Question
My neighbor has suggested filling in what is currently a valley between our two backyards so each of us has more level area to use.  Right now water tends to collect in this valley after heavy rains.  We recently had floods here in MA this past spring and the ground water level rose quite a bit filling in this valley a few inches deep.  It took a while for it to recede.  My question is whether it makes sense to lay down a perforated pipe before the fill goes in so the water will have an outlet.  Any advise would be appreciated.

Answer
Hi Brian,  You need to ask yourself a couple of questions...Where will this water go if the area is filled?
Will any "backup" on surrounding property?  Will the flow increase on lower properties?
If this is just a depression (equally high on all sides) where water accumulates during a rain and is absorbed into the ground, then filling it should be fine.  The runoff will follow the same course as the surrounding surface water.
If water is flowing from higher ground and exiting at one place, then pipes make sense. You are just carrying the same water to the same place, but if you condense the flow on either end, things change.
Legally you must accept the natural water flow from your uphill neighbor, just as your downhill neighbor must accept yours.  If you alter that, you can be held responsible for damages and fixing it, so use caution.
Without knowing the size of this area and the lay of the land, I would suggest you have a local engineer take a look at it before you do anything.
Here are some things to remember:
1.  Pipe condenses and accelerates flow.
2.  Pipe must be larger than you think you will ever need to prevent backup.
3.  Small pipe clogs easily.
4.  In many areas a permit is needed to do what you want to do, so this might be a way to get some advice from your code enforement people.
5.  Based on a site survey, you may need a small catch basin with drain pipes or possibly a dry creek.
6.  And most important, water takes the shortage, quickest way into your house. Consult an expert!

Jim