Some theories and ideas on on how to construct a whitewater feature.
BoaterTalk Post • Video • Waller Creek Site • Friends of the Falls
The best way to make a whitewater feature – basically accelerate water over a “slight” obstacle and “dump” it into still water. The smaller the obstacle it jumps the better. Too much rock and you get a hole. link
Semi-circle ‘U’-shaped rock pile to channel water and create hole / eddies.
Whitewater Park Architecture and Science has advanced dramatically.
Best practices include:
- Feasibility & Pre-design
- Concept Development
- Strategic Planning
- Business Modeling
- Limnology Studies & Habitat Design
- Local, state, and federal permits
- Venue Design
- Physical Modeling
- Computer Modeling
- In-stream Structures
- Boulder Placement
- Drop and Pool Structures
- Flow Hydraulics
- Flood Mitigation
- Water Safety
- Sediment Transport
- Target Species Habitat Restoration
- Facilities Construction
- Operations and Management
As far as creating a play feature the only thing I can really offer up is this. Play features are obviously in places where either A. the gradient increases and/or B. the velocity increases, coupled with a few good rocks or ledges to kick up or drop the water and form the play feature.
Remember that the flow (or volume of water moving downstream) in a river is constant no matter where you are on the run (obviously flows can increase or decrease over time depending on rain or dam releases). Even though you may be in a still pool, the river is still pushing a certain volume of water downstream. It just may not be as noticeable at wider spots as it is when the river chokes down in a gorge. Kind of like a garden hose. You turn the water on and you have a constant flow coming out of the spigot. Placing your finger over the end causes the water to come out faster even though the flow (volume of water) is still the same coming from the spout. The water must move faster given the smaller cross sectional area.
In order to maintain the upstream pool and allow for a play spot I would suggest something like a weir. You already have the gradient and the rocks to help form a feature. All you need to do is concentrate the flow in one area to increase the velocity of water traveling downstream.
Q = Volume (ft^3/sec)
V = Velocity (ft/sec)
A = Area (ft^2)
Q = V*A
By decreasing the area (A) of water coming over the dam, the river will have to increase the velocity (V) of water to allow the same flow (Q) to travel down the river. So instead of the water pouring over the whole river wide dam, arrange the rocks so that a smaller weir is created which leads to a smaller cross sectional area of water flowing through.
So in the equation, a smaller A results in a larger V. Larger V means faster velocity and wallah……..play spot…sort of.
The broken down dam on the Benson is a classic example of this concept. But I would think the placement of rocks to actually form the feature may be slightly more complex than that and this is where an experienced whitewater feature builder (not sure what their title would be) would come into play.
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