Level Sill Spillways vs. Normal Spillways

Geoff explains the difference between a level sill spillway and a standard dam spillway, and why the right choice depends on slope, soil stability and water flow.

This video is taken from Geoff’s Online Permaculture Design Course, which includes weekly Q&A sessions where he answers student questions. Learn more about Geoff’s courses at: https://www.discoverpermaculture.com

Key Takeaways:

Caven asks the difference between level sill spillways and normal spillways on the Zaytuna Farm water design legend.
Geoff explains a standard spillway suits a large lower dam on solid ground, especially where the safe overflow path drops into the valley.
A level sill spillway is useful on swales or dam extensions where overflow needs to be spread or moved away from vulnerable ground.
Level sills give designers more choice over where surplus water leaves the system, especially on steeper or less stable sites.