Measuring an eroding sustainability

WAIMEA — “I regard this as somewhat alarming,” said Keith Robinson as he described the devastating erosion that is eating its way through his land.

It’s 9 a.m., Wednesday, and Robinson is seated at a picnic table in front of Waimea Big Save. He has invited a group of environmental experts to partake in a conservation experiment.

Seated at the tables are Lex Riggle and Rick Bersheid, of the United States Department of Agriculture’s Natural Resources Conservation Services; Robert Ishikawa from the USDA Farm Service Agency; Alan Muraoka from East Kaua‘i Soil and Water Conservation District; Kawika Smith, Department of Land and Natural Resources; Howard Greene representing Gay & Robinson; and data collectors Daniel Hashimoto and Bill Sigurdson for the Pacific Journal.

Robinson introduced himself, each member of the group and then plunged into a little explanation about the history and nature of this conservation experiment.

As far back as Robinson’s teenage years he was aware there was a serious soil erosion problem in Waimea Canyon caused as a result of goats over-grazing.

Robinson left Kaua‘i for college and majored in field propagation production and minored in range management where he learned the importance of keeping the watershed and pastures intact. His professors emphasized this would someday become a critical issue. They warned water and good soil are natural resources that would eventually run out, not just on Kaua‘i, but worldwide.

Robinson continued with a brief explanation of the erosion problem on his reserve land.

“A serious rain falling on Olokele Canyon can supply around 70 to 100 million gallons a day rushing down the steeply graded mountains into the ocean and spreading out over the coral reef system,” he said.

“Before Hurricane ‘Iniki there was plenty of ground cover in Olokele Canyon but the hurricane blew away all the leaves on the trees allowing the sun to bake the top soil,” he said. “The leaves didn’t grow back for a month and during that month the water deliveries fell off 40 percent but gradually recovered as the leaves returned. Forty percent from 70 million gallons is significant in that the rain, rather than being soaked up by the soil, probably fell on hardpan and took a great deal of top soil into the ocean.”

Two years ago Robinson started a reserve on his land and decided to test his hypothesis that a severe amount of soil was being lost with each rainfall. There were a few people who argued the erosion was a natural process with nothing to be concerned about.

“There is a small red erosion patch on Makaweli ranch land and the drainage from that erosion patch funnels through a gully onto my property,” he said. “Forty years ago there was almost no erosion in the area of the patch. Today there is around five to seven acres of bare hardpan that continually drains directly into a little gulch on my property.”

So in 2007, Robinson decided to try an experiment.

“I said, ‘OK, I’m going to put some little dams in and see how much soil I can trap this winter,’” he said. “So I put in one concrete dam and since I was going to introduce some native plants along the gully, I cut down some guava trees to make room for the rare and endangered species, and threw the guava cuttings into the gully.”

Robinson theorized that after a few years he would get a few inches of soil built up behind the concrete dam and that would fill up the water ravaged gulch.

“However, upon returning to the dam I discovered five feet of soil had accumulated and the gulch was filled to overflowing even though it had been a rather dry winter with only a few rainstorms,” he said. “In addition to all this the sticks and branches I threw into the gully also filled up with a few feet of soil. This was at the end of winter 2007 and infinitely worse than what I had originally conceived. Suddenly I began to think, ‘What would happen during a really wet winter?’”

The plan

Robinson looked into the faces around the table and continued, “Before the winter rains come this year, I will have a much bigger experiment prepared with impartial observers to measure the depth of the gulches. After the wet season is over we will all return to measure it once again.”

The location is surrounded by Makaweli ranch land. Some 40 years ago there was very little soil erosion until the combination of cattle and pigs proved too much for the slope, he said.

“Once the erosion became serious it sent water rushing through some gulches that are now six- to eight-feet deep and this is only within the 40-year span,” Robinson said.

Robinson said if some useful data can be gathered out of this experiment it might shed light on red earth patches throughout Hawai‘i.

The conservation team packed up its gear and caravanned up the road to Keith and Bruce Robinson’s reserve, making their way past locked gates and rolling through muddy roads filled with dirty rain water.

As the line of four-wheel-drive trucks snaked their way up the dirt road to Keith Robinson’s reserve, Riggles shared his thoughts and opinions about erosion and the impact Kaua‘i will eventually face.

“On all the islands whenever we see red patches of dirt we know it’s contributing sediment into the ocean and reef systems,” he said. “There is one approach to reducing this is and that’s to keep the ground covered.”

Riggles broke conservation down into the three Cs: Cover — creating ground cover with grass or trees; Contouring — preparing the soil, planting and cultivating crops around a hill rather than up and down the hill; and Carbon — organic matter that acts like a sponge in the soil to help absorb water rather than allowing it to run off.

At the first stop along the way, Robinson laid a set of photos on the hood of his truck displaying the before and after affects of open grazing by goat, pig and cattle. He pointed out a small red erosion patch on a Makaweli site that funneled rain and debris onto his land.

Twenty minutes later the trucks came to a final stop and everyone set out on foot carrying buckets, machetes, chain saws and various tools. The crew slowly worked their way up the trail making one or two stops to take pictures of the concrete dam and the gullies along the way.

When they finally reached the area hit the hardest by the runoff, the team began the task of measuring and documenting the gully at different points. Depending on when the next rainy season ends, perhaps April or May, a second measurement will be taken and the results will be compared to determine the next step.

Who cares?

When asked why anyone from say, Lihu‘e or Princeville, should care about this experiment, Riggles said, “Ultimately, it’s about sustainability in both local food produce and recreational resources.”

A few of the conservation agents present agreed that losing precious top soil will seriously affect farmers who will find it increasingly difficult to raise crops.

Plus, the red dirt continues to flow into the ocean and reef life is continually being contaminated. This affects the lives of fishermen, they said, and the brown water could dissuade visitors from returning.

The state Department of Health is concerned about runoff and its affects on coral reefs. For more information, visit

“In 1980, I used to fish for akule down by the Waimea river mouth,” Robinson said. “Over the years the sediment from the runoff drove the akule away because they don’t like muddy water.”

Seeking a solution

“The key is to find a sustainable management strategy,” Riggles said.

There are two elements at work causing erosion. The first is natural. Sun and rain break down the soil.

The second is man. The pigs, goats and cattle that humans brought feed upon the plant life. This creates a hard pan area that undercuts restoration.

“Nature should best be left alone. However, manmade problems can be addressed and hunting is one legitimate tool to manage goats and pigs,” Riggles said.

Robinson said hunting, though vitally useful, has a few of issues that need to be resolved.

Liability is one. Illegal drugs are another. A third is ensuring the hunter is responsible for not introducing harmful plants into the ecosystem.

For example, Robinson said a hunter was allowed onto his reserve but he neglected to clean his horse’s tail which held and later dislodged invasive plant seeds that spread though a valley.

“Those patches of weeds had to be painstakingly removed,” he said.

Muraoka said a group of volunteers dropped bales of pili grass on Kaho‘olawe, an island used by the Navy as a bombing target that was also decimated by goats.

The pili bales were brought to propagate seeds in the soil to revegetate barren portions of the island. Pili grass is a hardy, drought-tolerant native grass that has a long hair on each seed that’s called an awn. When the seed is dry, the hair is straight but when it becomes wet the hair corkscrews into the soil to stop the soil runoff.

If the experiment is successful, Robinson said the next step is to enter into a discussion on responsible land management.

“This is important for Kaua‘i’s watershed problem and for future generations,” he said.


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