Environmental consequences of ship-induced drawdown in shallow waterways

Much attention has been devoted to detrimental impacts of shipping on coastal and inland infrastructure recently. Yet, transport over water remains several times more energy efficient than alternative transport modes and therefore plays a crucial role in global energy efficiency and decarbonisation strategies. Understanding and predicting these impacts is thus essential for developing effective mitigation strategies where necessary. Among the main phenomena causing damage to estuarine and other inland infrastructure is the so-called drawdown, a part of ship-generated primary wave system, representing a local depression of the water surface induced by vessel motion, particularly evident in shallow or confined waterways. This phenomenon alters nearshore hydrodynamics and sediment stability, and the associated return currents can also mobilise or erode bed morphology. Moreover, rapid water level depressions and subsequent surges pose safety hazards to recreational users and swimmers in nearshore zones. Understanding the environmental implications of drawdown is therefore critical for managing sediment dynamics, bank stability, and public safety in intensively navigated waterways. Exiting research on ship-induced drawdown is reviewed, integrating shallow and confined water ship hydrodynamics, ecological impacts, and mitigation strategies. The analysis highlights environmental effects associated with drawdown-induced sediment resuspension and shoreline erosion and identifies knowledge gaps in predictive modelling and ecosystem management.