Dealing With Flood Damage – Turfgrass Science at Purdue University

Dealing With Flood Damage

Though flooding damage so far this year is not as bad as last year, a number of areas have been hard hit with rainfall the last week (see the photo of Lafayette Municipal Golf Course). We don’t expect damage to be as extensive as last summer given the slightly lower temperatures, but some areas will likely need reseeding. Following is information on flood damage and recovery adapted from a July 2003 Midwest Regional Turf Foundation Factsheet.

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, but can be killed in as little as 24 hours when water temperatures are 86 degrees or higher (translation: June-July in IN). 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. Every turf site will respond differently, but we expect substantial damage wherever there was standing water, given the high temperatures the last two weeks.

Where to go from here
If the grass does not green up by the time soil begins to dry out, it is likely dead and reseeding or resodding is required. Since water damage will selectively kill weaker plants, it is likely you’ll have a patchwork of grass in some areas. The first decision to make is it worth saving the remaining turf or should you start over completely.

Saving what you have
Remove as much of the silt as possible with raking, hosing, power washing, etc. Follow this with aerification to help break up the soil and improve seed soil contact. Shallow, solid tine aerification on greens and tees will minimize further stress. On most fairways, roughs, sports fields, and lawns, hollow tines punched as deep as possible will prepare a seedbed as well as break up layers and relieve compaction. On large areas, it makes sense to “kill both birds with one stone”. Follow this with drop-seeding or power seeding, a starter fertilizer at 0.5-0.75 lbs N and 1.0-1.5 lbs P2O5/10002 before seeding and again at 4 weeks after germination, regular irrigation, and mowing as needed. We don’t expect enough residual from preemergence herbicides to affect emergence at this time of year.

It might not be worth saving
Significant flood damage might dictate starting over completely. This is a prime opportunity to change species or cultivars, improve surface or subsurface drainage, and make other major improvements. Resodding may repair an area quickly, but rooting is minimal and the sod may not be capable of withstanding significant traffic until September. Seeding is a possibility and since our prime seeding weather is about a month away, you may have time to make major improvements to the area.

Which grass species?
Whether you’re trying to save what you have or you’re starting over, the grass species and cultivar is a major decision. This decision will dictate future performance and maintenance.
Homelawns: Kentucky bluegrass is the best option for most of the state. If the homeowner wants a quicker green-up, include no more than 10% perennial ryegrass in the mix. Though Kentucky bluegrass is slow to emerge and establish, it pays for itself in the long run. Turf-type tall fescue is an option for lawns that will receive no irrigation and minimal fertilization.
Athletic Fields: Your decision here depends on when the field must be used. Perennial ryegrass is the only choice if you have to use the field this fall. Use 100% Kentucky bluegrass if the field doesn’t have to be used until next spring or summer, but it’s imperative to seed bluegrass in early to mid-August to be ready by April (and that still might be pushing it).
Roughs: Straight Kentucky bluegrass is preferred, but 10% perennial ryegrass in the mix won’t hurt. Tall fescue is a little too coarse and doesn’t withstand traffic well.
Fairways: It get’s more complicated here. Creeping bentgrass is the species of choice because of reduced disease susceptibility and surprisingly good drought tolerance at fairway height. Our best performing cultivars in West Lafayette include Century, Grand Prix, Backspin, Trueline, Penn G-6, Providence, Seaside II, and L-93. Creeping bentgrass should not be used if your golfers do not like hitting off 0.4″-0.5″ turf, you don’t have double or triple row irrigation, you don’t have lightweight mowers, or you don’t have the ability to aerify once or twice per year. That leaves us with Kentucky bluegrass or perennial ryegrass. Perennial ryegrass looks good throughout the year other than July, August, and September. It performs adequately at 0.75″, but it’s susceptible to numerous summer diseases and it is not a spreading grass, so overseeding will be needed often. We’ve conducted some preliminary work with “low-mow” Kentucky bluegrasses and they are not working very well so far. Our opinion is that they will not fare well over the long term. Greens: Obviously creeping bentgrass is the only choice and some of our best performers in West Lafayette include Penn A-4, A-6, G-1, G-6; Century Grand Prix, Imperial, and L93. Check our web page at or the National Turfgrass Evaluation Program at before making this decision.

The silver lining to flood damage at this time of year is that we are nearing the prime period for seeding. The flood damage may allow you to start with a clean slate and seed the best-adapted and best-performing cultivars currently available. Please call us at 765-494-8039 if we can help.

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