Numerous, irregular waves with drops and holes. Very difficult with cross-currents, fast water, and large, irregular waves. Extremely difficult with exploding waves, fast and powerful currents, cross- currents, large drops and heavily obstructed river beds. Ultimate limit of navigability. The seasons help determine water roughness.
Spring thaw provides huge volumes of water that runs very fast.
Fall often brings dam releases. During the summer the water can be calm, resulting in substantial discounts from many whitewater outfitters. Perfect for beginners.