Local creek restoration underway

AWARENESS-Consultant David Magney and Debbie Bruschaber from Mountains Restoration Trust explain to visitors about the need to restore Dry Canyon Creek. In heavy rains, Dry Canyon Creek near the Calabasas intersection of Old Topanga Road and Mulholland Highway could flood, causing serious damage to power, gas and water infrastructure unless the creek bed is restored, environmental officials said last week.

This summer, the State Department of Water Resources, Urban Stream Restoration Program and the United States Army Corps of Engineers will assist Mountains Restoration Trust and the city of Calabasas with a project to improve the natural stream habitat.

The creek is too narrow at Headwaters Corner, which speeds the flow of water, said David Magney, president of David Magney Environmental Consulting. Magney is working on the upcoming restoration.

"This is particularly a problem during flood events," Magney said. When water moves through a creek too fast it doesn't percolate into the ground and it scours away at the sediment, eroding the creek's banks and leaving them unstable, he said.

DRIED UP-Mountains Restoration Trust representatives lead a tour along the Dry Canyon Creek bed. Plans are underway to restore the area ecosystem at Mulholland Drive and Old Topanga Road in Calabasas. The work begins next month. Trees, roads and power lines, which surround the creek, could collapse if water eats away at the banks, as has been the case for several years, according to Magney.

In the past, cement rubble has been added to the creek bed to slow down the water and help prevent erosion.

"It serves one function," Magney said. "It may reduce erosion, but it eliminates all habitat. And so water quality needs to be improved because there are no plants to help (cleanse) the water."

Magney said Dry Canyon Creek is not a fully functioning wetland. He said the waters run into the Los Angeles River, which leads to San Pedro Harbor, Long Beach and other areas. Creek waters also carry many pollutants to those areas.

A wetland will naturally cleanse water, Magney said. But when people develop projects around the creeks, create concrete floors, or force the creek into cement tunnels under streets or other facilities, the wetlands can't function properly.

Cement tunnels cause water to flow faster and do not allow the natural filtering process to take place.

"Many of the plants that grow in wetlands have the ability to absorb various minerals and chemicals, and through their own processes, they're able to change the character of those chemicals," Magney said. "In other words, (the plants) retain them in their shell tissue and/or break them down so they're no longer toxic substances."

Because the wetlands haven't been preserved and conditions at the creek are deteriorating, more pollution is making its way to the beaches, Magney said.

The restoration project

MRT and the city of Calabasas hope to slow the water down by expanding the creek.

"We're taking steps to avoid mass flooding by restoring the creek's natural flow," said Mary Sue Maurer, a member of the Calabasas City Council.

According to Magney, someone altered the creek behind Headwaters Corner sometime in the 1950s. The property owner, Magney said, must've relocated the creek to open up the property. But the alteration created a problem that now needs to be fixed, he said.

Beginning next month, workers will restore the portion of the creek that had been redirected in the '50s. They'll remove the rubble, widen the creek by contouring the vertical banks into gentle slopes, increase the quantity and quality of vegetation along the banks, and remove two stream crossings (underground cemented tunnels) to reduce flooding, erosion and the transportation of pollutants to other waters.

MRT expects to have all the grading done by mid-October.

A second phase of the project requires the expansion of the creek even farther, onto property next to Headwaters Corner. Mountains Restoration Trust is in negotiations to purchase that land or a conservation easement to do that work, according to Debbie Bruschaber, a spokesperson for MRT.

The restoration project will result in the removal of nearly 70 trees, said James Dean, an oak tree consultant for the city of Calabasas. The city and MRT will relocate most of the trees, Dean said. Plants and trees are expected to grow back within 25 to 30 years.

This project received state grant funding last year, according to Susan Woolam, an environmental scientist and coordinator for the project, which has been in the works since 2001.

Magney said a group would monitor the work of the project, and also the creek's conditions five years after the project is completed. The city and MRT will make additional adjustments to the creek if necessary.