Six-Stage Flood Routing for Dams Having Gated Spillways


Abstract: A six-stage operation policy for the routing of flood hydrographs with return periods from 1.01 years up to the Probable Maximum Flood (PMF) is proposed for any dam having a gated spillway. The gate opening rules are determined, based on the recent pool level. The magnitude of the incoming flood hydrograph does not have to be predicted beforehand, as the fixed rules of the six-stage operation policy provide optimum routing for all floods, which are classified into six different groups based on their return periods. 10-, 100-, 1,000-, 10,000-, 100,000-year floods, and PMF are the upper limits for the six groups. When the PMF is routed, the rising and falling limbs of the outflow hydrograph have the appearance of a six-step staircase with sudden jumps and sudden drops at definite times and smooth variations between steps. The computer program developed to perform calculations of the six-stage flood routing model is applied sequentially to Yedigöze, Çatalan, and Seyhan Dams, all on Seyhan River in Turkey.

Keywords: Flood Routing, Dams, Gated Spillways

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