"Keyline design is a technique for maximizing beneficial use of water resources of a piece of land. The Keyline refers to a specific topographic feature linked to water flow. Beyond that however, Keyline can be seen as a collection of design principles, techniques and systems for development of rural and urban landscapes. Keyline design was developed in Australia by farmer and engineer P. A. Yeomans, and described and explained in his books The Keyline Plan, The Challenge of Landscape, Water For Every Farm and The City Forest."
In our site development, it's a contour line/channel or slightly sloped to "capture" water, slow it down and increase water absorption in the ground.
Here are a couple of keyline "swales" and "berms" to channel the water along the contours on our farm.
This morning's rainfall was a good first test of this water management system. We planted about a thousand trees in rows just below each swale (ditch) and berm (mound). As the trees grow larger their root systems will benefit greatly from the improved water absorption.