It is said that, while he was the lord of the Iwatsuki Domain, he built a drainage in Sasayama Village (Sasayama, Hasuda City) in his domain; the drainage became called 'Yamashiro hori' after the Tadamasa's title the governor of Yamashiro.
岩槻藩主時代、領内笹山村（蓮田市笹山）に溜井落し堀を造ったといい、忠昌の受領名　山城守からとって「山城堀」と呼ばれる様になったという。