07/10/2022
It's ! This will be a two-part post. Part two will be revealed next Sunday. For part one, a history lesson. It's a long one, so strap in!
Picture yourself driving into Provincetown from Truro on Route 6. The body of water to your right is known today as East Harbor. In the early 1800s, the East Harbor was a naturally occurring cove, deep enough to shelter Provincetown's fishing fleet during the winter and was connected to Cape Cod Bay through a 1,000-foot-wide inlet. This inlet effectively isolated Provincetown from Truro and other towns on Cape Cod.
Until the late 1800s, there was not a single road leading in or out of Provincetown – the only way to travel by land to the rest of Cape Cod was to first head north, traversing a series of tall, rolling sand dunes, and to then follow the thin strip of beach along the northern shore line, known as the "backshore". There was a wooden bridge installed at several points in time, but was routinely washed out by storms. Prior to the railroad's arrival in 1873, Provincetown was essentially an island and it relied almost entirely upon the sea for its communication, travel, and commerce needs.
East Harbor was then artificially separated from Cape Cod Bay and cut off from tidal flow in 1868, when a d**e was constructed across the inlet to facilitate the laying of track for the arrival of the railroad. The wooden bridge and sand road were finally replaced by a formal roadway in 1877.
The lack of tides changed East Harbor into a back barrier salt marsh lagoon. In the early 1900s, a real-estate developer named this lagoon "Pilgrim Lake". The lack of tides also caused salinity to decline from natural levels of ~25-30 parts per thousand to nearly freshwater by the time of the first documented fish survey in 1911. By this time, the native estuarine fauna were largely extinguished. Over time, the blockage of tides caused further ecological problems. The lack of tidal flushing deprived the system of salty, nutrient-poor, oxygen-rich Cape Cod Bay water and it became a stagnant freshwater pond. These conditions resulted in midge outbreaks, fish kills, and a proliferation of exotic species.
After almost 140 years of impoundment, no native salt marsh vegetation was left in or around Pilgrim Lake. Instead, the floodplain was taken over by a non-native cattail species and some highly invasive plants like purple loosestrife (Lythrum salicaria) and common reed (Phragmites australis).
After an oxygen depletion and fish kill in 2001, the town of Truro and the National Park Service began to explore options to restore the estuary. They focused on a drainage pipe connecting Pilgrim Lake to Cape Cod Bay. This ~700-foot-long (210 m), 4 feet (1.2 m) diameter culvert had been fitted with clapper valves to allow freshwater to drain out of Pilgrim Lake, but prevented marine tides from flowing back into the system.
To restore partial tidal exchange and to improve water quality, they opened the clapper valves, which have remained open continuously since November 2002. Despite limits on tidal exchange imposed by the pipe's small diameter, and the distance that it travels underground, they have observed a substantial response in the recovery of salinity and estuarine biota.
In June 2008, Pilgrim Lake was officially renamed back to its original moniker, East Harbor.
Read more about the story of East Harbor's restoration and stay tuned for next week's part two! https://www.nps.gov/caco/learn/nature/east-harbor-tidal-restoration-project-page.htm
Top, a map from 1835 shows East Harbor and its 1000 foot inlet, which allowed for natural tidal flow, but cut off Provincetown from the rest of the Cape. Below, a map from 1877 shows where the road was built up on top of the 1000 foot inlet to connect Provincetown to the rest of Cape Cod.
Image courtesy USGS