My newly planted scaevola has started turning brown. Maybe too wet soil? What an I add to the soil to minimize excessive wetness?

Adding organic content may help the texture, some. But can you build up the planting area, or redirect some flow?

You know... I actually had to tell someone to shut off his irrigation...
In all this rain...

Maybe plant something that likes the wet soil...

I doubt that you're going to fix the soil enough to grow something that doesn't like the conditions...

Right plant for the right spot...
You wouldn't plant cactus in a swamp...

I'm thinking some nice Louisiana iris or...curcuma or lobelia...
Tons of plants would be happy in that spot...

https://garden.org/frogs/view/...