I learned a while ago that much of the work done to reclaim land which is now known as Flevoland (2412 square km so one of the biggest reclamation projects in the world) was done during German occupation. I wonder if the Germans had any specific interest in this additional farmland for their own purpose(as the quest for lebensraum sent them into Russia or perhaps for strategic reasons) and if the Allies had any plans to disrupt the reclamation.
https://en.wikipedia.org/wiki/Zuiderzee_Works#Polders
I cannot find much about this, but seeing as the Germans had so many concrete (pun intended) plans for their conquered lands, I thought it would be obvious to have them think of a scheme!
A quick summary before the events in WWII is important: there have been plans to reclaim parts of the sea in Holland since the 17th century for various reasons. Besides an ideological motive (the Dutch conquering the sea / create it's own society) the two most important reasons seem to have been to stop the floods and to gain land for agriculture. You need sweet water for agriculture so to stop the salt water from coming in is a win/win.
The actual planning started in 1891 and started with the 'Afsluitdijk', this dyke (32km / 20 miles) cut off the inlet in Holland from the sea (creating a lake that would turn into sweet water) and was finished in 1932. The second part of the plan was to reclaim several parts of land (polders) in this inlet. The Noordoostpolder (north-east polder) was the second polder, construction started in 1937.
When the Germans invaded Holland in 1940, the construction was still ongoing. Nazi-Germany at first saw Holland as allies, fellow Germanic people and all that, and just like in WW I, Holland wanted to stay neutral. But later on the Germans feared the allied troops would enter Germany via Holland and decided Holland should be part of the German empire. Interesting to know is that, during the 5 day war, one of the few Dutch victories was at the Afsluitdijk (Battle of the Afsluitdijk).
Regarding the creation of the polders, because the reclamation meant more land for argiculture and the Germans needed the area for food supply (apparantly the Germans also admired the project), they wanted to finish the project - which it did in 1942 (there was however still a lot of work to be done to make the land suitable for agriculture)
Now the interesting part, during the occupation a lot of men in Holland were forced to work in Germany to support the war. However, an expection was made for laborors to work at the Noordoostpolder. If you had a special permit to work at the Noordoostpolder, you did not have to go to Germany. Obviously this permit (which had no fingerprints or photo) was popular and was widely used by the Dutch resistance. The abbreviation NOP (NoordOostPolder) became known as the "Nederlands Onderduikers Paradijs" (Dutch Hiding Paradise). The Allied forces also got wind of the large concentration of resistance members in the NOP. The desloate area became known as a place for Allied pilots to make emergency landings and the Allied forces dropped weapons twice to arm the resistance.
Eventually the Germans found out, In november 1944 they held a big razzia in NOP. 1800 workers were arrested and mostly send to Germany, most didn't return until after the liberation in may 1945.
https://www.canonvannederland.nl/nl/flevoland/flevoland/nederlands-onderduikersparadijs
https://www.canonnoordoostpolder.nl/ii-land/10-oorlogsjaren
https://isgeschiedenis.nl/nieuws/regering-neemt-de-zuiderzeewet-aan
https://geografie.nl/artikel/100-jaar-zuiderzeewerken-spiegel-van-een-veranderend-nederland
https://www.emmeloord.info/noordoostpolder/ned-onderduikers-paradijs/