Document Type : Research Article
Authors
1
Dept. of water sciences and engineering, faculty of agriculture, Jahrom University, Fars, Iran
2
Assistant Professor, Dept. of water sciences and engineering, faculty of agriculture, Jahrom University, Fars, Iran
3
Post graduate student of Hydraulic Structures, faculty of agriculture, Shiraz university, Fars, Iran
10.30482/jhyd.2023.408043.1661
Abstract
Introduction
In this research, the comparison of different routing methods and their impact on the hydraulic characteristics and dimensions of storm water conveyance pipes and the construction cost of different options is investigated. For this purpose, the rainfall-runoff simulation model (SWMM), is used for routing. Qaderabad city is taken into consideration as a case study with the aim of implementing different simulation options. The purpose of this study is to compare the construction cost of different hydraulic simulation options.
Methodology
In general, in SWMM model, the routing of the flow in the pipe and conduit is governed by using the one-dimensional Saint-Venant equation. The Saint-Venant equation is solved using the implicit finite difference method. Different options are available in this model including steady flow, Kinematic wave, Diffusion wave and fully dynamic. All methods are considered in this study to gain a better understanding of the each methods on outputs and construction expenses as well.
Results and Discussion
After setting up the model, the simulation was conducted in the selected return period with four mentioned simulation option methods: Dynamic, Diffusive, Kinematic and Steady flow. Subsequently, the dimensions of the pipes were determined. The construction cost of each flood routing method was calculated and compared with each other. The dimensions of the conduits were selected according to the dimensions of the concrete pipes available in the market and the existence of sufficient freeboard. Hence, no flooding was expected to occur in the nodes. Generally, the outputs of two fully dynamic and diffusive methods were similar showing the minimal effect of inertia term. How ever the results were quite different for other two methods. The first two methods yielded shallower depths leading to smaller dimensions and lower construction costs whereas all momentum terms were included. Another comparison between flow depth, discharge, time to hydrograph peak were also conducted. Construction costs were calculated using TAKSA software. The results suggest that applying fully dynamic simulation, despite more computational costs, puts the engineers on the safe side with lower construction costs.
Conclusion
The average dimensions of the conduits used in the main conveyance pipeline were the same in the dynamic wave method and the diffusive wave method; But compared to the kinematic wave and uniform flow method, it was at least 9.8% lower.
The dynamic wave method and the diffusive wave method had the same construction costs due to the same dimensions of the pipes used. However, the construction costs of these two methods were 55.7% lower than the kinematic wave method and 54% lower than the uniform flow method. Moreover, the construction costs of the kinematic wave method were 2.2% higher than the uniform wave method.
Keywords: Flow routing, rainfall-runoff model, SWMM, urban flooding, TAKSA
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