Time-varying storm surges on Lorentz\u2019s Wadden Sea networks

Koen R G Reef,Giordano Lipari,Pieter C Roos,Suzanne J M H Hulscher

doi:10.1007/s10236-018-1181-5

Abstract

We present an idealized network model for storm surges in the Wadden Sea, specifically including a time-dependent wind forcing (wind speed and direction). This extends the classical work by H.A. Lorentz who only considered the equilibrium response to a steady wind forcing. The solutions obtained in the frequency domain for the linearized shallow-water equations in a channel are combined in an algebraic system for the network. The velocity scale that is used for the linearized friction coefficient is determined iteratively. The hindcast of the storm surge of 5 December 2013 produces credible time-varying results. The effects of storm and basin parameters on the peak surge elevation are the subject of a sensitivity analysis. The formulation in the frequency domain reveals which modes in the external forcing lead to the largest surge response at coastal stations. There appears to be a minimum storm duration, of about 3–4 h, that is required for a surge to attain its maximum elevation. The influence of the water levels at the North Sea inlets on the Wadden Sea surges decreases towards the shore. In contrast, the wind shearing generates its largest response near the shore, where the fetch length is at its maximum.

Highlights

Storm surges, the raised water levels induced by strong winds in coastal areas, pose a serious hazard of flooding and of loss of life and property
To gain confidence in our model, we first present a hindcast of the 2013 Sinterklaas storm here. We will check both the qualitative and the quantitative performance of our model, by requiring that the simulated water levels ζmodelled do not show large phase lags compared to the measured water levels ζmeasured and that the maximum water level during the surge lies within the 20% error range
The storm surge of 5 December 2013 has been simulated on both networks of Fig. 1b,c by applying the measured time signals of Fig. 2a as a time-varying and spatially uniform wind field over the basin

Summary

Introduction

The raised water levels induced by strong winds in coastal areas, pose a serious hazard of flooding and of loss of life and property. This is amplified by trends such as a growing population pressure, sea level rise, and increasing storminess projections due to climate change (Pugh 1987). This article is part of the Topical Collection on the 18th conference on Physics of Estuaries and Coastal Seas (PECS), Scheveningen, Netherlands, 9–14 October 2016 Storm surges have their greatest impact on shallow seas, in embayments, and on shores of low-lying lands. Lorentz, asserted the necessity of a novel investigation based on first principles (e.g., Mazure 1963 and Kox 2007)

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