Historically, engineered structures such as seawalls and revetments were built to protect coastal banks from erosion and storm damage. However, these structures can cause serious problems along an eroding shoreline. First, they arrest the flow of sand from the bank to beaches and other properties along the shore—exacerbating erosion problems at these locations. They also deflect waves, increasing erosion in adjacent areas and ultimately undercutting the stability of the structure itself. In addition, these structures can alter groundwater flow and surface water runoff and destabilize the bank and adjacent areas. Because of these problems, the Massachusetts Wetlands Protection Act prohibits construction of most new engineered structures on coastal banks that serve as a sediment source.
For existing seawalls, revetments, and other engineered structures, plants can be used around the structures to help uptake water, control runoff, and buffer storm waves to help prevent further erosion and to protect vulnerable areas. Plants will also help beautify the area, provide wildlife habitat, and filter pollutants before they reach the ocean.
The landscape profile below shows a yard viewed from the house looking toward a seawall that has been landscaped according to the landscape plan for coastal bank with an existing seawall that follows. This plan incorporates a variety of native grasses, perennials, groundcovers, and shrubs that will enhance the property. The deep-rooting fibrous grass, switchgrass, was recommended to help control channelized runoff that could cause erosion. Pennsylvania sedge is used throughout the site as a substitute for lawn grass, as a durable erosion-resistant pathway to the stairway, and for low-maintenance accents in other areas of the garden. Native shrubs and perennials are used to screen the seawall, absorb stormwater runoff, and provide berries and shelter for wildlife. The plant list at the bottom of the page gives a complete list of all of the species used within the plan (as indicated by the appropriate plant icon).
Coastal Bank with Existing Seawall Landscape Profile by Betsy Rickards
Coastal Bank with Existing Seawall Landscape Plan by Betsy Rickards
|Plant icon||Botanical name||Common name||Height||Value|
|Perennials and grasses|
|Carex pensylvanica||Pennsylvania Sedge||6-12"||Low, clump-forming, grass-like perennial with pale-green arching leaves and a cluster of brown seed capsules high on the stem. The grass spreads quickly, grows well in sun or shade, and effectively binds the soil with its dense roots. (native)|
|Eurybia spectabilis||Eastern Showy Aster||1-2’||A purple-flowered, short-stemmed aster that is easily cultivated and makes a showy display in late summer. This perennial herb spreads and forms clones by rhizomes. (native)|
|Panicum virgatum||Switchgrass||3-6’||Valuable perennial grass with deep-rooted, rhizomatous roots, and a tolerance for both drought and moist soils. This grass is an ideal soil stabilizer. (native)|
|Shrubs and groundcovers|
|Ceanothus americanus||New Jersey Tea||3-4’||A deciduous shrubby perennial that grows in full or partial sun and average to slightly dry conditions. Cylindrical clusters of tiny, fragrant, white flowers arrive in the late spring and later turn to fruits. This plant adds nitrogen to the soil. (native)|
|Comptonia peregrina||Sweet Fern||2-4’||A spreading, colonizing nitrogen-fixing plant with slender upright stems with foliage appearing similar to fern fronds, which are fragrant when crushed. This shrub is useful as a ground cover for erosion control and species diversity in sterile, sandy soils. (native)|
|Myrica pensylvanica||Northern Bayberry||5-7’||A semi-evergreen, woody shrub with a thicket-forming character and aromatic leaves, flowers, and berries. This shrub is well adapted to coastal areas. (native)|
|Rosa virginiana||Virginia Rose||2-6’||A shrub with many spreading branches, thorny stems, and pink flowers that bloom from June to August. Virginia rose is good for attracting wildlife due to its edible rose hips and flower petals, and thick cover. (native)|
|Vaccinium angustifolium||Lowbush Blueberry||6”-2’||Hardy, low-growing deciduous, twiggy shrub with urn-shaped white flowers and bluish-black edible fruits that matures in mid- to late-summer. (native)|