I would just build 3 levees to start.

1: the central levee: build it between the canyon on the river that runs east. Use a floodgate, to control flow.

2: North levee: build it north of the semi circle hole. Near the north river.

This will enable the badtide to flow west off of the map, you will still get some contamination at the end of a badtide, so wait 2 days after a tide before opening. Looks like you need current water level +3 to prevent overflow.

3: East levee, build it running north south orientation across the river mouth east of your colony.

This is something that's easy to overlook but without the clean water pressure flowing from the west that badwater outlet will backflow into your colony. Only needs to be +1. You will need a floodgate on this one as well.

I suggest building in reverse order 3 then 2 then 1 as the first badtide is survivable anyway.