 His switch from Catholicism to Calvinism would mean that Pourbus became more intimately entwined with the Protestant upper class; he had already painted the portraits of various prominent Protestants in previous years, such as the wartime mayor Jan Wyts and Calvinist leaders such as Pieter Dominicle.During this period, Pourbus was mainly active as a water management expert and engineer; his artistic output decreased as a result.In 1580, he painted a plan of the Abbey of the Dunes that was intended to serve as a guide for the reconstruction of the monastic complex after the war.