Question
I live in Northern New Mexico.  My home has a "natural" arroyo running through our property.  As any arroyo, it drains rain water during our heavy monsoon storms.  We use cobble-stone for water drainage to prevent water spillage onto our neighbors property, per city building codes. Our problem:  We get a large amount of sand/silt deposits on our cobble-stone when we it rains.  We left the highest point of the arroyo without any cobble (approximately 1/3 of the arroyo's length) for several reasons:  1) this narrow section is pleached by native juniper trees, 2) it is comparatively steeper than the rest of the drain, 3) it is more aesthetically pleasing.  So, additionally, we get a large sand/silt deposit where the sandy portion of the arroyo meets the cobble stone.  Every year we have to remove this sand build-up on along both the cobble and the sandy portions of the arroyo.  City code requires us to keep this arroyo.  Part of this drainage is on the easement of our property, so we do not want to cement the "lower" (street end).  How can we minimize the sand deposits while maintaining rain water drainage?  FYI:  we do not have a problem with the arroyo handling the volume of water drained.  Again, our question is only regarding sand/silt deposits.  Thank you for any tips you might have.

Answer
Similar by what you are describing to the "dry streams" we will often build here in the Northeast to handle run off water and add aesthetic interest to a natural water course.

What you may be able to do is raise the cobbled portion by adding a metal screening to keep the stone off the base.  This would allow the silt to "drain" through and while it would have to be dredged out periodically, it should definitely limit the maintenance substantially.

Hope the idea helps and I would love to see photos!