Storm aftermath - not as bad as it could have been

Wednesday, December 15, 2010

by Diane Hettrick

I am sensing a tone of relief from our cities and county in the wake of this last storm. Having over three inches of rain in 48 hours, into ground already full of water, could have caused serious problems, but didn't.

King County Executive Dow Constantine pointed out that the damaged homes shown in the media were not those which had been permitted or built in the last ten years.

“Policies to limit construction on steep slopes and protections for flood hazard areas are doing a better job of making our homes and neighborhoods safer and more resistant to damage from severe weather.”
Ducks enjoy the Cromwell Park storm retention pond.
Photo by Tom Downer.
Shoreline has been working for several years to solve and prevent flooding. Cromwell Park, which was completed this summer, was designed to hold storm water and prevent it from flowing into Ronald Bog. In previous weather events, Ronald Bog overflowed its banks and routinely flooded a section of homes to the south of the Bog. One year it even covered a block of Meridian Avenue.

Ronald Bog overtopped its banks but did not flood Meridian.  
Photo by Janet Way, courtesy Of Paramount Importance blog

This year, while the Bog filled to the brim, it apparently did not flood nearby homes. Incidentally, the City obtained old aerial survey photos of Shoreline and discovered that the homes by Ronald Bog with the flooding problems are built on an area which used to be part of the Bog.

Shoreline Public Works had 22 calls related to flooding.
"While this is not an insignificant number, it is significantly lower than what the City has experienced in the past during a major storm event. A number of areas in the City that historically had severe flooding issues did not have any problems with this storm."
Shoreline did a lot of work ahead of the storm which they feel minimized the damage.
"City crews prepared the week before with street sweeping, catch basin cleaning, and jetting of problem lines. City crews will continue to take preventative steps throughout the winter."
Lake Forest Park
LFP built a sandbag wall to keep Lyon Creek in check.
Photo courtesy City of Lake Forest Park

Lake Forest Park has a much more serious problem. The Towne Centre sits at the outflow of two watersheds - McAleer/Ballinger and Lyon Creek. McAleer Creek comes from the joining of streams flowing out of north Shoreline and Lake Ballinger. Lyon Creek comes from the watershed to the north, which includes Lynnwood. The two streams are within feet of each other at the Mall. The Sheridan Beach neighborhood is in the path of these streams as they head for Lake Washington.

Flooding in Sheridan Beach.
Photo courtesy City of Lake Forest Park
Several years back, when flooding was rampant and hillsides were sliding, 40 homes in Sheridan Beach either were flooded, or worse, filled with sewage when the sewer lines filled with storm water and backed up into the houses.

That year, several homeowners told me, it happened so fast they barely had time to react. They went outside to look at the flooding and went back inside to a home full of sewage.

This year, knowing the potential problems, LFP was right on top of it.
"Staff joined the fire department to go house to house in the Sheridan Beach area, informing citizens about the flooding and to check on people. There was one sewer back up and the City responded with a pump to divert flows from one trunk line to another."
Part of Bothell Way was underwater.
Photo courtesy City of Lake Forest Park

Solving the upstream problems is complex and will be very expensive. The Lake Ballinger Watershed Consortium, which has included representatives from five cities, two counties, state and county officials, has been meeting for several years, working on solutions for flooding and pollution problems in that watershed. There is no consortium for the Lyon Creek Watershed.

Lake Forest Park is applying for Federal grants for flood control for an estimated three million dollars.

In the meantime, here is the link for the LFP sandbag depot and emergency information.

A final word of warning from County Executive Constantine,
“As our population grows and the recession eases, pressure will build once again to allow new business, residential and infrastructure investments in the floodplain,” said the Executive. “We need to keep in mind that we've had 11 Presidentially-declared flood disasters since 1990, and we must continue to site development and infrastructure in a way that will be economically viable, environmentally sustainable, and safe."

Other articles of interest:
Impacts of Big Storm on Shoreline Area by Janet Way, Of Paramount Importance blog


Janet Way December 15, 2010 at 8:01 AM  

Dear SAN,
Interesting point about the Ronald Bog homes built on fill where former bog was located.

Another interesting concept on this point is the
"hydrostatic pressure" on this area. This is the water that comes from waters below the surface. That is, as the bog fills up, waters emerge underneath these homes and may fill basements and cause damage from beneath. This is also a factor many are familiar with from groundwater or springs emerging in their basements.

It is just one more impact of development and to those buildings built in flood plains or old wetlands. This is something important for the cities to consider when they permit development in the future.

"Groundwater" is a huge issue that is not adequately addressed by local or State codes, but should be.

Thank you.

Janet Way

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