The https://welikia.org/ project to visualize the New York area before European explorers and colonists arrives is an incredible resource for anyone curious about the landscape of pre-contact New York.
Welika allows you to see how much more ‘pointed’ the lower tip of Manhattan was – jutting out into New York harbor – and how there were marshes, streams, ponds, and other water features in areas that are now part of Chinatown and the financial district.
Further north, in our neighborhood, you can see how Randall’s and Wards Island stood out, and were separated.
there is even an inlet or stream, paralleling East 108th Street to what is now the Harlem Meer in Central Park and then up (north) to the west of Marcus Garvey Park, and then over to 126/FDB.
In a zoomed-in view, the two hills in the yellowish marshland at the top of the screenshot are Big and Little Snake Hills. Big Snake Hill became Mount Morris. The smaller hill to the east (near Park/122) was leveled
All of this is to note that most of East Harlem is built on former marshlands or infill rubble. If you go to Lexington and 108th Street, for example, you can clearly see the depression that marks the former watercourse that essentially followed East 108th Street from the East River to Central Park.
The City has a great story on how a million-dollar report on the risk of flooding in East Harlem has not been released publicly: https://www.thecity.nyc/2021/1/25/22245050/de-blasios-1-million-flood-plan-shelved-and-hidden-from-high-risk-east-harlem. Indeed, a FOIL request for the report, resulted in a CIA level of redaction. It’s hard to believe that this amount of text on the topic of flood control needs to be hidden from residents:
But the De Blasio administration is afraid that something in there, beneath the blackouts, is somehow dangerous and something the public should not see.
Senator Brian Benjamin
Senator Brian Benjamin at work in Albany: