In the 12th century the mouth of the Oude Rijn at Katwijk had become blocked. To solve problems with incoming water, an organization was created that we can see as the beginning of the Rijnland water board. Since 1200, the crafts on both sides of the Oude Rijn have been discharging their excess water to the north, in the direction of the Spaarne and the IJ. Nevertheless, there was still a need for an extra discharge option at Katwijk. Since the early 15th century, plans were made to reconnect the Oude Rijn with the North Seato connect. In the years 1571-1572 a modest drainage was built. It turned out to function well, but the war conditions of the following years paralyzed the work of the water board. The discharge silted up and the cul-de-sac between the Oude Rijn and the dunes became known as the Mallegat.
In the 17th and 18th centuries several plans were made for a drainage near Katwijk, but within the administration of Rijnland these plans always met with resistance, especially from representatives of the city of Haarlem. They wanted to have the Rhineland load line run through the Spaarne as much as possible. The flowing water kept the Spaarne deep and that was beneficial for shipping. Only in the new political relations after 1795 could a city no longer hold back a work of common interest.