西南山区河流河床结构及消能减灾机制

青藏高原的持续抬升导致青藏高原周边河流下切。河流下切造成河床河岸失稳,崩塌滑坡及泥石流等灾害频发。通过十余年野外调查和试验研究发现,崩塌滑坡泥石流堰塞河流形成的自然坝实际上是河流下切的负反馈的结果。自然坝稳定后控制河流下切,保持河流稳定并且改善生态。这样的功能主要来自于自然坝上发育的河床消能结构。本文总结了河床结构和自然坝消能减灾的机理,归纳以阶梯-深潭为代表的河床结构消能率的量化计算方法,并提出下切河流综合管理中能量概算的理念及基本思路。本文还介绍人工阶梯-深潭系统防治泥石流灾害的成功实践,强调人工模拟自然坝消能结构应用在防灾减灾领域的可行性及有效性。最后,以消能理念为基础,提出西南下切河流开发和管理中应建立"串糖葫芦"式中型坝群库坝体系,以实现水电开发、消能减灾和改善生态的综合目标。

Bedforms, energy dissipation and disaster mitigation mechanism in mountain rivers of Southwest China

The continuous uplifting of Qinghai-Tibet Plateau results in the river incision on the margin of Qinghai-Tibet plateu. River incision leads to frequent disasters such as bank failures, avalanches, landslides and debris flows. Based on the field investigations and experiments over the past decade, it is found that natural dams, which are formed after landslides or debris flows block the channel, perform as the negative feedback to river incision. The natural dams are capable to control erosion and incision efficiently, stabilize the riverbed and improve the local ecology. The functions above stem from the bedforms developed on natural dams. The present paper summarizes the mechanism of bedforms and natural dams on energy dissipation and disaster mitigation. The quantification of energy dissipation rate of step-pool, which stands for bedforms, has been put forward. Furthermore, the concept and logic of energy budget in the integrated management of incised rivers is demonstrated in the present paper. The successful application of artificial step-pool system in a debris flow gully is introduced, to illustrate the feasibility and efficiency of artificial energy dissipaters mimicking natural dams in disaster prevention and mitigation. Last but not least, based on the idea of energy dissipation, we suggest that the successive reservoir-dam system consisting of medium-sized dams should be applied in the development and management of the incised river in southwest China, to realize the comprehensive objective including dissipating flow energy, stabilizing the riverbed and promoting the ecology.