The examples shown in Figures 14.28-A and 14.28-B present the range of landscape and slope design treatment of two drainage canal and water retention systems. The canal example 14.28-A is concrete lined, primarily treated with a hard, smooth surface to allow a swift flushing of the canal and reduce maintenance (area A). The upper slopes are planted with grass, allowing for informal recreation use (area B). The grass is easy to maintain but provides little in the way of visual variety or biodiversity. The canal example in Figure 14.28-B serves similar storm water conveyance and park functions but is more of an amenity, given the lush and diverse plantings. The canal in 14.28-B was designed to retain water at a prescribed level year-round, whereas the canal in 14.28-A is allowed to dry out during low-rainfall months.
A
B Figure 14.28-A Drainage canal also provides valuable park and greenway functions in Shreveport, Louisiana
Figure 14.28-B Retention canal and greenway in Voorhof, the Netherlands
Water Detention Swale Water detention ponds or swales can serve to slow down storm water and store it for later use, or function as a site design feature. In the examples shown in Figures 14.29-A, 14.29-B, and 14.30, a wide drainage swale was created in two parks, allowing for the detention of extreme storm water during heavy rains. Both were designed to accommodate a large quantity of water with a minimum slope that would slow the water, to let it penetrate into the soil, and would eventually become dry, allowing
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Landscape Site Grading Principles
