鹅掌河泥石流对四川邛海影响的初步研究

Preliminary study on the effect of debris flows from Goose Foot River on Lake Qionghai, Sichuan, China

沉积作用在湖泊的演化和消亡过程中至关重要,洪水泥石流的淤积作用对我国西南地区广泛分布的构造断陷湖泊是一个普遍的环境问题．通过调查鹅掌河泥石流发育背景,人类的活动对泥沙进入邛海的影响和对比1988年与2003 年邛海水下地形图得出:在近30年的时间内,鹅掌河洪水和泥石流改沿固定河堤流入邛海,在湖底形成浊流,将更大量泥沙带到湖中．浊流在鹅掌河河口的水下扇陡坡上形成一水下冲沟,在湖底沉积区形成一条长2 km的水下堤．计算发现, 鹅掌河泥石流带入邛海的泥沙远大于一般土壤侵蚀产沙量,其中以1996,1997和1998三年泥石流输入的泥沙量最多．鹅掌河洪水和泥石流对邛海的影响以及水下地形、湖泊基本特征和湖泊环境的变化,应引起人们对邛海保护的高度关注．

Aggradations are very important for the developing and dying-out of lakes. The aggradations of floods and debris flows are common environmental problems in fault lakes in southwestern China. Investigating the background of the basin of Goose Foot River, the effect of human activities on Lake Qionghai, Sichuan Province, China, and the underwater topography maps of 1988 and 2003 were analyzed. In the past 30 years, turbidity currents were formed by debris flows and floods of Goose Foot River and took huge sediment into Lake Qionghai. The sediment not only pushed the coastline of Lake Qionghai at Goose Foot River fan into lake, but also deposited in the lake to the opposite bank. Debris flows took much more sediment into Lake Qionghai than the soil erosion did in the same basin. There is an underwater levee on the underwater fan. The underwater levee is 2 km in length, 200 m （at south coast） to 600 m （ at north coast） in width and the average 2 m in height. The maximum height of sediment deposition at underwater levee is 8.29 m, or 0.55 m for every year. There is a channel on the slope of the underwater fan of Goose Foot River mouth eroded by turbidity currents. The main source of sediment is the sediment token by the debris flows in 1996, 1997 and 1998. It should be paid more attention on the environment issues, such as basic characteristics, underwater topography of Lake Qionghai and the effect of Goose Foot River debris flows on Lake Qionghai.