largestlargernormal
Logo bar of the Alaska Public Lands Information Center which are located in Anchorage, Fairbanks, Tok and Ketchikan
Bore Tide
text size
Printer Friendly
Bore Tides
 
What:
The "bore" is a tidal phenomenon in which the leading edge of the incoming tide clashes with the flow of the outgoing tide to form a wave that travels up a river or narrow bay.

These tides, which can reach 40 feet, come in so quickly that they sometimes produce a bore tide wave that can reach 10 feet high. Adventurous locals have taken to riding this wave out on a kayak or board - talk about extreme surfing!

Where:

The bore can only occur in long, narrow channels.

Alaska's Turnagain Arm and Knik Arm, that surround Anchorage, boast the second highest tides in North America after the Bay of Fundy. The best place to see the Alaskan bore tide is along Turnagain Arm, just south of Anchorage. In particular, Beluga Point, Indian, and Bird Point are easily accessible by road and are within an hour drive of Anchorage. Bird Point offers a small interpretive panel dedicated to the tide.

Bore tides exist in other places around the globe such as the Bay of Fundy in Nova Scotia, and the Tsientang River in China. The longest exists in the Amazon River in South America.

When:
It's pretty easy to predict when the bore tide will hit a given point if you know when low tide in Anchorage begins:

  • The first thing to take note of is that an average tide, without any wind, travels roughly 10-15 miles per hour.
  • Next, realize that wind plays a factor - a westerly wind means an earlier arrival, while an easterly wind means later.
  • Arrive at least half an hour before the predicted tide will arrive; bore tides may not arrive on time.
  • If you reach a point and the water is already rising, the bore has passed. Drive east to the next point and check again - water will be calm immediately before the tide comes in.

Finally, here are some times for specific areas when the bore tide typically arrives after low tide in Anchorage:

  • Beluga Point: 1 hour 15 minutes
  • Indian Poin: 1 hour 30 minutes
  • Bird Point: 2 hours 15 minutes
  • Girdwood: 3 hours

The best times to see a good bore are when the low tide in Anchorage has a high negative value, particularly if the good low tide is followed by a large high tide; this maximizes the "sloshing" effect that causes bore tides to occur.

CAUTION! Our bore tides are dangerous. Due to the quicksand-like mudflats that make up the beaches along Turnagain Arm, hikers may get stuck in the mud and drown or die from hypothermia. Always stay off the mud flats and observe the bore tide from a safe distance.

The bore tides are a must-see experience in Southcentral Alaska, as they occur in so few other places in the world. Be sure to enjoy this phenomenon from a safe distance, however, as they can be quite dangerous (see audio below) due to their height and speed of approach in addition to the mudflats mentioned above. Be safe, and enjoy!

Bore Tide PDF 







 
The conical peaks of the Four Mountains islands in the Aleutian chain rise above a dark blue ocean. Low clouds circulate just above the water. The sky is clear and blue. Did You Know?
The 1,200 mile long Aleutian Islands are a chain of over 300 small volcanic islands along the northern Pacific Ring of Fire. Spanning from southwest Alaska to Russia, 57 volcanoes are scattered across the islands’ range.