汶川地震引发的流域管理新课题

New challenges of river management induced by the Wenchuan Earthquake

汶川地震引发了大量的山体滑坡和崩塌.巨型滑坡夷平了山谷,创造了平缓坡地.这些新生地非常不稳定,易引发泥石流.尽快稳定和开发新生地是一个新问题.滑坡造成的堰塞湖引起剧烈河床演变,对河流地貌和稳定产生长远和深刻的影响.大量的崩塌体形成大石块堆积体,表面没有土壤,如何修复植被是一个严峻的挑战.本文通过野外测量和试验,对上述问题进行了探索并取得了初步成果.成果表明,采用阶梯-深潭结构稳定滑坡体,可以控制或减轻泥石流;发生于崩塌和滑坡体上的泥石流含水量小且大石块多,不是黏性泥石流而是两相泥石流,运动速度仅为黏性泥石流的1/10;堰塞坝发育成尼克点会显著改变河流纵剖面,稳定岸坡减少滑坡崩塌灾害;在花岗岩崩塌体上引种紫萼藓能显著加快植被演替,绿化裸露的石块堆积体.

The Wenchuan Earthquake have triggered many landslides and avalanches. Huge landslides buried valleys and created many gentle slope lands. The newly created lands are unstable and debris flow often occurs. Stabilization and development of the new lands is a new challenge. The second challenge is due to the damming of rivers and creation of quake lakes by landslides, which induces intensive fluvial process and may have long term effects on the river morphology. Many avalanche deposits consist of large stones without soil and fine sediment on the surface. Vegetation restoration on the avalanche deposits is the third challenge. These problems are studied based on field investigation and field experiments. Artificial step-pool system may stabilize the landslide body and control or mitigate debris flows in the incised gullies on the newly created land. The debris flow occurring in the earthquake area consists mainly of gravel, cobbles and boulders. They are two-phase debris flow rather than viscous debris flow although its specific weight is extremely high. The velocity of these debris flows is much smaller than that of the viscous debris flows because the collision of boulders and cobbles consumes a lot of energy. Quake lakes may develop into knickpoints, which will change the bed profile of the river and eventually stabilize the river. Planting Grimmia pilifera on the avalanche deposit carl accelerate vegetation restoration and finally green the bared mountains.