Officials have warned for years that heavy tree-felling and rapid hydro development were making a mountain area struck by China's deadliest mudslide in decades vulnerable to flooding and land slips.

Government reports last year urged work to restore a battered line of environmental defenses in a brittle landscape, deemed a "high-occurence disaster zone for landslides."

The Bailong River that rushes through the valley is swollen, some pent up behind a loose dam of landslide debris.

Officially, the landslide has been described as a natural disaster brought on by heavy rains, a drought that preceded it, and the huge 2008 earthquake that loosened the riverside slopes in Gannan prefecture, the mountainous region of southern Gansu.

But warnings about the fragile state of the river go back years.

Government documents issued before the disaster said the river and its surrounding slopes were prey to manmade problems, as the poor area sought to turn its forests and riverways into economic assets.

Specifically mentioning landslide risks in a document from April 2009, a government office overseeing the river highlighted the urgent need to rejuvenate the natural environment.

"Water volumes have fallen drastically, soil erosion is accelerating, and the trend of frequent land and mud slides and other geological hazards has not been contained.

"The repair of the Bailong River basin must not brook delay," the report warned.

Widespread tree-felling along the river since the 1950s had caused "grave destruction to the natural environment, creating serious erosion, worsening geological hazards, frequent natural disasters, a fall in water absorptioncapacity and shrinking flows," it said.

The Bailong River was over-exploited by rapid hydropower development on the Bailong River, said Zhang Qirong, an official with the Bailong River forestry authority.

The hydro dams appeared to have been a major factor - after loosening caused by the 2008 earthquake - in unleashing the landslides and clogging the river, he said.

In a recognition of the problems facing the river, the State Council in 2008 approved a plan to repair erosion and geological hazards there.

• restore [ri´stɔ:] vt.(使)恢复；修复 (初中英语单词)
• disaster [di´zɑ:stə] n.灾难，不幸 (初中英语单词)
• valley [´væli] n.谷；河谷；流域 (初中英语单词)
• frequent [´fri:kwənt] a.常见的，频繁的 (初中英语单词)
• repair [ri´peə] v.&n.修理，修补 (初中英语单词)
• destruction [di´strʌkʃən] n.破坏，毁灭 (初中英语单词)
• capacity [kə´pæsiti] n.容量；智能；能力 (初中英语单词)
• factor [´fæktə] n.因素；原动力；要素 (初中英语单词)
• recognition [,rekəg´niʃən] n.认出；认识；承认 (初中英语单词)
• landscape [´lændskeip] n.风景；景色；风景画 (高中英语单词)
• earthquake [´ə:θkweik] n.地震；大变动 (高中英语单词)
• surrounding [sə´raundiŋ] n.周围的事物 (高中英语单词)
• document [´dɔkjumənt] n.公文；文件；证件 (高中英语单词)
• environment [in´vaiərənmənt] n.郊区；周围；条件 (高中英语单词)
• swollen [´swəulən] swell的过去分词 (英语四级单词)
• officially [ə´fiʃəli] ad.以职员身份；正式 (英语四级单词)
• drought [draut] n.旱灾；干旱 (英语四级单词)
• mountainous [´mauntinəs] a.山多的；巨大的 (英语四级单词)
• fragile [´frædʒail] a.易碎的；虚弱的 (英语四级单词)
• urgent [´ə:dʒənt] a.急迫的，紧急的 (英语四级单词)
• widespread [´waidspred] a.广布的；普遍的 (英语四级单词)
• absorption [əb´sɔ:pʃən] n.吸收；吸收作用 (英语四级单词)
• riverside [´rivəsaid] n.河岸 a.河岸上的 (英语六级单词)
• geological [dʒiə´lɔdʒikəl] a.地质学的 (英语六级单词)