College of Resources and Environmental Science, Hunan Normal University, Changsha, 410081, China.
School of Geographic and Oceanographic Science, Nanjing University, Nanjing, 210023, China.
J Environ Manage. 2020 Jan 1;253:109687. doi: 10.1016/j.jenvman.2019.109687. Epub 2019 Oct 24.
Stream losses are extensively observed due to human activities in the world, and the patterns of stream loss vary in different land use types. However, relationship between stream loss pattern and land use covers is poorly understood. We select the lower Taihu watershed (LTWS) within Yangtze River Delta (YRD), which is dominated by agricultural and urban covers and a typical case of most urbanized watersheds in China. In this study, we measured the stream loss of LTWS from 1960s to 2010s and investigated its relation to different land use covers and impervious area percentage (IAP) in order to figure out the main factor of stream loss in this area. The results show that urban area has tripled with fractional contribution from 10.3% to 33.18% in the form of conversion from agriculture to urban area during 1990-2015. 12.5% of all the streams are lost and 1st-order streams contribute most (91.8%) to the total stream loss. Urban cover contribute most (76%) to total streams loss compared to other land use types. We find that 1st-order streams have highest stream loss intensity, which is mainly caused by urban expansion, but preferred protections are given to highest-order streams. The linear model of correlation of pixel-level streams loss and IAP shows that the streams loss is statistically significant positive with IAP of cells (R = 0.91). Tradeoffs between city expansion and river network make small channels sacrifice for the urbanization. Urgent measures including legislation must be taken to protect small streams during urbanization nowadays and in future.
由于世界范围内的人类活动，溪流流失现象广泛存在，而溪流流失的模式在不同的土地利用类型中有所不同。然而，溪流流失模式与土地利用覆盖物之间的关系还不太清楚。我们选择了长江三角洲（YRD）的太湖下游流域（LTWS）作为研究对象，该流域以农业和城市覆盖物为主，是中国大多数城市化流域的典型代表。在这项研究中，我们测量了 LTWS 从 20 世纪 60 年代到 2010 年代的溪流流失情况，并调查了其与不同土地利用覆盖物和不透水面积百分比（IAP）的关系，以确定该地区溪流流失的主要因素。结果表明，在 1990 年至 2015 年期间，农业向城市的转化使城市面积增加了两倍，其贡献率从 10.3%增加到 33.18%。共有 12.5%的溪流流失，其中一级溪流对总溪流流失的贡献最大（91.8%）。与其他土地利用类型相比，城市覆盖物对总溪流流失的贡献最大（76%）。我们发现，一级溪流的溪流流失强度最高，这主要是由于城市扩张造成的，但对最高级别的溪流给予了更多的保护。像素级溪流流失与 IAP 的相关线性模型表明，溪流流失与单元的 IAP 呈显著正相关（R=0.91）。城市扩张和河网之间的权衡使得小河道为城市化做出了牺牲。在当今和未来的城市化进程中，必须采取包括立法在内的紧急措施来保护小河道。
