Highly Urbanised Areas Waterlogging Risk Assessment

Global climate change leads to frequent extreme rainstorms and increasing urban rainstorm and waterlogging disasters,which seriously threaten the personal and property safety of residents.With the advance of urbanization,the urban heat island effect accelerates the water cycle and increases the rainfall,and the impervious rate of the underlying surface also increases the possibility of waterlogging.In the meanwhile,the population and property are increasingly concentrated in the city,and the occurrence of waterlogging will cause immeasurable direct and indirect losses.Therefore,it is of great theoretical and practical significance to construct an urban rainwater model suitable for the highly urbanized area and evaluate the waterlogging risk in the highly urbanized area to enrich the waterlogging assessment technology and guide the disaster prevention and mitigation work in the highly urbanized area.Taking the highly urbanized Changban area in Guangzhou as an example,this paper builds a rainwater model to simulate waterlogging and carries out risk assessment,and preliminarily establishes a technical method system for risk assessment and avoidance of waterlogging at small spatial scale in highly urbanized areas The main research results are as follows:(1)Select Guangzhou Chang Ban as a highly urbanized regions example,a coupling urban stormwater model was built(TSWM).TSWM is coupleded by SWMM(Storm Water Management Model)and TELEMAC-2D.The result shows that the coupling model can well simulate the waterlogging disasters in this area,which can provide a new reference tool for urban waterlogging simulation.(2)Based on the coupling model,the waterlogging situation in the study area under different recurrence periods were simulated.The results show that the drainability of network of drains near Chang Ban subway station is inadequate,even if in 1 year in a heavy rain scenario,there is still waterlogging occurs,indicating that the study area is facing a serious threat of waterlogging disaster.(3)Based on the simulation results and field investigation data,the return periodloss amount curve and the return period-damage rate curve were constructed.Under the scenario of rainstorm once in 100 years,the loss amount in the study area reached44,943,320 yuan,and the disaster loss rate reached 36.71%.Therefore,the study area was faced with great risk of waterlogging,and appropriate measures should be taken to reduce the loss of waterlogging.(4)Different LID(Low Impact Development)reconstruction schemes are proposed for the study area,and the effect of these schemes on reducing the risk of waterlogging are evaluated.For the study area,the effect of permeable pavement is superior to that of green roof.However,LID measures have little effect on reducing the risk of loss under the heavy rainstorm,and other measures,such as property transfer and pumping station drainage,are needed to effectively avoid property losses in the study area.