Central Austin sits on clay. Clay holds water, and most of the plants that survive our summers are the same plants that rot in a wet root zone. So a low bed beside a downspout is a plant graveyard regardless of what you plant in it.
Watch it rain
The cheapest diagnostic in landscaping is standing outside during a storm. Where the water goes, and where it stops, tells you more than any survey.
Grade, then drain, then plant
Usually a few inches of regrading solves it. Where it does not, a French drain to a daylight outlet does. Either is cheaper than replanting a bed twice.