What is the maximum side slope ratio allowed for a swale?

The maximum side slope ratio for a swale being 3:1 means that for every 3 units of horizontal distance, there can be a vertical drop of 1 unit. This ratio is significant as it strikes a balance between the effectiveness of the swale in managing stormwater runoff and the stability of the slope. A 3:1 slope is generally considered to provide adequate stability while allowing for efficient conveyance of water.

Steeper slopes can lead to increased erosion and instability, making them less suitable for long-term water management scenarios. Conversely, a flatter slope could require more space than is feasible in certain developments and might not effectively channel stormwater. Thus, the 3:1 guideline serves as an established standard in stormwater design practices to ensure both functionality and safety.