Drainage is one of the most important aspects in the longevity of your home, so give it plenty of attention. Water can be very bad for your house. (See page 19 for how to choose a dry place for your home.)
The object of the drainage system is to divert water away from your structure. You will be creating a dry island for your home to sit on. In some areas, a berm will be all you need to redirect water. In others, a French drain and/or a berm will redirect the water. There are more details about these drainage systems late in this chapter.
If you have the time, there are advantages to starting the drainage before building. While you are making your house, you can observe how the drain is working and adjust it if necessary. Cover the ditch with plywood to prevent accidents. It will lessen the risk of flooding during construction. And when you are finished building, you will be able to sit down and relax sooner in your new home! If your weather and timing is such that you are unlikely to get flooded out while building, the drainage can be done after you've finished the house.
The first part of the drainage job will be to get to know your land's natural drainage. In the wet season, dig a few test holes where you imagine your house will be, as well as digging some holes uphill of it. Do the holes drain well or do they fill up with water? This will give you a good idea about what's going on under the ground and how much you'll have to do to divert water. A sandy, pebbly soil will let water filter through. A soil with high clay content will expand when wet and block water from percolating through it. (Make a little fence around the test holes or cover them with flat rocks or plywood to avoid twisted ankles.)
You may want to use earth-moving equipment, if you have a big job or if there's equipment there anyway for the road building. If you do get machines in to do work, watch them very carefully! Their drivers probably do not have the same familiarity or respect for the land that you do, and can do a lot of damage in a short time. Digging by hand is usually more accurate and less destructive to the land.
The flooded homes I've seen were caused by poorly planned earth-works, human interference upstream (damming, clear cutting, destabilizing earth), or by building where it has always flooded.
Mark where your foundation will be with straw bales, stones, or wooden stakes. Step back and look at the site from a distance. Imagine where the underground water and surface water will flow.
On a sloped site, create a drain and/or berm starting uphill and flowing around the house. (See illustrations next page.) Your drainage system will direct water to the sides and downhill of your home.
Consider how you can make use of the water you divert from your homesite (a pond, garden,trees etc). At least make sure it isn't causing erosion. If you won't be catching the water from the roof gutters for drinking or gardens, you might want to channel it into the drainage system too.