>> a small berm on your side of the road to again 'deflect' the runoff,
I agree with this, if it's possible, and also with "don't divert it onto a neighbor's yard".
Can you diver flow towards a storm drain in the street?
>> Could a french drain at the top of your hill be of help, perhaps?
There's two places a French drain or slit trench could help. One is near the top of your property, catching water as it flows onto your land, and encouraging it to find a slanting path down towards some better place.
That's really the key thing: to find a place where the wtaer can GO without anyone suing anyone.
Is there a slope anywhere
down from your soggy spot? Or even a slightly lower spot with good drainage? If you dig tranches or drains from your lower yard to this
lower spot, you can keep it moving and rapidly lower the standing water in your soggy spot.
You can also build your low spot
up. A raised bed with 12-118" walls might sit well above your water table even right after a rain. Just don't make your bed in the shape of a dike that will hold water back from flowing downhill!
One way to make a raised bed is to first drag aside and save the existing good topsoil from the site of the bed, and surrounding few feet. Also recover some topsoil from the slope below the bed, in slanting diagonals.
Then excavate poor soil and sub soil from those downslope diagonals and any other spots where you want a deep drainage ditch. If you have a clay layer over some porous substratum, one deep hole might drain water down faster than it runs off.
Use all this subsoil to build a deep foundation for the raised beds. Then replace all the good soil that you dragged aside, on top of your new raised beds. If you amend all the good soil and some of the subsoil, you will increase the volume of soil, giving you an even taller bed.
The diagonals where you excavated now form "low spots" that will turn into puddles after a rain, but prevent the roots in your raised bed from drowning. I dug a hole just 24-30" deep "below" a small raised bed, and it was big enough to let that bed drain out after light rain. It takes several days for water to perk down out of that hole, but it is enough to keep the bed's root zone above water in any but the wettest weeks.
I see that is called a "soak away".
http://www.hintsandthings.co.u...
If the diagonals lead down to some better-draining spot, water won't even puddle. But if they lead to a neighbor's yard and water runs off instead of sinking down into the subsoil, you may have trouble.
