KANE'OHE — Over the years, pollution, poor water quality and erosion have taken a toll on Kawa Stream, but the city and Castle High School students are taking steps to combat some of the problems plaguing the waterway.

Next week dozens of students and other volunteers will plant 700 native plants on a slope that overlooks the stream behind the high school's Ron Bright Theatre. The goal is to control runoff from the slope into the stream that empties into nearby Kane'ohe Bay.

The city's Adopt-A-Stream program is sponsoring the project that includes classwork along with the field work for the Castle students.

"Basically what we're trying to do is look at the effectiveness of using some really simple erosion control measures there," said Iwalani Sato, city Adopt-A-Stream coordinator. "Specifically we're looking at erosion control matting and native vegetation. The goal is to compare some of the different plants that they'll be using in the area."

The plants selected are pohuehue, a beach morning glory; nanea, a ground cover; pohinahina, a shrub; and ahuawa, a sedge.

The students picked the plants and decided where to use them, said Kristen Mailheau, with Hui o Ko'olaupoko, a nonprofit environmental group that helped coordinate the project and prepare the slope along with the students.

"We gave them a general description of 10 different plants ... whether it's for filtration of pollution from water or grows like a vine across the ground so it would be some kind of erosion control," Mailheau said.

Students began the two-year project last year as freshmen and are continuing it this year. Their school work has them partnering with the city and Alu Like, which sponsored studies of the water quality in Kahana and Waiahole streams, which are more natural, and comparing them to Kawa Stream that has been heavily affected by development, said Sheila Cyboron, the students' science teacher.

"Erosion is the big issue for Kawa and my kids were clearly able to see that," she said.

Once the water quality course work was completed last year about 15 students decided to take the lesson further, volunteering for the Adopt-A-Stream program and working in the field to prepare the slope for the planting project, Cyboron said.

As part of this year's classwork the students will monitor the site to see how well the plants perform but they will also weed and maintain the area as part of their community service project, she said.

"They're getting a lot of community service credit and extra credit in science, so there's something in it for them too," Cyboron said. "I think they're learning quite a lot and they're taking pride that this is their project."

Sato, with the city, said the program is simple and aims to get people motivated to continue to help protect the environment.

"It really does get everybody to realize that it's everybody's responsibility," she said. "We all know that for us to tackle the nonpoint source pollution issue everybody needs to be on board and every little action really counts in terms of cumulative impact on the water."