Origins of the Dijkgraaf Family trees
You would expect the name Dijkgraaf to occur in the regions where there is a need for the occupation of dijkgraaf (see the Meaning of dijkgraaf) and that is also how it turned out to be (see maps below), except one which appears to have originated outside of the Netherlands, see Suriname Dijkgraaf Genealogy.
So far we know off five different Dijkgraaf family trees, plus we have a file of ones we haven't matched up to a tree yet, see Unlinked Dijkgraaf Genealogy. They are as follows;
South Holland Genealogy, this family has it origins around the Rotterdam region, including the districts of Voorne (Brielle), Putten (Spijkenisse) & Hoekse Waard in the province of South Holland
Delft Dijkgraaf Genealogy, also originating from South holland but a bit further north is the Dijkgraaf family that comes from the area around Delft.
Gelderland Dijkgraaf Genealogie, this family tree originated around the district of De Veluwe in the Gelderland province.
Zeeland Dijkgraaf Genealogie, this Dijkgraaf family tree originates in in and Zierikzee in the province of Zeeland.
Unlinked Dijkgraaf Genealogy, there are also people that have not been able to attach to one of the family trees above. These are included in this database. In here there are two family trees of the families of "van den(r) Dijkgraaf(f)".
Suriname Dijkgraaf Genealogie, this Dijkgraaf family tree comes originates in Barbedos and Suriname.
You can see the distribution of the names in the Netherlands in the below maps
1947 Dijkgraaf province distribution map from Database of Surnames in The Netherlands
This map made by www.familienaam.nl (site gone) and is based on 1993 telephone subscribers data.
Place the cursor over the map to see the names of municipalities (not all done yet)
2007 Dijkgraaf distribution map from Database of Surnames in The Netherlands