城市化对山区中小河流洪水特性影响研究

发布时间：2018-04-22 14:26

本文选题：城市化 + 中小流域　；参考：《重庆交通大学》2017年硕士论文

【摘要】：伴随着城市化发展,城市中小河流流域下垫面条件发生重大改变,且区域内气象环境变化和人类活动加剧的影响,使流域产汇流条件较天然流域发生较大改变。洪水峰值变大、径流总量加大、洪水历时减少、径流系数不断变大等给城市河道的行洪安全都带来了巨大的影响,由于山区特殊的气候环境和地形地貌条件,使这种影响更为突出。传统的水利推理公式和市政暴雨公式对城市化后中小河流洪水径流模拟均存在各自的不合理性,故本文通过运用SWMM模拟城市化后流域的产汇流变化情况以及出口断面的设计流量,分析城市化对山区中小河流洪水特性的影响,为工程设计以及相关研究提供依据。论文以重庆市巴南区龙洲湾堰河为研究对象,城市化后研究区域下垫面条件及地形地貌均发生巨大改变,不透水面积比例由20%增加到65%,流域内洪水特性发生了明显变化。论文采用SWMM模型模拟城市化前后,降雨历时为120min,重现期分别为5a、20a、50a、100a条件下产汇流变化情况,得到了城市化前后流域内洪水特性的变化规律。通过模型模拟计算结果对比分析表明:(1)在不同的降雨情景以及重现期条件下,流域累积雨量径流系数的变化趋势是:降雨初期,径流系数为零,当降雨发生到某一时刻,累计雨量才从零逐渐增加,且增大的斜率越来越大,经过一段时间后达到峰值,而后慢慢降低。(2)降雨重现期对雨量径流系数的影响相对较小,不同重现期下同一子汇水区域的径流系数相差较小,但用地布局的不同导致下垫面条件的改变,继而对流域产汇流情况的影响是巨大的,开发后流域的蓄滞能力降低、径流峰值和径流总量均比天然流域状况大。(3)在SWMM模型模拟计算流域产汇流时,下垫面要素对其结果的影响十分明显。其中,子汇水区域的特征宽度、透水性和不透水性粗糙系数N值即子汇水区域曼宁系数对模型产汇流计算结果影响较大,而坡度、不透水面积比、洼蓄值以及Horton下渗条件对结果影响的灵敏度相对较低。笔者还通过运用水利推理公式以及市政暴雨强度公式分别计算研究区域规划建设后的洪水径流情况,并与SWMM模拟城市化前后研究区域区间洪水值进行对比分析,得到了以下结论:(1)水利部门推理公式采用年最大值方法选样得到对应重现期频率进行暴雨洪水分析,而市政暴雨强度公式则采用非年最大值法即年多个样法,其得到的是次频率。与推理公式相比,市政暴雨强度公式的重现期较低,本文也总结了它们之间的转换关系。(2)通过将推理公式与SWMM模拟城市化后研究区域区间洪水值相比较,并分析得出:推理公式主要适用于天然条件下中小流域洪水计算分析,当下垫面发生巨大变化后,其计算得到的河道设计流量比实际值偏小,影响工程设计的安全性。(3)通过将市政暴雨强度公式计算值与SWMM模拟城市化后研究区域区间洪水值相比较,并分析可以看出,其主要适用于低重现期下小流域的降雨径流计算,其计算得到城市化后山区中小河流设计洪水值较实际偏大。
[Abstract]:With the development of urbanization, the conditions of the underlying surface of the small and medium river basins have changed greatly, and the weather environment changes in the region and the influence of human activities aggravate the conditions of the basin production and confluence larger than that of the natural basin. The peak of the flood is larger, the total runoff is increased, the flood water duration is reduced, and the runoff coefficient becomes larger and so on. The flood safety of the road has brought great influence. Because of the special climatic environment and topography and geomorphology conditions in the mountain area, the influence is more prominent. The traditional water conservancy reasoning formula and the municipal rainstorm formula have their own unreasonable characteristics on the flood runoff simulation of the small and medium rivers after urbanization, so this paper simulates the urbanization flow through the use of SWMM. The influence of urbanization on the flood characteristics of small and medium rivers in mountainous areas is analyzed by the change of the output and flow of the region and the design flow of the export section. The paper takes the Longzhou Bay weir River in Banan District, Chongqing as the research object, and changes the underlying surface conditions and topography and landforms in the study area after urbanization. The ratio of water permeable area increased from 20% to 65%, and the characteristics of flood in the basin changed obviously. The paper used the SWMM model to simulate the urbanization before and after the urbanization, and the rainfall duration was 120min. The reappearance period was 5a, 20a, 50A and 100A, and the variation of the flood characteristics in the flow field before and after the urbanization was obtained. The results are as follows: (1) under the different rainfall situation and the reappearance period, the variation trend of the cumulative rainfall runoff coefficient is: the initial rainfall, the runoff coefficient is zero. When the rainfall occurs to a certain time, the cumulative rainfall increases from zero gradually, and the increase of the slope is increasing, after a period of time, it reaches the peak and then slow. (2) the effect of rainfall runoff coefficient on rainfall runoff coefficient is relatively small, and the difference of runoff coefficient between the same subregion of the same subregion is small, but the difference of land use distribution leads to the change of the underlying surface condition, and the influence on the runoff yield is great. The total runoff is larger than that of the natural basin. (3) the influence of the underlying surface elements on the runoff yield is very obvious when the SWMM model is simulated and calculated. Among them, the characteristic width of the subwater area, the permeability and the N value of the water permeability roughness coefficient, that is, the Manning coefficient of the subwater area, have great influence on the result of the model runoff. The sensitivity of the impermeable area ratio, the depressions value and the Horton infiltration condition to the result is relatively low. By using the water conservancy inference formula and the municipal rainstorm intensity formula, the author calculates the flood runoff in the area planning and construction respectively, and compares the flood value with the regional interval of the SWMM simulation before the urbanization. The following conclusions are obtained: (1) the reasoning formula of the water conservancy department uses the annual maximum method to obtain the frequency of the corresponding recurrence period to analyze the rainstorm and flood, while the municipal rainstorm intensity formula uses the non annual maximum value method, that is, the annual multiple sample method, which is the secondary frequency. Compared with the reasoning formula, the recurrence period of the municipal rainstorm intensity formula is lower. The paper also sums up the transformation relations between them. (2) by comparing the reasoning formula with the SWMM simulation of the flood value in the regional interval, the inference formula is mainly applied to the flood calculation and analysis of the small and medium river basin under natural conditions. The flow of the river design is compared with the actual calculation. The value is small, which affects the safety of engineering design. (3) by comparing the calculated value of the municipal rainstorm intensity formula with the flood value of the SWMM simulated urban area, it can be found that it is mainly applicable to the calculation of the rainfall runoff in the small watershed under the low recurrence period, and the calculation of the design flood value of the small and medium rivers in the mountainous area after the urbanization is compared. The reality is big.

【学位授予单位】：重庆交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TV122

【参考文献】