Not all floods will kill your grass. As a matter fact most floods will not kill your lawn. But there are some conditions where flooding can do some severe damage. For instance, if you have had floodwaters on your grass for more than three or four days, they can start to do some pre-heavy damage. Lawns are more likely to survive if the average daily temperature is below 60?? during the time of flooding. Lawns will also have a much better chance of surviving if the water is flowing rather than stagnant. Flowing water provides more oxygen for the roots of the grass plants. Ideally, you don't want to have any major signs of erosion or you don't want to have a layer of mud and silt that is over the top of your lawn. Also, make sure that your lawn has been damaged by any soils or other man-made products.
If your soil has been damaged by a flood, you may want to try to fix your lawn as soon as possible. First of all, let your lawn start to dry out. Remove whatever sealed or bodies deposited on your lawn in order to try and save it. After that, look at the damage and assess whether or not you will need to do lawn repair. If you do need to do lawn repair, the first thing you need to do is figure out how to fix a lawn. Most lawns can be re-fixed by aerating and reseeding them. Under some conditions, you may want to put topsoil or PMOS on your lawn when you receive. Make sure to water your lawn regularly until the grass seed comes in and becomes established. It should take about 4 to 6 weeks for your grass seed to come in. Make sure to stay off of the lawn until your new grass has become tall enough to mow.