Manmade ditches in lowlands of New England Recently in travelling back to New England I discovered ditches in the lowlands/wetlands of the shoreline on Google Maps satellite view.  They are clearly man-made, but even with all the agriculture and fishing in the area, I cannot figure out the purpose of these.  I have discovered that they seem to be all over New England, but sometimes it's not a.
What is the purpose of the man-made lines that appear in all these satellite images?
An example image is below, but it is not very high resolution.  Here are some links that show the phenomenon:
Great Island near Old Lyme, CT
Near Stonington, CT
Marsh near Narraganset, RI
Goose Island near Old Saybrook, CT (maps view, not satellite, helps make the lines clear)
Near Marion, MA
they are drainage ditches intended to drain salt marshes.
They may be old and no longer maintained, it is impossible to tell for certain from satellite but it seems likely.
https://qsr.waddensea-worldheritage.org/reports/salt-marshes