The degree of damage caused to your lawn from excess water depends primarily on:
- What is in the water e.g. sewage, oil, debris
- How deep the water gets
- How long it lasts for
Lets start with the least worst scenario:
Rain Sodden Grass with no Flooding
Generally, sodden lawns will have some of the following factors that increase water ingress or retention:
- Low lying (maybe your neighbour has a higher garden)
- Run-off from hard areas
- Poor drainage due to a sunken lawn or a none draining sub layer
- Clay soil – usually heavy clay
Though the above can be problematic the lawn will usually recover once dry. Focus should be made on helping the lawn recover by coring (hollow tining), feeding and then resolving the cause.
The Seasonal Temporarily Flooded Lawn
Many people enjoy living near rivers and expect their gardens to flood on occasions. If your grass is under water for a week of less then it will usually recover. As it starts to dry rake off any excess silt, core aerate and get some fertiliser in. If you want to make sure of a good recovery over seeding should be undertaken. Assess the recovery for further action after about 30 days.
Major Lawn Flooding
If the lawn is submerged for more than a week the chances are the turf is dead. Further, if the depth of water is greater than about 10cm or 4″ then it will have caused some compaction. Depths over 30cm or a foot of water will cause major compaction.
Start by removing debris. Wear gloves as the area could be contaminated and contain glass and other sharp objects. Then start grading the lawn to get levels back to normal. This will definitely involve removing silt but may mean bringing in new top soil.
The whole area will then need to be rotovated to work the new soil in but also to relieve the compaction and get oxygen back into the soil. Adding humus (well decomposed green matter) and perhaps a dash of chicken poo will help build the organic content and get the bugs, microbes and worms working again. These are absolutely essential for a healthy soil.
Now you can continue as for preparing a new lawn with either turf or seed.