How to restore your lawn after a flood

For those with a home lawn in a flood plain or next to a waterway, removal of as much sediment and silt becomes job one.  Many will opt for a professional with equipment capable of moving large volumes of river sediment.  This is especially important to the homeowner as there is a high likelihood that the silt and sediment, being of the finest particle size, will trap and contain petroleum products, organic waste, or other undesirable materials.  Leaving the removal of such sediment to a professional can provide a measure of comfort to the home owner versus attempting such a daunting task themselves given the inherent risks.  After this “river frosting” is removed, the next phase is lawn restoration either this fall or next spring.
Damaged lawns will fall into two main categories ranging from a complete reinstallation with truck loads of loam down to basic turf treatments like core aeration, calcium lime, and fertilizer.  The more extensive the flooding and sediment layer, the more likely loam will need to be brought in, spread out with a tractor, seeded, and then rolled.  Any seeding this fall will pay dividends with quicker grass thickening versus having to wait for the soil to warm up and dry out next spring.
In many cases, a complete lawn renovation may well be the best choice compared to trying to patch up or fix thinned out or dead sections of lawn.  Attempting to match any existing grasses can leave a calico appearance to a lawn while starting over allows more desirable blends to be utilized yielding a more consistent turf cover. Before proceeding with a complete restoration it may also be the opportune time to decide how much lawn you really want in your planted landscape – do you love it and like the maintenance chores or do you really dream of creating other outdoor living spaces with patios, walkways, and gardens with native flowers, shrubs and trees? Only you can answer this question that Irene has raised….
The second type of lawn repair would be a partial renovation where perhaps the back or front was buried in silt yet or another area simply became either submerged in water or soaked by heavy rain.  Given the massive amount of rainfall during hurricane Irene, many soils, particularly sandy ones, will have lost significant nutrient value and will require supplemental treatment of Nitrogen and Potassium.  In this scenario, a normal lawn would do well to receive a balanced, low to zero phosphate, slow release fertilizer treatment to aid in improving turf health this autumn.
Any energy stored in October and November will be used to repair and establish a healthy root system prior to winter resulting in a better spring green up (see ‘winterizer’ blog post at mrgrassblog.net).  A high calcium lime treatment will aid in softening the soil itself while adjusting soil pH into a desirable range for the new and existing turf.  Core aeration is an excellent tool to reduce compacted soil, perhaps even those with some remaining sediment as a coating on the surface of the lawn.  These situations can be further improved by overseeding once the lawn is aerated with a superior blend of turf grass.
Most lawns can be seeded into late October and still have some germination prior to winter in a normal growing season.  Although you will not see a whole lot going on, taking the shot now is still normally worth the gamble of an early snow.  I have seen great lawns emerge in the spring from a late seeding and in the case of this catastrophe, I think the ‘doing’ outweighs the ‘waiting’ in most cases.
Although lawns may rate low on the scale of post-Irene reconstruction compared to bridges, roads, or house repairs, ultimately the job will arise and when it does, doing it right makes more sense than to not.