Saturday, October 18, 2008
The central Maine coast consists of long rocky points and equally long narrow inlets - following a linear pattern related to a combination of glacial scouring and metamorphic fabric. Bailey Island is the tip of one of these long points, but is in itself formed of several rocky ridges. And these ridges have ridges - the rocks exposed at Land's End and the rocks exposed at Giant Staircase and the rocks at Cook's all have the same ne-sw grain as the larger landscape.
The beach out in front of the parking lot at Cook's hasn't changed much since I was a toddler (hshipman, for more personal history). The rocky ledges trap small slivers of gravely beach and accumulations of broken shell and, in this case, snail (periwinkle?) shells.
I guess this is where I got started on beaches - although I didn't appreciate its role in my career at the time. Reid State Park is located downeast of the mouth of the Kennebec River and like Popham on the west side, derives its sand from the broad river deposits offshore of the estuary. The main beach at Reid is One Mile beach, which lies between Griffith Head and Todd Point.
It's sort of a pocket beach, although this may be complicated by transfer of sediment to and from the offshore deposits. It's a barrier, with dunes separating the sea from the broad marsh and lagoon on the landward side. The lagoon connects through a narrow, bedrock controlled tidal race under the park bridge.
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.
Friday, October 17, 2008
As the hotels built in the dunes (what dunes?) get bigger, this little beach resort starts to look like Myrtle Beach or Clearwater. Or at least what those sleepy towns looked like a few decades ago? Ironic, since Old Orchard may have been a beach resort long before those towns were founded.
The amusement park had closed down for the season and the pier was preparing for another winter. Old Orchard has gone through several piers - some considerably longer than this one - which was built to replace the one destroyed by the 1978 storm.
There’s a lot less of this little beach community than there once was, a reminder that one should not buy property next to a jetty or build a town on the land that often accretes very rapidly after a jetty is built!
In the spirit of throwing good money after bad, the Corps is considering building breakwaters to somehow prevent the need for annual rebuilding of the seawall. Not that there aren’t plenty of examples of poor public policy in other arenas, but it’s reassuring to know that coastal erosion management provides some of the best case studies.
Revere Beach is a large swash-aligned barrier - sort of the northern counterpart of Nantasket on the south side of Boston Harbor. This place must be crawling in the summertime when Boston takes to the water to avoid the mugginess. This beach has been nourished in the past and I believe is in the midst of planning for more - but I don't have a good sense of the geologic factors influencing it's stability. There is an inlet at the north end that probably complicates the sediment budget.
I was struck by how low the area behind the barrier appeared - speaks to the vulnerability of these area during big storms and rapid anthropogenically-induced marine transgressions.
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 five sisters are five detached and segmented breakwaters located offshore of Winthrop Beach - on the exposed Atlantic Ocean side of the peninsula. There's a long history here, one that I have not tracked down, but it's apparent that they have been relatively successful at building, or preserving, a beach in their lee (this site warrants checking out in Google Earth). But the beach vanishes to the north, exposing old groins and leaving evidence of a trail of seawall failures. This was probably an exciting place during the February 1978 storm.
It would be easy to make the case for finishing what was started at this beach, although doing so would be very expensive (and the costs would probably not be born proportionately by the beneficiaries of the project). I also don't have any idea what the environmental and public trust issues are on this coast that might be an obstacle to dumping several hundred thousand tons of rock and dredged sediment into viable marine habitat.
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?
Thursday, October 16, 2008
My excursion out to Cape Poge took a little longer than I had planned, so I had to race to get to the west end of the island before the sun set. My plans for a long walk on the beach below the bluffs at Gay Head were thwarted by coming darkness, but the view from above was still impressive. And there was no one else there.
Gay Head is an unusual glacial moraine composed of Cretaceous sedimentary rocks (80-100 million years old) thrust upward by the advancing glacier during the Pleistocene. Which makes a pretty neat story, though it sounds like this place also holds many other interesting geologic stories (but none that I was able to deduce from my brief visit). The boulders on the beach below the bluffs are derived from till on the surface. The cobble berm on the beach to the south would also have been fun to spend more time exploring. Sand dunes behind, cobbles on the berm and being pushed into the dune grass, and a sandy beach.
Chappaquiddick is a small island connected at times to the rest of Martha's Vineyard by the barrier that extends across the southern side of the islands - but it breached during the Patriot's Day Storm (April 07) and remains open. Barrier beaches wrap around the eastern side of Chappaquiddick, extending north to Cape Poge, and then hooking west and south back towards Edgartown. Cape Poge itself is a glacial knob that is sometimes referred to as Natick Island. It is gradually eroding westward and has required the lighthouse to be moved several times. What a bizarre notion - moving a lighthouse instead of building a seawall around it.
Usually lighthouses find themselves creeping towards the sea as the shoreline recedes. Edgartown's Lighthouse has done the opposite - attaching itself to the main island over time as the shoreline accreted. It was built offshore to mark a broad shoal at the mouth of the harbor, with access provided by a trestle. Eventually the trestle was turned into a causeway. Complex sediment dynamics have since filled in much of the area around the lighthouse, forming a remarkably natural looking spit and back barrier wetland. As with many spots in this region, much of the change occurred during the 1938 hurricane - showing such power can build land as well as take it away.
I didn't see any oaks on the bluffs at Oak Bluffs, but have no doubt there may once have been. The low bluffs are now armored with an aging seawall (part of which collapsed this winter). To the south, towards Edgartown, the bluffs give way to State Beach, the long barrier in front of Sengekontacket Pond.
There's more Martha's Vineyard in subsequent posts and at hshipman.
Wednesday, October 15, 2008
Cominicut State Park lies at the tip of an elegant cuspate foreland near the north end of Narragansett Bay. Although the greatest fetch is from the south, north storms must play a significant role in maintaining this feature's shape. The tip of the spit narrows to form the long bar that curves southward out to the offshore lighthouse. At the base of the landform, on the south side, the beach forms spits across the mouth of a small stream mouth estuary - the name of road is "Old Mill" and it appeared the site had a long industrial history prior to the residential development that dominates today.