For some homeowners, flooding is a yearly routine occurrence. For others flooding may become serious once every decade. Still others may only face the prospect of flooding every hundred years or so. But no matter when a flood strikes the effects can be devastating. Take the recent disaster in the Northeast for example. Superstorm Sandy may be long gone, but the impact of such widespread flooding will be felt for years to come. Not only can excess water harm buildings and structures, but our yards can also be damaged. Of course, if your lawn is the only thing damaged by a flood, consider yourself lucky. Once the floodwaters recede there are a couple things you can do to help your lawn grass recover as quickly and successfully as possible.
First, gather up and remove any loose debris that may have been deposited on your lawn during the flood. Be cautious though. Some materials may be hazardous, such as broken glass and jagged metal. Also wear gloves and wash thoroughly after cleaning up debris since it may be contaminated with toxic or contaminated water. After removing the larger debris, let your lawn sit for a few days until it’s dry enough to walk around on. Failure to let it dry sufficiently will result in a muddy mess.
Remove Silt, Aerate, Fertilize
Most lawn grasses will survive submersion in floodwater for up to four days. Survivability depends on grass species, temperatures, time of year, lawn health prior to flooding and how much silt was deposited on the lawn during the flood. First, spray off as much silt as possible from your grass using a pressure washer or garden hose. Any remaining silt will need to be broken up by raking vigorously with a steel garden rake. After removing and raking the silt, you should core aerate if possible to help the soil dry out. Follow this with an application of quick-release fertilizer at a rate of ½ pound nitrogen per 1000 square feet. While I usually encourage organic fertilizer instead of quick-release types, in this situation a lawn needs a quick boost of nitrogen to help it recover as quickly as possible.
Reseeding vs. Starting Over
For lawns that were submerged for more than four days or were covered with more than an inch of silt, the survival rate is slim. In these cases, remove as much silt as possible as soon as possible after the flood, core aerate and fertilize. After this, observe your lawn carefully for the next few weeks. If more than 60% of it is recovering, you can do a partial renovation by reseeding the bare areas in the late spring or early summer. If less than 40% of the lawn has recovered it would be more economical to do a complete renovation of the lawn by removing all remaining grass and tilling any extra plant material into the soil. Take this opportunity to test and improve the soil pH, add organic amendments and apply an organic starter fertilizer. You also have the opportunity to pick a different grass seed type as your lawn, if you so choose.
Temporary Lawn for Soil Stability
If there’s a possibility of more flooding or heavy rains, sometimes it’s best to establish a temporary lawn to limit any additional soil erosion to your yard. To do this, use a grass seed with a quick germination rate such as annual ryegrass. While annual ryegrass shouldn’t be used for permanent lawns, it can be used temporarily. Annual ryegrass seed usually germinates within 5-10 days after planting and will provide soil stability until you’re ready to establish a more permanent lawn. Simply till in the ryegrass when you are ready to establish your permanent lawn.