Predicting morphodynamics for beach intertidal systems in the North Sea: a space-time stochastic approach
Bogaert, P.; Montreuil, A.-L.; Chen, M. (2020). Predicting morphodynamics for beach intertidal systems in the North Sea: a space-time stochastic approach. J. Mar. Sci. Eng. 8(11): 901. https://hdl.handle.net/10.3390/jmse8110901
In: Journal of Marine Science and Engineering. MDPI: Basel. ISSN 2077-1312; e-ISSN 2077-1312, more
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| Author keywords |
time and space variograms; intertidal barred beach morphology; stochastic modeling; space-time covariance model; data-based modeling |
| Abstract |
The ability to accurately predict beach morphodynamics is of primary interest for coastal scientists and managers. With this goal in mind, a stochastic model of a sandy macrotidal barred beach is developed that is based on cross-shore elevation profiles. Intertidal elevation was monitored from monthly to annually for 19 years through Real Time Kinematics-GPS (RTK-GPS) and LiDAR surveys, and monthly during two years with an RTK-GPS. In addition, during two campaigns of about two weeks, intensive surveys on a daily basis were performed with an RTK-GPS on a different set of profiles. Based on the measurements, space and time variograms are constructed in order to assess the spatial and temporal dependencies of these elevations. A separable space-time covariance model is then built from them in order to generate a large number of plausible future profiles at arbitrary time instants t+tau, starting from observed profiles at time instants t+τ. For each simulation, the total displaced sand volume is computed and a distribution is obtained. The mean of this distribution is in good agreement with the total displaced sand volume measured on the profiles, provided that they are lower than 45 m3/m. The time variogram also shows that 90% of maximum variability is reached for a time interval tau of three years. These results demonstrate how the temporal evolution of an integrated property, like the total displaced sand volume, can be estimated over time. This suggests that a similar stochastic approach could be useful for estimating other properties as long as one is able to capture the stochastic space-time variability of the underlying processes. |
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