Sep 16, 2019
Open drains can carry a lot of stormwater. They are designed to capture water overland and also pipes can discharge water to them.
The open drain is to have sufficient cross-sectional area to take all flows. In general terms they should be designed to 1% Annual Exceedence Probability (AEP) and consideration be given where the water will go if the capacity is exceeded.
The slope of the channel should be steep enough to carry water without water ponding and the side slopes should be not too steep so they can be easily maintained.