Where Does the Brown Water Come From?

Many people believe Enchanted Lake is polluted and brings brown water to Kailua Bay when the sand berm at the beach park is opened. While brown water does flow through the lake, it is not the source of this sediment-laden water. Does it come from the wetland, then? No, it’s also just a conduit, although it does filter some of the sediment out before it gets into the lake. So where does this brown water come from? All we need to do is follow the dirty water upstream.

During the storm of March 10, 2021, most of the brown water came through the Kaopa Subdivision Sediment Basin from several key sources:

Olomana Heights home lots,
Home construction sites along the Old Kalanianaole Highway with inadequate erosion controls.
The City’s storm drain sinkhole repair project on Kanapuu Street.

This video starts with a very typical development construction site at Olomana Heights in Kailua. The storm water flows from the unprotected site through the Kaopa Settling Basin, which was designed to capture sediments and hold back floodwaters. As you can see, the basin no longer provides any sediment settling function to stormwater. A berm internal to the basin that is supposed to pond the water allowing the sediment to settle, has been allowed to degrade over the past 50 years.

From the settling basin, the water flows into the hardened channel all the way to the Kaelepulu Wetland Bird Preserve and quickly enters Enchanted Lake on its way to Kailua Beach.

This interactive panorama shows one of the sources of the silt-laden water development at Olomana Heights. There are several other construction sites that also contribute to the brown water. You can click-and-drag to navigate, use your mouse scroll wheel to zoom, or use the buttons at the bottom for navigation. The right-most button will enlarge the image to full screen.

This is the stream mouth on March 14, 2021