Hydrology

Surge Flow Waves

NPS photo

The Niobrara is not characteristic of most Great Plains Rivers, simply flowing over and around obstacles. Instead, it exhibits a pattern called “surge flow” where periodic surges (or bores) move along the water surface, eventually forming a cresting or surf-like breaking wave before receding again. At times these waves can reach heights of three feet or more!

These waves, sometimes known as pulsating periodic bores, are most evident during higher water levels (especially winter flows) when large amounts of sediments are suspended and transported within the stream. A steep gradient, relatively shallow waters and swift current are necessary for surge flows to occur.

Surge flows have been noted in streams in the Southwest, Rocky Mountains and Northwest, but the sediment-dependent pulsating flow found in the Niobrara is generally regarded by scientists as an uncommon geologic feature. Surge flow is recorded at one other National Park Service site, Great Sand Dunes National Park and Preserve, in Colorado.

Be cautious when canoeing or kayaking through these waves—if your boat turns broadside to these waves you may easily capsize.

 

Duration:

16 seconds

The rare phenomenon known as surge flow appears almost as standing waves, especially in the winter on the Niobrara National Scenic River.