Sextus Julius Frontinus (40 - 104 AD) was an influential Roman magistrate and writer. As governor of Britain under Vespasian he reduced the Silures, a rebellious tribe in SE Wales, and pacified Britain within its borders. His success allowed his successor Agricola to later pacify the bulk of the province.
From his experience as curator aquarum, or water commissioner, he wrote De aquis urbis Romae, which greatly details the water supply of Rome, with complete descriptions and history of the aqueducts. He also wrote the Strategematica, which is important as a guide to Roman military tactics and strategy.
De Aquis Urbis Romae (The Aqueducts of Rome)
De Agri Mensura (History of Civil Engineering)