Channels and runnels are concrete or stone lined pathways used to carry rainwater runoff along the surface or subsurface to other stormwater features and systems. Runnels are smaller, shallow systems while larger, deeper channels carry larger flows.

Benefits & Problems Addressed

Multi-distributed flows: Instead of concentrating flow in curb and gutter systems, channels and runnels distribute water more evenly across the landscape. When directed to landscaped areas, these systems act like natural irrigation.

Decorative hardscape: Varied hardscape and grills can add interest (and serve for educational opportunities).

Ease of maintenance: Shallow systems are more easily maintained, cleared and repair that large sub-surface pipes.

Tips & Techniques

Candidate sites: Channels and runnels are typically part of public works installations for upgrading existing plazas, sidewalks and landscaped areas in corridors or small area planning. Hence, Business Improvement Districts and contributions from large development projects are often candidates.

Common elements: Channels and runnels are part of programs with several elements, including sidewalks, landscaped areas (street trees, landscaped areas, bioswales), and overflow areas. 

Hot Buttons: Channels/runnels require complex engineering and take up a larger surface area than piped centralized systems. The varied surface can be difficult to maintain and pose navigability challenges.

Resources

SF Better Streets: City and County of San Francisco

Image: Sandy Sorlien