Investigation and classification of dams as traditional structures in water and soil protection and agriculture (Case study: Shahid Parsa Dam watershed)

Bandsar is a traditional and Intelligently method of exploiting floods in arid and semi-arid areas, which can be implemented in a wide area with the participation of watershed residents. This structure, in addition to controlling floods and feeding the aquifer, expands flood agriculture in the region, and by collecting sediments from floods, it leads to soil enrichment. To this end, in this research, the structure and function of Bansadrs in the Shahid Parsa Dam watershed in the north of Sarayan city in South Khorasan province were investigated. First, using topographic maps and satellite images, the Bansadr's location was determined. Then, with field visits, measuring the dimensions of the Bansadrs, the way of construction, and land use, samples were harvested from the soil inside the Bansadrs. The results showed that Bandsars in the region are divided into two groups, mountain and plain, and according to their structure, they are divided into four types. Thus, the dewatering of Bandsars started in March, and usually, it is done two to three times a year. The time for land preparation and planting is from mid-May to mid-June. The amount of crop production in the years of relatively good rainfall is at least 3.5 t of plantation product and 1 t of fodder per ha, the average annual income is up to 6.11 billion Rials from all farms. The depth of sediments in Bansadrs varies from upstream to downstream and has a decreasing trend so that the thickness of sediments was 25 cm in one year in the beginning and less than 2 cm in the end dams. Therefore, Bansadrs can be suitable structures for flood and sediment control, flood irrigation, and soil regeneration in the region.