Tuesday, December 18, 2012

Storm on the Strait


Waves topping bulkheads!
December 17, 2012 STORM!  Monday morning Douglass and I awoke to a huge storm blasting down the Strait of Juan de Fuca from the West.  The high winds kicked up tremendous waves that coincided with high tide. The waves blasted into the bulkheads, and a large quantity of water came over the top into our yards. The water turned into a river running down the street and collected into one foot deep ponds in the lowest-lying lots (Tim & Kayana and Betty), and 3-6 inch deep water covering the other lots.  This storm was more intense than any I have seen at high tide. 


Bulkheads:

Some bulkheads did better than others.  Our bulkhead lost several pilings where the termites had been eating away at the cores.  Betty's bulkhead fared very well because they had a layer of landscape fabric and large cobbles directly behind the pilings.  Consequently, they didn't have much erosion, although the large cobbles were thrown 15 feet back from the bulkhead.  This is in contrast to Larry's lot next door, where pilings were backed by sand and there are now enormous pits of erosion where the flushing water took the fine particles away with it.  The piling bulkheads that did not have any landscape fabric, but had coastal dune ryegrass did a much better job retaining soil than those that were ryegrass free.  The extensive root system of the coastal dune ryegrass, combined with a plywood barrier, was most effective at retaining the soil in our lot even after the pilings had broken away.  

Another notable example of bulkheads working well could be found in Brad's tall rip-rap.  Brad's contractors did an admirable job because there is not any damage at all.  On the other hand, it is clear that the shorter rip-rap (found by George and Joe's) allowed in a great deal of higher energy water with every wave.  If that bulkhead had been built one course higher, it would have functioned much more effectively at breaking up the wave energy. The rip-rap bulkheads by Ralph's had a great deal of erosion behind them, and the foundation rocks have dislodged.

The one bulkhead that has been set back from the others (Cheryl) has functioned very well in previous, lower intensity storms.  In this storm, it was no more effective than the others.  Cheryl had similar amounts of water over her bulkhead as everyone else.

All bulkheads were challenged when they contained boat ramps.  The gradual slope of the bulkhead is an invitation for water to flow up onto the land.  Many of the boat ramps have large erosion points on the east sides where the water flowed back out.  In many cases the concrete is undercut.

Lessons learned: 
1. Bulkheads do best when backed by landscape fabric or plywood.
2. Bulkheads do best when they have a healthy network of coastal dune ryegrass to stabilize the soil.
3. Bulkheads need to be high enough to deflect strong wave energy. 
4. Old, termite infested bulkheads are not strong enough to deflect high wave energy storms and must be replaced.
5. Boat ramps flood, so a path for receding water should be designed in.
6. There is no path for the water to escape once it comes over the berm and must percolate through the soil. Low lying lots bear the brunt of this. If those lots bring in fill for building, a similar event's saltwater will flow across the road to the hill-side ditch system. 



Septic Systems: 
We'll all want to have our septic systems pumped out.  They are all filled with salt water now, and this will kill the correct microorganisms that break down waste products.  The drain fields also got a good flushing out with salt water.  It was interesting to locate the ends of our drain field lines by watching for the bubbles emerging into the standing water. Everyone with mounds systems should be happy to know that the drain fields stayed clear of the standing water, but the tanks were usually underwater - so those should be pumped too.

Plants:
Most of my new landscaping (new grass and rhodies) is probably shot.  We'll have to see which trees will be able to withstand the salt shock.  Luckily many plants are dormant, so if we have enough rainfall this winter, some plants may make it.  Our experience with flooding down at Thompson Spit shows that many trees can take the flood once in a while, but if there is a repeated inundation, they cannot survive.  Salal, oceanspray, coastal dune ryegrass, gumweed, sea thrift, Oregon grape, some ferns, iris, daffodils, and pines should be ok.  

Community Boat Ramp:
The boat ramp looks like it fared just fine, but there are some enormous logs washed up on it that will have to be pulled off.

Beach Height: 
The sand height is unusually high on the beach side of the bulkhead right now indicating that a lot of sediment was deposited in this storm.  That makes sense because the water color of the crashing waves was amazingly brown.

Sheds:
Elevate them!