Question
This will be wordy.  I apologize.  I am desperate for some help with this problem because it is making my life very difficult.  I have moved into the home of my elderly parents to care for them full time.  The backyard slopes down toward the patio and house.  We have drainage problems in that the water runs down the slope and collects at the edge of the patio and at the fence line.  We dug a trench and put in a plastic pipe to try to run the water out to the fence.  It's better, but still very wet.  My father decided to till up all the grass on the slope because it was difficult for him to mow.  This happened before I moved in.  He had a stroke while tilling and now is confined to a wheelchair.  Consequently, I have to do all the yardwork.  I have a lab who runs around the backyard and tracks mud into the house.  I thought it might be good to either build a retaining wall to terrace the yard and plant shrubs and ground cover on the upper terrace and grass on the lower, or plant grass all over.  I need to know what to do to take care of the drainage problem before I spend any money to do anything that will not last because of the water problem.  Cost is an issue as I have no income currently and my parents are living on a fixed income.  I am hoping for solutions that I can implement with very little professional assistance.  Do you have any advice, suggestions or resources for me?  Thank you so much for your help.

Answer
Maggie,
This will also be wordy,but I am famous for that.
There are several things you could do,but we need to concentrate on the most minimal cost to you and that narrows the choices,but there is always a solution to every gardening problem.Mother Nature is a strong force,but human intervention is just around the corner.

I have been presented with the most daunting landscaping predicaments in my many years of gardening and I can tell you,drainage problems are probably the biggest nuisances I have encountered.Luckily they aren't impossible to fix.

The first thing I would concentrate on is how to stop the water from getting on your patio.A retaining wall would be ideal,but you would need big stones that are used for walls or bricks or your cheapest way to go would be those big lumber ties.You would need help loading and unloading them,so you need to seek the assistance of someone,preferably a man(they do come in handy sometimes)with some muscle.Maybe a friend or relative.The lumber ties will be cheaper than brick or stone unless you have some stuff laying around.
I would dig a pretty good sized trench on all 3 sides of the patio.I am assuming that the patio is directly accessed from the back of the house.(Photos would help me if you have them,by the way.I am just going by what you have described to me.)Dig the trenches at least 1 foot deep and as wide as the lumber ties.You will need them on all 3 sides of the patio.I would use 3 or 4 high on each side.That would mean at least 9 to 12 ties.After they are stacked in place get something to brace them from the back.
A garden or nursery center should be able to show you what you need to brace them.Some sort of metal bar or bracket.Most lumber ties are treated so they may not last forever,but they should last at least 8 to 10 years with the exception of perhaps the bottom tie that will get all the standing water.If you know of a railway yard or any nearby train tracks you could snoop around and ask if they have any old ties laying around that have been replaced.They work fine as long as they don't have any major damage.They are also rustic looking and add some character to the lanscaping if used properly.

You have lots of ways to decorate them too.You can actually nail things on them,like some hanging baskets and window boxes or just potted plants on top.Window boxes can be made from anything.I got some little wire baskets at the $1 Store once or twice for one dollar a piece and filled it with spanish moss,potting soil and annuals.One was a heart shaped wire basket and it is really cute with Pansies and Alyssum that spills over the front and sides.You could easily nail these to the lumber ties.Flowers will soften and brighten up the lumber ties immensely and your parents would enjoy the outdoor display.I have some elderly customers that love their flowers and are quite saddened if they can't work with them.So I try to put some pots of flowers close to the door and windows so that they can water and deadhead them and even plant in them at the right level.

This is only one solution,but it is probably the most economical one.

The slope can be tackled next after all that is complete.Instead of having the headache of mowing the slope,use a groundcover like Ivy,Pachysandra or Ajuga.Kill off all the grass first before planting.Make SURE it is ALL dead.This needs to be done when the sun is at it's hottest.Summer is the best time to kill grass.Get a strong commercial weedkiller like farmers use.If you have a farm co-op or Southern Sates around there, go ask them what the strongest kind is.If you buy Round Up,which is easily bought at WalMart or Lowes or Home Depot,make sure you get the concentrated kind so you can mix it super strong.If you don't it won't kill the grass completely and you will have to do repeat spraying.Believe me when I tell you this because unwanted weeds and grass is THE biggest time consumer in gardening. When you are sure the grass is completely dead,which may take as long as a week with commercial kind or even 2 weeks with repeated spraying with an average,"over the counter" weed killer like Round Up. After the grass is completely dead you don't even have to break up the soil with a tiller.I know some people say my methods are unconventional but when you are a woman landscaper you have to look for other ways to get the job done.I do my own digging and hauling.The only thing I subcontract is bigger projects like grading and digging large holes,so i know what it takes to get a place looking good,just plain hard work.Anyway,you are ready to plant.This is why you want the grass completely dead,simply for the fact that you are NOT tilling.The plants should be tough,strong varieties so there won't be any maintenance.I don't know where you are located but I will give you some websites to go to to look at some perennial groundcovers for your zone.Also,check at a local nursery.They will know exactly which plants are best for your area.

Here are some great sources to look at on the web:White Flower Farm,Wayside Gardens, Shady Oaks Nursery,Walters Perennials(or Gardens),Jackson & Perkins,Khelm's Song Sparrow Perennial Farm,Van Bourgondien Bulbs,Van Dyck's Bulbs,Brent & Becky's Bulbs,Plants by Mail,Gardener's Supply Co.,Bluestone Perennials,Sheperds Seeds

All these companies offer free catalogs too and a lot of specials if you order online.Some are way overpriced though so I use them mainly for reference.
Hope this is helpful.If you need more info let me know.Good Luck! You can do it.