The Principles of Land Grading

Survey

• To complete the effective grading of land, construction sites and other areas are usually designed by a land survey completed by an engineer. The uses of land grading include the movement of water to help maintain the current level of drainage to reduce surface runoff, soil erosion and sedimentation. Land grading is often used in areas with steep slopes in the land surrounding construction. Grading stabilizes these slopes and can reduce the velocity of surface runoff.

Surface

• Drainage of an area through the grading of land can be completed through the use of above or below surface drainage. Land grading allows surface runoff to be directed through the introduction of slopes to move water away from a building. Little maintenance is required where slopes are built correctly. Other options, including the introduction of subsurface drainage and percolated pipes, requires maintenance and monitoring to ensure they do not become blocked. Runoff areas should allow the storm water and runoff water to percolate through the subsurface as it moves away from the building, maintaining the natural drainage of the land.

Slope

• In moving water away from a building, one of the basic principles required in the design of graded land is a downhill slope extending at least 5 feet from a building, to allow water to drain away from the structure. Areas of a construction that are paved, such as patios, should have a slope for drainage that does not exceed a 2 percent fall. In other words, it shouldn't drop more than 2 feet for every 100 feet. Where a construction site borders another property, the drainage of water should not increase the amount of water movement into the neighboring property. A principle of land grading is that the movement of water into a neighboring property should not be increased. Any improvement in drainage should attempt to decrease the amount of runoff moved into a neighboring property.

Traffic

• High-traffic areas within a property should be graded gently. There should be no concentrated water flow through a high-traffic area. Areas with large trees and vegetation should be protected by the grading of trees. Land grading should protect vegetation to avoid damaging plant roots with construction equipment.