Recommendations for fish passage relative to tidal cycles

A longitudinal profile showing a road situated next to a tidal water body. A culvert is constructed through the road and water is flowing through the culvert. The culvert is a fish passage barrier at low tide and is back watered at high tide. The title elevation where fish passage is required is shown within the culvert. Below the title profile is a graph depicting elevation on the vertical axis and time on the horizontal axis the tidal range elevation is shown as a sinusoidal curve with a full tidal cycle depicted. The fish barrier time must be less than 10% of the tidal cycle or less than 1.2 hours in a 12-hour period.