You want your drainage ditch to carry water away from your home. So, the ditch will need to slope away. The rule of thumb for proper drainage is one inch of downward slope for every ten feet.

The general rule of thumb is to provide a grade of 1/2 in. to 1 in. per foot for a minimum of 6 to 10 feet on all sides of the house. That’s a drop of 5 to 10 in. over 10 ft. This slope should be adequate to get the water safely away from the foundation into a drainage ditch, swale, storm sewer, or level lawn area.

Slope: The slope of the drainage ditch is crucial for proper water flow. Aim for a gentle slope of around 1-2% to ensure that water moves efficiently along the ditch. If the slope is too steep, water may flow too quickly and cause erosion, while a flat slope may cause water to stagnate.

For water to properly drain, your drainage trench must slope downwards at least 1 inch every 10 feet of length.

A rock drainage trench should slope about 1/8inch per foot which is a 1 degree slope. Curves can be used to catch more water and make the trench look natural.