Seaweed and erosion

The Ministry of Agriculture has licensed three contractors to remove beach-cast seaweed from a five-kilometre strip of beach in Deep Bay.

The Ministry of Agriculture has licensed three contractors to remove beach-cast seaweed from a five-kilometre strip of beach in Deep Bay from Sept. 2014 to Feb. 15. Licences were increased from 600 to 900 tonnes or 180 kg of seaweed for every linear meter of beach. What does that mass of seaweed look like?

A curb sized garbage can holds approximately 30kg of fresh seaweed (well compressed). It would take 30,000 large garbage cans full of seaweed for 900 tonnes. Pack them in rows of six containers wide, one row every linear meter for the entire length of the five-kilometre licenced area. That’s what 900 tonnes of seaweed looks like. No wonder the government has had no meaningful scientific study for the past seven years.

VIU is apparently “studying” this issue, having tied 100 small bundles of seaweed with brightly colored ribbons in mid-December and tossed them in the water to determine seaweed drift. Unfortunately this two-month study is over on Feb. 9 before the seasonal change of wind direction that often redistributes beached seaweed during neap-tides and storms. Apparently the VIU students are having difficulty finding their bundles.

Seaweed floats when detached from the plant and forms large uniform six inch thick floating mats in water.  Ocean tides and breezes deposit seaweed along a shore only to re-float it at the next high tide, repeating the process well into spring. This process creates spongy berms of seaweed and gravels that buffer wave scouring. Changing wind directions can redistribute the loose seaweeds considerable distances — that is unless it is removed from the beach before wind changes.

Much of the five-kilometre beach now has little or no beach cast seaweed. Accelerated erosion has occurred in several areas, including along Shoreline Road where fill has been added to protect the road and water mains. An RDN-built beach access has been blocked off due to damage. The cushiony seaweed and sand berms that normally form along the beach are not there to buffer the waves. There is no seaweed.

The ocean water in Deep Bay turns a beautiful turquoise blue along the entire five-kilometres beach from spawning herring in March. The eggs attach to beach cast seaweed. Did the Ministry of Agriculture consult the herring?

Dianne EddyBowser

Parksville Qualicum Beach News