苏北里下河典型区河网水系演变特征研究

Evolution Characteristics of the River Network in the Typical Area of Lixiahe Region

在自然地理气候变化和人类活动胁迫的双重作用下,平原河网地区水系格局发生了很大的变化。以江淮下游里下河典型区——盐都区为例,基于1970s、1980s和2010s年的3期水系数据,利用GIS和遥感解译等技术,选取河网水系数量、结构和连通指标,对河网水系时空演变特征及其影响因素进行分析研究。结果表明:(1)研究区河网密度和河网水面率均呈不断减少趋势,两者分别下降21.3%和10.2%。研究区河流曲度较小,河网连通性较好,河网曲度和连通度总体上变化较弱。(2)研究区河网水系变化存在时空差异性。河网水系在缓慢城市化时期(1970s^1980s)的衰减率高于快速城市化时期(1980s^2010s),特别在城镇化发展缓慢区域表现显著。城镇化发展快速区域,其河网水系持续减少且变化剧烈。(3)研究区河道变化存在着等级差异性。城镇化等人类活动对河网水系的影响,呈现出先低等级(Ⅳ级)河道、后高等级(Ⅰ~Ⅲ级)河道的特征规律。其中,低等级河道数量持续减少且变化强度剧烈,高等级河道数量变化不大且其面积和长度均有所增加。

Under the dual effects of natural geographical climate change and human activities,the pattern of river system in plain river network has changed greatly. Based on the river network data in the 1970 s,1980 s and 2010 s,the river quantity,structure and connectivity were selected as indicators. By employing GIS and RS methods,the characteristics of the indicators were analyzed in terms of the spatial and temporal evolution,exemplified in the the river network of Yandu district,the typical area of Lixiahe region in the lower reaches of the Yangtze River. The results showed that：（ 1） The river density and water area ratio of the whole Yandu district decreased steadily by 21. 3% and 10. 2%,respectively. The degree of river curvature was relatively small and the connectivity of river network was fairly good. The curvature and connectivity of the whole river network changed little.（ 2） There was a temporal-spatial variations in the river network change of Yandu district. The decay rate in the low urbanization period（ 1970 s - 1980 s） was greater than that in the high urbanization period（ 1980 s -2010 s）,especially for the low level of urbanization areas. The degree had been changing dramatically in the high level of urbanization areas.（ 3） There was variability among different river grades. Impacts of urbanization on river network demonstrated an order of the lower grade（ IV） rivers,followed by the higher grades（ I-III） rivers. The number of lower grade rivers decreased constantly at a strong changing intensity,while the higher grade rivers demonstrated minor changes in river quantity,but a gentle increase in river area and length.