Saturday, March 05, 2016
This fall the rock revetment between the boat ramp and the pier was removed and that section of beach restored. I've included a picture of that beach at the bottom of this post, but this entry is really about a portion of the same beach another 100-200 meters to the south.
We think the wetland used to be much larger, extending to much of the area now occupied by lawn, but there's still a large marsh behind the beach at the south end of Bowman Bay. It collects runoff from a fairly large area, including Pass Lake up on the main road. It drains through a 12" culvert that exits on the lower beach. This keeps the normal water level of the wetland pretty low.
But this winter wasn't normal. It was wet. And the wetland was filling faster than it could drain through the pipe. A couple of weeks ago, the water level got so high it flowed over the berm creating a new outlet (or at least re-establishing the old outlet -- the history isn't well known). The trail crosses this spot on a bridge, so presumably there's been some history of a channel or of flow through this area before, although the structure normally seemed more like a boardwalk with hand rails.
As the rains diminish (really, I'm sure they will!), the water in the marsh will fall, and the new channel will dry up. Waves will push gravel into the gap and rebuild the berm across the outlet. But what's interesting is that there has been talk in the last few years of restoring a more natural connection between the wetland and the bay. The conditions of the past couple of weeks actually provide useful hints about how that might work. Maybe there is some simple replumbing that would allow the natural outlet to be the primary outlet, and relegate any pipes to more an overflow feature.
The photo below is of the main beach where the restoration work was done this fall. At the time, I posted about the site (Bowman Bay) and noted the steep scarp that had formed during a big storm that occurred right after the project was completed. This photo shows the scarp remaining, but it has been broken down by foot traffic and the beach in front has built back up, reducing the overall effect. Personally, I think this beach needs a few good high tide storms to cut that upper bank back another 10-15', dropping that big super-elevated log down a couple feet to a more natural position and creating a more natural berm for the dune grass to recolonize.