基于物源动态演化过程的地震区泥石流风险预报机制研究

Debris flow’s formation and development are affected by frequent seismic activity and different scale rainfall of in the seismic disturbance area. As the debris flow disaster large-scale frequent happened, a rational methods of debris flow risk is urgent need to establish in Wenchuan earthquake impact area. The highway of Du jianyan to Wen chuan in earthquake hit areas is selected as the research object. The internal and external dynamic conditions control the occurrence and the activity characteristics of debris flow are discussed. Based on GIS and RS technology, mathematical statistics theory, the material source’s dynamic evolution in gullies along the highway within a few years after the earthquake is analyzed. The hazard assessment model of debris flow is established by considering the factors of landform, the ground motion parameter, the scale of rainfall and the dynamic evolution of the material source. The highway is divided into two categories: fixed and mobile bearing disaster body. Combined with damage ways, structural resilience factor of bridge, roadbed, tunnel and other fixed bearing disaster body are extracted. And the vulnerability assessment system of the mobile bearing disaster body include population and vehicles, is established based on probabilistic model. And then debris flow risk forecasting system and risk management method with timeliness feature is established along the highway in the earthquake zone.

频繁的地震活动和不同规模的降雨影响着地震扰动区的泥石流形成和发展。汶川地震后大规模频发的泥石流灾害使泥石流影响区迫切需要建立合理的泥石流风险研究方法。本研究以汶川地震区都汶公路为研究对象，分析控制泥石流的发生及活动特征的内外动力条件。基于GIS、RS技术，数理统计等理论，分析地震后数年内公路沿线各沟谷流域内泥石流物源的动态演化规律。综合考虑地貌因子、地震动参数、降雨规模、物源动态演化条件，建立地震区泥石流危险性评价模型。将公路分为固定承灾体和移动承灾体两大类。结合危害方式，提取桥涵、路基、隧道等固定承灾体的结构性抗灾能力因子，基于概率模型建立人口、车辆移动承灾体的易损性评价体系。进而建立具有时效性的地震区公路沿线泥石流风险预报体系和风险管理方法。

2008年汶川地震距今已11年，地震诱发的大量崩塌滑坡为震后泥石流提供了丰富物源，在汶川县境内发生过多次群发性泥石流灾害。本项目选取8个典型泥石流沟谷，通过收集2008年、2010年、2013年、2015年、2017年五期多源遥感影像，探讨泥石流流域内物源滑坡活跃时间。利用GIS、RS技术，对各沟谷流域内的崩塌滑坡进行遥感解译，计算其面积、体积变化率，并通过回归模型，结合流域面积等地貌参数，推算汶川地震区泥石流物源演化经验公式。并进一步对各泥石流流域在不同气候条件、地震动参数条件下的危险性进行评价分区。以道路、桥涵等为承灾体，对汶川县区域内的两条主干道进行了易损性和风险分区。研究结果为泥石流勘查设计、防灾减灾提供参考。