城市雨洪放大效应驱动因子时空演变规律分析

城市雨洪具有复杂的放大效应,引起该现象较直接的原因包括大暴雨的频繁出现、可渗透地表面积的骤减以及排蓄水能力的改变和排水管网的扩张等。以武汉市为例,选择降雨强度、不透水面积比例、排水管道密度作为洪水放大效应的驱动因子进行趋势分析和演变规律分析,计算表明:从20世纪80年代开始,暴雨雨量和历时明显增加;不透水面在20世纪90年代初增加较快;排水管道在1990~2006年间缓慢增长,2007年跳跃式增长。降雨量和历时的增加使城市洪量增大,排水压力随之上升,在一定程度上增加了内涝几率;不透水面积的逐年增多以及水体等天然蓄水区的减少,不但增加了产流量,也使汇流时间更短,且雨水管渠的建设缩短了天然汇流路径,导致城市洪水呈现峰高量大,洪峰提前的放大效应。研究成果可用于城市雨洪放大效应对其驱动因子的定量响应研究,为进一步量化城市内涝风险与驱动因子间的关系提供依据,从而为内涝风险调控措施提供技术支撑。

Spatio-temporal evolution analysis of driving factors in amplification effect of urban flood

Urban flooding presents complex amplification effect because of the increase of heavy rainstorm, sharp decrease of impervious surface, change of drainage and impound capacity and expansion of drainage pipelines.Taking Wuhan as an example, we selected rainfall intensity, impervious area proportion and drainage channels density as driving factors to analyze the amplification effect of urban flood.The results showed that the total annual precipitation and duration increased obviously since 1980s in Wuhan;the impervious surface increased quickly in the early 1990s, and then remained relatively stable growth;the drainage pipe grew up slowly from 1990 to 2006, while had jumped since 2007.The increase of precipitation and rainfall duration caused the increase of the total amount of urban flood, and brought more probability for rainstorm waterlogging.The increase of impervious surface and the decrease of water storage areas not only led to the larger flood amount but also the shorter time of confluence, and the construction of storm-drainage channels shortened the natural flow path, thus, amplification effect of urban flood occurred with high and advanced peak.The results can be used for quantitative response research of flood amplification and driving factors, and provide the basis for the quantitative relationship between urban waterlogging risk and driving factors, thus to support for waterlogging risk control measures.