<p>In order to defend low land against flooding in worst-hydrological and meteorological circumstances the present invention provides a method to reduce the wind setup in shallow water and a system of trenches in order to realize the method. As the wind setup largely contributes to a water level rise in shallow water in case of a strong onshore wind, a reduction of the wind setup provides that there is no need to heighten the present water barriers in response to a climate sea level rise.</p>
