A massive concrete seawall constructed along the northern New Jersey coastline to shield a public highway and beachfront properties achieved its goal of protecting landward structures, but caused the complete loss of the sandy shoreline it sat upon. According to a coastal hazard report published by the United States Geological Survey (USGS), titled Coasts in Crisis (Circular 1075), the artificial wall deflected wave energy directly downwards into the surf zone. Over time, the intensified wave reflection scoured away the remaining beach deposit until the ocean reached the base of the concrete barrier, leaving no recreational sand exposed even at low tide. The findings show a long-standing environmental dilemma along developed barrier islands, where armouring the shore to defend fixed infrastructure often accelerates the erosion of adjacent natural habitats.
Deflecting wave power into the sand
The construction of hard coastal defences along New Jersey’s shorelines began as a response to severe winter storms and steady coastal retreat. Local authorities installed bulkheads, groynes, and seawalls across vulnerable strips such as Sea Bright and Monmouth Beach to secure coastal roads, utility lines, and multi-million-pound residential homes built on low-lying barrier spits. The USGS report notes that while seawalls successfully prevent ocean waves from overtopping landward properties, they do not reduce the energy carried by incoming sea swells. When waves strike a fixed vertical wall, their kinetic energy reflects downward and seaward rather than dissipating gradually across a sloping, sandy incline. This downward deflection creates intense localized turbulence at the foot of the wall. As the reflected water rushes back out to sea, it drags loose sediment away from the shoreline faster than longshore currents can replace it.
A vanishing coastline in Monmouth County
Over several decades of continuous wave impacts, the elevation of the seabed in front of the seawall dropped significantly. The USGS study documents how the natural movement of sand along the barrier island was interrupted, stripping away the upper foreshore. Eventually, the entire visible beach disappeared under high water levels, leaving ocean waves to break directly against the vertical stone and concrete barrier. Researchers at the USGS pointed out that hard engineering structures inherently change the dynamic equilibrium of coastal systems. By locking the shoreline into a rigid position, the seawall prevented the natural landward migration of the barrier island, a process that normally allows beaches to retreat and rebuild during periods of rising sea levels. Without room to migrate backward or sand to replenish the surf zone, the beach was systematically scoured away until only the wall remained.
The heavy toll of coastal armouring
The loss of the beach in Sea Bright and surrounding boroughs presented fresh economic and infrastructural challenges for coastal managers. While the highway and residential communities behind the wall remained structurally intact during routine weather, the disappearance of the sandy beach eliminated the first line of defence against storm surges. In natural coastal ecosystems, wide beaches and sand dunes act as shock absorbers, absorbing the force of crashing waves before they strike inland structures. Once the beach eroded down to bedrock or deep water, larger waves were able to strike the seawall with full force, increasing the risk of structural failure during major Atlantic storms. Furthermore, the loss of recreational beach access damaged local tourism, forcing state and federal agencies to intervene with expensive artificial replenishment projects.
Artificial pumps and sand bypass systems
To restore the eroded shoreline, federal agencies including the US Army Corps of Engineers eventually launched massive sand pumping operations along the Monmouth County coast. Dredging ships harvested millions of cubic metres of sediment from offshore shoals and piped the slurry onto the bare ocean floor in front of the seawall. Although beach nourishment temporarily re-established a sandy shore, USGS scientific assessments caution that such engineering interventions require perpetual maintenance. Because the underlying seawall continues to reflect wave energy during storms, the dredged sand is continuously pushed offshore, requiring regular re-application at significant taxpayer expense. The USGS report Coasts in Crisis concludes that while engineered barriers can successfully protect high-value infrastructure built close to the water’s edge, they frequently sacrifice the natural beach environment in the process, turning dynamic natural coastlines into permanent concrete embankments.
