Tech Notes Issue 4

How Susceptible are Turfgrasses to Flooding

Heavy rains the past several weeks have resulted in flooding along some of the coastal regions of Australia.

At this time what does flooding do to turf? Flooding injury as outlined by James B Beard in Turfgrass: Science and Culture) is through erosion, deposition of soil, salt and debris to the extent that the turf is killed, and through direct injury of the turfgrass from submersion.

Regarding submersion, injury is dependent on:

- Depth of flooding (leaf blades above water, plant more resistant to injury than totally submerged). Having leaf blades above or floating on top of the water is demonstrated when we often see stolons from creeping bentgrass extending from pond or stream banks into the water.

- Type of flooding (stagnant versus running water). Stagnant water is much more damaging.

- Repetition of flooding (more injury with repeated flooding). Turfgrass plants become less resistant to flooding as the frequency increases

- Physiological condition of plant. Dormant plants are generally more resistant than actively growing plants. Couchgrass has excellent flood tolerance while the

submersion tolerance of creeping bentgrass is good, and Kentucky bluegrass (Poa pratensis) and wintergrass (Poa annua) are fair.

- Temperature of water. The warmer the water temperature the likelihood for turf injury is higher. In studies done at Michigan State University, Drs. Jim Beard and David Martin looked at the submersion tolerance of four cool season turfgrasses. They found at 30C (86F) water temperature that turfgrass survival beyond 5 days was not high (creeping bentgrass was the only one that survived to any extent beyond 5 days compared to Poa pratensis, Poa annua, and fine fescue.

-When the experiment was done at 20C (68 F) survival percentages were higher for all of the turfgrasses with creeping bentgrass having a 60% survival rate after 30 days.

- Turfgrasses in general become more susceptible to flooding injury when exposed to multiple flooding events. 

If you are in a situation where flooding has occurred do not allow the turf surface to become sealed with debris and particulates.