Slippery slope

Shoring the sides of Morning Canyon should save houses from destruction by heavy winter rains. CORONA DEL MAR -- It looks like a bunch of chicken wire and rocks, but a project the city of Newport Beach is building in Morning Canyon means peace of mind for families with homes along the canyon’s rim.

The canyon has eroded dangerously over the last 15 years because of runoff from urban development, said Bob Stein, an engineer in the city’s public works department.

In the past, water running down the canyon carried loose sediment, which replaced any dirt that got washed away. But now that the land above the canyon is developed -- covered with rooftops and pavement -- there’s no fresh supply of dirt, so runoff just scours away at the canyon.

“When there’s no sediment, you erode the bottom,” Stein said. “When you erode the bottom, the sides start caving in.”

That’s what happened behind properties owned by the Wynkoop and Walton families. Until recently, a sudden torrent of rain may have had Chris Wynkoop wondering if his backyard pool would still be there next time he looked out the window.

After some haggling over who should pay for the nearly $800,000 worth of work, the City Council declared an emergency to allow the improvement project to start in October. If it hadn’t gotten underway this winter, Stein said the city might have had to red-tag the Wynkoops’ house.

“We knew that if this year was like last year [with heavy rains], we were going to lose some slopes and potentially a house or two,” he said.

The fix will include a total of seven structures called gabions, which look like three-foot-high wire baskets full of rocks. They’ll eventually be landscaped with native grasses and plants so the canyon will look natural and wild.

The canyon now consists of several flat areas that get successively lower, and as the water travels down them it resembles a series of waterfalls. The force of the crashing stream of water blasts away the soil; the gabions, which are filled with river rocks that won’t erode, will help absorb some of that force.

The project also includes a wall of wire and rock to buttress the slope on one side of the canyon. Construction of the second gabion began Monday, and the whole job should be finished in January.

Chris Wynkoop said he’s ecstatic that the project is bringing his 10-year battle with erosion to a close.

His family and their neighbors, the Waltons, have spent more than $250,000 on their portion of the work, though they hope to be reimbursed by the city for some of that. The two families are paying for the extra support needed at the bottom of their slope.

“We’re happy the city’s fixing the entire canyon, and it’s two birds with one stone,” he said. “It probably would have been impossible without the city going in there.”

Stein said the Morning Canyon project is the first canyon stabilization of its kind in the county and it could be a model for other eroding areas, including nearby Buck Gully.

Urban development caused more erosion than would have occurred naturally in hundreds of years, Stein said. The fix could last up to 100 years, and it can be deemed a success if there’s not a disaster during that time.

“You will know in the next rainstorm, when the slope doesn’t fail, that it worked,” Stein said.20051220irrss8ncDON LEACH / DAILY PILOT(LA)A backhoe operator piles rocks that will be used to limit erosion and protect homes along the creek in Morning Canyon. 20051220irrsroncDON LEACH / DAILY PILOT(LA)Workers in Morning Canyon clear debris while installing wire baskets filled with stone, which will reduce erosion during storms.