Spring rains have turned into spring floods. With every inch of ground saturated and heavy rain still falling, our twenty-year old, low-tech contours and drains have proven effective when we needed them most. Floods usually mean erosion, and our top priority from the start 20 years ago was to reduce soil erosion to zero.
To get erosion to zero we contoured every pasture. The highest contour became a cut-off drain (soil spoil goes down-hill) to capture run-off from the ridge and force it under ground laterally into the soil profile. Not only does this wet the deep soil profile, it can wet and remove the dry clay pan. Down-slope from the cut-off drain, at every 2ft. contour, we placed a contour berm (soil spoil goes up-hill) to catch any slight soil movement and begin to flatten out the contours.
Boys playing in top contour 350 ft. long cut-off drain
Each of these features need not be perfect or complete. Every year they can be expanded and repaired. They were all dug by hand and can thus be repaired by hand. The photo with the two boys gives you an idea of what a 350ft long cut-off drain looks like after a 4 inch rain. There is a release point at one end so that when the water reaches a given elevation on the berm free-board it can run into a grassed swale and flow into the contour ditch below—zig-zagging across the pasture rather than sheet flowing and eroding one area where it might have collected and over-flowed.
Our entry road demonstrates another water control structure—the swale. Soil for the road was pushed up to form the road bed leaving a gently curved ditch at slightly greater pitch (fall) than the roadbed. This swale not only captures the run-off from the road (via its miter drains) but also collects the excess from the pasture above it. Water from the pasture flows through smaller grassed swales into this large one. This road-side swale will never over-flow its sides-slopes. You cannot see the release point, but properly placed, it keeps any amount of water moving uniformly down the slope to the culverts and into the pond. The Cypress trees are deeply watered by this slow moving river.
Road-side swale transporting run-off from 500 ft. road and pasture
Finally the water flows under the entry gate through some culverts. The shape of the grassed stilling chamber allows a massive surge of water to enter the culverts without cutting the soil face holding them. Clean water then flows into a 14ft. deep pond that supplies our aquaculture and holds enough to irrigate our pastures if we have a dry summer.
Crystal clear water flowing into stilling chamber and entering culverts
These pictures reveal rather unimpressive but extremely functional water and erosion control structures that have worked well for us for 20 years. Let it rain!