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This is the third in a series of articles about how landowners can harness “The Power of Plants” to maintain shorefront property while following the rules established to protect these environmentally sensitive areas. The Harpswell Conservation Commission is organizing the series, with articles by local experts.
The author of this article, Sven Pulsifer, lives in Cundy’s Harbor, where he owns and operates The Island Arborist LLC.
Harpswell’s 216 miles of coastline, more than any other town in Maine, attract droves of visitors, but require legal and ethical responsibility to protect the marine environment. What flows off the lawn or out of the woods ends up in clam flats, estuaries and coastal waters. The headline-grabbing stories of Maine ponds taken over by algae are bemoaned as recreational fishing and water quality are impacted.
Similar runoff effects can be slower to appear in our tidal landscape, but are no less damaging in the long run. A recent commission formed by the Maine Legislature under L.D. 646 is studying how unmanaged stormwater can lead to clam flat closures, toxic chemical-contaminated fish, and beach closures. Nitrogen-heavy fertilizers can cause saltwater algal blooms. The recent PFAS spill in Brunswick is a somewhat extreme example of ocean contamination.
Because Harpswell lacks municipal stormwater systems like those in Lewiston or Auburn that flow into a river, the responsibility for stormwater management lies with the landowner. As required in shoreland zoning codes, responsible land management should slow down rainwater runoff and maximize infiltration, thereby recharging the local aquifer and reducing shoreline erosion. Thankfully, this isn’t a doom-and-gloom task, and fulfilling it can actually add to the aesthetics of a property while reducing the need for landscape maintenance.
How much water gets retained on-site is determined by ground cover, slope and area, and each can be modified. Each surface has a different coefficient of runoff that can be used to calculate the volume lost in a rain event: pavement (0.70-0.95) sheds almost all the water that falls on it, while woodlands (0.05-0.25) shed the least, depending on soil type and slope. An inch of rain over an area measuring 50 feet by 50 feet amounts to about 1,550 gallons of water, which preferably ends up back in the aquifer that supplies our drinking water. Shrubs, trees, forest duff and downed woody material are essential for shoreline and aquifer resilience.
Clay-heavy lawns leading right to the ocean are prime candidates for runoff management. Creating a wide buffer of low shrubs and mulched perennials will reduce long-term maintenance while maintaining water views and minimizing nutrient runoff. Increasing the area of improved water-retaining ground cover will be more impactful than having the perfect lawn with a small mulched buffer. On new sites, this is best accomplished by pushing the building envelope back more than 75 feet from the shore and minimizing lawn area.
Another effective and low-expense technique for steep banks is laying logs or brush along a slope to act as a berm. The berm can be backfilled with woodchips or left as is. Rainwater carrying silt, leaves and conifer needles will dam up against the log, creating a carbon-rich sponge. As fungi colonize and create a mycelial root-like mat, the benefits increase over time. Such berms can be created using already downed material from storm damage or when trees are removed. Some or all of the material should be cut to lay flat and tucked along the shore bank.
Rotting logs also provide habitat to red-backed salamanders, whose prey include ticks. One study found that logs with a diameter of at least 14 inches are needed when used in an exposed setting. These amphibians are a favored food of birds, including the hermit thrush.
Maintaining a stretch of shoreline that aids clam flats, waters and wildlife can be simple, affordable and impactful on any scale with modest work and a basic understanding of how best to manage stormwater runoff. The most tasteful views and waterside landscapes are created through a mix of structure and plants that one can watch through the seasons, framed by and tapering into the surroundings.
