Effective planting arrangement on floodplains to reduce soil loss in a flood regime: Study using physical models

Abstract

In Taiwan, many floodplains are used for agriculture because flood discharge cannot be blocked, and farmers must be willing to accept the noncompensation offer from the government should their plants be destroyed by floods. Moreover, a scour problem has been observed in floodplains with some kinds of plant, such as bananas. Through a series of laboratory experiments, physical modeling was conducted to develop a planting design to reduce the erosion problem. Five different interval spacings between successive plant models were designed to observe the three-dimensional flow field and sediment transport. The results showed that four low-velocity zones formed around plants when a flood bent them. Among them, the fourth low velocity had the largest influence range. However, if the length of the interval spacing was less than the length of the bent plant, it would cause a shelter effect. This effect would limit the appearance of the fourth low-velocity zone and diminish downstream erosion. In addition, it is suggested that plants be planted using the half length of bent plants as an interval spacing to reduce soil loss. The transverse distance between plant rows should be larger than the half length of the bent plant to avoid contraction scour effects on floodplains. This practical planting method could meet human needs (through added profits) and prevent environmental damage (reduce erosion) simultaneously, making it an effective management strategy for ecological engineers in floodplains.