Paull Tidal defence optimisation using 2D and 3D physical modelling

East Riding of Yorkshire Council is undertaking the Hull and Holderness Flood Alleviation Strategy: Phase 1 - Paull Tidal Defences. The flood alleviation strategy envisages embankments, revetments and walls offering improved 200 year protection against flooding to 1,461 residential properties, with 962 of these currently at high risk. The main defence includes an existing compound concrete seawall with a recurve wave return wall, to which has been added a 1m high glass wall to achieve the 200 year protection standard. As part of the performance assessment for these defences, it was apparent that there were no calibrated empirical methods available for predicting overtopping for this particular configuration. The most robust approach is to use physical model studies to determine the overtopping performance of the structure; especially as rudimentary predictions had demonstrated uncertainties of the order of ±x100. 2D and 3D Physical Models were therefore commissioned to investigate both normal and oblique wave attack. The seawall cross-sections were optimised in 2D and the results were used to construct the 3D model. 3D results showed local increases in overtopping at the seawall junctions / corners and at sections under oblique wave attack that could not have been assessed in 2D. Discharges were unlikely to cause flooding nor hazards that could not be managed for the worst conditions. It provided the owners with performance specifications and confirmation of the design not available by other means