Operational monitoring and forecasting of wave run-up on seawalls

Abstract

In this work, a wave run-up monitoring system and a model for forecasting the wave run-up height on a seawall were developed. Electrical conductivity sensors were installed on the seaward slopes of seawalls to measure the wave run-up heights. The general packet radio service protocol was used to transmit the measured data in real time to the desired remote location. The Princeton Ocean Model and WAVEWATCH III were used to predict the water levels and ocean waves, respectively, by using the available wind fields. The empirical formulas recommended in the Coastal Engineering Manual (2011) and EurOtop (2018) were adopted to estimate the run-up height. The wave run-up heights were forecasted 72 h in advance and were renewed at 6-h intervals as new wind fields became available. The developed monitoring system and forecasting model were combined for operational monitoring and forecasting of wave run-up on seawalls. The wave run-up monitoring system was set up at three seawalls along the southwestern coast of Taiwan from 2013 to 2016. Consistency between the forecasted and measured wave run-up heights during typhoon periods demonstrated the feasibility of using the proposed method for monitoring and forecasting wave run-up heights. Furthermore, the multi-model ensemble approach was adopted to improve the unsatisfactory run-up forecasting performance during typhoon periods, and the forecasted run-up heights were eventually presented as a band with upper and lower limits as opposed to single values. The forecast results can be used to provide advance warning of possible wave overtopping and associated coastal flooding during typhoon periods.