Field Investigation and Presentation a new formula for Determination of Threshold Slope at the Upstream of Check Dams

Check dams are constructions which could be utilized with the aim of not only decrease of river slope and flood velocity; but also، control of river bed erosion. Furthermore، ultimate slope plays an important role in determination of check dam''s distances. In this Study، a survey and investigation has been done on Goush and Bahreh catchments، Kortian، Kameh and Dasht basins which are located on upstream of Kardeh، Torogh، Shahid Yaghubi and Golestan dams respectively. Consequently، the performance of constructed check dams in term of stability، sedimentation and slope stabilization has been investigated. Moreover، longitudinal section profile، ultimate slope، location، distances and height of dames with acceptable performance about upstream ultimate slope has been measured. Meanwhile، characteristics related to bed aggregates has been sampled and determined. Then، with the measure of dimensions regarding the ultimate slope، some equations which were based on primary slope of river direction has been developed. With the comparison between mentioned equations and the ones which were suggested with other researchers، we argued that one equation that has been defined just based on channel slope could be obviously accepted and the reason originated from the fact that not only this equation did not require any sampling data about river bed aggregates; but also، could result accurate results.