What should the longitudinal slope of a grass channel be?

The appropriate longitudinal slope for a grass channel is crucial for effective stormwater management. A slope of less than 4% is recommended because it allows for adequate hydraulic capacity while preventing excessive flow velocities. If the slope is too steep, the water can flow too quickly, leading to erosion of the channel's surface, which can diminish its effectiveness and ultimately result in sedimentation of downstream water bodies.

Maintaining a slope of less than 4% also ensures that vegetation can establish a robust root system, which is important for channel stability and water quality. The vegetation in a grass channel plays a key role in slowing down the water, filtering pollutants, and improving the aesthetics of the landscape.

In contrast, steeper slopes may undermine these benefits by increasing the risk of erosion and reducing the channel's ability to detain and treat stormwater effectively. Therefore, the choice of a longitudinal slope of less than 4% aligns with best practices in stormwater management, supporting both environmental integrity and functionality of the drainage system.