Since the Ecchu Province was suffered from flood disaster due to flood of river in the medieval period, Narimasa built bank during his few years of administration in Ecchu, so he was well-liked by people in his dominion.
中世の越中は河川の氾濫による水害に悩まされていたが、成政は僅か数年に過ぎない越中統治期間に堤防を築き水害を防いだため領民に慕われた。