A new proposal to fix some of the problems at this park on the Tacoma Narrows led me to swing by for a quick stop last week. I was also hoping to see how the stream mouth behaved during a heavy rain, but unfortunately the rain had pretty much stopped by the time I got there. The flow from the outfall structure was way above the normally low levels, but far from what I'd call exciting. Exciting would be if the pipe was full and mud and trees were washing across the park - but that might have made driving down the ravine a bit tricky.
The concrete stream mouth, which marks the end of a pipe a couple hundred feet long (tough for a salmon), acts like a groin to the northerly drift, contributing to the ongoing erosion problems on the north side (but making a nice little sandy beach on the south side). The stream leads to another problem, too. During higher flows at lower tides, the stream erodes the upper beach, carrying sediment down the profile, which may also contribute to downdrift erosion.
This is the"logs-in-bondage" site described two years ago (Narrows Park). Ideally, it would be great to remove the concrete structure and daylight the stream, but this will require a considerable rethink of the park. Meanwhile, folks are looking at modifying the outfall structure slightly, relocating the big logs higher on the profile, and patching the worst of the erosional scars.
Fort Popham is located at the mouth of the Kennebec River. This is a heavily indented bedrock coastline and the river has no exposed delta, but the lower estuary and river mouth contain large submarine sand bodies and exhibit a complex pattern of sediment movement between the estuary, the offshore, and the adjacent beaches.
The beach wraps south around the point to Hunnewell Beach and then west toward the State Park. This shoreline undergoes large cyclical patterns of erosion and accretion, in part related to the offshore dynamics and complicated by the shifting mouth of Morse Creek to the west and its position relative to the somewhat ephemeral tombolo that forms between the main beach in the park and Fox Island. At this time, the dunes at the Park are eroding back, forming a distinct scarp with old dune surfaces, buried logs, and park debris (from how long ago?) poking out of it, but the beach to the east towards Hunnewell, where so many homes were threatened in the past, is doing fine. At the east boundary of the park, riprap protects the few cabins that are near the shoreline.
(the substance of this is gleaned from overly quick scans of stuff by Duncan Fitzgerald, Joe Kelley, and others. If you are writing your report on erosion at Popham, you should go to those sources. Don't cite me, I'm just a tourist from Washington State making some informed guesses!)
I came here with friends on Senior Skip Day in May, 1976 – when my interest in the beach was simply as a distraction from the final days at Brunswick High. Big events in the beach's history, like the 1978 Northeaster that dramatically altered so many northern New England beaches, didn't catch my attention as they might today.
I couldn't help but be impressed by the level of effort that has gone into protecting this little point of overbuilt low land. A new seawall on the south side and a lots of new rock on the north. Apparently, the Corps has helped save another community from judgment (poor judgment?). It provides good pictures for those "adaptation to sea level rise" talks we keep getting asked to give.
The islands in Boston Harbor are glacial knobs and drumlins, formed of outwash and shaped by the ice. At one time, this must have been paradise for eccentrics who sought out eroding bluffs and gravel beaches and the more exotic classes of barrier landforms. It probably still is if your eccentric has a boat, a good map, and a stomach for granite revetments. The revetments are both elegant and extensive, transforming miles and miles of outwash bluffs and mixed sand and gravel beaches to monotonous cliffs of paleozoic gneiss. Don't get me wrong - if you're going to bury a beach under big rock, it is far better to use use nice rock and stack it carefully than to dump poor quality stuff in pile of rubble! Looks better, lasts longer, is easier to walk across.
Deer Island is another island wannabee - partly connected by tombolo to the mainland (or at least to Winthrop) although at some point historically there was a cut (or gut, locally) between them (in this case, Shirley Gut, which later became Yizzell Beach). Deer Island is the site of a major sewage treatment facility - apparently a centerpiece of the effort to clean up Boston Harbor - and is surrounded by a park and trails. And oh, did I mention, lots of rock.
But there are gravel beaches, too. In several places, the configuration of the shoreline allows for pocket beaches. Some of the pockets are deeper than others, but they go to show that beaches are perfectly possible, even where wave energy is high. Here they collected mussel shell and provided a nice place to get down to the water.
Winthrop lies just northeast of Boston. Like so much of the waterfront in Boston, it probably began as an island, tied together to the rest of Massachusetts by a tombolo or barrier, and now linked more substantially with bridges, causeways and fill. I suppose the west side was once an eroding bluff of glacial outwash, but now it's mainly large (but not excessive) homes, concrete walls, and great views of Boston beyond the runways and activity of Logan. A series of street ends provide access to the shore.
There is a lot of marsh grass on what's left of the beach, though it's distribution is irregular and I wondered if it reflected the presence of favorable substrate beneath the gravel. The grass often quit a few feet short of the seawalls, leaving a strip of unvegetated gravel. Is this the upper limit of the grass as imposed by the tides, or is it the result of waves reflecting off the walls?
