Use of GPS and X-Band Radar to track tidal currents around the shore parallel breakwaters at Sea Palling, Norfolk, UK

Sea Palling on the East coast of the UK has a series of 9 shore parallel rock breakwaters. The numerical model TELEMAC2D has been used to simulate tidal currents around the system to assess the tidal contribution to sediment budgets and transport pathways. Numerical simulations are particularly useful for identifying the important processes involved in a complex system such as these breakwaters and understanding how the breakwaters might effect the local coastal region. Models are classically evaluated using a number of measurement stations to calibrate and then check it is giving realistic results. It is important to assess both the spatial and temporal performance of a model, but this is difficult with a model having tens of thousands of nodes, based on only a few discrete locations. This paper presents a method using Lagrangian data to assess confidence that can be applied to model performance. Measurements were made by deploying drogues tracked by X-band radar or GPS receivers throughout the breakwater system during calm “no wave” and “no wind” conditions to ensure that only tidal effects were measured. Modelled deployments were made at coincident times and locations for comparison and model performance statistics were calculated. Evidence of a number of features predicted by the model were found, giving confidence to its performance. Radar drogues are cheap to make and data capture onshore reduces the risk of data loss. GPS drogues can be used in a wider spatial area, however their onboard data storage requires drogue retrieval for data download.