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@en

A computer program for the calculation of the internal hydraulics of outfalls equipped with multiport diffusers is developed and applied to different geometric configurations. The program calculates the velocities, pressures, head losses and flow rates inside the diffuser pipe and especially at the diffuser port orifices. Possible geometries consider simple ports, high risers and more complex discharge configurations for the openings, as well as various supply pipe configurations. The calculation is based on the application of the continuity and work-energy equations between the ambient fluid at the discharge point and the effluent inside the diffuser pipe. Preliminary calculations show the sensitivity of the geometric manifold features. Further calculations may aim at the design and optimization of the diffuser structure under different ambient and discharge conditions. The overall design objective is a balanced flow distribution under most of the operational conditions with minimized energy losses. @en