Recent climate change has caused water level fluctuations in freshwater bodies to become more intense, making it difficult to conserve large aquatic plant communities. Physiological characterization for recovery is important and can be applied to overgrowth. Southern cattail (Typha domingensis) communities contribute to biodiversity and help to purify water. However, overcrowded southern cattail communities become a nuisance to local people as they often block waterways. Proper management is therefore required to control southern cattail communities for optimization of their benefits. In the present study, we investigated the effect of shoot damage treatment on flood tolerance during the vigorous growth stage which occurs in summer. First, as shoots are damaged by bending or cutting when disturbed under natural conditions, damage treatments were carried out by either cutting or bending the plant shoots at 10 cm above the ground surface. The results showed that bending the shoot had the same or greater inhibitory effect as cutting. Second, the shoots were then cut at a height of 10 cm above the ground surface at the start of the experiment and placed in five different water depth conditions from the ground surface to the water surface. As a result, the maximum depth at which damaged shoots displayed considerable growth was 40 cm. Undamaged plants with a shoot length of about 75 cm displayed considerable growth in water depths of up to 60 cm. These information are useful for management of T. domingensis communities for both of control and conservation.