One of the ways that costal cities expand is 'wharfing out'.
Wharves are built to provide more dock area, and then later people
come along and fill in the area between the wharves to get more land
area. Similarly, one of the ways houses expand is to build a porch,
and then later make it part of the house. Both of these are
expansion in stages, increasing the interface with the outside and
then descreasing it. A straight up expansion is also possible, but
going through the intermediate step of wharves or porches makes the
next step easier to picture.
(Read about city expansion in gaining
ground: a history of landmaking in boston and house expansion in
buildings learn, what happens after they're built. I really
liked both of these books.)
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