STEP 1:Determine the growing area’s slope steepness

Look at a topographic map of your site and its contour lines to determine how steep the slope is across the whole growing area of interest. Use a Google Earth Elevation Profile tool for a quick check-up.

Note that you can only install swales on gently to moderately sloped land (0° to 20°) with less than 3:1 ratio (not more than 1 foot of drop over a 3-foot run). Any steeper than this and you risk blowout from too much water buildup, overflow, and soil destabilization.

–>Action step: Use the Google Earth elevation profile function to analyze the growing’s area slope steepness.

STEP 2: Mark the first reference contour on your map

Zoom in to the area that you want to transform into a food forest and first mark what I call a ‘reference row’. This will be the initial swale that you’ll use as a starting point for your layout design.

It’s good practice that this first swale is at the highest point of the area of interest.

This is a very important principle of harvesting water, as this way you slow the flow as soon as possible. Otherwise, the flow might cause erosion before it gets to your swale further downslope.

–> Action step: Look at your map and try to find the longest contour line at the highest possible elevation.

Click the ‘Add path’ tool on the Google Earth toolbar (1) to draw a ‘swale line’ following or on top of the contour line (2).

Note: Where you begin and end your swale is entirely up to you. In most cases, the restrictions of the surrounding landscape (access, property boundary, fencing, etc.) will be your guide.

STEP 3: Decide on the distance between the swales

If you’re planning on having more than one swale, you’ll need to determine how far apart to make them. This will depend on your site goals and rainfall and runoff conditions, but the overarching rule of thumb is: the greater the runoff, the closer the swales should be spaced.

In general it will be 5 – 20 m (15 – 65 feet). But again, the greater the runoff the closer the swales.

For example, on steep, overgrazed or disturbed land, you will be confronted with large volumes of fast-moving sediment-laden water in intense rainfalls so you should place your swales at close intervals. On gentle slopes covered with thick native grass, the watershed can absorb more rainfall before significant runoff begins so you’ll need fewer, and more widely spaced, swales.

–>Action step: Decide on the distance between the swales

STEP 4: Create the final layout

Now, based on the desired distance, mark the remaining swales, going down the slope from the initial swale.

–>Action step: (A) Click the ‘Ruler’ tool on the Google Earth toolbar (1) and switch to the line tab (2). Measure the desired distance to the next swale (3).

–>Action Step: (B) Click the ‘Add path’ tool on the Google Earth toolbar (1) to draw a ‘swale line’ following or on top of the contour line (2).

–>Action Step: Repeat measuring the distance (A) and drawing swale lines (B) until you outline everything.

Now you have a final food forest layout with swales.

–>Action Step: Repeat measuring the distance (A) and drawing swale lines (B) until you outline everything.

Now you have a final food forest layout with swales.

STEP 5: Define access points

Finally, think through how the newly created swales relate to the existing main access points. 

–>Action Step: Define where you’re going to locate pathways that enter the newly created growing areas between the swales.

STEP 6: Check the layout on the site

With this layout in your hands, you can now go to your site and crash test the map against the territory:

–>Action Step:  Save your work on the desktop app version of Google Earth, open the file on the smartphone version of the app, and visualize your layout as you walk around the site.