Rehabilitation and protection of Colwyn Bay beach: a case study

Abstract

Colwyn Bay beach is undergoing a process of erosion. The present study aims at characterizing the beach dynamics and developing alternative solutions for beach rehabilitation and protection. The method applied to characterize the foreshore morphological evolution was the assessment of the shoreline evolution, the analysis of the foreshore 3D evolution and the analysis of cross-shore profile evolution. The sedimentologic contents of the beach were characterized based on the analysis of superficial samples. The hydrodynamic characterization was based on the analysis of the wave climate at three inshore points in front of the beach and of the tidal and surge levels. These data provided the necessary information for the characterization of the longshore transport and evaluation of the beach active zone. The first part of developing alternative solutions was the definition of the optimum long-term recharged beach profile, which, due to the high tidal range, was calculated based on the 2S-EBP method. The beach berm was designed to avoid direct wave action on the seawall existent at the beach backshore. For that, a morphodynamic model was applied to test the beach retreat under storm events. Finally, alternative long-term solutions based on a nourishment strategy were tested with two shoreline evolution models. Two initial alternative solutions of beach recharge with different grain size sand followed by six alternative solutions of beach recharge with sand retention structures arrangements were tested. The results, here qualitatively and qu