A drainage trench or channel is a shallow and narrow excavation in the ground around a house or other building to allow rainwater and groundwater to flow and be diverted elsewhere, preventing soil accumulation and damage to the property. Many people refer to it as a "French drain" because it was originally invented by a French civil engineer.

Here are some steps you can follow to build a drainage trench:

• Choose the appropriate location and depth:

  Before starting construction, ensure that there is sufficient water flow in the selected area and determine the depth and length of the drainage trench. The depth of the trench should be deep enough to reach the water table.

• Start excavating:

  Use a shovel or excavator to dig a long and shallow trench, with a width of about 10-12 inches. If wider drainage is needed, it can be dug wider.

• Add stones:

  Add 2-3 inches of stone to the bottom of the trench, then compact the stones to improve the efficiency of the drainage system.

• Install the drainage pipe:

  Place a PVC drainage pipe on top of the stones, ensuring that the angle of connection with the adjacent house or building is steep enough for smooth water flow without obstruction or blockage. Typically, the slope angle should be at least 1%.

• Add filter netting:

  Add filter netting around the drainage pipe to prevent sand and other debris from entering the drainage system. The filter netting not only keeps the pipe clean but also prevents roots or other plants from growing into the pipe.

• Fill gaps:

  Cover the drainage pipe with stones. Then fill the soil above the drainage trench until the ground is flat, ensuring safe walking.

• Test the drainage system:

  After completing the construction, test the drainage system to check if it works properly. Water the soil to test, check for standing water around the drainage trench, and ensure good flow of water through the trench.

Overall, building a drainage trench is a relatively simple and effective solution that can help reduce the cost of property repairs and maintenance. However, for more complex drainage problems, such as houses that need to be connected to the city's drainage system, it is best to consult a professional for advice and assistance. It is also essential to wear appropriate protective gear (such as gloves and safety shoes), exercise caution during excavation, and ensure the safety of oneself and others.