In 2013, Maryland used dredged river sediment to rebuild Battery Island to about 11 acres; crews planted about 60,000 native plants as the island was restored

For decades, wind and waves wore away at a small artificial island near the mouth of the Susquehanna River, until a 2013 dredging project rebuilt it to about 11 acres and gave its historic lighthouse solid ground again. It is a modest engineering story, but it suggests one way to address a disappearing coastline: using sediment dredged during routine river channel maintenance. The island, formerly part of Susquehanna National Wildlife Refuge, is at the mouth of the Susquehanna River in Harford County and is locally known as Battery Island. According to the US Fish & Wildlife Service, clean dredge material was used to raise the island to roughly 11 acres of upland habitat in a horseshoe shape around existing land. For those who believe that coastal restoration often requires costly imports of construction material, here is a case study where it could be found directly in the river channel.

A shrinking island and its fading lighthouse

Before the restoration, the area faced serious problems. Wind and wave erosion had shrunk the island to under an acre, far smaller than its historical land area. The location formerly supported a shad fishing business and afterward, a fish hatchery. Remnants of a lighthouse also remained at the site. The lighthouse itself dates to 1851, according to the National Oceanic and Atmospheric Administration's National Centers for Coastal Ocean Science. By 2011, little high ground remained on the island. The undertaking wasn't driven only by environmental concerns; the U.S. Army Corps of Engineers also needed to dredge the navigation channel adjacent to the island.

Turning dredge spoil into new land

The construction process was straightforward. According to the U.S. Army Corps of Engineers, Baltimore District, the dredging project included removing roughly 200,000 cubic yards of sediment from the Susquehanna River channel and placing it without containment structures, forming a new 11-acre island. NOAA's report provides more detail on how the sediment was placed. The sediments were arranged into a tall U-shaped berm that was 125 feet wide and extended seven feet above the mean lower low water, with a gently sloped outside surface and a steeper slope facing the original island. The material included medium-grained sands, and the construction process included no seawall or hardened shoreline. This suggests that climate infrastructure can also rely on sediment and habitat restoration.

Sixty thousand plants against erosion and geese

Returning sediment to the island solves only part of the problem. Sediment moves fast when nothing holds it in place; so planting came next. About 60,000 plants were planted on the island, with various species selected for different elevations. Tasks included not only creating habitats for black ducks and Caspian terns but also preserving the rest of the lighthouse. The work did not end there. Visitors' feet and geese grazing had damaged so much vegetation that restoration continued in the fall of 2013, with the addition of 1,600 more plants and the seeding of three more acres. The Corps' own report notes the project used eleven plant species.

What the island looks like now

The island was not the same size in the end as it was from the beginning. On the website of the NOAA National Centers for Coastal Ocean Science, as of December 2024, this island was 16 acres in a plot of land by 2014, the year of completion of its creation; about an acre of this new island was lost during the construction because they planted more grasses and seeds in the fall of the same year. Erosion at the northern and western ends in 2015 reduced the island's area to about 10 acres, and since then it has remained approximately the same size. Moreover, an elevation survey of the island conducted in 2023 found that the crest of the central ridge is about 1.5 feet lower than initially intended, likely because the slopes slid down over time. However, it remained above the mean high-water level.

Meanwhile, the switchgrass planted in 2013 has survived a decade on these elevated grounds, although the parallel rows in which they were planted can still be seen from above. Trees grew naturally, including locusts, oaks, sycamores, and willows, and recreational boat traffic was heavy on the island. The result differed from the original design, but it created land where there was none before and helped preserve the lighthouse.

What this Maryland island tells US coastal towns

This is one example of a strategy the Corps of Engineers has also used on islands like Poplar and Swan. Battery Island offers a small-scale, well-documented example of combining dredging with habitat restoration. But it did keep one small island, and the lighthouse atop it, above the waterline for years longer.