Study On The Delimitation Method Of Flood Risk Control Line In Territorial Space Planning

Climate change and urbanization are the major challenges facing human beings.Flood and waterlogging had a significant impact on our country.Prevention of flood disasters has become one of the national priorities.At present,the control of flood disasters is mainly through the construction of artificial regulation and storage facilities,and less consideration is given to natural regulation and storage facilities.The delineation of flood risk control lines in territorial spatial planning and the delineation of natural and artificial storage areas in advance is of great significance to the construction of ecological cities and the avoidance of flood risks in cities.Firstly,the definition of flood risk control line is analyzed,and the included elements and reference space of the line are determined.Secondly,the research on the delimitation of flood risk control lines was completed.The specific steps were as follows:combining the delimitation reference space to screen and subdivide the delimitation content and determine the delimitation criteria;analysing the factors included in the study area and preliminarily delineating the flood risk control line;constructing a drainage model for the study area,complete the delimitation of the flood risk control line by formulating a governance plan and improving the delimitation scope.Finally,suggestions are made on the control measures within the flood risk control line.The main work and results of this study are as follows:(1)The flood risk control line marking process was constructed.By analyzing the flood control and drainage system and the definition of flood risk control lines,it is determined that the layout of rainwater pipes and canals,urban roads,urban blue lines,urban green lines,and the layout of regulation and storage facilities are the reference spaces for the delimitation of flood risk control lines,and a flood risk control line delimitation process is constructed based on the reference space range.(2)The flood risk control line has been preliminarily delineated.Combining the delineation method of reference space,analyze the delineation content and criteria of flood risk control lines,divide the flood risk control lines into three categories,and clarify the elements contained in each category.Preliminary delineation of flood risk control lines for elements within the control line is carried out using Arc GIS.In this study,the results of flood risk control line delimitation are summarized as the delimitation area,and a total of 50.9 km~2 of flood risk control line area is preliminarily delineated,accounting for 4.9%of the total area of the city.The natural storage control line has an area of 50.2 km~2 and the artificial storage control line has an area of 0.7 km~2.(3)The river drainage capacity of the study area was evaluated.Extract partial data from the study area through Arc GIS,and import existing data into SWMM(Storm Water Management Model)to build a river drainage model.A comprehensive rainfall model with a30-year return period and a 50-year return period coupled with a long and short duration were selected to simulate the drainage capacity of the river channel in the study area.The results show that the rivers in the study area that overflow under the 30-year and 50-year rainfall scenarios account for 17%and 19%of the total rivers,respectively,indicating that the comprehensive drainage capacity of the study area is strong,but there is still a problem of river overflow,and the river overflow in the study area is more serious under the 50-year rainfall scenario.The locations where river overflows occur are concentrated in the southern and northern ocean regions,and most of the overflowing locations are distributed in the old urban areas with lower elevations.(4)Improve and complete the delineation of flood risk control lines.Through clarifying the process of waterlogging control,the principles and methods of waterlogging control plan are obtained.The waterlogging in the study area was controlled by widening river channels,expanding lakes,and constructing new flood storage areas.The SWMM river drainage model is improved in combination with the waterlogging control plan.Comparing the simulation results before and after the treatment under the 30-year return period rainfall scenario,it was found that the river overflowing in the drainage channel model before the treatment accounted for 17%of the total river channel.The improved drainage channel model eliminated the overflowing river channel,and the filling degree of most river channels decreased to below0.25.Therefore,the river drainage capacity of the study area has been greatly improved after treatment.Revise the elements in the governance plan that involve changes in the elements of the flood risk control line,and complete and delimit the flood risk control line according to the delimitation criteria.The final area of the flood risk control line is 73.9 km~2,accounting for 7.1%of the total area of the city.The area of the natural storage control line is 53.5 km~2,and the area of the artificial storage control line is 20.4 km~2.(5)The flood risk control method within the control line is proposed.Based on the analysis of the timing of delimiting flood risk control lines,the principles of flood risk control line control are determined.Research on flood risk control line management methods from different management and control perspectives.The determination of control methods is of great significance for ensuring the use of land within the flood risk control line.