flash floods, plenty of rain and swales

It seems that most permaculturists when talking about earthworking and swales are typically addressing the problem of not enough rain.  I am however curious about the reverse.  Where I am planning to farm has a history of flash floods and rains just about every day.  Are swales useful to regulate regular rain?  or will this cause the soil to have too much moisture giving my trees and plants "wet feet"?

I don't see any reason why you can't design them so they drain excess water, while keeping soil in place, and providing higher ground for plants that want those conditions.

You can also use that available resource and plan to use lots of plants that like wet feet.

I would think that holding water and moving it slowly off ones land would retain more of the nutrients and soil, as compared with flash floods and rain rain rain.  If you have this type of weather then your plants are already used to having wet feet.  Carving up the land to control the water would be a good idea.

If you're talking about a larger piece of land, and not just a garden, then swales would probably cause problems,
simply because most of the moisture would end up turning the valleys into mud pits.

That's where the P.A. Yeomans' Keyline design system comes into play, which you can read about here:
http://www.soilandhealth.org/01aglibrary/010125yeomans/010125toc.html

If that's too complicated, I'm sure Darren Doherty would explain it to you at one of his workshops .

I'm thinking around this too.
Since the Brisbane floods I have really more than respect of flash floods, or any floods.
I don't understand why swales turn valley into mud.
At one point every storage capacity (swales, ponds, soil) is full and you must have a concept to get rid of the water, if  not you whole garden will float away, maybe with the house.
Eventually the overflow capacity will be at the maximum and everything is under water.
You might think on something to prevent water flowing into your property. Maybe with a flexible door to open and close it.

Swales are for small properties on even land. As soon as you have ridges and valleys, the water, even with swales,
will end up soaking the valleys because of gravity. As I said, you can read about it if you want.

I've just linked to something here that will probably grow quite well in a lot of water :
https://permies.com/bb/index.php?topic=6137.msg61815#msg61815

hügel wrote:
If you're talking about a larger piece of land, and not just a garden, then swales would probably cause problems,
simply because most of the moisture would end up turning the valleys into mud pits.

Wouldn't the extra water naturally form creeks in the valleys?  There are creeks in all valleys around here, even small ones.  We have two seasonal creeks just on our 20 acres.

Of course - if you have complete groundcover, and you don't let animals graze there, erosion will be quite slow.
I'm simply saying that a swale is inferior to a Keyline, unless the piece of land that you have land is small and flat.
Keyline is designed to stop erosion by redirecting rainfall evenly across the landscape, taking into account points of varying elevation - which swales can't.
To say anything beyond that is rather pointless, unless we get more details on the property in question.

What you're saying is swales can't move water up the landscape, whereas keyline can.  Is that correct?

That's the essential difference, yes; it counters gravity, which will always leave you with an uneven distribution of moisture.
Of course it doesn't pump water up a hill, it simply runs (it) away from valleys and towards the ridges.

how much rain are we talking, like A LOT of rain?

in situations like that i prefer terracing to swales. if you have the terraces in a keyline type system you can re direct water to holding ponds for use of water later on. or if you live in the tropics and you get insane amounts of rain, re direct it to some stream or river.

swales, berms brush piles or even crescents of rocks will slow down the water from moving downhill..so if you are getting erosion and want to slow the water down, sure..otherwise..if the drainage is good and you don't want the extra moisture..don't use them.