SNOHOMISH — The levees flanking the Snohomish River appeared to be holding Friday, but there was worry whether that will last.
The levees, designed to let high waters spill over the top, can begin to weaken after sustained soaking, said Don Bailey, a commissioner for the Marshland Flood Control District. The district maintains one of the major levee systems in the valley.
“They’re just earthen berms,” said Bailey, whose 400-acre farm is along the upper end of the flood plain adjacent to Highway 9. “After a day or so of that torrent of water going over, they can fail.”
Water began flowing over the top of the levees Thursday afternoon. The river was running high and fast, and expected to be in a major flood stage through late Saturday.
Deep-rooted grasses on the levee help keep the berm from eroding. During a flood, that grass can start to wear away, Bailey said. Even when the water stops overtopping, there’s a risk of “boils.” That’s what happens when sustained high waters scour a hole into the lower part of the levee, or find a weak spot created by a burrowing animal and push through somewhere else.
Many of the farms in the valley can withstand slow rising waters, but a sudden break in a levee is a dangerous situation, said Don’s wife, Barbara Bailey.
“We can handle the water, but when the dikes break, we’re in trouble,” she said.
That’s just what happened during the record 1990 flood. Homes near the broken dike were inundated with water and knocked off their foundations. A section of Highway 9 was picked up, carried downstream and dropped into a field.
The U.S. Army Corps of Engineer plans to keep close watch on the levees, at least until today, said Rieta Kauzlarich, an intelligence officer for the corps’ flood team.
Through Friday, the flood-control earthworks in the valley appear to be working as designed. The exception was a stretch of dike along Ebey Island. It breached Thursday night. The Corps attempted a repair Friday, and a work party of inmates placed sandbags there to prevent more sloughing, Kauzlarich said.
On Friday morning, Don Bailey walked the levee near his farm. He said the recent cold, snow and subsequent melt has left the levee berms mushy.
“We were really surprised and pleased this morning,” Barbara Bailey said. “It looks like the levees overtopped and everything went according to the master plan.”
The Marshland Flood Control District covers 6,000 acres from Fiddler’s Bluff to Lowell in Everett. Landowners in the area pay $29 per acre each year to maintain the system, which not only handles flooding, but also funnels rainwater runoff from fields into a system of ditches. A pump station in Lowell moves the runoff into the river.
Snohomish County has five diking districts, two drainage improvement districts and four flood control districts. Before the 1990 flood, landowners bickered about the heights of levees and dikes, regularly building up the berms near their land to be higher than their neighbors. When the flood hit in 1990, levees blew in two spots along Springhetti Road and caused widespread damage.
After that, landowners met at the old Silver King Cafe in Snohomish and worked out a solution, Don Bailey said. It became known as the Silver King Agreement. Over the past decade, levees along the Snohomish were rebuilt to a uniform height so they would work in concert. Now when floodwaters top levees, everyone takes some water and that distributes the pressure evenly over the entire system.
“It took forever for people to stop fighting with each other,” Barbara Bailey said. “Now, it really works.”
The levees along the Snohomish River are at 32 feet above the river bottom, with the river level usually varying between 10 and 17 feet, said John Engel, public works supervisor for Snohomish County.
Levees and dikes function differently. Levees are made of earth and reinforced on each side with grass and plants to hold the soil and reduce erosion and the chance of a breach.
Dikes are built as walls and are designed to hold the water back.
Snohomish County mostly has levees but some dikes are located in the Stillaguamish Valley, especially in the lower reaches near Port Susan Bay, Engel said.
These are actually designed more to hold back sea water at high tide than to prevent river runoff, he said.
When water goes over levees upriver near Arlington and Silvana, it tends to run downstream and flood the plains south of Stanwood, Engel said.
Then the water runs over the tops of the saltwater dikes and floods the area. The dikes have gates in them, however, designed to let the water back into the river channel. This speeds up drying out when the water recedes, Engel said.
Reporter Debra Smith: 425-339-3197 or dsmith@heraldnet.com.
Talk to us
> Give us your news tips.
> Send us a letter to the editor.
> More Herald contact information.
