Some examples provide methods, systems, devices and/or apparatus related to reducing and/or restricting water from entering underground transportation system, and more Specifically, to reducing and/or restricting water from entering underground transportation systems via vents based on the weight of the water, while not restricting ventilation airflow when water is not present. Some example systems for restricting water flow in a surface vent may include a frame that receives water, a door pivotally coupled to the frame(where the door may pivot between a first position and a second position), and a reservoir pivotally coupled to the door. The reservoir may collect the received water and may cause the door to pivot between the first position and the second position based on weight of the collected water.