Clearing the Flume

My friend John Cross and I worked on the flume at the farm today, clearing some roots from a rose apple tree that had grown into the flume channel. The root mass looked like a huge hapu‘u tree lying in the channel, and it diverted quite a lot of water out of the flume. This is the flume running after the root had been removed.


Here’s how much water was spillling over before we removed the roots. In that first photo, John was walking on the exact spot where all the water spilled out. They are “before and after” pictures.


Full flow downstream


This is where we will pick up the water in a pipe. It is about 200 feet downstream from the head works, where the flume originates.


The original concrete flume turns into a natural channel before reaching a concrete works downflume. The bottom is made up of ‘ili‘ili, small river rock.


We needed to find out what was causing the obstruction in the flume, which is why I called my friend John Cross. No one knows more about flumes that John. He managed the Hilo Coast plantations for C. Brewer and knew every flume on the Hilo Coast. He was in charge of making sure they were all in good repair.

We thought clearing our flume was going to be a big job. John went up there and took a look, and the following day he brought some 2 x 12s and a large sheet of plastic. The first thing he did was to cut one of the 2 x 12s the width of the flume. Then he cut the bottom of the board to fit the contour of the flume channel bottom. He cut a second board the width of the channel and then a third one.

He then set a 2 x 4 on the sides vertically, to hold the boards in place when the flow of the river would press the boards up against the 2 x 4s. He cut a piece of plastic that was a little larger than the boards. The water pressing against the plastic would make a nice seal.

When he put all those pieces in place, they stopped the flume flow and the water spilled off into a side channel. Now I know why it was slightly lower than the regular flume. I would have not known that it was a spillway, had John not actually used it.

John told me that when he put everything in place, the flume dried up. And in a short bit, an army of prawns started marching upstream toward him. That, and the river ‘opae started making their way upstream in the little rivulet, around and over the ‘ili‘ili on the bottom of the flume.

While he was watching the prawns make their way upstream, he heard a flap of wings above his head and saw an ‘io dive down, grab a prawn and fly on down the channel. It flew around a bend, went through a tunnel of overhanging trees and disappeared. John said it was a surreal moment.

Last week I spent several hours cutting the rose apple roots out, and today John and I took the rest out. It is surprising how much water flows through that flume.