Interceptor Swales

Interceptor swales capture uncontrolled surface water flows above steep and unstable slopes and convey flow to a stable discharge point. Swales can be excavated to form a channel and then seeded with a hearty erosion control grass mix. It is a very economical drainage technique that can also be used as a temporary erosion control measure. Figure 15 shows a typical swale system.

Figure 15. Typical swale system.


Swales should not be sloped greater than 5 percent. Needs a minimum 1 foot width at the bottom with 1 foot minimum depth and 2H:1V maximum side slopes.


Available construction materials and inexpensive construction. Easy to place many swales at different locations. Easy to landscape around.


If permeable (sand and gravel) soils are crossed by the swale, conveyed water could infiltrate into the soils adding to local groundwater.