Aquatic barriers is one of several ecological settings variables that collectively characterize the biophysical setting of each 30 m cell at a given point in time (McGarigal et al 2017). Aquatic barriers measures the relative degree to which road-stream crossings (i.e., bridges and culverts) and dams may physically impede upstream and downstream movement of aquatic organisms, particularly fish. It is derived from a custom algorithm (see below for details) applied to dams and derived road-stream crossings. Briefly, each dam has an aquatic barrier score based either on dam height or attributes indicating whether the dam has a partial/complete breach. Similarly, each road-stream crossing has an aquatic barrier score based either on an algorithm applied to field measurements of the crossing structure or predictions from a statistical model based on GIS data. Aquatic barriers is scaled 0-1, where dams and road-stream crossing are assigned values >0 (with 1=complete barrier) and all other cells (including terrestrial) are assigned 0.