river floods from threatening the city of talaghan. trees are also a kind of wall they create a beach in the river bed. this is one of the examples of biological coastal walls built with native species of cypress, willow and raspberry. which prevents the movement of water and sediments into lands and facilities in the 120,000-hectare watershed of taleghan , 40,000 hectares, all kinds of water management operations have been carried out in 5 sub-basins with a length of 5 kilometers and an area of 5,000 cubic meters. in 1998, 70 mm of rain was repeated as in 1971, but there is no news of damage to this coastal wall. there was no flood the design of this wall captures floods with a return cycle of 500 years, the wall has done its job, and the city and residential areas behind it, the park that has been created, has kept it free from the risk of flooding, according to the statistics of the soil protection and watershed management research institute, the amount of soil erosion. and water on the banks of the rivers 8 annually. per hectare,