Grade in land development is the slope of a specific section of ground whether that section is covered with woods, meadow, grass, or impervious area such as paving.
Land grade can be determined through a simple calculation where the change in height of a section of ground (the change in elevation) is divided by the change in distance over that same section. The changes in height and distance are measurements that can be taken either at the site or off of a scaled plan with an engineering scale.
Why Proper Land Grade Matters
Having the proper land grade ensures that a land development project can properly drain during rainfall events. Flat areas and grade slopes of near zero percent can cause ponding and other drainage issues. Areas that are too steep can create areas that are prone to erosion.
You also would not want grades that are too steep that might create proposed conditions that are not safe. This can especially be the case in areas of vehicle traffic such as driveways and parking lots.
Where to Find Land Grade Requirements
Probably the most common place to finding land grade requirements would be a land development ordinance established by your local municipality.
This ordinance should provide you with minimum and maximum slopes that would be allowed in a proposed land development design depending on the use of the ground.
Grades Commonly Used in Land Development Design
The following are examples of areas with ranges of grades that are commonly used in a land development design.
1) Driveways – 1 percent to 15 percent
2) Parking lots – 1 percent to 5 percent
3) Detention basins – one percent at the bottom to 33 percent for the side slopes on the sides of the embankment
4) General graded areas – 1 percent to 33 percent
An Important Component of Land Development
Proper land grade is an important part of a land development project in that it allows for a safe design that drains properly. The proper professional would know what the right requirements should be for your particular project.