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When you construct your street-side stormwater-harvesting basins, described in my last post, Harvesting Stormwater with Backwater or Eddy Basins, you’ll of course want them to be as successful as possible; to that end, understand and equip yourself with these important engineering tips:

Fig. 1. Elevation view of curb cut and backwater or eddy basin with important elevation and slope relationships shown

Figure 1. Elevation view of curb cut and backwater or eddy basin with important elevation and slope relationships shown

Important Elevation Relationships of Backwater Basins
The following is based on tip 9 (Three Key Elevation Relationships of Water-Harvesting Earthworks) from chapter one of Rainwater Harvesting for Drylands and Beyond, Volume 2, by Brad Lancaster.

Elevation 1: Bottom of basin, and the top of the mulch within it, is lower than the elevation of the curb-cut inlet so the structure accepts and holds street runoff. The deeper the basin in relation to its overflow, the greater its water-holding capacity.

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Figure 2. Harvested street runoff has filled up to Elevation 1, nearly to the rain-garden Terrace Zone

Elevation 2: Curb-cut inlet is the low point of the basin’s perimeter, so water will overflow at (or back up to) the inlet and the pavement-stabilized street-curb gutter.

Planting terraces are typically the same elevation as the curb-cut inlet (and higher than the bottom of basin), so plants less water-tolerant than those in bottom of basins will thrive—allowing for a greater diversity of plantings. Terraces also reduce the otherwise-sudden drop a basin would represent along adjoining paths and pedestrian platforms.

[. . .]

For the Elevation 2 illustration, Elevation 3 text, a learn-from-my-mistake opportunity, and a few guidelines for inlets of curb cores or curb cuts, read the rest of this post on my Drops In a Bucket blog.

For more information and examples, including how to increase the capacity of these basins, buy, read, and share these award-winning books (most of the info on this page came from Volume 2):

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