城市新区极端雨洪汇流淹没特性与致灾机理调查研究——以郑州“7.20”特大暴雨(郑东新区)为例

Survey research on characteristics of extreme rainstorm flood and disaster-causing mechanism in urban new district:Taking Zhengdong New District in Zhengzhou’s“7.20”heavy rainstorm as an example

近年来全球极端暴雨发生的可能性与不确定性提高,增加了城市遭遇特大洪涝灾害的风险。城市雨洪与河道洪水有显著差异,灾后雨洪信息快速采集与调研对认清雨洪特性与致灾机理尤显重要。本文以郑州2021年“7.20”特大暴雨为例,结合郑东新区地理与社会环境特点,采用野外调查测量、口述记录、多源数据分析、数值模拟对比相结合的方法开展了城市雨洪汇流淹没特性及致灾机理的调查研究。针对城市雨洪洪痕特征,拟定调查基本方法与适宜工作程序,根据调查区93处洪痕数据绘制了区域雨洪淹没分布图,分析了城市雨洪峰值水位分布特征及调查区汇流特性,探索了道路雨洪汇流流速及行洪道路阻力参数的确定方法。研究表明,城市雨洪地表主要泄流通道是街区道路,汇流方向受连续阻水、导水建筑与路网布局影响,雨洪淹没深度分布与下垫面条件和雨洪汇流特性有关。致灾机理研究分析表明,极端暴雨汇流远超城市排水管网泄流能力,雨洪选择阻力小的街道快速行洪,街道交汇处壅阻引起局部积水严重,这是极端暴雨致灾的直接诱因;而城市新区水系泄洪排涝关系不协调以及清障不力,导致城区河流行洪不畅,干支流异常高水位的顶托,严重降低了管网排涝功能,则是城市雨洪严重积涝致灾的深层原因。研究成果可为城市雨洪调查标准方法的建立与城市新区防洪排涝体系规划提供技术参考。

In recent years,the possibility and uncertainty of extreme rainstorms have increased in the world,increasing the risk of severe floods in cities.The characteristics of urban rainstorm flood are significantly different from river flood.It is extremely important to investigate and collect information of urban rainstorm for recognizing its characteristics.In this paper,taking“7.20”heavy rainstorm in Zhengzhou as an example,based on the geographic and social environment characteristics of Zhengdong New District,the converging and submerging characteristics of urban rainstorm flood and the disaster-causing mechanisms were investigated by means of survey,oral interview,data analysis and numerical simulation.The characteristics of urban rainstorm flood marks,and the basic method and routine of rainstorm flood marks survey were investigated.Based on the 93 flood marks in the survey area,the regional submergence map of the rainstorm flood was figured,and the distribution characteristics of the peak water level of urban rainstorm flood and the confluence characteristics in the survey area were analyzed.Then,the measuring method of the road confluence velocity of the rainstorm flood and the resistance parameter of the road for discharging flood were explored.The results show that the main discharging channel of urban rainstorm flood is the road of the block.Therefore,the confluence direction attributes to the geographic environment and the layout of road network.The distribution of submerging depth of rainstorm flood is related to the underlying surface condition and the confluence characteristics of urban rainstorm.The disaster-causing mechanism of the urban rainstorm flood shows that,the converging volume of the extremely rainstorm is far exceed the discharging ability of the underground pipeline network.The surface runoff chooses the road with low resistant as the discharging channel of the rainstorm flood,and the flow velocity of the flood is also increased comparing with the normal rainstorm flood,worsening the disaster.Besides,the backwater and resistance effect around the junctions of the channels would aggravate the waterlogging.That’s the main incentive of the extremely rainstorm disaster-causing.Moreover,the lack of coordination in flood discharging abilities between river lake systems as well and the rare dredging work of the river in the new developing city district leads to the flood channel obstruction of the urban river.There would turn up extremely high water level,and the backwater in the intersection of mainstream and tributaries,decreasing the capacity of flood discharging of the pipelines highly.These are the determine reasons of the severe water logging disaster-causing of the extreme urban rainstorm flood.The findings of the research might supply valuable technical support for establishing standard survey method of urban rainstorm flood and designing of flood control and drainage system in new developing district.