If the waterlogging in your garden is not severe and the water excess is only on the soil surface you can divert this water by shaping garden surfaces so that the water will flow into drainage ditches. If problem is deeper you can improve the drainage by installing an underground drainage system. It is best to hire some specialist contractor to do this job for you. If drains already exist and you still face the waterlogging problem then you should check for blockages in the drainage ditches or for damaged pipes. Underground drains will not work if there are any drainage barriers above them, like a hard pan for example.
There are different methods you can use to improve soil drainage in your garden depending on each situation. The best method of carrying away any excess water from the surface is a system of open ditches. These should be 1-1.2 m deep with sloping sides. Another method just as effective but less obstructive is a system of French drains. These are gravel-filled drainage ditches topped with upturned turf and topsoil.
For sites where there is surface compaction of the soil an effective method of drainage is a soakaway. This is a rubble-filled pit into which excess water runs via underground drains or drainage ditches. This method is effective since it breaks through any layer of hardpan. To build a soakaway dig a hole approximately 1 m wide and at least 2 m deep. Fill it with broken bricks or stones completely surrounded by geotextile fabric. To lead the water from the surrounding land to the soakaway you should install perforated plastic pipes or tile drains at least 60 cm below ground level.
An alternative method is to create a water storage area where the water will collect in a pond or large container or gradually soaks away. Having a pond in your garden is beneficial to wildlife, but its success depends on the degree of sediment in the drainage water as too much sediment will make the pond rich in nutrients, therefore becoming prone to silting up and excessive algal growth. If you are not creating a pond and you will collect the water in containers, you may recycle it for further use in the garden. Collecting water that is allowed to soak away gradually helps to replenish groundwater reserves and reduces silt pollution of rivers.