Side weirs are structures used to control water flow in drainage and irrigation systems. A new design method for side weirs has been developed based on the De Marchi equation. The study found that the flow over a side weir is influenced by downstream conditions and the dimensions of the channel and weir. The flow rate is determined by the depth and speed of the water downstream, as well as the height of the weir and the width of the channel. The researchers created charts and guidelines to help engineers design side weirs effectively.