desert berm plants

I just did some swale experiments where i had drought intolerant plants in the swale with some drought tolerant beans in the berm. I had to leave for 2 weeks so i put someone else in charge of the watering and upon returning the plants in the swale where thriving but almost all the soil in the berms had washed into the swales. This left all 11/12 bean seeds exposed and dead with only one sprouted and living. I'm thinking the person i put in charge of watering watered too much and too hard. should i try this again or would i be better off putting some different plants in the berm that'll hold it together better? if so which plants should i put there.

Im still wondering what i should do, I have tepary beans in there right now, but the berm dries within 5 hours of watering it. should i water more frequently, or should i but something else in the berm

Need a picture.  It sounds like you're overwatering, or like your earthworks aren't done right.  Is your berm uphill of your swale?  If so, it should be the reverse--swales should catch water flowing and your berm should be on the downhill side, and that's where your initial plants should be.

Various cacti and succulents might be good on the top of desert berms.  Most other things probably won't be able to take the heat and drought of a desert berm.  In the wet season you might be able to establish some drought tolerant native herbaceous plants.

If the berm keeps falling into the swale, the berm may be built too steeply.  Gradual slopes are more stable.