Improving Water Productivity over Three-Side Spillways with Focus on Effective Length of the Crest

Multidimensional spillways are important hydraulic structures for regulating water level and flow in canals, rivers and reservoirs. The main hypothesis for the development is to increase the conveyance capacity through the spillway crest length at a given width. Finding an appropriate geometry has always been an important issue for designers in achieving maximum water productivity of hydraulic structures. In this study, several plans were simulated numerically considering effective length of spillway crest. Results showed that the highest reduction in the effective length of spillway crest occurs for plans with greater interference area at normal and lateral flows. Also, spillway model No. 5 was recommended as a sufficient plan in terms of flow capacity because of having just one interference area for normal and lateral flows and insignificant compaction during falling streams due to long lateral arms.