Legal Definitions - tidal

The term tidal describes a body of water, or a specific location within it, that is regularly influenced by the rise and fall of ocean tides. This means the water level at that spot periodically changes as water flows in and out due to the gravitational pull of the moon and sun. For a river, a section is considered tidal if it consistently experiences this ebb and flow, even if the water itself is fresh rather than salty.

• Example 1: Coastal Property Development

  A developer plans to build homes along a coastal inlet. Local zoning laws specify different setback requirements for structures built on land that is always dry versus land that is submerged during high tide. The developer must survey the property to determine the average high tide line.

  Explanation: The inlet is considered tidal because its water levels regularly fluctuate with the ocean tides, alternately exposing and submerging parts of the shoreline. This daily rise and fall directly impacts the legal boundaries for construction and land use.

• Example 2: River Navigation for Commercial Vessels

  A shipping company operates large cargo barges on a major river that empties into the sea. Even 30 miles upstream from the river mouth, the river's depth changes significantly throughout the day, affecting when the barges can safely pass over shallower sections, despite the water being entirely fresh.

  Explanation: This upstream section of the river is considered tidal because, despite its distance from the ocean and its freshwater composition, it experiences the regular ebb and flow of the ocean's tides. The daily variation in water depth, driven by the tides, is a critical factor for navigation and scheduling.

• Example 3: Environmental Habitat Protection

  An environmental agency is designating protected wetlands. They identify a particular marshland area where unique plant species thrive in brackish water, and the water levels visibly rise and fall twice daily, connecting and disconnecting various pools from a nearby bay.

  Explanation: This marshland is a tidal habitat because its water levels are directly and consistently influenced by the daily rise and fall of the ocean tides. This constant movement of water creates a unique ecosystem that requires specific environmental protections due to its direct connection to the tidal cycle.