that site selection wascorrect.