Water Ponding

John Schinnerer eco_living at yahoo.com
Sun Dec 16 18:12:22 EST 2001


> I have lots of drains coming down from the hills around my place.
> Some are fairly wide, and some almost 10 feet deep. 
> ...With heavy rains  over a few days volumes are impressive, and 
> fairly swift. 

Swift enough to cause ongoing erosion?  Slopes for drains in keyline
systems are typically 1:100 at *most*.

> Regarding key lines...
> I've read some of the literature...but am still a bit confused.
> For example would drainage ways that lead down and converge from the
> hills on either side of the hills to the hollows be keylines?

Technically, a key line is a contour line passing through a key point
(which, technically, is the point of slope change from convex to
concave in a primary valley).  Some confusion may arise because after
defining this, Yeomans then also names his whole land development
system "keyline"...

So your example drains would not be on keylines, if I understand your
description correctly.  They are concentrating water from the
hills/ridges to the hollows, is that correct?

A main intent of keyline design is to do the opposite of that - that
is, move the water out from where it naturally concentrates (valleys,
hollows) to the places it naturally runs off of (ridges).

John Schinnerer, MA
- Eco-Living -
Cultural & Ecological Designing
Food - Shelter - Community
john at eco-living.net

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