Understanding Tides and Currents in PWS
Prince William Sound has large tidal ranges that present challenges to all vessels. The vertical rise and fall can exceed 15 to 20 feet over a six-hour period. These large volumes of water moving through narrow channels create rapid currents and standing waves, especially near bay entrances and shallow river deltas.
Critical Tidal Hazards
1. Tide Rips (Standing Waves)
Tide rips are areas of turbulent standing waves. They occur when strong currents flow over shallow bars, around points of land, or through narrow passes like Valdez Narrows, Esther Passage, or Canoe Passage.
- Wind-Against-Current: When strong winds blow in the opposite direction of the current, waves stack up into steep, vertical walls that can swamp small boats.
- Action: Plan your transit through narrow channels to coincide with slack water (the period when tidal flow changes direction and stops moving).
2. Mudflats and Shallow River Deltas
Much of the eastern Sound, including areas near Cordova, Orca Inlet, and river mouths, consists of shallow mudflats and deltas.
- Stranding Hazard: High water can cover these flats, making them look like deep passages. During a falling tide, these shoals dry out quickly, potentially leaving your vessel grounded on mud or rocks.
- Action: Maintain a safe distance from low shorelines and delta areas. Do not cross shallow bays without a depth sounder and local knowledge.
3. Beaching and Shore Stranding
When landing on a beach, do not leave your boat floating free or sitting right at the water’s edge.
- Tidal Swing: A rising tide can float your kayak or skiff away, while a falling tide can leave your boat grounded high on the beach, requiring a long wait for the next high water.
- Action: Haul your vessel completely past the high-water mark and secure it with a line tied to a fixed shore anchor like a tree or log.
Guidelines for Anchoring and Coastal Navigation
- Check Tide Tables: Note the high and low tide times and heights daily.
- Scope Calculation: When calculating anchor rode, include the maximum high tide height in your depth calculation. Aim for a scope ratio of at least 5:1 or 7:1 to handle wind shifts.
- Low-Tide Depth: Verify that your chosen anchorage has enough water at the lowest expected tide to prevent your hull or propeller from hitting bottom.
- Shore Safety Gear: Always carry communication gear and basic survival supplies when going ashore, in case you are separated from your vessel by a sudden shift in tide or wind.