Published on July 19th, 2013 | by Neil Egsgard1
Surf Anywhere: Drop & Flow
Surf waves can be built anywhere you have enough fast water. Figuring out where you have enough drop and flow is the first step to building a wave. The Surf Anywhere Project and Riverbreak are sharing this information to help you build waves everywhere.
Drop Provides Wave Speed
If you have a 1 metre drop in a river with a 30 cms flow you can build one of the best waves in the world.
The drop in elevation from upstream of a river wave to downstream is the wave’s energy source. The larger the drop the faster the water. The faster the water the more energy available for the wave. The Eisbach has a drop of about 1.1m or 3’7” from the channel bottom above the drop to the channel bottom after the drop. If you have a 1 metre drop you can build one of the best waves in the world provided you have enough flow. The figure below depicts how these components relate to each other and how they work together so that a river wave forms.
Flow Provides Wave Thickness
The flow is the volume of water per second going through a river (depth X width X velocity). The more flow you have the bigger and thicker the wave can be. The average flow rate of the river above the wave, on the wave and below the wave is always the same. If you increase the velocity than the width and/or velocity or must decrease. The Eisbach has a flow of about 30 cubic metres per second (cms) or 1,060 cubic feet per second (cfs).
How Water Changes With Drop and Flow
Making Waves With Drop and Flow
High Flow + Wide + Big Drop = Wave
If the channel is too narrow then the water will be too deep for a wave. If the drop is too small the water just fills in the wave.
Small Flow + Narrow + Small Drop = Wave
If the channel is too wide then the water will be too shallow for a wave. If the drop is too big the water will be too fast and therefore too shallow for a wave.
Amwelle: Low flow, narrow, small drop and a fun wave
Eisbach: Higher flow, wide, larger drop and a good wave
Surf Anywhere Project
This is the first of a number of articles on building river waves driven by the Surf Anywhere Project. The other articles will cover different fundamentals of river wave building making it easier for surf waves to be built everywhere. If you have any questions about building waves near you or information to share, please contact me – negs (at) riversurfing.ca