A longitudinal functional connectivity comprehensive index for multi-sluice flood control system in plain urban river networks

• Dynamic quantification of hydrological function connectivity in complex river network is solved. • A new quantitative indicator of longitudinal functional connectivity is established. • The Longitudinal Functional Connectivity Comprehensive Index of Changzhou city is obtained. In the process of urbanization development, human activities have a great impact on rivers because of social and economic demands, which directly or indirectly lead to changes in the structure and function of river networks, thus making hydrological patterns tend to be chaotic and ecological environment deteriorates. In order to clarify the hydrological connectivity change mechanism of plain urban river network, the main urban area of Changzhou was taken as the study area, the Longitudinal Functional Connectivity Comprehensive Index (LFCCI) was defined. The results of temporal and spatial variation analysis of LFCCI in the study area showed that the average LFCCI in the main urban area was 1.34. Among them, the average LFCCI in flood season (May to August) were higher than those in non-flood season, the maximum and minimum values of LFCCI were 1.7 (May) and 0.63 (December) respectively, indicating that the scheduling of stations in flood season was more complex. Meanwhile, the average LFCCI of Jiuli station was the highest (2.95) and Wujin station was the lowest (0.30). However, further analysis showed that Weicun, Zaogang and Xiaohe sluices were important stations that affect the LFCCI in the study area. The evaluation method solved the problem of hydrological connectivity evaluation under the background of complex dispatching rules, and it provided important technical support for river network connection project and water environment improvement.