Hierarchical River-Chief System Management Based On River Network Characteristics In Beijing

Multi-graded river network is an important part of the material cycle,is an important freshwater ecosystem,and is also the basis of comprehensive watershed management.In the process of comprehensive management of river basin represented by "River-Chief System",the river network is "broken" by the administrative boundary.However,existing river identification methods only focus on the natural gradation of river network.River in Beijing as an example,this study studied under natural watershed division and administrative boundaries to interrupt the corresponding river classification statistical characteristics,reveals the watershed comprehensive management in the basin natural boundary and administrative boundary of contradictions,provides a theoretical basis for reasonable allocation of river wardens and river basin sustainable management for the implementation of the "River-Chief System".Firstly,the statistical characteristics of river classification in natural watershed are analyzed.By 30 m by 30 m DEMs extract the river network in Beijing,using Horton grading rule statistics under the natural watershed division at all levels,statistical river morphological parameters including number of rivers,river frequency,bifurcation ratio,river length ratio,area ratio and curvature and so on.The research shows that the Beijing river network is divided into 11 levels,and 38 rivers are counted from 6 to 11.The average river frequency,bifurcation ratio,river length ratio,area ratio and curvature of Beijing natural river network were 0.852,3.630,2.184,3.832 and 3.705 respectively.Secondly,the hierarchical statistical characteristics of river network are analyzed.The provincial,county and township administrative divisions are superimposed on the river network,and a series of structural parameters of the river network have been broken by administrative boundaries at all levels.Results show that with the loss of the administrative levels(province — county — township),administrative region number increasing,the administrative boundary of river network interrupt frequency increases,the degree of "administrative fragmentation" increase.The influence of the statistical characteristics of river classification is: the number of rivers at all levels increases,and the average length,average bifurcation ratio and average river length ratio at all levels decrease.Thirdly,it reveals the main contradiction in the comprehensive management of river basin.By comparing the natural watershed division and administrative boundary break after two case management required number of river wardens,founding that the integrity of natural river from source to sink and the fragmentation of river network are the biggest contradiction in the process of comprehensive management of river basin represented by "River-Chief System".By setting the rule of the number of rivers,it is estimated that in the natural watershed,the management of the Beijing river basin area greater than 10 square kilometers of the river needs 469 river wardens.And after the watershed administrative boundary,the management of the Beijing river basin area greater than 10 square kilometers of the river needs 76 ~ 77 provincial river wardens,178 ~ 334 county river wardens and 1052 township river wardens.This paper provides a theoretical basis for the comprehensive coverage of the river and lake required in the "River-Chief System" of the city.This research clarifies the influence of administrative management on river network classification characteristics,and provides theoretical basis for sustainable management of watershed.