Rapids of the Hudson River

The Rapids of the Upper Hudson River

By: Dan Rice
Published: 8/16/17

What causes the rapids?

Photo Credit: Melody Thomas Photography

     Whitewater happens for 3 reasons, often simultaneously:

1.) Obstruction - to block or close up with an obstacle; make difficult to pass.  An example of this are submerged, or semi-submerged rocks and boulders.

2.) Constriction - to draw or press in; cause to contract or shrink; compress.  An example of this is where, in some places the riverbanks are close together and the whole flow of the river needs to pass through a narrow section.

3.) Descension (Descent) - the act of moving from a higher to a lower position.  An example of this is seen in places where the river descends more quickly than in others, flowing downhill faster in some places than others.  In extreme cases, this might be exemplified by the river flowing over a waterfall.

     Water has the property of cohesion.  This is to say that it sticks to itself and happily flows along with the quintillions of water molecules around it, this might be a brook, a creek, or even a river.  When all of this connected water hits an obstacle, like a submerged boulder, the cohesion is temporarily broken and air becomes temporarily trapped in the flowing water making the water opaque and giving it a white appearance.  Both descension and constriction cause the river to move more quickly.  The faster the water is moving, the more likely it is to lose it’s cohesion when encountering an obstacle.   

What are the classes of rapids?

Photo Credit: Melody Thomas Photography

    The intensity of any given whitewater rapid or river feature is generally referred to by roman numeral and are rated by class from I(1) to VI (6).

• Class I - Easy.  Smooth water. Light waves with clear passages, obvious, or no obstructions. 
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• Class II - Intermediate.  Moderate-quick water.   Regular waves, clear passages between rocks and ledges.  Maneuvering required.
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• Class III - Moderately difficult.  Many large irregular waves. Rocks and eddies with clear but narrow passages requiring whitewater paddling experience to run safely.   Scouting required if rapids are unfamiliar.
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• Class IV - Difficult.  Long and powerful rapids with standing waves.  Precise maneuvering required.  Scouting or previous experience paddling the specific rapid is mandatory.  
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• Class V - Extremely difficult.  Long, violent rapids, with few eddies.  Constant dangerous obstructions, extremely steep.  Scouting from shore may be difficult. Rescue preparations mandatory.  Expert whitewater experience necessary.
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• Class VI - Nearly impossible, often unrepeatable.  Extraordinarily difficult.  Navigable only when water levels and conditions are at a certain precise level.  Every possible safety precaution must be taken, then try to come up with a few new precautions.

     To put it into perspective, on the Upper Hudson, in the summer, the hardest rapids we paddle are Class III.  In the spring, at higher water levels, we see some Class IV.   There are some nearby rivers with more Class IV rapids, like the Moose River in Old Forge, NY and the Boreas River near Minerva, NY, but these are both weather dependent and generally run at a raft-able water level in the spring.

What classes are the specific rapids in the Upper Hudson Gorge?*

Photo Credit: Melody Thomas Photography

Indian Head - Class II

Gooley Steps - Class III

Cedar Ledges - Class II

Beaver Dams - Class I

Virgin Falls - Class I

Good Enough - Class I

Blue Ledge In - Class III

Blue Ledge Out -Class II, Class III in spring at high water.

The Narrows - Class III, Class IV in spring at high water.

Ospreys Nest - Class III

Mile Long (Carters section) -Class III

Mile Long (Nasty Brothers section) - Class III, Class IV in spring.

Mile Long (Wrap Rapid section) - Class II, Class III in spring at high water.

OK Slip - Class II, Class III in spring at high water.

No Name - Class II

Giveny's Rift - Class IV (Because it should be scouted if never seen before.)

Gunsight In - Class III

Gunsight Out - Class II, Class III in spring at high water.

Harris' Rift - Class III

Fox Den - Class II

Bobcat Den - Class II

Boreas Flats - Class I, Class II in spring at high water.

Black Hole (aka Bus Stop) - Class III, Class IV in spring

Dodge City - Class II

Burnett's Folly - Class II

     These impressions are certainly open to interpretation.  The beauty of the Upper Hudson River Gorge is that the river is weather-dependent and can behave much differently at different water levels, so the rapid classes I've described above can be significantly different at different water levels.  In some ways, it's like rafting a completely different river from spring to summer.

*Note:  These characterizations depend on the water level.  At high water, it's best to treat every rapid as a class IV since the area is so remote and the potential for flipping a raft and taking a long swim is ever-present.