Research On The Urban Flood Disaster Carrying Capacity Evaluation Model Based On Remote Sensing Technology

In recent years,the urban flooding and waterlogging disaster attacked China both in northern and southern cites,even some of those facing a challenge that "watching sea in the city" in every flood season.In the view of urban hydrology,the increasing ratio of impervious surface caused by urbanization is an important factor that leads to negative hydrological effects.Some researches addressed that as the background of global warming and rapid urbanization,the possibility and strengthen of extreme events such as urban flood disaster would increase in some areas of China in the future.Facing the severe situation of urban flood disaster,it was necessary to eliminate the negative hydrological effects and evaluate the ability of urban infrastructure objectively to mitigate urban flood disaster.Research about urban flood disaster carrying capacity is in the scope of risk assessment which mainly focus on the spatial extension distribution of "flooding".And the main methods including statistical analysis,index system,numerical simulation and remote sensing & GIS technology are used in urban flood risk assessment and inundation scenario simulation are used in flood risk assessments.However,there is few research focus on the perspective of urban environmental carrying capacity,combining with the spatial heterogeneity characteristics of hydrological response of urban underlying surface.In this paper,the urban flood disaster carrying capacity was defined as “The carrying capacity of urban flooding and waterlogging event under the condition of normal operation of urban functions and undisturbed activities of citizens” referring to the indicator of “measurement” in physical and “safety standard” in biology.Based on the study of spatial heterogeneity of urban hydrological response by using remote sensing and spatial information technology,the evaluation model of urban flood disaster carrying capacity was constructed and applied in Wuhan.The main work and achievements were as follows:(1)As the concept of "carrying capacity" is widely used in ecology,environmental science,resource science,urban planning and management,this paper proposed the concept of "urban flood disaster carrying capacity",defined its general form and basic connotation,and elaborated the research methods.(2)Based on VIS-W underlying surface model,a method for evaluating the urban flood carrying capacity was proposed.The urban underlying surface VIS model is widely used in the study of ecological water exchange,whose components "V" and "S" can reflect the characteristics of urban infiltration and rainwater retention,and its component "I" can reflect the characteristics of urban confluence.As the VIS model cannot reflect the characteristics of urban regulation and storage,this paper extended component water(W)into the VIS model as VIS-W(vegetation,imperious surface,soil and water)model.Furthermore,in term of VIS-W model,an urban flood disaster carrying capacity evaluation model which combines the following characteristics: the underlying surface terrain characteristic,the yield of rainfall-runoff,and the distribution of low-lying area was constructed.(3)A method basing sliding window to re-classify shadow adjacent water to solve the misclassification problem of shadow was proposed.It is common that the misclassification between shadow and water in very high resolution remotely sensed imagery classifying.Due to the spatial proximity between the water body and mistakenly classified shadow area,a new shadow re classification method was proposed based on the region growing method which is a typical neighborhood homogeneous pixel search algorithm.And the proposed method was verified by the initial results including vegetation,impervious surface,bare soil,water body and shadow identified by the maximum likelihood classification(MLC)method,and the results indicated that the proposed method could improve the final accuracy of water body.(4)A sub-watershed delimitation method of considering both topographic connectivity and precipitation was proposed.As the traditionally sub-watershed delimitation method adopting filled DEM could not keep the reservoir characteristics,a new watershed delimitation method in term of no-fill DEM basing the ideas of multi-direction method and active submergence was proposed.And the sub-watersheds delimitated by the proposed method was compared with by the distribution of 40 typical waterlogging points occurred in the flood disaster at the beginning of July 2016 in the Third Ring Road of Wuhan City.The results showed that the proposed method could reflect the characteristics of confluence of underlying surface and the distribution of waterlogging risk to a certain extent.(5)Taking Wuhan as example,its urban flood disaster carrying capacity and improving space were estimated.In this paper,the proposed urban flood disaster carrying capacity model was applied in Wuhan,and the result was as follows: 1)The flood disaster carrying capacity of sub-watersheds including Lake Bei,Lake Houguan and Lake Panlong were relatively weak;2)that of sub-watersheds in Lake East and Lake South were normal;and 3)that of sub-watersheds contain Yangtze River and Han River inside of the study area were strong.Furthermore,the improvement space of urban flood carrying capacity in Wuhan considering the main 16 rainwater pumping stations and new drainage and rainwater control projects from 2017 to 2018 in the downtown of Wuhan was discussed.It was concluded that,1)the existing flooding disasters might be mitigated in condition that fully schedule the strong carrying capacity of Yangtze River and Han River if the new drainage ability by the five new pumping stations,such as Huangpu Road Pump Station,etc.;2)the flood disasters carrying capacity in the areas of Lake Bei,Lake Houguan and Lake Panlong might be improved if well utilizing the drainage capacity of the newly built open channel of highway 21 th,Lake Hou-IV pump station and Donghu low discharge pump station,and 3)the flood disaster carrying capacity in the areas of Lake Dong,Lake Nan and Lake Qingling might be improved as the new drain water ability to the river by Gangxi Pump Station and Jiangnan Pump Station.