| Summary: | 碩士 === 國立中興大學 === 土木工程學系 === 90 === Abstract
Land development is known to cause a large coefficient of surface runoff. When rainfall happens, more floods occur downstream than upstream. A detention pond must be constructed to reduce the peak time and peak discharge by making use of storage volume. This study utilizes detention pond experiments to verify that the numerical routing of continuity equation, and discusses the hydrology characteristics of detention with triangle or trapezoid inflow hydrograph by using a rectangular spillway and an orifice outlet. The results of this study are outlined as follows:
1.The foundation of numerical routing is the hydrology continuity equation (3-3). By using the Runge-Kutta method, we can calculate the governing equations (3-19) ~ (3-22) of triangle and trapezoid inflow hydrology. The verification of detention experiments shows us that the outflow hydrology is close to numerical result no matter what kind of outlet is used. It shows that the continuity equation can accurately simulate the characteristics of a detention pond.
2.In this research, the experience formulas for peak reduction κ are (5-5) and (5-6) with triangle hydrology and formulas (5-8) and (5-9) representing trapezoid hydrograph. In addition, figs.5-16 and 5-30 show the relationship between dimensionless peak lag time Ts and peak outflow Qop/Qip. The value of Ts is less when Qop/Qip is larger under the triangle inflow hydrograph. Under the trapezoid inflow hydrograph, Ts is larger than 0 when the value of Qop/Qip is equal to 1. It means although peak discharge can’t be reduced, peak time can lag.
3.Figures 5-17, 5-20, 5-31, 5-34 show the differences of storage volume between triangle inflow hydrographs and trapezoid inflow hydrographs. The detention of trapezoid hydrograph needs larger storage volumes and less size of an outlet than the triangle hydrograph. In addition, the storage volume for the orifice is less than the spillway; this means the outlet for the rectangular orifice has a better detention effect.
|
|---|
