Tuesday, October 15, 2013

Ross Bay

I guess our little tour of southern Vancouver Island is taking on a bit more urban flavor - from Pacheedaht to Ross Bay. They're both spectacular beaches. But that's pretty much where the similarity stops!

Ross Bay is a large embayment on the south shore of Victoria. Dallas Road follows the back of the beach, protected by a large seawall. The seawall was built to protect the bluffs around 1912, following a particularly large storm that threatened to wash away the cemetery behind the southern portion of the beach.

Google Maps:  AERIAL VIEW

Around 2000, Victoria undertook a major gravel nourishment project, building a beach to protect the base of the seawall. The design involved several rock groins and an awful lot of well-sorted gravel (2-3 cms). The result is a remarkably steep beach (well-sorted, highly permeable gravel typically does this). This is probably a pretty durable solution to erosion and seawall damage.  And it's probably a more pleasant and more accessible beach with the seawall largely buried in gravel.

It is probably not a terribly great biological solution, at least when looked at through a narrow lens. The coarse gravel probably doesn't support a terribly rich biota, and certainty not the same biota that would occupy a sandier, less steep beach.  And the placement of the gravel would have covered whatever was there before. This is actually a pretty common debate about the use of nourishment - although the details vary from the Salish Sea to the Atlantic Seaboard.

Ultimately, I suppose you need to consider the alternatives. Maintaining the seawall presents its own problems - costs, safety, aesthetics - and is probably not doing the biology much good, either. Removing the seawall and trying to restore the beach of 100 years ago is probably not practical, for all sorts of reasons. Not only would the road and cemetery and any other development be lost, but the community would have to accept ongoing erosion and bluff retreat into the future. Nourishing the beach with a more natural mix of sediment would have benefits, but would also occupy a much larger footprint and represent a larger disturbance to the existing benthos, although in the long run, I wonder if it would be a more realistic option. Unfortunately, from an engineering perspective, sand is probably harder to keep where you want it and there might be a greater need to occasionally add more material.

These projects always have a lot more angles than I can represent in a simple blog post and in a setting like this, I can imagine there are some pretty strong opinions, too.  I guess if there was an easy solution, it just wouldn't be as interesting!

No comments: