How do seawalls, jetties, and groins influence a beach?
Seawalls are shore-parallel coastal engineering structures that are meant to protect properties behind them, not the beach or sand dune system. They have been determined to harm the beach and sand dune system per the Coastal Sand Dune Rules (Chapter 355). About 50% of Maine’s sandy beaches are lined with seawalls. Seawalls inhibit the natural migration of the beach and dune system by providing a solid barrier which deters the movement of sand from the dune and beach. When a wave strikes a seawall, the energy of the wave is dissipated on the wall and reflected both up, and down, into the beach. This leads to the movement of beach sand offshore, into quieter water conditions. Wave action on seawalls can lead to a gradual lowering of the beach and loss of dry beach. Along many seawalled beaches, there is no dry beach at high tide. New seawalls and the extension of existing seawalls on beaches are illegal in Maine. Groins are shore-perpendicular coastal engineering structures. Groins are u
