Holding a doctorate in mining geology from École des Mines de Paris, Emmanuel Manier began his career at the Laboratoire des Ponts et Chaussées in Rouen. A recognized expert in natural hazards and earthworks, he moved to the Central Laboratoire des Ponts et Chaussées, in the Paris region, in 2003, where he led major projects and research programmes in these fields and carried out assessments abroad. 

He joined SNCF in 2008, taking charge of a technical department (Geology, Environment, Routing) within the infrastructure engineering branch. He was appointed Regional Director, then Territorial Director for Normandy in 2013. In 2016, he became head of Talent at SNCF Réseau, overseeing employment and skills strategy, as well as career development for management staff. In 2018, he took charge of the South-East Engineering Division. In 2025, he was appointed Deputy Managing Director for the Atlantic Region at SNCF Réseau.