are reporting that Israel is ordering Gazans to evacuate a three-kilometer buffer zone all along the border. The map is taken from the linked report. This appears to be intended to eliminate tunnel networks near the Israeli border and isolate Gaza further.
At the same time, however, if intended to be permanent, it will reduce the area of the Gaza Strip by nearly 40% of the total area of what is already one of the world's poorest and most densely-populated political units.
While it is true that the bulk of Gaza's population is concentrated along the seacoast, creation of such a buffer zone would concentrate the population even more, and require evacuation of the town of Beit Hanoun and other localities. See also here and here.