Figure 1. Eddy or backwater basins. The upper edge of the farthest-downstream section of the basin (A) must be higher (ideally at least 4 inches [10 cm] higher) than the basin’s curb-cut, or curb-core, inlet (B) to ensure pooling water calmly backs up to the inlet. Inlet must be on the upstream side of basin to maximize capacity and avoid mulch flowing out of basin. Arrow denotes water flow.

Figure 2A. Using a laser level to get a reference elevation for an eddy basin’s inlet elevation.
For other ways of measuring elevation relationships see figure 1.6 and appendix 1 in “Rainwater Harvesting for Drylands and Beyond, Volume 2, 2nd Edition.”
Photo: Brad Lancaster

Figure 2B. Using a laser level to get the elevation of the eddy basin’s downstream edge to make sure it is at least 4-inches (10 cm) higher than the curb cut inlet elevation measured in fig. 2A.
Note: These elevations must first be taken when laying out the basin’s perimeter and length to ensure all will be correct once built.
Photo: Brad Lancaster

Figure 3. Water-harvesting eddy basins created by Eden on Earth on a curb-less street in Clarkdale, Arizona.
Before the work, road runoff would flow up against and flood the house. After the work, the dirt dug from the street-side basins created a raised walkway that acts as a berm ensuring no basin water or street runoff can flow up against the house.
Before the work, there was no walkway; now there is a wonderful path wide enough for two people to walk side by side, separated by the trees from cars and street. Now the trees have grown to shade both walkway and street.
Photo taken by Carol Luhman just after the work was completed in 2007.