Evaluation of the Effectiveness of a Living Shoreline in a Confined, Non‐Tidal Waterway Subject to Heavy Shipping Traffic

Abstract

AbstractRiver bank erosion is a point of concern along navigable waterways because it increases the likelihood of bank failure. In non‐tidal and restricted fetch waterways, bank failure is mainly the result of extreme weather events and ship wave action. To counteract progressive bank erosion, nature‐friendly bank protection (a ‘living’ shoreline) has been installed in a stretch of the Lys (Belgium). It consists of off‐bank timber piling, which separates the fairway from the shallow water riverine environment, and a reed belt, planted at the base of the vertical cut bank. To evaluate its effectiveness, short‐term and long‐term field studies were carried out. The long‐term topographic survey did not reveal a clear difference in bank erosion rates between the surveyed nature‐friendly protected and naturally eroding embayments. Horizontal bank retreat could however not be linked directly to occasional flooding events and frequent ship wave action, although the latter's influence was inferred qualitatively. Based on velocity and turbidity measurements, the short‐term study pointed out the importance of an individual ship's wave action on bed and bank erosion behind the off‐bank timber piling. All ships were able to resuspend sandy bed sediments; yet, only a significant higher sediment volume was transported because of shipping traffic of the European Conference of Ministers of Transport (ECMT) classes IV and Va. If ship wave energy exceeded 45 Jm−2, silty bank particles were dislodged from the river bank. Although validation of the results by longer term assessments may complete the physical insight in river bank erosion, the study indicated that this particular bank protecting configuration does not provide sufficient protection against ship wave action and does not adequately prevent further bank erosion. Copyright © 2014 John Wiley & Sons, Ltd.