白河河湾迁移速率及影响因素分析

白河为黄河源区典型弯曲河流,2016年和2017年对白河9处典型河湾进行了考察采样。分析表明,白河河湾凸岸植被呈环形条带状分布,一般有2~3个植被群落;湾顶从前至后的树木尺寸显示出明显的由低矮到高大的梯度变化。对凸岸树芯和圆盘样本进行年轮分析,获取了树木的分布和树龄数据,提出了通过树木年轮和距离计算河湾迁移速率的方法。通过绘制树龄分布云图找出关键样本,测算白河河湾迁移速率为0.38~6.1 m/a,与遥感影像估算得出的迁移速率基本一致。对白河河湾迁移速率与水流流速、河宽、滩高等数据进行回归分析,建立多元线性回归模型,结果表明水流流速和比降是白河河湾迁移速率的主要影响因素,迁移速率与流速和比降均成正比。

Analysis on the Baihe River bend migration rate and its influencing factors

The Baihe River is a typical meandering river in the Yellow River source region. Field investiga-tions and samplings were carried out in 9 river bends of the Baihe River in 2016 and 2017. The analysis of them shows that the vegetation distributes in a shape of zonal arc along the convex bank of the Baihe River, with 2-3 vegetation communities in general, and the sizes of trees present evident gradient changes from low to high in the direction from front to back of the bend. The tree distribution and tree ages in the convex bank are obtained though tree ring analysis on the sampled tree cores and disks, and a method for estimating bend migration rate based on tree ages and tree distance is proposed. The key samples are identi-fied by drawing the tree-age distribution cloud map, and the bend migration rates of the Baihe River are estimated to be 0.28-6.1 m/a, which is basically consistent with the migration rate estimated by re-mote-sensing image. A multiple linear regression model is established based on the regression analysis of bend migration rate with its potential influencing factors. It is concluded that the flow velocity and river slope are the main influencing factors for the bend migration rate, and the migration rate is proportional to flow velocity and river slope.