Hm, yeah, I see what you mean. My idea was that the SW corner is a salt-water marsh caused by the East-to-West flow of ocean water -- the water rushes through the narrow channel and then overflows into the SW corner, creating a big marsh. The "river" and "tributaries" you see there are meant to be INFLOW, not outflow. Which I didn't really know how to indicate, given that it's kind of a ridiculous notion in the first place.

So that's not grassland, that's marsh. :/