Introduction
Coastal inundation produced in the emerged beach area during storms is an instantaneous process and quantitative measures of this phenomenon used to be scarce. However, video monitoring techniques nowadays provide frequent and accurate measurements of coastal inundation.
Figure 1: Planview image from Noordwijk beach, The Netherlands, showing coastal inundation.
Objectives
The main aim of this study is to quantify the inundation produced during severe storms at a sandy multiple-bar microtidal beach (Noordwijk, The Netherlands) using video monitoring. Furthermore, we demonstrate that the observed inundation is predicted reasonably well by a simple inundation parameter that includes a run-up expression, the wave conditions, the surge level and the beach foreshore slope.
Methods
The seven highest storm events between 1999 and 2005 affecting Noordwijk beach were selected using hourly time series of offshore wave parameters (height, period, direction). We identified storm events as periods of at least 30 hours during which the root-mean square wave heights, Hrms, exceeded 2 m and the surge level, η, (the difference between measured and astronomical water level) was larger than 0.5 m. The threshold for the start and the end of each storm was a Hrms less than 1.5 m and a positive surge level. Beach inundation for each storm event was obtained hourly by means of an Argus video system (Figure 1). The inundation parameter was calculated for each storm event using the wave dataset, an average beach foreshore slope and the corresponding surge level.
Results
Preliminary results have shown that beach inundation ranged between 10 m to 120 m during the analyzed storms. In general, this beach inundation was not homogeneous alongshore. The correlation between the inundation parameter and the measured inundation has shown to be reasonable good. Also, this correlation suggests that the temporal variations in inundation at Noordwijk beach are primarily due to variations in the surge level, and not in the run-up.
Future work
The next step is to model inundation during the storms studied using the open-source quasi-3D model XBeach and to compare the results obtained with the observations.
Links
The open-source quasi-3D storm model XBeach.
Coastal monitoring station of Barcelona ELB.
This project was carried out while the author visited the Department of Physical Geography, Utrecht University, funded by the CSIC through a JAE-predoc grant.
Please contact Amanda Sancho García for more info on this project or for more information about inundation in Barcelona's (tideless embayed) beaches, Spain.