Remember that each town--regardless if the coastline is on the left or right side--will have 20 acres, 5 across, 4 down. Only 12 acres are "full acres", and that means there are 8 coastline, or beach acres; ONE COASTLINE ACRE WILL HAVE A RIVER ACRE/waterfall. So that's one river acre. Four more acres are devoted to Re-Tail, the town hall, the train station, and the Event Plaza. Eight coastline, including the one river acre+four points of interest acres=12 acres. At minimum, 6 river acres can be in a town, and one river acre is with one coastline acre. Let's just say that the coastline and river/waterfall acre combine. Add the remaining 5 river acres to the 12 we have, and that's 17. Add the maximum 3 full empty acres, and you get the full 20.
Your town has 7 river acres and 2 full empty acres. One full empty acre is next to Re-Tail, in the corner, but it has a pond. The acre below it, with the campsite, is another full empty acre. The train station acre will always be in the middle of the northern part of town. It's in between the Re-Tail acre and town hall acre in your map. Next to the town hall acre is the coastline acre. In total, it's 5 acres across. The Event Plaza is in the middle part of the third row acres (where your waterfall starts), in the third column acres. The train station is also in the third column acres.
I hope this helped. If you want to mark out each acre, go to the top left corner of your map, and dig a 16x16 square. You should be able to fit 12, for the 12 full acres.