A check dam constructed across the Kudamuruti near Valangaiman breached on Wednesday, resulting in reduced flow of water in irrigation channels. Cracks developed on the southern side of the decade-old dam recently and widened further after water was released into the river. Water flow into Poondi, Sandhana and Thillaiambur channels were affected. PWD officials took steps to plug the breach using sandbags, sources said.