BTB Reader Randy Schmidt sent us these great photos, taken around 11 a.m. Saturday morning (Nov. 29), from the private access on the north side of Three Tree Point, looking north as bulkheads were being destroyed from logs and waves (click images to see larger versions/slideshow):
Big storms like this – combined with high tides – often batter the beaches and waterfronts of Puget Sound. Another similar storm four years ago ended up destroying the Three Tree Point home of Dane Johnson and Kathy Justin on Nov. 23, 2010 – read about their ordeal here.]]>
Wow! I can’t imagine living there without a bulkhead. Beaches with storms like this are what make Puget Sound Waterfront unique and awesome.
You don’t have to imagine it. Just look at the foreground where there seems to be a beach with drirftwood.. That beach has much less spectacular violence because it dissipates the energy naturally. The bulkheads reflect and amplify the energy directed at the beach. That is how they increase erosion of the beach and undercutting of the bulkheads and why we have the eternal quest to make bigger and stronger bulkheads.
Alternatively, our ever so knowledgeable ecology review for bulkhead installation and maintenance could discourage vertical seawalls and instead allow homeowners to create irregular and sloping bulkheads that would mimic the rough edge of a driftwood filled beach. This would, of course, entail “building” the toe (or base) of the seawall out beyond normal high-water line into the Sound – something practically forbidden under the regulations as currently written. I have watched various armoring schemes around the Sound carefully for only 10 years, but the same hydraulic principles apply world wide. Irregular toes for seawalls are far superior to the mandated continuation of existing vertical walls.
There is no mandate for vertical bulkheads and everyone I’ve been involved with on this issue knows that irregular bulkheads would be better (and none would be best). However, armoring farther down the beach would create more problems overall (which is why it is prohibited) and moving landward isn’t possible since our beach front property is so developed. We are pretty much stuck with vertical bulkheads.
I think a possible solution might be to borrow a relatively new technique from levy builders and anchor large woody debris up against the bulkheads with chains or cable. This would help dissipate wave energy, provide some critter habitat and not interfere with the littoral drift.
Lee, I agree that current codes do not mandate vertical seawalls. As you also point out, the majority of the current seawalls are of the vertical style and you agree that codes do not allow modification seaward of the mean high water mark.
However, you are incorrect in your statement that vertical seawalls amplify wave energy directed at the beach. Physics shows that passive reflectors (vertical seawalls) cannot “amplify” energy, they can only redirect (and may locally concentrate) energy. Amplification of energy requirers a energy input to the system, something a passive seawall cannot do. And current interpretation of codes does not encourage capture and retention of driftwood along seawalls, something that “best science” might support.
As for irregular seawall toes creating more problems on the beach, that is a matter of both design and opinion. Irregular toes do enhance splash zone habitat in a manner not unlike adding woody debris to the front of vertical seawalls. Please note that you assumed an irregular toe would not contain woody material, but as a design option would carry more frequent maintenance requirements in seawall construction, in addition to revised codes.
Hey B-Town Blog….Any pictures of how our new Seahurst Beach is doing ?
I checked out Seahurst Park Beach this afternoon and didn’t notice anything unusual – have you seen any changes?
thanks,
scott