I plan to produce a 4ft long by 8" diameter spiral using a sheet of medium density plastic I scavenged as a sort of submersible turbine to use in a drainage causeway with some boards to concentrate the flow. Is this worth trying? Last rainstorm, I figured the water was traveling roughly 10ft/s, or about 12,000GPM across the causeway.
I plan to use this specifically for powering a bilge pump to empty leaking water out of a basement in times of heavy rains, so the fact the drainage causeway will be dry half the time is no problem.
-Andrew