Wow. First of all thank you for all your thoughtful and obviously informed input. Upon seeing your responses, there does appear to be some additional information it looks like I should provide:
– The runnel will be completely gravity fed (no pump anticipated) with slopes that may vary between 0.5% to 1%.
– The system will not be recirculating. Although we had initially explored a recirculating system, since a portion of the feature will be exposed for potential bodily contact, the County Health Department considers the feature a water play element and it becomes subject to some strict regulations. A recirculating feature would require restrooms with showers and infared and chemical treatment which the project has neither the space or budget.
– To reduce the water to drain “waste” we are designing the runnel to only contain water when activated by a “switch” in the vicinity of the water source. That switch would trigger the release of a set volume of water at a set flow rate just sufficient enough to produce a visible and audible “plug” of water that could be followed down the runnel. This is where the proper volume calculation would come in. Thank you Thomas for reminding me of some of those calculations and coefficients I have not used in a while.
-The grates will be ADA compliant and will occur wherever the runnel passes through a paved surface. The exposed runnel section occurs where the runnel passes through a lawn space. The plan is to use a light edging material (concrete or pavers) at the surface on either side of the runnel to provide a visual contrast against the darker green grass.
I’m sure there may be more I should explain, but I’ll leave it there for now. Please keep the suggestions, experience, comments coming. They are very helpful and appreciated.
