River banks are exposed to destruction and bank erosion. Providing human requirements and reduce

river's dangers is one of the river engineering's purposes. The extent and risk of this phenomenon must be

recognized. Groin is suggested as one of the control methods to reduce erosion. Besides, it is helpful way

to reclaim lands. Groin's length has effective influence on bank erosion control. Laboratory models were

used to investigate river protection and reduce bank erosion. Tests were done in 3 groin's lengths and 5 discharges.

Results show that increasing groin's length from 25 up to 35 cm, and discharges from 15 up to 25

lit/s can reduce bank erosion about 20-40 percent.