Downhill Water Flow in Red Hook Brooklyn

In the attached map, GRASS 6.4.1 was used to produce a downhill flow map using local elevations.  The thin black lines shows the direction of water flow and the colors according to the legend show hypothetical low downhill water density flows in the area.  Areas east, near Prospect Park show stronger downhill water flows.  Hurricane Sandy was a sea surge event in New York City with relatively light amounts of rain.  The map shows that in case of large rainfalls, Red Hook is not in any danger and thus the flooding from Sandy was a sea surge.  Areas with more black lines shows increased downhill waterflows.