Waterflow
Oneawa Canal was created as part of the Kawai Nui Flood Control Program. It rerouted the marsh drainage and is now the only drainage canal for Kawai Nui Marsh.

Potentially harmfull water flows from Kawai Nui Marsh, through Oneawa Canal, to Kailua Bay while most likely picking up contaminents on the way. Storm drains fill the canal with both water and pollutants.

The waterway is largely brackish because of tidal exhange with Kailua Bay.