Water Collection from Hillside

I have a pretty steep hill on my property with an order trail cut into it to allow access to the top.  I have a bunch of corrugated flex plastic pipe, and was planning to trench along the inner side of the trail (closest to hill above), and building a long french drain to collect water for retention.  Seems like a way to avoid having to pump water from the house which is down below.  Does anyone have any experience with this, or recommendations for the best way to maximize rentention?  Here on CA Central Coast, we have very distinct wet seasons, and would allow me to plant sub-tropicals along the hillside.  

I haven't been in this exact situation, but I've worked with swales, ditches, french drains, etc. I think it sounds like it might work.
I would lean more towards a series of mostly level catchment pipes, as opposed to one large pipe draining down the hillside.
I would consider finding a way to put a valve/overflow on the flex pipes before sending water down the hill. If possible I'd maybe connect to the top of the flex pipes, so that water only flows when full and keeps sediment out of smaller pipes, before plumbing to your reservoir.  
Depending on your reservoir size and rainfall, you may have to deal with diverting overflow.
Minimizing the overflow by keeping the water moving as slowly as possible, will likely allow for cleaner water and also help keep the excess uphill where your vegetation will benefit from it.

I agree with J Brun on this. It seems to me that a drainage pipe along the trail will simply help drain the water down the hill and away. I assume that what you want is to reduce the run off as much as possible. You will need to be careful not to destabilise your slope - landslips can be a real possibility if water is mismanaged.
this site has some simple explanations of swales and other water retaining earthworks for different situations. My gut feeling is that the "fishscale swales" may be most appropriate for water retention for you. As regards the track, you may want to make some features to reduce the possibility of water erosion if your rain tends to be heavy when it comes. This Californian site which may be of interest, suggests placing large boulders on the inside of the track to slow down water so erosion is less likely - sort of the opposite of what you're thinking of, and using native planting on contour to stabilise the slope and increase water retention. I hope this helps.

Colin, there are many questions before the answers can be clear;
- What is the soil type on the track?
- how steep is the track?
- would water run at 3 feet per second or more? Erosion starts about then.
- How far is your dam to hold the water from the track?
- Does the track run into the dam?
- could small holding bays be built along the track, IE dry stone walls to catch silt and hold water?
- what size is the pipe?
- What is the rainfall intensity when it drops out of the sky?
- Does flooding occur when its a downpour?