Federal, state and local government agencies as well as private industry manage large networks of road systems in cold regions. These roads often use culverts or other hydraulic structures to pass water underneath them. Proper design and construction of these structures must balance the operational needs of the road system, the geomorphology and ecology of the water feature crossed, and both initial and long-term (operation and maintenance) cost. The purpose of this research is to evaluate how size of hydraulic structures relates to operation and maintenance (O&M) effort and impacts to fish passage and stream function.