涪江流域江岸防护林带淤沙固岸效果的研究

Research on Effects of Bank Protection Forests in Depositing Sand and Fixing Banks in the Fujiang River Valley

在涪江中下游典型江岸营造1000亩淤沙林带,江岸防护林系统经1988年洪水淹后林带内淤积泥沙,在1981年特大洪灾冲成裸露的卵石滩上重新淤地300亩,现已在林间点种农作物;在凸岸营造的淤沙林带,一次洪水淹没后,淤泥沙普遍在20cm以上;凸岸林带内淤沙与乔木胸高断面积成正相关,数学模型:Y=0.0448+0.8558X(Y:淤沙厚度,X:胸高断面积)。当胸径达8cm时,测定单株树干对洪水阻力为6kg,全部冲成倒伏状。凹岸营造固岸林带后,一次洪水淘深河床20cm;固岸林生物工程组合乔草型林网结构与防洪堤水利工程配套后,造成堤与林带区域淤积。

There are about 1,000 mu sand deposition forest belts established on some typical banks of the middle and lower reaches of the Fujiang River. After undergoing the flood in 1988,the bank protection forest system silted up mud and sand within its forest belt. For example, some crops have been sown between trees on the re-deposited flood land of about 300 mu which lies on some pebbly beaches exposed by a catastrophic flood in 1981. The sand deposition forest belt planted on the convex bank can generally silt up more than 20 cm thick sand and mud after a flood. Sand or mud deposited in the forest belt on the convex bank have a positive correlation with the breast-height basal area of arbores,and their mathematical model is as follows:y=0. 0448 + 0. 8558x,where y is the thickness of deposited sand or mud and x the breast-height basal area. When the breast-height diameter reached 8 cm,it was determined that the reaistance of an individual tree against floods was 6kg and all trees were lodged by floods. After bank fixing forest belts were established on the concave banks,a flood could dredge the river bed by 20 cm. A forest network of arbores and grass in combination with breakwater will bring about the regional deposition of sand and mud between breakwater and forest belts.