After widespread flooding, many question how well turf will survive. Turf injury from flooding depends on water temperature, species, duration of submergence, and depth of submergence. Turfgrasses can withstand submersion for up to 60 days when water temperatures are 50 degrees or less. Injury is increased under stagnant water compared to moving water, and injury also increases with depth of water. Of the cool-season turfgrasses used in IN, creeping bentgrass is the most tolerant of submersion, Kentucky bluegrass being less tolerant, and annual bluegrass and perennial ryegrass being the least tolerant to submersion. Additionally, silt and flood remnants like corn stalks, trash, and branches can further exclude light weakening a turf stand. I would doubt if we see much direct damage from flooding.
However, the current cold front has kept water frozen over the turf and cause significant ice damage. Ice damage is most common when an inch or more of solid ice forms immediately above the soil, thus suffocating the turf. Ice damage is rare if an ice layer forms and then the water drains out from underneath leaving an air space. This is most common with flooding. Annual bluegrass and perennial ryegrass are most susceptible to ice damage.
What to do now
Remove silt and trash as feasible and break up solid ice layers if they have formed directly on the turf. This can be tried with ice picks, an aerifier, or a light layer of a dark organic fertilizer (very low in nutrients), which will heat up and melt the ice.
A waiting game
The real measure of flood or ice damage cannot be made until spring green-up. If large areas aren’t greening up, introduce more seed with power seeding or aerification followed by drop seeding. Avoid early applications of preemergence herbicides in case you’ll need to seed. Post-emergence crabgrass herbicides like Drive and Dimension can be used after the seedlings emerge. If areas are just thinned by winter damage and not killed, applying 0.75 lb N/1000 ft2 in mid-April, Mid-May, and mid-June will help improve density. Do not use rates higher than this because you may encourage too much vertical growth at the expense of root growth and summer stress tolerance.
More information on general turf management is available at our web page at http://www.agry.purdue.edu/turf/. Specific information on flood damage can be found at http://www.agry.purdue.edu/turf/tips/2004/flood618.htm