The TerEx Tool automates the process of mapping terraces and floodplains from high resolution topography data (works best on <3m grid resolution). The tool maps terraces and floodplains from user-defined parameters including, a local-relief threshold selected by a variable-size moving window, minimum area threshold, and maximum distance from the channel to identify and map discrete terrace and floodplain surfaces. Subsequently, the tool automatically measures planform area, absolute elevation, and height relative to the local river channel for each terrace polygon. TerEx can be run in a Python environment or as a GUI plugin for ArcMap. See Stout and Belmont, 2014 and the users manual for explanations of tool functionality and several test cases that provide guidance on parameter values for a wide range of landscapes.