Hurricane Preparedness in the Garden, Pt. 2
By Bob Randall, Ph.D.
Basic permaculture tells us that in flat humid areas, we should not select housing or gardens at the bottom of the hill because water runs downhill, and flooding will happen eventually. It should be no surprise that many of our freeways are built on the watershed highpoint between bayous, but it is surprising that many don’t realize where the hill bottoms are. In any case, if you are at the bottom of the hill, there isn’t much I can suggest for gardening except annual plants that are easy to replace or perhaps native perennials like Louisiana iris or mayhaw that can take a lot of flooding.
If you didn’t have feet of water over the whole yard during Harvey, Imelda, or Allison then there are many things you can do. First, consider where the water is heaviest. In most yards, it is coming off a roof. From just one inch on 1 square foot there are 0.623 gallons of water. So, there are 62.3 gallons falling when 1 inch of rain hits 100 sq. ft. of your roof. Since the same amount hits the land, if rain pours off your roof, there are about 120 gal. of water hitting the soil from 1 inch or rain. 24 five-gallon buckets of water area lot for a plant to deal with. During Harvey our garden had 36 inches of rain in 4 days and during Allison, 24 inches in 3 days. We had tens of thousands of gallons off our 1200 sq. ft. house roof. (*1)
It’s easy enough to see that even if your house escapes flooding, your waterlogged soil will remove oxygen from the soil to the benefit of anerobic root-rotting microbes like Phytophthora infestans and to the detriment of most types of plants. So, what can you do?
- If you can, get double-wide gutters and rain tanks to catch some of the water and keep it from pouring off.
- Use water’s love of gravity to move it away from aerobic, soil-loving plants.
- Use compost to improve clay soils to create tilth and make the soil better at absorbing rain.
- Build up with raised beds 6-10 inches high for the terrestrial annuals, and move excess roof water away from beds, and plant trees and shrubs on earthen berms/mounds made by digging some of the soil out of a nearby area and piling it up.
- In the low spot created by digging earth or clay for the berm, make a raingarden and plant water-loving Gulf Coast natives like Louisiana and spuria Iris, hymenocallis, or Southern swamp lily.
- Then enjoy the flowers.
(*1) 36 inches of rain times 1200 sq. ft. roof times 62.3-gal water per 100 sq. ft. per inch of rain, equals about 27,000.