Much of the outer portion of this area is made up of low-rise residential development.
I think here "development" is used to describe a group of new buildings that have all been planned and built together on the same piece of land. According to the dictionary, it is a countable noun when it is used as the meaning. So Should the "development" in the sentence be corrected as "developments". Why? Why not? Thanks！
As @FumbleFingers points out either is acceptable. I think the distinction is very slight but present and depends on the point the author was making.
If he had used "developments" that would have called attention to the fact that there are several different developments that make up the outer portion of the area. I would have used developments, therefore, if my point was about the fact that these multiple independent developments ultimately cost more than if a single developer had been contracted to develop the whole area (for example).
In this case, though, I think the author was less interested in talking about them individually and just wanted to focus on them collectively. I think the author's point was in the low-rise nature of all the development in that area regardless of who had built which parts. Thus development was used.
