Roadside Drainage Swale

Ultimately, the surface water is collected in a catch basin or directed to a rain garden or planting area, where the water may be absorbed into the ground or held in a landscaped retention area.

Figures 14.20-a and 14.20-B Concrete drainage channels to carry surface water from a parking lot to an adjacent road

The swale shown in Figure 14.21 was created to carry surface water from the adjacent roadway and the surrounding sloping landscape area. Note the culvert at the end of the swale, which allows surface water to continue under an entrance drive to a continuation of the swale along the road.

Surface water is carried by gravity in a grassy swale toward the culvert that allows the water to flow under the access driveway. The grass serves to slow down the water, allowing some percolation into the soil. The grass also protects the swale from erosion, particularly when water runoff is high and large quantities of moving water could cause soil erosion. Grass or other vegetative ground cover also serve to

Figure 14.21 This drainage swale was created along a campus road, instead of using a curb and gutter design