The name of "de Nieuwe Hollandse Waterlinie" does not translate well into English, but if it did would be something like "the New Hollandic Waterline" except that "Hollandic" is the name of a dialect.
Hollandse means "of Holland" the region held safe behind the defensive inundation system along with Utrecht.
North and South Holland, two of eleven (now twelve)* provinces, have long been vastly richer and more-densely-populated than other parts of the Netherlands. They contain Amsterdam, the cultural and financial capital; the Hague, political capital, and Rotterdam, a major port at the mouth of the Rijn (Rhine.) All of these, along with Utrecht city, are part of the Randstad, a ring-shaped megalopopolis.
The Nieuwe Hollandse Waterlinie is "new" in relation to the original north-south defensive inundation zone which did not encompass Utrecht. It incorporated improvements in the technique and regulation until its obsolescence by air warfare.