| Lots of problems about urban drainage have appeared with the acceleration of the urbanization process recently, such as the destruction of natural waterways and the expansion of impervious areas. One of the most prominent problems is the connection between urban waterlogged drainage and municipal drainage. Urban sewerage and drainage system includes waterlogged drainage and municipal drainage, and they are governed by water conservancy department and municipal department. However, the differences between the two department standards lead to more implementation deviations, and the relationship between them is increasingly close with the integration of the water affairs. Therefore, it is necessary to clear the differences between the two standards and explore the transformation relationship of return period between the two systems for the better development of urban drainage management.Taking drainage and waterlogging engineering in the Haikou city as an example, the relationship between urban waterlogged drainage and municipal drainage was analyzed combined with the statistical data of the rainfall. The main contents and results were as follows:(1) Rainfall measured values were comparatively analyzed with different sampling methods on the basis of the measured rainfall date of Haikou city, the applications of different sampling methods in urban waterlogged drainage and municipal drainage was conducted in quantitative analysis as well. Annual multiple sampling method was used to design rainfall when return peroid was less than 5 years. Annual multiple sampling method and annual maximum method both could be design rainfall when return periods were 10 years and 20 years, and this depended on the date collected. Annual maximum method was used to design rainfall while return periods were 50 years and 100 years.(2) Rainfall formula and its compilation method between water conservancy department and municipal department were distinguished. In view of the existing municipal rainfall formula in Haikou city lasts a long time, and it could not accurately reflect regular changes on the current rainfall.Therefore, parameter optimization and rework for single rainstorm intensity formula of Haikou city was carried out through the method of regression analysis. The accuracy of the formula obtained was given as follpws: the average square error was Xm=0.022mm/min, and the relative square error was Um=2.6%, and this conformed to code requirements.(3) The design flow of drainage and waterlogging engineering in waterlogged areas of Haikou city was caculated based on the principle that return period varied with calculation methods for different flow on the same design flow, and then transformation relationship of return Period betweenwaterlogged drainage system and municipal drainage system was established as follows: municipal-drainage return period of 1 year corresponded to water-drainage return period of 9.5-13.5 years, municipal-drainage return period of 2 years corresponded to water-drainage return period of 15.0-20.0 years, municipal-drainage return period of 3 years corresponded to water-drainage return period of 20.5-30.0 years, municipal-drainage return period of 5 years corresponded to water-drainage return period of 30.0-40.0 years, municipal-drainage return period of 10 years corresponded to water-drainage return period of 45.0-60.0 years, respectively.(4) Transformation relationship between return period of municipal drainage system and waterlogged drainage system conformed to polynomial model: Tw=-0.306TD2+7.799TD+4.597(R2=0.9987). It was worked out based on the previous research results on the other cities that the general switching model between return period of municipal drainage system and waterlogged drainage system, and the model is Tw = ATD2+BTD+C, where A, B and C varied from hydrological and climatic conditions with different regions and the specific values should be determined according to the statistical data. |
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