Flood Control Mechanism of Multiple Dams Constructed in a Series Based on Cascade Method

Abstract

Using numerical simulation, we clarified the mechanism that the flood control capability is dramatically strengthened by using multiple serial dams efficiently, based on a new flood control concept that let dams overflow through emergency spillways. Numerical analysis results for a group of dry dams were used to quantitatively evaluate this effect and to derive an empirical formula. The conventional flood control approach sets the design high water discharge of individual dams, even when dams are constructed serially, ensuring that no overflows occurs in any of the dams, here called the “conventional” method. By comparing the group of dry dams based on the conventional method and a method on the same scale but set based on a new concept that we called Cascade method, we found that when the flood peak is cut in conventional control, the latter half of the cutoff flood peak must be cut again, making flood control redundant. The Cascade method avoids this redundancy in storage use and cuts the flood peak efficiently and linearly.