浙江省典型河流滩地时空演变分析

Analysis on spatial-temporal evolution of typical river floodplains in Zhejiang Province,China

河流滩地是河流廊道的重要组成部分,是维护河流健康的重要屏障。以浙江省钱塘江、瓯江、椒江、飞云江、鳌江、甬江六大干流省级河段滩地为研究对象,应用1985—2020年典型时段的遥感影像资料,获取滩地几何形态特征及空间矢量信息,并应用景观格局理论,计算主要滩地质心移动距离、滩地扰动度等,分析了滩地时空演变特征。结果表明:(1)1985—2020年,浙江省六大干流省级河段滩地数量增加225.51%、面积减少14.73%,主要滩地质心平均移动距离约369 m。滩地变化主要发生于2017年之前,以2013年前更为明显;(2)滩地扰动度分析需综合考虑河流整体与局部河段,大尺度研究情况下,不同河段的综合效应会更凸显;(3)钱塘江、瓯江滩地主要受电站、航道等涉水工程建设影响,椒江、鳌江、飞云江、甬江以及瓯江入海口等区域滩地,主要受围垦及潮汐顶托泥沙沉积影响。引起滩地时空演变的因素多样,需因地制宜,合理施策,才能有效遏制滩地破碎化和功能退化的趋势。

The floodplain is an important part of river corridor and an important barrier to maintain river health.This paper took the provincial river section of Qiantang River,Oujiang River,Jiaojiang River,Feiyun River,Aojiang River and Yongjiang River in Zhejiang Province as the research object.Based on the remote sensing image data of typical periods from 1985 to 2020,the geometric morphological characteristics and spatial vector information of the floodplain were obtained.The centroid moving distance of the main floodplain and the floodplain disturbance index were calculated using the landscape pattern theory,and the spatial-temporal evolution characteristics of the floodplain were analyzed.The results showed that:(1)the number of floodplain in the six main streams of Zhejiang Province increased by 225.51%,the area decreased by 14.73%,and the average movement distance of the geological center reached about 369 meters from 1985 to 2020.The change of floodplain mainly occurred before 2017,especially before 2013.(2)In the analysis of floodplain disturbance index,it was necessary to comprehensively consider the whole river channel and some river sections.In the case of large-scale research,the comprehensive effect of different river sections would be more prominent.(3)The floodplain of Qiantang River and Oujiang River were mainly affected by the construction of hydropower stations and navigation channels.The floodplain of Jiaojiang River,Aojiang River,Feiyun River,Yongjiang River and the estuary of Oujiang River were mainly affected by the reclamation of the floodplain and the sediment deposition caused by the tide jacking.The factors causing the temporal and spatial evolution of floodplain were diverse,and it was necessary to adjust measures to local conditions and implement reasonable policies to effectively curb the trend of beach land fragmentation and functional degradation.